Quality, Slaughter, Transport
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High-quality Seafood Products based on Ethical and Sustainable Production
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From Cage to Table
Ragnar Nortvedt1), Marit Espe2), Ingrid S. Gribbestad3), Leif Jørgensen4), Ørjan Karlsen5), Håkon Otterå5),
Mia B. Rørå6), Lars Helge Stien1),5) and Nils Kristian Sørensen7)
1) University of Bergen, 2) NIFES (National Institute of Nutrition and Seafood Research),
3) Norwegian University of Science and Technology (NTNU), 4) North Trøndelag Research Institute,
5) Institute of Marine Research, 6) Akvaforsk – The Institute of Aquaculture Research, 7) Norwegian College
of Fishery Science, University of Tromsø
High-quality Seafood Products based on
Ethical and Sustainable Production
High-quality seafood is an important contributor to human health, regarding
both malnutrition and obesity. The Norwegian vision should be to produce
healthy seafood products by focusing on improved processing methods, new
nutritious ingredients, and development of products from underutilised marine
species such as blue whiting and krill. Even more marine resources should be utilised for human consumption by conversion into marine ingredients and by improved processing. The production of healthy and safe seafood has to be based on
sustainable ethical principles. Seafood may become a substantial part of the
daily diet of people who suffer from malnutrition in some parts of the world. At
the same time there is likely a growing market in other areas for more tasty,
trendy and nutritious seafood among school children and youngsters, as well as
among the expanding group of single elderly. A positive and practical benefit of
ethically based quality research on seafood is that ethical, sustainable fish farming also ensures better welfare and thus quality of the fish, which subsequently
should lead to increased income for the fish farmer. When the market demands
documentation of quality in all parts of the trade chain, the operators of catchbased and traditional fish farming, product development and further HACCPbased processing will all achieve added value. Norway enjoys a unique
opportunity to supply the market with fresh products from clean waters.
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Aquaculture Research: From Cage to Consumption
Fresh seafood is attractive
All kinds of seafood are available in today’s
global food market. High product quality is important not only to consumers, but also to processors, as it may open access to new markets
and thereby increase profit opportunities. The
basic quality parameter for a food product is
that it is safe to eat. In addition, the product can
be of high or low quality, which most often is
reflected in the sales price. One important trend
today in quality-conscious markets, e.g. Europe
and Japan, is that fresh or even live seafood
fetches very high prices. The supplier to these
markets is dependent on raw materials from
nearby fishing grounds or products from aquaculture. In this respect Norway has a competitive advantage, situated close to rich fishing
grounds and having a highly developed aquaculture industry. At the other end of the price
spectrum are the twice- frozen fillet products.
These are based today on fish captured on the
high seas, frozen on-board as headed and gutted, shipped to a country offering low-cost
labour for hand filleting and refreezing, then
sent to the international markets as a commodity
product at medium quality and low price. The
demand for these inexpensive frozen products is
high as long as they are safe and offer acceptable quality and price. They have taken a large
share of the seafood volume in many supermarkets. The Norwegian industry cannot compete
with these low-price products. Its challenge is
to satisfy the higher-paying segments demanding fresh, high-quality seafood offered as special cuts with traceable and documented high
quality and presented in elegant packaging.
Norwegian companies, with their skilled and
experienced personnel, can accomplish this and
offer value for money. Tailoring products to
special markets and customers can further
145x100//Kap01-fig01.eps
Figure 1. Customers are asking for more documentation of quality. These fishmongers at the Torget fish market in Bergen
improve both the visual appearance and the quality of their products by cooling fish and seafood in ice.
(Photo: Ragnar Nortvedt)
Thematic area: Quality, Slaughter, Transport
29
develop this advantage. Such products can include seafood graded according to size, cut, fat
content, fat distribution, skin and flesh colour,
and pre- or post-rigor cut fillets offering special
texture.
When choosing tailor-made and designed seafood, customers also ask for more documentation regarding raw materials and production
processes, including traceability – now a prerequisite in many important markets (Figure 1).
There is increasing focus on fish welfare, especially in aquaculture. The result is that ethical
considerations related to feed production based
on sustainable fish stocks, GMO-free feed, gene
technology, controlled use of medicine, density
of fish in the pens, slaughtering methods and
possible use of additives are much-discussed
among customers and consumers. Fish welfare
considerations are important for the industry,
from the fish farmer to the exporter marketing
the product. Most consumers are also very interested in the good taste and other benefits
from eating high-quality seafood. Seafood provides high-quality protein, important vitamins
and trace elements, in addition to the valuable
polyunsaturated fatty acids in the fatty fish species. During the past few years, research has
been moving towards producing safe seafood
145x100//Kap01-fig01.eps
Primary quality
• intrinsic/biological quality (species, size,
season, health status)
• workmanship in handling and production
• product quality (hygienic, sensory, technological, nutritional, ethical)
Secondary quality
• market quality (delivery according to
specifications)
• perceived quality (subjective – hedonic)
30
Aquaculture Research: From Cage to Consumption
145x100//Kap01-fig01.eps
Figure 2. Sea urchins are easily accessible along the
seashore. (Photo: Arne Duinker)
with defined quality, offering documented shelf
life, and being based on ethical and sustainable
production. Most important to the consumer,
though, is that the seafood is tasty – a fancy
food that is “light” in calories and easily digestible, whether eaten at home or in a restaurant
(Figure 2).
Quality is multifaceted
The quality of most products is defined according to government regulations in the exporting
and importing countries, in addition to market
demands and consumer trends. The quality of
our foods is of major concern to public health
authorities and food producers. The basic requirement for food is that the product must be
safe to eat.
Quality can be defined in many ways. It can be
defined objectively, according to measurements
related to composition, or subjectively, relating
to what one prefers. In industry, quality can be
defined as “supply of a product according to the
demand and specifications of the customer”.
Customers may have very different demands,
specifications and expectations of a product, depending on who they are, where they are and
why they are purchasing seafood. It can therefore be of interest to connect the concept of
quality for seafood to two main areas. Firstly, it
is the seafood itself and its specific properties,
from being alive (intrinsic quality) to becoming
a product: in total, the primary quality. The second main area relates to what is offered together
with the seafood product to make the product
special. This quality is related to delivery (of the
product) according to contract, i.e. the customer
gets what he has ordered, on time. But it also involves the degree of satisfaction the consumer
experiences when eating the product. This is the
market and perceived quality, called the secondary quality.
The different sides of quality are dependent on
each other. Most important for the consumer to
consider are aspects of product quality; i.e. its
sensory, hygienic, nutritional, technological
and ethical quality (Figure 3). It is not so much
of interest to know how these properties have
been built into the product. The consumer expects a positive experience when eating fish,
confirming the message that fish is tasty, easy
and quick to prepare, light in calories, easy to
digest and a very healthy food.
Most consumers relate freshness to time after
capture or death of the fish. Freshness then
means high eating quality and that the fish is a
“good” product that is highly appreciated. In
other segments of the market, “good” quality is
the natural, real, clean, pure or biodynamic
product. But a Japanese customer who is celebrating a special occasion may focus on size or
colour of the seafood rather than optimum
freshness. Her interest is the service quality and
not only the taste of the product. This is “eating
with the eyes”. Both types of customers are
145x100//Kap01-fig01.eps
Figure 3: Aspects of seafood product quality.
quality-conscious, demanding supply of correct
quality, meaning according to specifications.
The concept of primary and secondary quality
can be described as being composed of five
main areas, constituting the overall quality of a
fish product:
Most consumers will assess the sensory part of
the product quality first, as it is most important
in describing the eating quality of the seafood.
The taste becomes the most important parameter. As the English say, “The proof of the
pudding is in the eating”. The important product
quality is also the most difficult one to control.
Over time, the biological material in the seafood will change, whether alive or dead; this
cannot be stopped without altering the product
properties.
When the fish is alive, feed intake and sexual
maturation will lead to changes in its quality
with regard to muscle composition and colour
of skin and flesh, among other things. It is of interest to know that a farmed salmon should not
be sexually mature when sold, as it looks different from immature fish. In sport fishing in rivers
it is quite common to catch mature salmon, and
this catch is highly appreciated both as food and
as a trophy, although it has a more pronounced
exterior colour and less-bright flesh colour. It
can definitely be eaten, but it is different from
the standards of farmed salmon, which should
have a consistent quality with regard to exterior
shape and colour.
Thematic area: Quality, Slaughter, Transport
31
When it comes to Atlantic cod, the mature fish
is most appreciated, containing large amounts
of eggs (roe) or milt, in addition to liver, which
altogether is the basis for a perfect, traditional
meal. During maturation, the cod eats less and
the production of gonads leads to a reduced protein content, increasing water content in the
flesh. One main utilisation of the spawning Atlantic cod, mainly caught in the Lofoten area, is
to make stockfish, i.e. drying the whole gutted
fish in open air over a period of several months
from catching during winter until late spring.
The catches of Lofoten cod at the start of the
season are not so mature, leading to a thick
stockfish due to high protein content, while the
late catches are mature fish with higher water
content, resulting in a thin stockfish after drying. In the main market, Italy, the skinniest fish
fetches the highest prices in the north, while the
thick and heavy stockfish has a better market in
the south at a lower price per kilo. Quality is
definitely multifaceted, related to region, tradition and use.
Product quality changes during the life of seafood, and during slaughter, handling, processing, storage and distribution. Eating quality,
defined by the sensory aspect, is usually most
important to the consumer, while the processor
is also very interested in the technological quality: how well the raw material is fit for a certain
processing, be it fresh or frozen, or for cooking,
canning, slicing, smoking, etc. During the handling and processing steps, most critical is that
the product stays safe to eat, although it may
lose characteristic quality criteria such as flavour, taste, colour and nutritional value, due to
storage, freezing or heating.
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Aquaculture Research: From Cage to Consumption
Ethical and environmental
aspects related to quality
Over the past ten years, ethical aspects have become an important part of the concept of quality
when producing food. Ethics came to the forefront with the increasing focus on environmental pollution, radiation, gene technology
and welfare when raising animals, including
fish. The concerned consumer is increasingly
interested in fish welfare. Fish farmers and animal welfare groups want to reduce unnecessary
stress and pain during the production and harvesting of the fish. It is a challenge to handle
large numbers of fish rapidly and effectively in
an industrialised operation at slaughter with a
minimum of stress and pain to the fish. Several
research projects have been started the last few
years related to fish welfare and ethics in fish
farming. Much focus has been put on water
quality, density of fish in pens, medication, feed
quality and methods of killing fish. One result
in Norway has been the introduction of new
regulations regarding slaughter of fish,
demanding that the fish must be fully anaesthetised before killing, which must be done by
cutting the blood supply to the brain. An important side of ethical quality is related to the perception of pain by the fish. It is not clear how
fish can feel pain, and even more important,
whether the pain leads to suffering similar to the
way we perceive pain. Anaesthesia may be used
before slaughter to reduce pain to a minimum.
Most people do not know the technology involved during farming and slaughter of fish and
are often afraid of unknown consequences.
Consumers should have the possibility to know
how fish and other seafood are captured, farmed
and treated before they end up as products on
the shelves in a shop. Then the consumer is able
to assess if the product is produced according to
personal standards – he can buy the product or
refuse it. Lack of information from the farmer
and processors may therefore have great financial implications if consumers do not believe in
the product. Today, this type of information is
available on labels and company homepages
and is most often part of a product traceability
system that is now demanded in many markets.
Some of the ethical questions that may be raised
by consumers regarding farming fish are:
• Was the fish fed enough and with correct
feed?
• Was the feed produced from sustainable raw
materials?
• Was the fish farmed with a minimum of negative environmental impact?
• Did the fish suffer from chronic stress – due
to high fish density, low water quality, predators, handling routines?
• Was the fish harvested and slaughtered with
no unnecessary stress and pain?
When this type of information is available the
consumer can decide whether to buy the product. The level of quality of a product is in this
way not only decided on the basis of taste, appearance, nutrition, microbiology and technical
properties, but also on the sustainability, welfare and ethics in production. No farmer or fisherman is interested in making a product
resulting in low output or reduced quality. On
the other hand they must produce with some
profit, which may not allow farmers to keep the
very highest focus on e.g. low density of fish in
the pen.
For farmers and processors it is a challenge to
combine the demand for welfare and ethics in
production with the demand for economical
production, focussing on capacities and quantity produced. It may be that the product being
produced under special welfare and ethical con-
ditions must carry a higher price. Many customers say they are willing to pay this price, but will
this willingness be expressed in practice? Products under ecological labels and labels referring
to sustainable production are usually found in
the market at a higher price. It is probable that
this will be an interesting niche for some farmers and processors. They need to document that
welfare and sustainability has been taken care
of throughout production by quality assurance
systems, including HACCP (Hazard Analysis
of Critical Control Points) and traceability.
In the slaughter process of both farm animals
and aquaculture fish, stress and/or exhaustion
level are important factors that affect biochemical reactions in the animal after death and may
affect flesh quality. For years, industrial producers of pigs have been aware of the reduction
in flesh quality if the animal is stressed at
slaughter. The meat is then described as pale,
soft and exudative (PSE meat) or dark, firm and
dry (DFD meat), depending on level of stress or
exhaustion that is reflected in energy level and
pH in the muscle and subsequent drip loss during processing if pH became too low. This has
not been very clearly observed in farmed fish,
because the amount of connective tissue (collagen) is much lower in fish than in land animals. The stress level influencing the energy
level of the muscle in fish is most important
when onset of rigor mortis is concerned. With
fish farming it is possible to start processing
(e.g. filleting) immediately after slaughter. Traditionally this has been difficult because the fish
came into rigor mortis very quickly after death.
This is due to quick reduction in energy level,
measured by muscle pH. The energy reduction
is closely correlated to muscle activity coming
from slaughter stress that induces escape reactions, movements and in the final stage exhaustion. If the fish is harvested in a rested state, the
Thematic area: Quality, Slaughter, Transport
33
energy levels are high and the onset of rigor
may start as late as 20–30 hours after death.
This delay in onset of rigor mortis allows
enough time for processing this very fresh fish,
for example by pre-rigor filleting, and at the
same time achieve a better bleeding out from
the fillet. Then distribution can start immediately and the shelf life of high quality fillets can be
extended.
This new concept of producing very fresh
farmed fish has gained much interest in industry
and several ongoing projects have goals related
to documenting and improving product quality,
utilising the by-products from filleting, reducing distribution costs and offering a fresher
product to consumers.
Nutritional quality
Nutritional quality may be defined as a food
item containing components of high nutritional
value for the human body and concomitantly
not containing any harmful substances for human health. Aquaculture, including feeding
wild-caught fish at acceptable market sizes,
provides an excellent opportunity to produce
fish of high quality as compared to wild-caught
fish. The quality of the fish may be affected by
the genetic codes and thus may be selected for
different quality traits by genetic selection.
However, quality is also affected by feed compositions as well as by the different feeding regimes chosen. Thus upon choosing different
strategies the final quality may be tailored to the
different qualities asked for by the different
markets. By producing niche products as requested by the different markets, a higher price
may be fetched for the fish as well.
In recent years research regarding fish qualities
has focused on two different main areas, food
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Aquaculture Research: From Cage to Consumption
safety and production of tailored fish to suit different markets. Food safety has mainly focused
on surveillance and ensures safe production of
fish containing no harmful substances or substances that might be converted to any harmful
substances in the fish. Fish tailoring mainly has
focused on producing a fish of high nutritional
quality for the consumer as some ask for food
items that are healthy while others are more focused on the taste of the fish and the enjoyment
of eating fish and fish products. Profitability has
generally been difficult for producers of niche
products, but in recent years some have succeeded, so it is possible.
Healthy seafood and different
market preferences
Generally seafood is regarded as beneficial to
human health, mainly due to its content of the
long-chained fatty acids EPA (eicosa pentaenic
acid) and DHA (docosa hexaenoic acid) as well
as the content of zinc, selenium and iodid. Also
the fatty fish contains rather high amounts of
the fat-soluble vitamins. In addition all seafood
contains proteins very well balanced in their
amino acid composition, as required by the
human body, and is highly digestible.
It is well known that the chemical composition
of the fish is affected by the composition of the
feed offered to the fish. Thus feed composition
has typically been one of the main factors studied when it comes to nutritional quality. Traditionally, research has focused on maximising
the growth and reducing the period of time
spent until fish reach slaughter size. Historically, this has been achieved by increasing the
energy levels in the diets by increased addition
of lipids while reducing the protein content, as
well as by changing feeding regimes and using
constant light in the grow-out seawater phase.
The increased dietary lipid content thus spares
the protein for anabolic growth, and even if the
fish grows fattier its increased lipid content is
regarded as nutritionally beneficial due to the
high content of omega-3 fatty acids. In the fish
species containing high levels of lipids in the
muscle tissues, such as Atlantic salmon, it is
easy to increase the lipid-soluble components
by dietary treatments. On the other hand the
non-lipid soluble components are not easy to
tailor by dietary treatments. Due to this, research has mainly focused on tailoring of total
lipid content and fatty acid profiles as well as
tailoring of the lipid-soluble vitamins, while research has been limited regarding the protein
and amino acids as well as water-soluble components.
While in the fatty fish species the fatty acid profile in the muscle reflects the fatty acid profile
of the diet, this is not the case with the lean fish
species, such as Atlantic cod. Although the fatty
acid profile of the phospholipids of the muscle
will reflect the diet, the impact is low due to the
low total lipid content of the muscle. As Atlantic cod stores excess lipids in hepatic tissues, the
lipid profile has been found to reflect the dietary
lipid profile. Also, the size of the liver increased
when the dietary lipid content increased.
The amino acids constituting the protein in fillets, of course, are determined by the genetic
code, and as amino acids cannot be stored, imbalanced dietary protein are catabolised and
used for energy. To minimise catabolism and
maximise protein deposition, diets balanced in
amino acids for maximal protein deposition are
of utmost importance, also in reducing the
waste of nitrogen. When tailoring the minerals,
research in recent years has shown that some
might be tailored while others are impossible to
regulate.
Since the catch of wild fish cannot be increased
to provide more lipids and proteins to the growing aquaculture industry, much research has focused on alternative to fish meals and oils
without jeopardising either the growth or the
composition of production fish. It has been estimated that the supply of available fish oils will
be limited before the supply of protein sources,
but lately the available fish meal has been limited, causing very high prices for fish meals. So
for the aquaculture industry to grow, sustainable
protein and lipid sources are needed. Much research has been done on replacing marine oil
and protein with plant proteins and oils. Plant
proteins generally contain anti-nutritional factors, though some of these might be inactivated
upon processing prior to feed production. Still,
the amino acids are not balanced to maximise
growth. Therefore one has to mix different plant
proteins or add crystalline amino acids to fulfil
the requirements of the fish. Furthermore, the
fatty acid profile in plant oils differs from the
fatty acid profile in the marine oils, and as
dietary lipid profile determines the muscle profiles in the fatty fish, this of course will have an
impact on the nutritional quality of the produced fillets.
Several studies have been done regarding the effects of replacing the marine oils with plant oils
or mixtures of plant oils. All of these showed
that neither the growth nor the quality of the
produced fish was significantly affected, with
the exception of the fatty acid profile. Atlantic
halibut can also be fed diets in which 50 per
cent of the dietary lipid content is soy oil, with
no negative impact on sensory parameters or
storage properties. Since nutritionists as well as
markets might ask for fish containing high levels of omega-3 fatty acids due to their beneficial
effects on human health, the possibilities of
slaughter feeds containing a marine fatty acid
Thematic area: Quality, Slaughter, Transport
35
profile have been studied. Upon using such
slaughter feeds for different periods of time
prior to slaughter, the preferred marine fatty
acid profile is achievable.
During the programme period investigation began into the possibilities of utilisation of the
Calanus and krill as alternative marine feed ingredients for production fish. However, to fully
utilise these rich marine resources, improved
technology for fishing, storage, processing and
utilisation of such feed items by the farmed fish
need to be studied in more detail.
Several studies have involved how the largest
European markets for Atlantic salmon accept
the different quality of produced fish, especially
the fatty content of fillets. A study in which
German and French consumers tested several
different tailored qualities of colour, consistency and lipid content of Atlantic salmon showed
that colour was the most important quality
parameter to consumers, although increased
lipid content was also regarded as positive. German consumers appreciated salmon if it was
soft and lipid-rich or hard and lean. The big and
lipid-rich Atlantic halibut was also regarded as
better than the smaller and leaner halibut in a
study by chefs in four Norwegian cities. Whole
Atlantic halibut stored for a period of 21 days
was judged better in taste as well as smell when
compared to vacuum-packed stored halibut.
The bigger fish (5.4 kg) were considered tastier
as well as having a better texture than the smaller halibut (1.8 kg). The eating quality thus was
good in the big halibut even after being stored
for 21 days, while the smaller ones were not so
acceptable.
Smoked Atlantic salmon is generally marked by
country of origin, and a different pricing system
often occurs due to the country of origin in sev-
36
Aquaculture Research: From Cage to Consumption
eral markets. Thus a study was done to evaluate
any chemical or quality differences in salmon
originating from three different countries (Norway, Scotland and Ireland), but all smoked by
French commercial smokehouses. Fish were
collected every second month for a period of 12
months, and at each sampling time the consumer test was also taken by about 100 respondents.
The conclusion of the test was that the typical
French consumer was able to detect differences
between the smoked salmon, but none of the
fish were preferred over the others. Nor had the
country of origin a high impact on the chemical
composition of the smoked salmon. Generally
the fish from Ireland was redder and contained
more cantaxanthine than the Norwegian salmon, while the Norwegian contained more of the
highly unsaturated fatty acids. The Scottish fish
was always between the Norwegian and the
Irish fish. All of the fish analysed was of high
quality and none contained any harmful substances. The study thus could not find any
chemical differences or preferences by the general consumer that should support any differences in the price of the smoked salmon.
One may conclude then that several aspects influence the final product quality of seafood, all
of which need to be studied in more detail. In
addition, the quality of both the marine proteins
as well as the lipids clearly has impact on human health and as such may contribute to improving health status in all parts of the world.
Seafood and health
Fish and seafood contain a well-balanced amino
acid composition as well as the long-chained
fatty acids of high nutritional value for human
beings. In addition, these components have a
positive effect on human health, a fact which
has received particular attention during the past
Food safety
Microbiology and hygiene
Fish contains nutritional components that are
easily digested and consequently more easily
attacked by microorganisms. Fish also has a
high water content, which may induce a poten-
7.0
6.0
Plasma cholesterol (mmol/l)
decade. When it comes to beneficial health effects of fish and seafood, focus has been put on
the effects of the lipid content and fatty acid
profiles of Atlantic salmon on different health
aspects. Feed manufacturers have cooperated
with medical and fish research institutions on
investigating how consumption of fish as well
as its chemical composition affect different patient groups or persons at risk for developing
lifestyle-related diseases such as coronary heart
disease, lipidemia and also psychology related
diseases. As the fatty acid composition in lipidrich fish such as Atlantic salmon reflects feed
composition, it has been important to investigate which components in the fish have the
greatest impact on human health. It has been
shown that consumption of Atlantic salmon by
humans with health problems results in positive
health effects, even if a significant part of the
dietary fish oils has been replaced with vegetable oils. Thus other parts of the fish muscle
besides the fatty acids, such as its protein or
minerals and vitamins, also contribute to the
health benefits of consuming fish. This underlines the significance of the multivariable interaction between nutritional components in fish
and seafood. Within the food and health sector,
there are opportunities to create niche products
for specific customer segments, including functional food – where fish is used as a means of
supplying humans with desired components
from fish feed, or for the significant effects of
fish protein in e.g. lowering blood cholesterol
levels in humans (Figure 4).
5.0
*
4.0
*
3.0
2.0
1.0
FPH
Soy
Casein
Protein source
145x100//Kap01-fig01.eps
Figure 4. Total plasma cholesterol level as a function of
different protein sources, such as fish protein hydrolysate
(FPH), soy protein or milk protein (casein). (Modified after
Wergedahl et al. 2004)
tial high water activity (Aw >> 0.6), a prerequisite for microbial activity that makes the fish
more prone to putrefication as compared to
many other foodstuffs. Furthermore, the optimal activities of the enzymes in cold-water fish
are adapted to low water temperature, which results in high autolytic activity that starts soon
after slaughter and continues through cold storage and processing. The bacterial flora in newly
caught/slaughtered fish depends on water purity, and bacteria associated with water will also
be present on the fish, though in low numbers.
Slaughter of the fish initiates enzymatic and
chemical reactions that result in loss of muscle
freshness. Firstly, due to oxygen depletion, lactic acid is produced and will lower the pH depending on the amount of glycogen available in
the muscle tissues; thereafter the autolytic processes start, and further storage may result in
growth of microorganisms that limit shelf life
upon refrigeration or vacuum storage.
To avoid potential contamination during processing aimed at increasing shelf life, hygiene
Thematic area: Quality, Slaughter, Transport
37
throughout processing has major implications
and should be very strict. In salmonids, the
microorganism Listeria monocytogenes, which
may be introduced during processing, grows
even at low temperatures as well as in vacuum
products. In both Atlantic salmon and rainbow
trout, this microorganism has been studied during smoking and fermentation methods and
subsequent vacuum-packing. During fermentation it is particularly important to keep the storage temperature constant, both to prevent
growth of potential L. monocytogenes and to
improve the sensory characteristica of the food.
The occurrence of L. monocytogenes and total
bacterial count in smoked salmon collected in a
hypermarket in France was investigated; bacterial content varied with time of year as well as
with different smoking facilities, while the content and variation in the raw material showed
little variation. This indicated that treatment
during processing was the most important factor for contamination with L. monocytogenes.
Pollution
Fish live in the oceans, and over the past 100
years pollutants have routinely been accumulated into the oceans by human activities. Since
pollutants know no borders and are distributed
by wind and ocean currents, pollutant levels
may be rising all over the planet. Different pollutants may accumulate in the oceans, some
with the possibility of accumulating in wild fish
used for human consumption or for producing
fish feeds, thus appearing in farmed fish as well.
By using only feed ingredients free of harmful
pollutants, producers can avoid food-borne pollutants in their farmed fish. However, those arriving from the water are harder to avoid. Due to
increased concerns over food safety in the past
5–10 years, special attention has been paid to
the occurrence – and the legal limits – of any
38
Aquaculture Research: From Cage to Consumption
harmful pollutants present in farmed fish, and
feed components. Several potentially harmful
substances exist in the marine environment that
may pose a risk for food safety, such as nondegradable organic compounds and metals.
Whether these are potentially harmful or not depends on the amount present in the food, their
chemical structure, and whether they are absorbed by the fish or not. Chemical contaminants may be added to the fish through
processing, for instance PAH (poly aromatic
hydrocarbons) during the smoking process, or
PCB (poly chlorinated biphenyls) from plastics
or from contamination of feed ingredients. Pollution of the aquatic ecosystem may also contribute to contamination (for instance PCB,
dioxin, bromated flame retardants) and accumulation in the food chain, in particular in lipidrich parts of the fish. Future research thus needs
to focus on optimising the methods to separate
these from feeds and fish to secure pure feed ingredients for fish feed production. Research regarding bioavailability and toxicity of such
components is also needed.
Metals occurring in the marine environment
have a natural origin from geological activity
such as erosion and volcanic activity, but they
may also originate from industrial processes,
for instance from metallurgic industries, from
galvanisation or from battery waste, e.g zinc,
cadmium, lead, arsene and mercury. In contrast
to the organic pollutants, most of the metals are
water-soluble and are bound to the protein fraction of the fish muscle. Bacteria in marine and
freshwater environments transform organic
mercury into methylated mercury, which is
more poisonous than the inorganic forms.
Methylated mercury leads to damage in the central nervous system in both animals and
humans. The mercury level in smoked farmed
fish is fortunately far below the limits set by
legislation.
Rancidity problems in farmed fish
Fish such as Atlantic salmon that contain high
levels of polyunsaturated fatty acids also contain high levels of EPA and DHA, which are
more prone to oxidise post-slaughter, as compared to fish containing less of these fatty acids.
The oxidation of the fatty acids may result in increased rancidity, which is documented in the
smoked salmon market. This is due to that the
fact that fatty acid oxidation increases exponentially with the number of double bonds in the
fatty acids. In addition, some lipid oxidation
may occur in vivo, but the organisms have protective mechanisms to handle this smaller-scale
oxidation. These mechanisms, however, do not
function post-slaughter and during storage of
the fish, since no new generations of antioxidants are produced and meanwhile the antioxidative enzymes lose their efficiency. The degree
of oxidation post mortem is therefore due to the
status of antioxidants in the muscle at slaughter,
additions of antioxidants through processing,
and factors such as the presence of oxygen and
blood residues during processing and storage of
the product. Measuring rancidity of the product
is complicated and generally not sensitive, since
there are many products that may increase or
decrease depending on how far along the degradation process is. One can measure rancidity in
primary products, such as peroxide levels (number of hydroxyperoxide groups present) or in
secondary products, such as aldehyds (anisidine
levels or TBARS that measure thiobarbituric reactive substances). Level of rancidity is also
often expressed as total oxidation, based upon
both anisidine and peroxidation level (anisidine
+ 2*peroxide).
The freezing temperature as well as the period
the fish is kept frozen affect the development of
rancidity in fillets of fattier fish such as Atlantic
salmon. To study this in more detail, gutted Atlantic salmon were frozen at two temperatures
(-20 and -30 °C) at two different storage periods
(one and four months), thereafter thawed, filleted and refrozen for a period of months. The
product quality was assessed using a trained
sensory panel, a consumer panel of 45 participants, and with chemical analysis after filleting
and after refreezing. One of the main conclusions was that salmon that was thawed and refrozen performed well with only minor effect
on the final quality. Increased storage time at
the higher temperature (-20 °C) reduced product quality, although the reduction was small, as
stored samples had acceptable quality after the
treatment. Chemical analysis confirmed that no
dramatic changes appeared in the salmon,
though prolonged storage at the higher temperature (-20 °C) resulted in slightly elevated rancidity compared to those stored at the lower
temperature (-30 °C).
New methods in quality
research
The most widely used variables applied as measures of fish quality are condition factor, chemical composition, microbiological criteria,
yield, bleeding, shelf life, fillet and skin colour,
pH, rigor-development, fillet gaping, waterholding capacity, texture, smell and taste. Traditionally these quality criteria have been measured by means of labour-intensive and
destructive methods such as manual observation and chemical analysis. The demand for
more detailed, more objective and faster methods (primarily online) have led to significant
efforts in the programme period to develop new
measuring methods for fish quality. Projects
Thematic area: Quality, Slaughter, Transport
39
Automatic image analysis methods for describing various quality-related parameters of fish
have been developed in the programme period.
Image analysis methods for describing rigor
contraction in pre-rigor-filleted fish fillets in
various fish species are one example. The output from this analysis is graphs showing how
the fillets change in shape during rigor mortis
(Figures 6 and 7). Image analysis methods have
also been developed for quantifying fat percentage, colour, peritoneum area and melanin spots
in salmon fillets. These methods have potential
16
9
14
8
12
7
10
6
5
8
4
6
3
4
Sensory score
The Quality Index Method (QIM)
The Quality Index Method represents a “retro
culture” to instrumentation relying on traditional manual inspection of selected characteristics in stored fish. The different attributes, e.g.
the shape and the colour of the eyes, the smell,
the colour and the mucus of the gills and the
texture of the fish, are given scores 0–3 according to a documented scale, where 0 indicates a
fresh fish. A maximum acceptable score after
ice storage of each single species is achieved
before the fish is no longer rated as fresh and
must be discarded. Efforts have also been made
to calibrate the manual observations to instrumental methods that do not rely on traditional
chemical methods and thus contribute to a
future latent quality index. In the programme
period researchers have evaluated how the QIM
score of Atlantic cod (Gadus morhua) can be
influenced by different slaughtering methods. It
is possible to calculate instant shelf life status
according to QIM score determination
(Figure 5). This method has also become a
practical way to determine quality at international fish auctions, and hopefully the fishmongers will implement this method as well in
their daily quality assurance routines.
digital cameras is an efficient and non-destructive way to measure quality attributes in fish.
There is no need for direct contact between the
camera and the product. Image analysis can also
be very quick and give a description of a product in milliseconds. Another advantage is that
image analysis gives an objective result, in contrast to visual judgement of colour, for example.
Quality index (QIM points)
under the Aquaculture programme have put particular emphasis on the quality index method
(QIM), digital image analysis, magnetic resonance (MR), computer tomography (CT) and
near infrared spectroscopy (NIR/NIT).
2
cassation limit
2
1
2
4
6
8
10
12
14
Days in ice
145x100//Kap01-fig01.eps
Figure 5. Principle for calculation of remaining shelf life,
based on the Quality Index Method (QIM). A linear relation
(blue line) is tailored to the accumulated QIM vs. number of
days in ice. By tasting prepared fish, an expert panel can
Image analysis
Access to increasingly advanced digital cameras, faster computers and smarter image analysis
techniques has made image analysis an important tool for the fishing industry and research institutions alike. Application of images from
40
Aquaculture Research: From Cage to Consumption
report the sensory score (green line) and determine the date
of cassation, which is 12–14 days for Atlantic cod. By
inspecting the fish in the refrigerator, a fishmonger or an
experienced customer may define the QIM score, find the
corresponding nos. of days in ice on the x-axis and thus also
calculate the remaining shelf life compared to the theoretic
date of cassation.
a)
b)
Figure 6. Pre-rigor cod fillets (a) without bones, i.e. without “reinforcement”, contract substantially until they end up in
rigor mortis (b). (Photo: Lars Stien)
145x100//Kap01-fig01.eps
for implementation in the fish industry to measure the quality in fish fillets in real time as they
pass by on a conveyor belt. Another significant
observation has been that image analysis of digital pictures of salmon cutlets taken by a common table scanner can be used to estimate the
fat percentage and colour of the muscle, thus
representing a good alternative to far more expensive methods. From scanned pictures of
salmon cutlets it is also possible to measure
145x100//Kap01-fig01.eps
Figure 7. Percentage of original fillet length = 100*current
length/original length measured during the rigor-process
for four different treatments of farmed cod: stressed (filled
squares) and unstressed (open squares) stored at 4 ˚C
(dotted lines) and at 20 ˚C (solid lines). The predefined
biological time of initiation of rigor (b.t.2), during rigor
variables that previously have been practically
impossible to quantify in large scale. These
variables include the size of the dorsal fat deposit, the size of the ventral fat deposits and the
size of the loins. The conclusion therefore is
that automatic image analysis has great potential both in the fish industry and as a research
tool.
Magnetic resonance spectroscopy (MR)
MR is a method used both for imaging (MRI)
and for studies of chemical composition (MRS)
in fish. MR makes it is possible to look into the
fish and get images at all levels. The contrast in
the MR images can be changed by choosing different recording options. Lately MRI has been
applied to study the distribution of water and
lipids in fish, salt distribution in fillets and anatomical deformities. This technique has been
applied in the Aquaculture programme to study
different freezing regimes and to see how the
cold front moves into the fish at different temperatures. MR has also been used to study the
formation of ice crystals during the freezing
process.
(b.t.3–5) and full contraction (b.t.6) are marked in
succession along the continuous graphs. (Modified after
Stien et al. 2005).
Thematic area: Quality, Slaughter, Transport
41
145x100//Kap01-fig01.eps
Figure 8. The shelf life of tempting high-quality seafood may in future be instantaneously determined by a handheld nondestructive NIR probe at the fish market. (Photo: Ragnar Nortvedt)
MRS has proved to be a good method for measuring chemical compounds in fish. It gives a
broad picture of the biochemical composition.
The method has been applied on muscle extracts, fillets and whole fish. MRS gives information on changes in metabolites in fish
through the rigor process.
Near infrared and Raman spectroscopy
Measured reflectance (NIR) or transmission
(NIT) of light irradiated on a sample at a broad
spectrum of wavelengths is the rough principle
for Raman and near infrared spectroscopy.
Some of the irradiated light at each specific
wavelength is absorbed by the sample, and the
energy is converted to vibration and stretching
energy for specific molecules in specific parts
of the spectrum. The energy can be measured
indirectly by reflection, transmission or by a
combination of the two, called transflection.
Common to all these principles is that they generate spectra with a range of close peaks from
several similar wavelengths. No peaks stand out
as the specific response for a particular molecule. Multivariate methods need to be applied to
calibrate this multivariate information against
other quantifying methods. Following the introduction of personal computers with increased
42
Aquaculture Research: From Cage to Consumption
and easily accessible calculation power in the
1980s, not to mention the software developed,
these methods achieved their breakthrough.
Calibrations between a range of traditional chemical methods and quality of different food products were developed before the methods were
applied on fish. The quantification of protein in
grains by NIR has been established as a standard
method in the USA. At the end of the 1980s and
beginning of the 1990s, calibrations were established between fat, protein and dry matter in
minced fish for several species. Once the calibrations were established the method became simple
to use and several variables (fat, protein, water,
salt, pH etc.) could be determined simultaneously
in a new sample in seconds. Both NIR and Raman
have been successfully used for predicting the total content of saturated, mono- and polyunsaturated fatty acids in complex mixtures of fat, protein
and water. The measuring principle for NIR is,
however, limited by not measuring specific
micronutrients or quantities below percentage
levels. The methods have nevertheless become
more advanced during the programme period
since basic research has made it possible to measure directly through the fish skin and establish
the respective calibrations. Raman spectroscopy
shows even higher chemical selectivity than NIR.
Fate
Function
Molecular and
comparative
nutrition
Resources
Processing
Human health
Quality
Health
Health
Biomarkers for fate and function
145x100//Kap01-fig01.eps
Figure 9. Fate and function of the biomarkers along the entire value chain, from raw materials through processing to
quality documented products. The results of scientific testing in comparative nutritive studies (cell cultures, animal
models and human intervention studies) may contribute to improved human health.
Raman spectroscopy has thus also been successfully applied to quantify carotenoids at mg/Kg
concentration levels. This leads to the very interesting opportunity of gently netting live fish from
a net pen, sedating it by ethical routines and measuring it by these spectroscopic methods, giving
an instantaneous picture of its water, fat and pigment content before returning it live to the net
pen. In this way the scientist and the fish farmer
can predict the expected body composition in different dietary feeding regimes before slaughtering. The spectroscopic methods cannot be more
accurate than the traditional chemical methods
they are calibrated against but they have proved to
be more precise than the traditional methods and
even more accurate than the Torry Fatmeter. In
the final phase of the programme period, one
project has also started to establish calibration
models between NIR records and manually
determined quality, according to the previously
described QIM. This activity opens the door for
an appealing future application where a handheld
NIR probe can measure remaining shelf life directly during transport, during storage or at a fish
market (Figure 8). In this way modern instrumental technology and traditional manual evaluations
may be combined in a practical, handy documentation tool for quality of seafood.
Future quality focus
Based on the quality-oriented topics described
in this chapter, future research is predicted to
turn more attention towards ethical aspects and
further development of instrumental methods. It
is also expected that more resources will be devoted to cooperative research across institutions
along the entire value chain from raw materials
through processing to the final products. One
should test the human health effects from intake
Thematic area: Quality, Slaughter, Transport
43
of marine ingredients through comparative nutritional studies of both cell cultures and animal
models (fish included) as a basis for conducting
intervention studies on humans. This kind of research would demand more than ever that the
scientists apply the whole toolbox of methods
from biology, chemistry, process technology,
medicine, molecular biology, informatics and
multivariate modelling, in such a way that it is
possible to identify and follow both the fate and
function of certain biomarkers along the value
chain (Figure 9). The biomarkers may in turn be
used to predict how specific raw materials and
ingredients may be utilised to benefit human
health – in a global perspective.
References
Bjørnevik, M., Karlsen, Ø., Johnston, I.A. and
Kiessling, A., 2003. Effect of sustained exercise on
white muscle structure and flesh quality in farmed
cod (Gadus morhua L.). Aquaculture Research,
34(1), 55−64.
Espe, M., Ruohonen, K., Bjørnevik, M., Frøyland, L.,
Nortvedt, R. and Kiessling, A., 2004. Interactions
between ice storage time, collagen composition,
gaping and textural properties in farmed salmon
muscle harvested at different times of the year.
Aquaculture, 240, 489−504
Martinez, I., Bathen, T., Standal I.B., Halvorsen, J,
Aursand, M, and Gribbestad, I.S., 2005. Compositional analyses of cod (Gadus morhua) and Atlantic
salmon (Salmo salar) by high resolution 1H MR:
Application to authentication analyses. Proceedings, 34th WEFTA meeting, 12−15 September
2004, Lübeck-Germany.
Mørkøre, T., 2002. Texture, fat content and product
yield of salmonids. Dr.Scient. thesis, Akvaforsk and
Dep. of Animal Science, Agricultural University of
Norway, 50 p. + V papers.
Nortvedt, R. 2000 (Ed.) Kunnskapsstatus for produksjon av laksefisk. Rapport fra Område Bioproduksjon og Foredling, Research Council of Norway,
ISBN 82–12–01 369–3, 71 pp.
Otterå, H., Garatun-Tjeldstø, O., Julshamn, K. and Austreng, E., 2003. Feed preferences in juvenile cod estimated by inert lanthanid markers – effects of
moisture content in the feed. Aquaculture International, 11(1−2), 217−224.
Roth, B., 2003. Electrical stunning of Atlantic salmon
(Salmo salar). Dr.Scient. thesis, Dep. of Fisheries
and Marine Biology, University of Bergen, Norway,
47 p. + IV papers + Errata paper IV.
Rørå, A.M.B., 2003. Raw material characteristics and
treatment-effects on yield and quality of coldsmoked Atlantic salmon. Dr.Scient. thesis,
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Aquaculture Research: From Cage to Consumption
AKVAFORSK and Dep. of Animal Science, Agricultural University of Norway, ISBN 82–575–
0564–1.
Solberg, C., Saugen, E., Swenson, L.-P., Bruun, L. &
Isaksson, T. 2003. Determination of fat in live
farmed Atlantic salmon using non-invasive NIR
techniques. J. Sci. Food Agric., 83, 692−696.
Stien, L.H., Hirmas, E., Bjørnevik, M., Karlsen, Ø.,
Nortvedt, R., Rørå, A.M.B., Sunde, J., Kiessling,
A., 2005. The effects of stress and storage temperature on the colour and texture of pre-rigor filleted
farmed cod (Gadus morhua L.). Aquaculture Research, 36, 1197−1206.
Stien, L.H., Amundsen, A.H., A., Mørkøre, T., Økland,
S.N., Nortvedt, R., 2006. Instrumental colour analysis of Atlantic salmon (Salmo salar L.) muscle.
WEFTA 2005 Proceedings, Accepted.
Stien, L. H., 2006. Application of machine vision to
quantify rigor development, colour and fat content
in slaughtered fish. Dissertation for the degree
philosophiae doctor (PhD) at Department of Biology, University of Bergen, Norway. 111 p. + V papers.
van de Vis, H., Kestin, S., Robb, D., Oehlenschläger, J.,
Lambooij, B., Münkner, W., Kuhlmann, H., Kloosterboer, K., Tejada, M., Huidobro, A., Otterå, H.,
Roth, B., Sørensen, N.K., Akse, L., Byrne, H. and
Nesvadba, P., 2004. Is humane slaughter of fish possible for industry? Aquaculture Research, 34(3),
211−220.
Wergedahl, H., Liaset, B., Gudbrandsen, O.A., Lied, E.,
Espe, M., Muna, Z., Mørk, S. and Berge R.K., 2004.
Fish Protein Hydrolysate Reduces Plasma Total
Cholesterol, Increases the Proportion of HDL Cholesterol, and Lowers Acyl-CoA:Cholesterol Acyltransferase Activity in Liver of Zucker Rats. J.
Nutr.,134 (6), 1320−1327.
Anders Kiessling1), Marit Bjørnevik2), Magny Thomassen1), Mia B. Røra3), Turid Mørkøre3), Bjørn Roth4),
Ulf Erikson5) and Odd Jordheim6)
1) Norwegian University of Life Sciences, 2) Bodø University College, 3) Akvaforsk – The Institute of
Aquaculture Research, 4) University of Bergen, 5) The SINTEF Group, 6) Norwegian Seafood Centre
From Cage to Table
The concept of “good quality” in fish can have as many meanings as there are consumers. Everyone has an opinion about what tastes good. People also associate
safe food with quality. Scientists prefer to deal with objective criteria and properties that can be measured and evaluated, but such criteria are not always relevant
for consumers and their taste experiences. Cooks, who in their daily lives transform
raw materials into tasty meals, acquire a great deal of experience with the way differences in raw materials affect the end results of their labours. When a structured
quality researcher who wishes to document differences meets a chef who may well
be emotionally involved in his work, bridges can be built between research data
and consumer experience. This chapter’s point of departure is that research data
can be used to steer fish production in the direction of obtaining good-quality fish
in the form of firmer flesh, a reasonable fat content, fat with a healthy profile, reddish colour in the case of salmonids, and several other factors. This chapter will follow the fish from the farm, via slaughter and post-harvest processing, to the
multitude of products and types of packaging produced by the Norwegian seafood
industry to satisfy the demands of new markets and new consumer groups. Today,
salmon are the driving force of the Norwegian aquaculture sector. One question to
be posed is whether this species will continue to play this role in the future, or
whether other species are waiting in the wings for their great breakthrough. Norwegian salmon is still the most common salmon in the world, but many other
countries have learned from this development and are eager to compete. Strong
efforts on the part of Norwegian scientists to reach an understanding of what
makes a high-quality salmon that is good and safe to eat have led to “Norwegian
Salmon” being recognised as a sign of both quantity and quality. Maintaining this
position is a challenge for the future.
Thematic area: Quality, Slaughter, Transport
45
The production phase is
essential for product quality
Different markets have different requirements
regarding quality-related characteristics. So
knowledge that enables the aquaculture industry to tailor fish products according to different
market demands is essential. During the growth
phase, it is possible to control certain parameters of quality in fish through feed and environmental conditions. Starvation produces a
somewhat slimmer salmon, and in cod and halibut it can be seen that starvation results in a
higher proportion of connective tissue, which in
turn leads to less gaping in fillets. Water temperature in the egg and fry phases affects
muscle fibre recruitment and growth, which in
turn are important for texture and gaping. The
time of release of salmon smolt to seawater,
whether in spring or autumn, is important for
growth and fat accumulation in the seawater
phase.
During the past few years, growing awareness
of omega-3 fatty acids for human health has
emphasised the importance of optimising the
content of these beneficial fatty acids in farmed
fish. At the same time, however, the limited
availability of marine oils has led to the use of
vegetable oils in aquaculture feeds. This has led
to changes in the fillet fat composition, as the
fatty acid profile in the diet is reflected in the
fish fillet. The first study that demonstrated the
effects of graded admixtures of rapeseed oil and
soya oil was carried out as early as 1988 (1), but
only during the past few years has this problem
aroused the interest of the fish-farming industry.
A number of studies of these and other vegetable oils have been carried out in Norway and
elsewhere. This is also discussed in the chapter
entitled “High-quality seafood products based
on ethical and sustainable production”. Most attention has been focused on the significance of
46
Aquaculture Research: From Cage to Consumption
dietary vegetable oils on the nutritional quality
of the fillets, but it is possible that altered fatty
acid composition of the fillet also influences,
for example, storage stability, taste and smell,
as well as colour and texture characteristics.
One question that has been asked concerns the
possibility of interactions between modified
fatty acid composition in the cellular membranes of the fish and the pattern of processes
related to the development of rigor mortis and
subsequent muscle breakdown. In connection
with research on pre-rigor processing of salmon
and cod, comparative studies have been carried
out on salmon fed on fish oil and rapeseed oil.
A tendency towards more rapid onset of rigor in
the rapeseed group was observed, but the differences were small and not statistically significant (2). However, in a similar study of cod, the
onset of rigor was much more rapid in fish fed
soya oil (Mørkøre 2006). The underlying mechanisms are still unknown, but these observations underline the importance of knowledge
and control of all aspects of product quality in
aquaculture.
Recent years have seen a great deal of attention
being paid to the size and number of muscle
cells and muscle fibres in fish. Fish muscle is
structured somewhat differently than in mammals. Like ours, it has rapid (sprinter) and slow
(marathon) types of fibres, but in fish these two
types lie in separate layers. In mammals they lie
within the same muscles, but to different extents, depending on how we train and what our
genes permit. Figures 1 and 2 show how fish
muscle is built up.
In a Scottish study, two groups of salmon were
kept at two different temperatures throughout
the freshwater phase, before being released into
seawater and followed up until slaughter. The
145x100//Kap03-fig01.eps
Figure 1: The schematic drawing to the left shows a cross-section of a fish muscle, with the distribution of red (highly
aerobic, slow-contracting), pink (highly aerobic, highly glycolytic and rapid-contracting) and white (anaerobic, highly
glycolytic and rapid-contracting) muscle fibres (from Bjørnevik et al., 2003). The upper right-hand image is a histochemical cross-section of bovine muscle stained to show different types of muscle fibre (rapid, slow and intermediate).
(Photo: Karl Heintz Kiessling). The photomicrograph to the lower right is a cross-section of a fish muscle stained to illustrate
its aerobic capacity, and showing the localisation of red and white muscle. (From Kiessling and Ostrowski, 1997.
Photo: Anders Kiessling)
group that had been kept at the lower temperature always had more, and thinner, muscle
fibres. A number of studies have been carried
out on salmon to find out whether there is a relationship between fillet firmness and muscle
fibre size. Several studies now suggest that
salmon with thinner muscle fibres have firmer
flesh than those with thicker fibres, although the
relationship is not unambiguous. A number of
factors probably determine the texture of fillets,
in which connective tissue, fat content, pH and
muscle fibre all play a part.
Fish has much less connective tissue than does
mammalian meat. Nevertheless, collagen has a
significant effect on the texture of both raw and
Figure 2: White muscle of rainbow trout stained for
glycogen (PAS stain), showing the difference in glycogen
content of small (young) and large (old) fibres. (Photo:
Anders Kiessling)
145x100//Kap03-fig01.eps
Thematic area: Quality, Slaughter, Transport
47
145x100//Kap03-fig01.eps
Figure 3: Schematic image of texture measurement and of
how different fibre thicknesses are believed to affect the
texture of fish muscle.
cooked flesh. Raw fish muscle that contains 1–2
per cent collagen is soft, whereas fish containing
above 8 per cent collagen has a very tough texture. In cooked fish, the connective tissue contributes less to the texture since collagen
denatures long before it reaches the boiling point.
Figure 3 illustrates the principle of mechanical
measurement of texture and how we believe that
different fibre thicknesses affect texture.
It turns out that the connective tissue that keeps
the muscle fibres together becomes weaker as
the pH falls, and this may lead to more muscle
gaping. Farmed cod have large stores of glycogen year-round, leading to a higher susceptibility to muscle gaping. Recent studies have
demonstrated that starving farmed cod for a few
7,4
Glycogen
Lactate 7,2
pH
7,0
7
6
5
6,8
4
6,6
3
6,4
6,2
2
Muscle pH
Muscle glycogen and lactate content (mg/g)
Fillet gaping is an economic problem for the
fish-processing industry. Fillets have a less at-
tractive appearance, and problems arise when
the skin is being removed and the fillets are cut
into smaller portions or sliced. Gaping may take
the form of rips between blocks of muscle.
These can range from small cracks in the flesh
to the extent that the musculature comes apart
all the way through to the skin. Gaping can also
occur when rigor contraction is particularly
strong, which may happen if the fish is subjected to stress or high temperature during the
slaughtering process. Live-chilled, unstressed
fish that have been filleted pre-rigor thus display much less muscle gaping. We see a similar
outcome in well-nourished cod, whose postmortem muscle pH falls rapidly due to their
large glycogen stores (see Figure 4).
6,0
1
5,8
5,6
0
0
4
Days post mortem
8
145x100//Kap03-fig01.eps
Figure 4: Relationships between pH, lactic acid and glycogen levels in cod muscle post mortem (Førde-Skjærvik et al. 2006,
Aquaculture, 252, 409–420)
48
Aquaculture Research: From Cage to Consumption
weeks before slaughter produces markedly less
gaping, but without loss of weight1. This is also
the result when cod are starved during the summer. The reduction in gaping in fillets of starved
cod is most likely to be due to higher connective
tissue strength, as post-mortem pH remained
constant during up to two months of starvation.
Previous studies have shown that starving cod
results in thicker, stronger connective tissue.
Histological studies of halibut indicate that in
this species, too, starvation increases the
amount of connective tissue between individual
muscle fibres2.
Contradictory results have been obtained with
regard to the question of muscle fibre thickness
and fillet gaping. Johnston et al. (3) indicate that
thinner muscle fibres in fillets also produce less
gaping, while other studies have described a
negative relationship between muscle fibre
thickness and gaping (8). Each individual muscle fibre is surrounded by connective tissue, and
1. C. Solberg, personal communication
2. Ørjan Hagen, personal communication
a muscle with many thin fibres will therefore
contain more connective tissue than one that
consists of thicker fibres. Any relationship between muscle fibre and gaping is probably a result of a higher proportion of connective tissue
rather than of thinner fibres. It has been shown
in Atlantic salmon that levels of total collagen
and insoluble collagen are negatively correlated
with gaping frequency, while more soluble collagen has been found in salmon with a greater
tendency towards gaping (5, 6).
Appearance is an important quality parameter
in fish. This is particularly true of salmonids,
whose flesh is preferred to be red. Colour is also
important in whitefish. A pure white colour
such as is seen in cod is regarded as more inviting than the grey flesh colour of saithe, a factor
that also affects relative prices. Colour can be
regarded as a function of light reflection and absorption by the muscle and we can therefore expect to find a relationship between colour, fibre
thickness and texture. A number of studies have
attempted to demonstrate such a relationship.
Figure 5: A salmon fillet can be discriminated from its background with the aid of digital imaging. In the future, this type of
analysis will allow quality assessment of fillets as they pass along a production line for factors such as colour, fat content
(amount of white fat), gaping (connective tissues split up in the white lines of fat between the muscle fibres), shape, and
spots of blood (note the dark fleck on the ventral surface). (Photo and data analysis: Lars Stien)
Thematic area: Quality, Slaughter, Transport
49
Relationships between fibre density and flesh
colour has been found in some studies (7, 8)
while others have failed to demonstrate any correlations (4). Fillet colour has also been reported to vary with texture. It has been shown that
the toughness of salmon fillets correlates positively with light and negatively with red colouring (8). In cod a negative relationship between
texture and green colouring is found (4). Texture is determined by a number of different factors, including the amount of connective tissue,
fat content, water content, muscle-fibre size,
pH, etc., so that any relationship between the
colour and texture of a fillet is due to its chemical and structural composition.
Fish transport, storage and
slaughter – what is the
relationship with quality?
Transport
Transport by well-boat
The method of transporting fish to slaughter by
well-boat is one that functions well enough for
routine transport operations (9, 10). In order to
remove the contents of the digestive system
(food remains), reduce the oxygen requirements of the fish and calm them down before
transport, a minimum of two to three days of
fasting is necessary, depending on water temperature. Siphon loading (with biomass/fish
counter) has turned out to function well. Water
quality during transport is good because transport takes place with open seawater valves, i.e.
the water quality is virtually the same as pure
seawater. During the summer, the water is often
oxygenated when large quantities of fish are
being carried. Typical transports operate with
fish densities of 80–200 kg/m3, although some
transport operators have employed even higher
densities. Tests have shown that this can be
done without lowering fillet quality (10). For
50
Aquaculture Research: From Cage to Consumption
discharging, some boats have recently installed
movable bulkheads with video monitoring of
the behaviour of the fish when they are being
crowded together. Some vessels are able to
pressurise the fish hold. In both cases, the fish
can be unloaded without lowering the water
level in the fish hold. This should help to reduce
the level of handling stress to which the fish are
exposed.
Transport of salmon for slaughter in closed systems (closed valves) produces certain advantages, such as reducing the risk of infection
when the transport passes close by certain fish
farms, as well as cooling/calming the fish before they are delivered to the slaughter plant.
During long journeys, however, closed systems
may involve a serious risk of mortality as water
quality gradually deteriorates. From an ethical
point of view, we are not yet certain whether
transport in closed systems is an acceptable solution. General use of the concept for long trips
probably ought to require the installation of onboard water-treatment systems (scum separator,
etc.) and not least, a great deal of experience on
the part of the crew. A particularly important aspect of water quality is ammonia (NH4+/NH3)
build-up. As is well known, it is primarily NH3
that is toxic to fish, and the proportion of NH3
is dependent on the pH of the water. Under unfavourable conditions (pH > approx. 8), even
small amounts of ammonia can lead to acute
fish mortality. However, carbon dioxide produced by the fishes’ own metabolism lowers the
pH of the water, thus considerably reducing the
risk of ammonia poisoning. We therefore need
to be careful about ventilating the water (to remove CO2) and mixing in fresh seawater with a
higher pH. Transport in closed systems also
leads to the production of large quantities of
scum (probably from glycoproteins in the slime
of the fish). Transport in closed systems is not
currently practised in Norway, but the method
has been successfully employed in a short (twohour) transport by well-boat (10).
Crowding and pumping
At the slaughter plant, transfer from the wellboat to the plant takes place either by pumping
the fish directly into the slaughtering pens or by
transferring them to holding pens. In the latter
case, the fish will usually be allowed to rest for
12–24 hours before slaughter, when they are
crowded together to a density of 200–300 kg/
m3 before pumping.
The use of holding pens has advantages and disadvantages vis-à-vis slaughtering directly from
the well-boat. The greatest advantage of holding pens is that this method saves money, since
the well-boat does not have to be paid for waiting by the quayside, while the plant is able to
slaughter fish from several different producers
on the same day. It is unlikely that keeping fish
in holding pens will improve their quality. The
most important disadvantage is probably the
greater risk of disease and of escapes associated
with keeping fish in sea cages. Using holding
pens may be more difficult in the case of cod
than with salmon. Cod are less well adapted to
water surface temperatures as they are farmed at
greater depths, and they are more inclined to try
to avoid being pumped, so that they need to be
forced together more severely. Little documentation is available regarding pumping and how it
affects the welfare, stress and quality of the fish.
Anaesthetisation and sacrifice
One of the greatest challenges when fish are to
be anaesthetised and slaughtered is that of striking a balance between fish welfare, quality and
process-related costs. In the case of salmon,
CO2 or large quantities of ice water have traditionally been utilised to calm fish down so that
their gills can be cut and they die from loss of
blood in the bleeding basin. In other species
such as eels, ammonia or sodium hydroxide
have been employed. The problem with these
traditional anaesthetisation methods is that they
are relatively inefficient. Removing the blood
supply to the brain means that the process of dying may take anywhere from five minutes to
several hours, depending on species and temperature. Similarly, a range of flight reactions
(anaerobic swimming activity) during anaesthetisation and bleeding can have a number of negative effects on fillet quality (11–17). In order to
satisfy demands for better fish welfare and to
meet future legislative requirements, a number
of new methods have been adopted, including
electric anaesthetisation and killing by a blow to
the head.
Live chilling
The most common method of anaesthetising
salmon and trout used to be to anaesthetise them
in a relatively small tank containing carbon
dioxide, before placing them in a refrigerated
sea water (RSW) bleeding basin (1–5 oC), possibly in combination with chilling after gutting
and washing in a tank of RSW (0–4 oC). Live
chilling in RSW gradually arrived on the market. This method had two objectives: 1) live fish
can be chilled more rapidly than dead fish
because their blood circulation and gill arch
surfaces act as heat exchangers, and 2) the fish
are sedated in the tank by rapid chilling. In the
process line, the live chilling tanks used to be
located before the CO2 tank. However, this
turned out to be an unfortunate method, because
sedated fish from the live-chilling tank tended
to waken again when they were transferred to
the CO2 tank, and they were – as before – completely exhausted before they were anaesthetised. Subsequently, carbon dioxide and oxygen
were added directly to the live-chilling tank. By
Thematic area: Quality, Slaughter, Transport
51
2005, most large Norwegian slaughter plants
were utilising this method to sedate and (partly)
chill their salmonids.
A number of different technical methods for
RSW live chilling exist. Fish are usually
pumped from the well-boat or holding pen into
the RSW tank, which may be divided into a
number of rotating chambers. A certain number
of fish are pumped into each chamber. After a
given period of time, which depends on rotation
speed, the chambers are emptied and the sedated fish are sent on to be bled. One method is
based on the fish and the RSW passing in opposite directions. Carbon dioxide and oxygen are
then mixed into the chilled water before it enters the tank. It is important to realise that when
such large volumes of water (20–40 m3 per
tank) are mixed, a large proportion of the water
is recirculated, and this affects water quality
(see below). In another live-chilling method, an
open tank (not divided into separate chambers)
is employed, in which the supply and holding
time of the fish are controlled by a movable grid
which is moved back and forth along the long
axis of the tank. Another concept has been developed in which the fish are gradually chilled
by transferring them from the well-boat to onshore reception tanks (2 x 1000 m3) in which
they are allowed to recover before being slaughtered. When the fish are to be slaughtered they
are pumped into 2 x 150 m3 chilling tanks at
-1 oC before being sent on to the slaughter line
(2).
Water quality
In order to anaesthetise large salmonids by carbon dioxide, it is estimated that 200–400 mg
CO2/l are required. It gradually became apparent that this was a source of considerable stress
for the fish. The recommended level was therefore lowered to around 80–150 mg/l when it
52
Aquaculture Research: From Cage to Consumption
was decided to change to adding the gas directly
to the live-chilling tank. It is important to be
aware that given that the chilling tank is a
(partly) closed system, carbon dioxide will
always accumulate in the tank whether gas is
added or not. The point of adding a certain
amount of this gas is to maintain its concentration at a given level, sufficient to anaesthetise
the fish. At the same time, oxygen is added (70–
100 per cent saturation) to ensure that the fish
have sufficient oxygen. It is also important to
avoid high oxygen super-saturation, as this is
capable of leading to abnormal behaviour
(unethical) and a potential reduction in quality
(“soft” muscle).
Depending on the proportion of RSW that is recirculated, and how often water is drawn off to
cleanse the tank, the water quality will deteriorate to a greater or lesser extent. This will result
in the water gradually becoming less transparent as a greater amount of biomass passes
through the tank. The quantity of organic matter, mainly slime, also increases significantly.
The water in the live-chilling tank is often reddish, probably due to an accumulation of blood.
We can assume that this blood is due to injuries
incurred by individual fish during pumping
(from valve gates in the pressure/vacuum
pump) from the well-boat or holding pen to the
live-chilling tank. Significant quantities of ammonia from the metabolism of the fish also accumulate in the tank. Because of the low pH
(<6.4, thanks to the added CO2), it does not accumulate in its toxic NH3 form (18).
Sedation
Fish are usually anaesthetised in the course of
2–3 minutes. Carbon dioxide is typically the
primary agent of anaesthetisation. The sedative
effect of rapid chilling (hypothermia) is probably slight because the difference between the
acclimation temperature of the fish (temperature of the seawater in the sea cage) before
slaughter and the temperature of the water in the
live-chilling tank is usually small (T <10 oC).
Hypothermia can be an efficient method of
anaesthetising warm-water fish (T >10 oC). In
late summer Norway can have high water temperatures (18–20 oC), so rapid cooling to
0–2 oC can then have a sedative effect (used in
conjunction with CO2). If the processing line
from the holding pen or well-boat to bleeding
operates satisfactorily, the initial muscle pH of
the anaesthetised fish will be around 7.4±0.1 in
unstressed fish. As a matter of comparison it is
worth mentioning that completely exhausted
fish have an initial pH of 6.7±0.1, while the
final pH of salmon flesh (measured one day
post mortem) is typically 6.3±0.1 (18).
Chilling
Depending on the circumstances, Atlantic
salmon begin to die at -0.7 to -1.7 oC (19, 20).
Thus, in order to obtain the highest possible T
for chilling (the “driving force” for heat transport from the fish to the chilled water), the
recommended temperature of the water in the
live-chilling tank should be held at about
0.0±0.5 oC. One also needs to remember that
salmon and rainbow trout react differently to
rapid chilling, in that chilling to 0.5 oC leads to
a severe stress reaction in rainbow trout. A
higher water temperature should therefore be
employed for this species. When rainbow trout
are subjected to rapid chilling, as many as 25
per cent of the fish may suffer water-filling of
the stomach, which can raise stress levels, measured as higher plasma osmolality. In order to
lower the body temperature of the fish sufficiently, it is important that the fish remain long
enough in the tank. The appropriate holding
time will depend on seawater temperature, biomass, flow conditions and the temperature of
the water in the tank. It is important to remember, however, that as the fish gradually cools
down, T, i.e. the rate of heat exchange, will
gradually decrease. In a process line, with its
need to maintain a rapid, regular flow of production, little will be gained in practice by keeping the fish too long in the tank. At high water
temperatures (summer) live chilling may be an
efficient method, but during the winter the chilling effect is slight (typically 2–4 oC). During
periods of low seawater temperature, the livechilling tanks act primarily as anaesthetic tanks.
Company chilling strategy should therefore also
be considered in connection with other chilling
methods: RSW bleeding tanks, RSW buffer
tanks, or other chilling methods such as ice
slush.
Slush is a relatively inefficient method of anaesthetising and killing warm-water species such
as turbot. Behavioural and blood-gas measurements in turbot raised at 14 oC have shown that
this species responds to tactile stimuli at deepbody temperatures as low as 0.25 oC. Deepbody temperatures below 1 oC result in muscle
contraction in most individuals, which prevents
the fish from expressing responses, while blood
measurements indicate that metabolism continues down to -0.5 oC. No fish died as a result of
chilling to -0.5 oC, but one fish died within 12
hours of this treatment (21).
Fish welfare
If the cessation of brain activity can be taken as
the criterion of good fish welfare, the use of
CO2 is a matter of dispute, as carbon dioxide
anaesthetises the fish too slowly (minimum 2–3
min) (22). How this circumstance will affect the
current use of RSW live chilling as an industrial
method of chilling and anaesthesiology remains
to be seen.
Thematic area: Quality, Slaughter, Transport
53
Slaughter by percussion
Percussion machines are potentially very interesting as a slaughter method for salmonids and
cod. However, the efficiency of anaesthetising
and slaughtering fish with a blow to the head
depends on the design of the percussion head
and the pressure of the blow (22, 23). Since the
pressure required for efficient anaesthetisation
is in the same range as that which can result in
eye injury, the industry will need to tolerate a
certain incidence of eye injuries if this method
is to be employed more safely. However, the
force needed to immobilise a salmonid permanently is not in the same range as that which can
produce serious eye injuries such as eye popping. Where the efficiency of the design of a
particular hammer is concerned, a flat or
rounded hammerhead is the most efficient
method of transforming kinetic energy into a
shock wave. If the fish is to be killed with a
sharp-pointed “Iki jime” hammer intended to
penetrate the neurocranium and destroy the
brain, the region around the cerebellum needs to
be destroyed in order to obtain permanent
insensibility. The problem with percussion
machines is that at present they usually require
operation by human beings, and in order to
improve the process of automation the fish
should preferably be sedated or calm before
treatment.
Electric anaesthetisation and slaughter
Electric anaesthetisation has often been
employed on fish. With salmonids, the principal
challenge is to anaesthetise the fish instantaneously without injuring it (24). Injuries occur
when the dorsal aorta bursts, causing a haematoma. However, the injury problem can be
reduced by employing new frequencies in the
500–1000 Hz range (25, 26). In salmonids,
injury can be completely avoided by using very
low frequencies and voltages for longer periods
54
Aquaculture Research: From Cage to Consumption
of time, a procedure that will have effects on the
onset of rigor (15). The use of electric current as
an instantaneous method of anaesthetisation
appears to be difficult for salmonids, but unpublished data on cod and flatfish show extremely
promising results. Trials using 50 Hz current
have shown that these species do not suffer
injury. For such species as eel, turbot and possibly halibut, electrical anaesthetisation is a
potential method of slaughter in which the fish,
once it has been anaesthetised, is exposed to a
weak current and pulsed frequencies for 2–5
min (27, 28).
Bleeding
The most common method of slaughter is still
to stop blood circulation by cutting the gills.
Gill-cutting can be regarded as an important
method of ensuring death, irrespective of the
method of anaesthetisation or slaughter
employed. For salmonids (and possibly cod)
cutting the gills while the fish is unconscious is
synonymous with an unconscious death, but for
other species such as turbot and eels, and possibly halibut, the fish may regain consciousness.
For this reason, it will be important in the future
to be able to evaluate the effectiveness of methods of anaesthetisation combined with slaughter. Bleeding is also regarded as essential for
complete blood loss, but as soon as the fish is
quite dead, it can be further processed without
negative effects on the loss of blood (29, 30), as
long as bleeding takes place immediately, or at
least within 30 minutes of death (31).
Types of processing, transport
and logistics – an industry in the
process of changing
Norway has largely been a supplier of fish raw
materials, where much of the value-adding process has been transferred to the receiving coun-
tries. This, in conjunction with growing competition on the production side from countries that
often have lower cost levels, has led to more
attention being focused on how to exploit Norway’s particular advantages to increase value
adding and competitive advantage. The spotlight has been turned particularly on how to
exploit advantages in the production of salmon,
trout and cod pre-rigor in an integrated slaughter and filleting process. Such a process could
not only lower production costs, but also open
up the prospect of supplying the market with
super-fresh, high-quality filleted products – at
higher prices than for conventional post-rigor
filleted fillets.
Pre-rigor filleting
The development and adoption of new methods
of rapid, humane slaughter at the end of the
1990s has made pre-rigor filleting a practical
possibility. Pre-rigor filleting is carried out immediately after slaughter, which means that the
Norwegian fish-processing industry can exploit
its unique advantage of lying physically close to
production sites to supply the European market
with super-fresh products. Apart from the potential of even greater freshness on delivery to
the customer, it has been shown that pre-rigor
filleting of salmon gives fillets better colour,
firmer texture and less gaping early in the
course of storage, compared with fillets that
have been processed post-rigor (32). A firmer
texture and less gaping have also been found in
pre-rigor than in post-rigor filleted cod (33). To
guarantee good, stable pre-rigor filleting, the
time aspect from slaughter until the onset of
rigor is critical. In the course of the past few
years, a number of studies have looked at factors that affect the window of rigor, particularly
the effects of different types of stress, temperatures and handling during the slaughtering process (34, 35).
The post-processing of pre-rigor raw materials
has also been focused on, particularly salting
and smoking. Early processing affects both the
uptake and distribution of salt in salmon (36)
and cod (37). Generally speaking, it is more difficult to obtain good salt uptake in pre-rigor filleted raw material than in post-rigor filleted
fillets, due to muscle structure and physical
conditions during the rigor stage. The results of
a number of studies are not in complete agreement, but the most promising method of salting
so far is injection salting, while methods of
treating raw materials need to be further developed.
In the course of the past few years, a number of
industry-oriented projects have aimed at developing salmon and trout slaughter process lines
that will allow the fish to be filleted and postprocessed in their pre-rigor state. In order to increase value-adding even more, greater attention has been paid to fillet portions in individual
packages and to the main challenges presented
by greater automation of portion packaging of
salmon. Pre-rigor filleting also means that other
parts of the fish than the fillets themselves become available, and both research and industry
have begun to regard it as a matter of importance to study the optimal utilisation of the rest
of the fish, whether fresh or frozen.
The difficulty of removing bones from pre-rigor
raw material has acted as a limiting factor in the
utilisation of this process. With new technology,
however, the fish-processing industry is now capable of producing virtually boneless fillets that
cost less and fetch higher prices. The technology is based on pinching out the bones from
the fillet and then x-raying it in order to locate
any remaining bones. Projects that have studied
strategies for increasing value-adding in the
Norwegian seafood industry have pointed out
Thematic area: Quality, Slaughter, Transport
55
that non-material capital, in the shape of competence and knowledge systems, will be of
growing importance in attempts to increase
value-adding in Norway. It is therefore recommended that companies should more than ever
be creating powerful knowledge systems anchored in the industry itself, and be developing
cooperative models that are capable of outweighing the disadvantages of small-scale
operation.
Transport and logistics
Process chain traceability and verification of
origin of foodstuffs have been priority areas of
interest for the European food industry in recent
years. Particularly within the EU, a rising level
of interest in these topics has contributed to ensuring that the final consumer is able to put to
the test the systems that have been developed.
As well as the international standardisation and
implementation of traceability systems, the research and industrial sectors have also been
working on methods of mapping traceability,
new marking technologies, and data-capture
and IT technologies that will streamline the
transfer of traceability information between
companies in the value chain.
More pre-rigor filleting and processing in Norway in general will be of great importance for
the efficient transport of farmed fish. At present
very large quantities of ice, as well as unmarketable parts of the fish, are transported. Pre-rigor
processing opens up the logistical prospect of
bringing fresher fish to the market. The demand
for high-quality fresh-fish products is growing,
and exports of fresh fillets have increased in recent years. The use of super-chilling to prolong
shelf life could expand the market for fresh fillet
products. Prolonging quality retention will also
bring greater flexibility to production and enable Norwegians to increase the proportion of
56
Aquaculture Research: From Cage to Consumption
fresh versus frozen products. As an example of
this trend, industry-oriented projects have been
carried out on cod super-chilling. These have
focused on the entire value chain from production, via refrigeration during transport, to market acceptance. Most people regard the distance
to the market as long, and it takes four days
from the date on which fish are packed in
Northern Norway until they are delivered for
onward distribution in Europe. The most common method of transport is in insulated boxes,
each containing ice-chilled fish or fillets. In order to keep fillets in good condition for another
couple of days and thus retain their high quality
for longer, studies of super-chilling have been
carried out. This process involves chilling the
fillets to a temperature at which some of the water in their tissue freezes. After it has evened
out, the temperature will stabilise at around
-1.5 oC, and the ice in the product helps to
maintain a low temperature throughout the
transport chain. The ice in the product during
transport will have thawed by the time the fish
are presented for sale in shops, so it is important
that they should not be chilled more than necessary to maintain the good qualities of the fresh
fish. Trials have shown that after four days in
transport, the temperature of super-chilled fillets was still as low as -1–0 oC, and their quality
was judged by both customers and chefs to be
just as good as or better than iced fillets, suggesting that this method has the potential to improve the efficient transport of processed fish
products.
Packaging – new products –
different markets
The seafood industry is a rapidly growing sector
in Norway. Its range of products is expanding,
and new markets are being developed. Exports
of whole round fish in traditional expanded
polystyrene cartons still make up an overwhelming proportion of turnover of fresh
wares, but the degree of processing is on the increase, and with it, the need for packaging materials.
inate sales, nowadays there is a much greater
range of packaging and presentation. The need
for rapid food preparation at home is growing,
and the number of small households is also increasing; the keyword here is flexibility.
Packaging makes it possible to transport and
store fish, maintain product quality and ease the
handling of goods in the transport chain. It also
tells customers something about the product,
profiling it and thus increasing sales. Packaging
also has the important function of protecting the
product from contamination and ensuring its
safety in terms of health. This in turn allows
seafoods to be sold in self-service counters.
Suitable packaging reduces transport costs,
damage and losses. Optimal packaging solutions throughout the transport chain involve
good utilisation of the environment and resources, thus benefiting both society and the individual consumer.
Product exposure in the shops is a decisive factor when shoppers are deciding what to buy.
Customers want to see the products on offer.
Many people wish to be able to choose products
on the basis of price and to compare seafood
with meat and chicken. Some shops have therefore chosen to sell seafood in the form of prepriced consumer packs. A steadily rising proportion of customers also wish to see their food
packed in environmentally friendly packaging.
For the companies offering these products, the
cost-effectiveness of the production process is
the most important aspect, but the economics of
packaging is also important. Companies need to
balance economics against customer satisfaction and to take both national and EU requirements into account. In recent years, the EU has
issued directives that aim to reduce or eliminate
environmental impacts. These directives already are, and will continue to be, of importance for the evolution of product packaging.
Purchasing patterns and trends
There has been a trend in the direction of offering consumer packs of seafood in self-service
counters. This trend is particularly evident in
the European market. There are ongoing research efforts to improve the efficiency of packaging methods. Advertising expert Leo Burnett
once said, “Packaging is the primary display
opportunity.” Good packaging sells. It should
be safe and capable of maintaining quality. It is
the combination of appropriate quality, graphic
design and technical design that turns packaging into a solid, serious and not least, effective sales tool for seafood. No matter whether it
is fresh, salted or frozen, seafood needs to be
sold in watertight packaging that can tolerate
being turned upside down.
Buying patterns are changing. While traditional
fish counters featuring whole fish used to dom-
Trends in consumer packaging
There are three main types of consumer packages of seafood products:
Vacuum packs
These are used for both fresh and frozen products, and they allow products to be attractively
profiled. When the air is sucked out and the
plastic tightly surrounds the product, both
colour and consistency can be particularly well
profiled. It is also easy to handle products in the
store, as they can be presented either lying flat
or hanging vertically. Studies have shown that
vertical presentation tends to increase sales.
Thematic area: Quality, Slaughter, Transport
57
is chilled is also critical to the quality of the
end-product.
This type of packaging enjoys important advantages in that it can be distributed or delivered to
stores together with other product groups.
MAP (Modified Atmosphere Packaging)
This is winning a growing share of the market
in important export markets for Norwegian seafood. Though still relatively small in Norway,
MAP is much more important abroad. However, there are good reasons for supposing that
this type of packaging will take a larger share of
the market in the future.
Figure 6: MAP-packed cod. (Photo: Norwegian Seafood
Centre)
145x100//Kap03-fig01.eps
This packaging method is not particularly
advanced, and it requires little investment.
Environmental taxes may be imposed in certain
markets, but these focus little on food stores.
This type of packaging largely complies with
the wish of customers to see the products on
offer before they actually decide what to buy.
In recent years, chilled prepared foods have
grown in popularity. “Sous vide” food products,
which are vacuum-packed and heat-treated, can
give products a shelf-life of 10–12 weeks when
they are kept at 0–2 oC. This means that consumers do not need to freeze their purchases,
and that they stay fresh for a long time. To
maintain their quality, products need to be
handled in an unbroken cold chain from the
production stage until they reach the consumer.
The way in which seafood is handled before it
58
Aquaculture Research: From Cage to Consumption
MAP products are sold in self-service counters
and have become a common sight in most food
stores (see Figure 6). The gas used in these
packs slows bacterial growth and thus prolongs
the shelf life of the product. A relatively large
volume of gas is required to obtain the desired
shelf-life, which means that such packs take up
a good deal of space on the shelves. Recent research suggests that seafood can be pre-saturated with gas, thus reducing the large volumes
required. Traditionally, it appears that those
types of fish that release most liquid are least
suitable for MAP production. In the international market, there is a clear trend in the direction of MAP and vacuum-packing.
Seafood packed in trays
These products are portion-packed either in the
store itself or in a packing plant. This type of
presentation is labour-intensive, but it satisfies
certain customer requirements. For the customer, pre-packaged portion packs are easy to
relate to in the sense that they are clearly priced
and the price can be easily compared with the
quantity in the pack. This is thus similar to how
meat is presented, and products are cleanly cut
and boned. The range of pre-packed portion
products is rapidly growing in Norway, and they
are a good supplement to manned fish counters.
Studies show that these products also appeal to
customers who would not normally ask for
fresh fish. This type of packaging also allows
fish-counter staff to be more efficiently
employed in pre-packaging their products.
New aquaculture species – are
there alternatives to salmon?
Sustainable growth in the marine sector depends largely on an expanding and diversified
aquaculture. Not all species can be developed
simultaneously, and environmental conditions
determine the suitability for growing particular
species. Goal-oriented marketing and sales efforts, and production of fish with “the right
quality” are also important success factors.
Norway’s government is currently taking steps
to ensure that new species can be introduced to
aquaculture by encouraging research and development efforts within this area.
Norway lies at the forefront of research on marine coldwater species, but scaling up production and commercialising new aquaculture
species are resource-intensive and time-consuming processes. This was also the case with
salmon farming, where it took a long time to
reach profitable large-scale commercial production. In the past few years, the development
of cod as a new aquaculture species has been
prioritised, but halibut and mussels are also at
the scaling-up stage. Expectations are high for
the economic potential of these species. Other
species also have potential in terms of volume
and niche production.
Cod
Commercial activity based on farming cod is
growing rapidly, largely thanks to goal-oriented
research and practical trials. Cod farming is
based on the production of fry or on raising captured cod. Commercial up-scaling in the future
will require farming of cod from the fry stage,
while raising captured cod will be a relatively
minor part of the industry. Market orientation
and good co-existence between the value chains
for farmed and captured cod will also play central roles in the development of this sector. The
production of fry and juvenile fish is progressing, and work on feeds and cod breeding is underway. Research financed privately and by the
public sector has improved operational aspects.
The quality of farmed cod differs to a certain
extent from that of wild cod. Farmed cod usually has a firmer texture, its flesh is whiter in
colour and it produces thicker fillets. Most markets regard these characteristics in a positive
light. On the other hand, farmed cod is more
likely to lose moisture during storage, particularly when stored frozen. The past few years
have seen a certain amount of research on this
topic. Appropriate handling before, during and
after slaughter, as well as correct storage, are
important aspects of maintaining quality. Recent research results also suggest that specially
designed feeds given before slaughter can help
to improve the ability to bind water.
The greatest challenge facing fish production
today is that of postponing sexual maturation so
that growth to slaughter size is not held back
and flesh quality does not deteriorate. Cod
make up part of the global whitefish market, in
which farmed cod can complement wild-caught
fish. During the first phase, the European freshfish market will most likely be the primary market for farmed cod.
Thematic area: Quality, Slaughter, Transport
59
Halibut
In Norway, the greatest efforts have been put
into farming halibut as a new marine species.
Since the mid-1980s, the public and private sectors have invested large sums into making commercial halibut farming possible. To some
extent, these efforts have been successful. Production of fish for human consumption was expected to pass 1,000 tonnes in 2005. Improved
control of fry production and greater attention
to the sea cage environment has created confidence that we are approaching the stage of being able to implement an efficient halibut
production line.
Cod is considered the aquaculture species with the
greatest growth potential today. (Photo: Per Eide,
Halibut quality is generally good. Fillets are
usually firm and white, but there is a need to
standardise methods of slaughter. We also need
to ensure that both male and female halibut
maintain good growth and good quality yearround.
Norwegian Seafood Export Council)
145x100//Kap03-fig01.eps
In 2004, production of farmed cod reached
4,500 tonnes. Current prognoses suggest that
production will surpass 50,000 tonnes as early
as 2010.
Shellfish
Shellfish are a important item in terms of global
consumption, and Norway enjoys good natural
conditions that could enable it to become a major player in shellfish farming. Mussel farming
is growing in scale and is the shellfish industry
Table 1: Candidate species for aquaculture in Norway, apart from salmon and rainbow trout. (source: KPMG)
Species on which work has
Species on which little work has
been done in Norway
been done in Norway
Non-fish species
Other marine animals
Cod
Halibut
Hake
Shellfish
Sea urchins
Angler fish
Mussels
Sea cucumbers
Catfish
Atlantic bluefin tuna
King scallops
Charr
Haddock
Flat oysters
Turbot
Redfish
Crustaceans
Eel
Lumpfish
Lobster
Plaice
King crab
Sole
Edible crab
Lemon sole
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Aquaculture Research: From Cage to Consumption
sector that has progressed furthest. The mussel
farming industry has gone through a phase of
consolidation, and now has better control of its
production.
Important quality characteristics of shellfish include meat content, colour, texture and shell
strength. These properties display considerable
variation from one site to another and at different times of the year. Mussel farming has considerable potential for growth, provided that
greater efforts are made in the areas of controlling stocks, ensuring reliable supplies and providing quality based on market demands. A
national harvesting plan based on geographical
and seasonal variations in quality would contribute to meeting specific market preferences
and ensuring constant quality, and thus better
prices.
Other species
Charr, turbot, plaice and sole are considered so
well developed that they should be ripe for com-
mercialisation; it should be up to the industry itself to decide whether it is economically
interesting to scale up farming of these species.
Intensive lobster farming is in transition between the pilot phase and up-scaling, while flat
oysters, king scallops and catfish have been at
the pilot stage for some years. Flat oysters and
catfish could be niche products for the Norwegian aquaculture industry, but their commercial
potential is considered limited.
Scallops are believed to have greater potential.
Ballan wrasse and sea urchins are not yet far
enough along to be ready for up-scaling; their
commercial potential is regarded as medium.
Other species at a very early stage of farming
include angler fish, haddock, king crabs, lemon
sole, hake, Norway lobster and edible crabs.
These species may have potential in the long
term, and there are concrete plans for commercial development of some of them. Table 1 offers an overview of species on which work has
been done in Norway (38–40).
Thematic area: Quality, Slaughter, Transport
61
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