Food Control 17 (2006) 942–949
www.elsevier.com/locate/foodcont
Development of new quality index method (QIM) schemes
for cuttlefish (Sepia officinalis) and broadtail shortfin
squid (Illex coindetii)
Paulo Vaz-Pires
a,b,*
, Pedro Seixas
b
a
b
ICBAS—Instituto de Ciências Biomédicas de Abel Salazar, University of Porto, Largo Professor Abel Salazar, 2, 4099-003 Porto, Portugal
CIIMAR—Centro Interdisciplinar de Investigação Marinha e Ambiental, University of Porto, Rua dos Bragas, 289, 4050-123 Porto, Portugal
Received 24 November 2004; received in revised form 4 July 2005; accepted 4 July 2005
Abstract
This article describes the development of sensory schemes for freshness grading of cuttlefish (Sepia officinalis) and broadtail
shortfin squid (Illex coindetii) based on the recent quality index method (QIM). As preliminary work, four storage experiments were
performed to choose the relevant sensory parameters for building the schemes. From an initial large set of parameters, some were
chosen to be attributes for the QIM scheme. For cuttlefish, appearance, odour and mucus of skin, texture of flesh, cornea and pupil
transparency, odour of the mouth region and connection between bone and head tissues; and for squid, appearance, odour and
mucus of skin, texture of flesh, appearance of the eyes and ocular tissue brightness and odour of the mouth region. Five storage
experiments were then used to test the tables and to shelf-life studies. The shelf-life, as measured by sensory attributes, is considered
to be 10 days in ice for cuttlefish and 9 days in ice for squid. Sensory and shelf-life differences between these two species can be
explained by morphological and biological reasons that probably include higher rigidity of the cuttlefish caused by the presence
of the internal bone. For both species a high correlation between the quality index and the storage time in ice was obtained.
Ó 2005 Elsevier Ltd. All rights reserved.
Keywords: Cephalopods; Sensory analysis; Quality index method; Squid; Cuttlefish; Shelf-life
1. Introduction
Cephalopods are regarded nowadays as important resources that can be exploited all over the world. They
are recognised as promising species for the future of fishing because of their abundance, rapid stock renewal and
short life cycles. Depending on the species, their life cycles may vary from six months for small species to three
years for larger ones (Mangold, 1987). They are com-
*
Corresponding author. Tel.: + 351 22 206 22 72; fax: +351 22 206
22 32.
E-mail address: [email protected] (P. Vaz-Pires).
0956-7135/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.foodcont.2005.07.004
mon in Mediterranean and in Oriental countries, particularly Japan, South Korea and China. The world total
landing of cephalopods is highly dependent on the fisheries of the four top producing countries: Japan, China,
Korea and Argentina (FAO, 2003).
Cephalopods are also promising in terms of farming
potential. Some species of octopus, cuttlefish and squid
are believed to be among the new species with high potential for aquaculture in the future. Their rapid growth,
high reproductive rate, acceptance of natural and artificial foods, and high market price are the main characteristics that influenced the first aquaculture attempts in
countries like Japan, Italy, Spain, France and Portugal
(Vaz-Pires, Seixas, & Barbosa, 2004).
P. Vaz-Pires, P. Seixas / Food Control 17 (2006) 942–949
Cephalopods are also important among other seafood sources in terms of yield: due to the lack of bones,
the average edible part of cephalopod species is between
80% and 85% of the total body, which is higher that that
of crustaceans (40%–45%), teleosts (40%–75%) and
cartilaginous fish (25%) (Kreuzer, 1984).
During the last few years, there has been a great progress in marketing, quality assurance and freshness
assessment of fish products, but there have been only
few studies on cephalopods quality, most of them being
directed to squid.
Once caught, cephalopods undergo very rapid protein degradation due to endogenous and bacterial
enzymes. Such high proteolytic activity produces an
increase in levels of muscle-derived nitrogen, hence
favouring proliferation of degenerative flora and rapid
decomposition (Hurtado, Borderı́as, Montero, & An,
1999; Hurtado, Montero, & Borderı́as, 1998).
As seafood spoils, it goes through a sequence of
changes that are detectable by the human senses. Sensory methods are the oldest and still the most satisfactory way of grading and assessing the freshness of fish
and fish products (Branch & Vail, 1985; Howgate, Johnston, & Whittle, 1992) and sensory evaluation is commonly considered as the most important method for
freshness evaluation in the fish research (Martinsdóttir,
1997).
In Europe, the most commonly used method for
quality assessment in the inspection service and in the
fish industry is the EU Freshness Grading (or EC
scheme) (EC Council regulations nrs. 103/76 and 104/
76, Howgate et al., 1992; EC regulation nr. 2406/96).
There are three levels in the EC scheme for quality grading of fish products: E (Extra, the highest quality), A
(good quality) and B (satisfactory quality). Below level
B (lower than B is sometimes called unfit or C) fish is
no longer acceptable for human consumption and thus
is rejected or discarded. However, this kind of scheme
is somehow limited when classifying the quality of some
species. It does not take into account differences between
species and it only uses general parameters to describe
the changes for iced fish (Luten & Martinsdóttir, 1997;
Nielsen, 1995, 1997). Another limitation is that all
parameters analysed must be divided in four levels or
grades, which is not always appropriate. The EC scheme
only presents one table dedicated to cephalopods, applicable exclusively to the species of cuttlefish Sepia officinalis and Rossia macrosoma.
These generally recognized limitations of the EC
scheme and other previous schemes originated improved
freshness quality grading systems, like the quality index
method (QIM). QIM is based upon objective evaluation
of certain attributes of raw fish (skin, eyes, gills, etc.)
using a demerit points scoring system (from 0 to 3).
The scores are summarized to give the quality index
which increases linearly with storage time in ice. As no
943
excessive emphasis is laid on each of the attributes, a
sample is not rejected on the basis of a single criterion;
there is not too much influence of slight differences in
the total QIM scores (Luten & Martinsdóttir, 1997).
The QIM system is expected to be the main future sensory method for use in laboratories, for research purposes, and possibly also in fish auction markets, for
more precise inspection and clear decisions about fish
quality. A complete list of the species for which QIM
schemes have been developed was compiled by Barbosa
and Vaz-Pires (2004).
These authors have recently developed a specific QIM
scheme for whole iced octopus (Octopus vulgaris) based
on the analysis of some freshness quality parameters, as
follows: appearance/colour, odour and mucus of the
skin; texture of the flesh; cornea and pupil of the eyes;
colour, odour and mucus of the mouth region and
finally presence of material in the sucker of arms.
Recently developed QIM schemes were presented for
raw gilthead seabream (Sparus aurata) (Huidobro, Pastor, & Tejada, 2000) and for farmed Atlantic salmon
(Salmo salar) (Sveinsdóttir, Hyldig, Martinsdóttir,
Jørgensen, & Kristbergsson, 2003).
The aim of this set of storage experiments was to
design specific QIM schemes for cuttlefish (Sepia officinalis) and broadtail shortfin squid (Illex coindetii), that
may be used to better assess the ‘‘freshness level’’ of
both species stored in crushed ice.
The development of the QIM schemes as presented in
this article is the first of a series of steps, which includes
also the writing of a manual with photographs and
explanations, the inclusion of both tables in the QIM list
of schemes, the addition of these schemes to the list
available in software form and the training of assessors
for the correct use of this new QIM schemes (Martinsdóttir, Sveinsdóttir, Luten, Schelvis-Smit, & Hyldig,
2001).
2. Materials and methods
2.1. Cuttlefish and squid source
Cuttlefish (S. officinalis) and broadtail shortfin squid
(I. coindetii) were purchased at the first sale auction market in Matosinhos fishing harbour, north of Portugal,
from February 2004 to September 2004. Cuttlefish were
caught along the coast of Portugal, between Porto and
Aveiro, by artisanal boats using nets. Squids were
caught by bottom trawling boats operating along the
coast of Portugal, between Porto and Sesimbra. Cephalopods were transported from the market to the laboratory (1 h maximum) in clean and insulated containers;
both species were placed inside plastic bags and surrounded by crushed ice. At the laboratory they were
measured, weighed and briefly washed with tap water
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P. Vaz-Pires, P. Seixas / Food Control 17 (2006) 942–949
in order to remove the excessive ink. The cephalopods
were then placed in boxes with crushed ice, with perforated bottom, to allow the drainage of melted water to
an empty box placed underneath just to collect drained
water. Cephalopods were finally covered with crushed
ice. Boxes were stored at refrigeration temperature
(2 ± 2 °C). Crushed ice was added daily as required in
order to maintain cuttlefish and squid always surrounded by ice. In all these experiments ice was in direct
contact with the skin of the cephalopods.
A total of 39 whole raw cuttlefish with an average
weight of 536 g (range 176–823 g) and 59 whole raw
squid with an average weight of 190 g (range 63–577 g)
were used.
2.2. Preliminary experiments
In order to design the QIM, three assessors with previous experience in seafood sensory analysis described
day-to-day changes that occurred during storage of
whole raw cuttlefish and squid along 13 days of storage
in crushed ice. The first four experiments were used for
training the evaluators and for choosing the appropriate
parameters for the last five experiments, where the first
versions of the tables were tested extensively. Each of
the three assessors evaluated daily all samples available
(between 8 and 12 for each species) in ice for each experiment. The species were evaluated separately in relation
to time but, for some of the experiments, they were
obtained simultaneously.
2.3. Development of QIM
The definition of the time of rejection is a step
needed for the QIM development. As previously done
for O. vulgaris (Barbosa & Vaz-Pires, 2004), sensory
characteristics were used to define the time of rejection, mainly general skin appearance and smell, both
Table 1
QIM scheme for whole raw cuttlefish (Sepia officinalis) stored in crushed ice
Freshness quality parameters
Description
QIM score
Very bright, dark brown or brown, iridescent reflexes all over the mantle
Bright, becoming white-beige or light-grey
Rather dull, rose-purplish specially in the fin and sides of the body
Dull, purplish in the sides, central portion of the mantle becomes brownish
0
1
2
3
Odour
Seaweedy, (sea) fresh
Slightly seaweedy, neutral
Fishy, metallic
0
1
2
Mucus
Transparent, watery, shining
Slightly milky, moderate or absent
0
1
Elastic, very firm, white
Soft, wrinkles when pulled, pink
0
1
Very firm, tense, consistent
Firm, less consistent
Soft, flaccid
0
1
2
Translucent, watery, shining
Slightly opalescent
Opalescent
0
1
2
Black shining
Black, tarnished
Dark red, red bloody
0
1
2
Seaweedy, fresh
Neutral
Slightly fishy
Fishy, intense, sulphurous
0
1
2
3
Firmly attached to the upper part of the head region
Loosely attached to the upper part of the head region
0
1
Skin (dorsal side)
Appearance/colour
Skin (ventral side)
Elasticity/colour
Flesh
Texture
Eyes
Cornea
Pupil
Mouth region
Odour
Internal ‘‘bone’’
Connection bone/head
Range of QIM score
0–17
P. Vaz-Pires, P. Seixas / Food Control 17 (2006) 942–949
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Table 2
QIM scheme for whole raw squid (I. coindetii) stored in crushed ice
Freshness quality parameters
Skin (dorsal side)
Appearance/colour
Description
QIM score
Very bright, well defined pigments of different
sizes and colours (brown, purple, rose and dark red), iridescent skin
Bright, becoming discoloured
Rather dull, without shine, purplish in the central
axis of the body, general orange/pink areas
0
1
2
Odour
Seaweedy, (sea) fresh
Slightly seaweedy
Neutral, slightly fishy
Intense, metallic, fishy
0
1
2
3
Mucus
Transparent, watery, shining
Slightly milky, moderate or absent
0
1
Firm, tense, consistent
Soft, less consistent
Flaccid, flabby
0
1
2
Convex
Flat
Concave
0
1
2
Translucent, watery
Slightly opalescent
Opalescent
0
1
2
Seaweed, fresh
Neutral
Slightly fishy
Intense, fishy, acid
0
1
2
3
Absent or clear transparent
Slightly yellowish
0
1
Flesh
Texture
Eyes
Shape/appearance
Ocular tissue
Mouth region
Odour
Mucus
Range of QIM score
considered as the more important parameters that affect
selling and consumption in the whole form. Three assessors with previous experience in cephalopod sensory
analysis and commercial characteristics of these species
were asked to indicate if they consider samples acceptable or rejectable for commercial use and human consumption. A total of 20 cephalopods in three
experiments for each species were used. Rejection was
defined when at least two of the three assessors considered the samples rejectable. Taste analysis was not used
because it is not considered as ideal for use with cephalopod species whenever these are sold in the whole form;
this was already explained by Barbosa, Bremner, and
Vaz-Pires (2002) and Barbosa and Vaz-Pires (2004).
From the initial set of parameters observed, the ones
that showed more visible and clear variation during
storage time were used to build the first versions of the
QIM schemes. These first versions were then used and
tested in a total of three new experiments, in order to
rearrange the table and improve precision. The quality
index graphs were plotted only from the last two experiments on a total of 12 individuals for each species,
0–16
because this was the moment where the table was completely developed. Adjustment to a linear shaped curve
was obtained.
3. Results and discussion
Several different parameters were initially observed
and registered for both species. For cuttlefish, they
included, at the dorsal side: skin appearance, skin colour, skin elasticity, skin odour, skin mucus, presence
of black blots under the skin (above internal shell), cornea transparency, pupil colour, eye general appearance,
colour and odour of head and arms, texture of the flesh,
connection between internal bone and the head and colour of the fin. At the ventral side, skin appearance, skin
colour, skin elasticity, skin odour, skin mucus, mouth
region odour and presence of mucus, presence of ink
surrounding the mouth, colour of the mouth region, colour of the suckers, arm odour, arm texture, presence of
black blots under the skin and colour of the internal
bone (observed after removal).
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P. Vaz-Pires, P. Seixas / Food Control 17 (2006) 942–949
18
16
14
Quality index
12
10
8
6
4
y = 1.6227x + 0.3485
R2 = 0.9939
2
0
0
1
2
3
4
5
6
7
8
9
10 11 12 13
Storage time (days in ice)
Fig. 1. Quality index for iced whole cuttlefish (Sepia officinalis). Filled
line: regression analysis line for values between 0 and 10 days in ice.
Dashed line: theoretical QIM line (from origin to rejection point).
Vertical bars represent means ± s.d. (data from the two last storage
experiments, performed by three assessors; each point represents the
mean of 12 cuttlefish).
18
16
14
Quality index
12
10
8
6
4
y = 1.7884x – 0.1561
R2 = 0.9954
2
0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
Storage time (days in ice)
Fig. 2. Quality index for iced whole broadtail shortfin squid (I.
coindetii). Filled line: regression analysis line for values between 0 and
9 days in ice. Dashed line: theoretical QIM line (from origin to
rejection point). Vertical bars represent means ± s.d. (data from the
two last storage experiments, performed by three assessors; each point
represents the mean of 12 squid).
For squid, the initial parameters were skin appearance, skin colour, skin elasticity, skin odour, skin
mucus, eye shape and surrounding colour, ocular tissue
transparency, colour and odour of head and arms, texture of the flesh, mouth region odour and presence of
mucus, colour of the mouth region, colour of the suckers, connection between suckers and arm, arm odour,
arm texture, connection between head and mantle and
colour of the fin.
For cuttlefish, 8 parameters were chosen: appearance,
odour and mucus of dorsal skin, colour and elasticity of
the ventral side skin, texture of flesh, cornea transparency and pupil colour, odour of the mouth region and
connection between bone and head tissues, totalizing
17 demerit points at rejection (day 10).
For squid, appearance, odour and mucus of skin, texture of flesh, eye shape and ocular tissue transparency
and odour of the mouth region were the parameters
selected to be part of the scheme, ending with a total
of 16 demerit points at rejection (day 9).
The final scheme for cuttlefish is presented in Table 1
and for squid in Table 2.
Fig. 1 shows the graph of the quality index over time
for cuttlefish (last two storage experiments), and Fig. 2
the same for squid. From these graphs it can be
observed that the characteristic linear shape of the
QIM graphs was obtained, with high correlation coefficients for both species. In these graphs, the theoretical
QIM line between the origin and the rejection day was
plotted, as usual in all QIM schemes. The rejection
around days 10 (cuttlefish) and 9 (squid) means that
the shelf-life of cephalopods is much shorter (approximately between 50% and 80%) than for most fish species
stored at similar temperatures and conditions. This fact
reflects the morphological and biological fragility of the
cephalopods as food, namely their more simple and
fragile skin, lack of scales, higher softness and exposure
of muscular tissue, and specially the general biochemical
composition, much more easily degradable in this
group, mainly due to rapid and effective autolysis (Hurtado et al., 1999).
One of the possible uses of the QIM values, apart
from the estimation of the storage time in ice, is to
obtain remaining shelf-life estimations (Luten & Martinsdóttir, 1997; Martinsdóttir et al., 2001), by application of the tables to samples of unknown time of
storage and by subtracting the days in ice already spent
from the total until rejection. These estimations, however, must take into account that in the particular case
of cephalopods, the shorter storage time until rejection
(or shelf-life) means all degradation phases are consequently also quite shorter. This means that the errors
in these estimations can be comparatively higher than
for fish or other seafood groups; consequently, safety
margins for cephalopod shelf-lives should be carefully
established. QIM schemes can have a precision of
±1.5 to 2 days in ice, as it occurs for farmed Atlantic salmon (Sveinsdóttir, Martinsdóttir, Hyldig, Jørgensen, &
Kristbergsson, 2002), which is much more useful and
P. Vaz-Pires, P. Seixas / Food Control 17 (2006) 942–949
Skin (dorsal side)
Skin (ventral side)
2
2
1
Appearence
QIM demerit points
3
QIM demerit points
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1
Odour
Elasticity/colour
Mucus
0
0
0 1 2 3 4 5 6 7 8 9 10 11 12 13
0 1 2 3 4 5 6
2
QIM demerit points
QIM demerit points
Eyes
Flesh
2
7 8 9 10 11 12 13
Storage time (days in ice)
Storage time (days in ice)
1
1
Cornea
Texture
Pupil
0
0
0 1
2 3 4
5 6 7 8
9 10 11 12 13
0 1
Storage time (days in ice)
2 3 4
Mouth region
9 10 11 12 13
Internal bone
2
QIM demerit points
3
QIM demerit points
5 6 7 8
Storage time (days in ice)
2
1
1
Odour
0
Internal bone
0
0 1
2 3 4
5 6 7 8
9 10 11 12 13
Storage time (days in ice)
0 1 2 3
4 5 6 7 8 9 10 11 12 13
Storage time (days in ice)
Fig. 3. Graphical representation of the attribution of demerit points for each sensory characteristic of cuttlefish, showing the different onset of the
several parameters tested (data from the five last storage experiments, performed by three assessors). It should be noted that the different number of
quality index points for each parameter (between 0 and 1 until between 0 and 3) reflects the division in a certain number of categories and help to
show the onset of the changes (sooner or later) for each characteristic considered.
precise than other common sensory schemes like the EC
scheme.
The attribution of demerit points for each separate
sensory parameter is shown in Fig. 3 (cuttlefish) and
Fig. 4 (squid). From the graphs of Fig. 3, obtained with
data from the last 5 experiments, it is possible to observe
that some cuttlefish parameters show an early variation,
like skin appearance (dorsal side) and eyes, while others
only vary later within the degradation period, like skin
appearance (ventral side) and internal bone connection;
the same kind of observations can be drawn for squid on
graphs of Fig. 4, where skin (all data) and eyes are
examples of earlier variations, while the mucus on the
mouth region is only perceivable after 5 days of storage
in ice. The presence of characteristics with variations
within all the storage period is convenient, as it helps
to increase the precision of the QIM schemes in both
earlier and later degradation phases.
In the particular case of the cuttlefish, it should be
noted that the skin at day 0 (first hours after catch) is
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P. Vaz-Pires, P. Seixas / Food Control 17 (2006) 942–949
Flesh texture
Skin (dorsal side)
2
2
1
Appearence
Odour
Mucus
0
QIM demerit points
QIM demerit points
3
1
Flesh texture
0
0 1 2 3 4 5 6 7 8 9 10 11 12 13
0 1 2 3 4 5 6 7 8 9 10 11 12 13
Storage time(days in ice)
Storage time(days in ice)
Eyes
Mouth region
3
1
Shape
Ocular tissue
0
QIM demerit point
QIM demerit points
2
2
1
Odour
Mucus
0
0 1 2 3 4 5 6 7 8 9 10 11 12 13
0 1 2 3 4 5 6 7 8 9 10 11 12 13
Storage time(days in ice)
Storage time(days in ice)
Fig. 4. Graphical representation of the attribution of demerit points for each sensory characteristic of squid, showing the different onset of the
several parameters tested (data from the 5 last storage experiments, performed by three assessors). It should be noted that the different number of
quality index points for each parameter (between 0 and 1 until between 0 and 3) reflects the division in a certain number of categories and help to
show the onset of the changes (sooner or later) for each characteristic considered.
normally dark brown, due to the expansion of the chromatophore organs. This general dark pattern is soon
lost, due to the post-mortem relaxation of the chromatophores. It was decided to separate clearly these two early
stages in the skin (appearance/colour) parameter, in
order to allow the correct differentiation within day
zero, which means also the zero demerit points are theoretically attainable.
The differences found between the choice of attributes
for cuttlefish and squid were due to biological and morphological factors, which include the different general
resistance given by the internal ‘‘bone’’ that is thick
and very strong in the cuttlefish, but thin and flexible
in squid. The presence of the bone could interfere with
storage capability, probably increasing it, but these
experiments were not designed to clarify how this
occurs. When compared to the QIM scheme for octopus, for which a shelf-life of 8 days was defined (Barbosa
& Vaz-Pires, 2004), both cuttlefish and squid show
slightly longer shelf-lives, but the general parameters
used in sensory tables are very similar. Octopus seems
to be more fragile and sensitive to spoilage than squid
and, specially, cuttlefish.
4. Conclusions
Previously unavailable QIM schemes for cuttlefish (S.
officinalis) and broadtail shortfin squid (I. coindetii) were
obtained within this study. Cuttlefish table is based on 8
parameters, totalizing 17 demerit points at the rejection
at day 10. Squid table is based on 9 parameters, ending
with 16 demerit points at rejection (day 9). These schemes
can be used for more discriminatory and precise sensory
evaluations and grading of the species, in the most common commercial presentation (whole, box and iced).
Further work can be focused in other commercially
relevant cephalopod species (like the squid Loligo vulga-
P. Vaz-Pires, P. Seixas / Food Control 17 (2006) 942–949
ris) and/or other commercial presentations, as QIM
schemes are specific for the products and conditions
assumed during scheme development. One possibility
of such a product is packaged eviscerated mantle plus
corresponding arms, one of the most common products.
Many of the sensory degradation problems found in this
study are probably derived from the presence of the
organs inside the mantle cavity, namely the intestinal
tract and the ink sac. This means the QIM schemes on
products without viscera are expected to present many
differences from the ones presented in this study.
Acknowledgements
Authors would like to thank Dr. Micaela Mota for
her precious collaboration on laboratory evaluations.
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