Funded by the European Union’s
Seventh Framework Programme
Effects of processing on nutritional value of fish
products
Assoc. Prof. Sabine Sampels, Ph.D.
Nutritional value of fish
• Fish are a good source of the essential long chain n-3
polyunsaturated fatty acids (PUFA)
• More recently also the fish proteins have come into
focus and scientific interesst
• Fish are also a good source of certain minerals and
vitamins (phosphorus, calcium, iron, zinc, selenium,
iodine (marine species), vitamine D and B12 as well as
Vitamin A
Fatty acids and nutrition
• Energy source
• PUFA have an important function in the cell membranes
• n-3 and n-6 fatty acids are precursors of eicosanoids
with important functions in the human body
• A low ratio of n-6/n-3 prevents cardiovascular diseases
-> Recommendation for humans: n-6/n-3 = 1-4
• Mammals can not synthetize 18:3n-3 and 18:2n-6 and
have only limited ability to elongate these towards the
longer chain derivatives.
Parameters influencing the fatty
acid composition in fish muscle
•
•
•
•
•
•
•
Species
Season
Feeding strategies
Handling, transport
Storage conditions
Preservation and processing techniques
Preparation
From raw material to
ready product
Preservation/storage stability
Creating a new product
Microbial hazards
Effects of processing oxidation:
cutting, light, heat, salt...
• Effects on nutritional composition
• Addition of various ingredients....
•
•
•
•
Frozen storage
• During freezing ice crystalls are formed. Big
crystalls can destroy the cellmembranes > lead to
increased enzymatic breakdown and thereby to
increased oxidation during thawing since free
fatty acids oxidize more easy
• Oxygen can easier reach the phospholipids in the
membranes and cellorganells
• Decrased binding of water -> increased losses
• The faster the freezing process, the smaller the
crystalls will be -> new freezing techniques!
Freezing
Micrographs of
unfrozen and frozen
Atlantic salmon
tissues.
Alizadeh E, et al. 2007 ;doi:10.1016/j.ifset.2006.12.003
Freezing and thawing
Prevention of lipidoxidation in longtime-frozen chicken by addition of oregano-oil and
α-tocopherylacetate
(A) Directly after thawing;
(B) After 7 days of cooled
storage
Food Research International
Volume 36,
Issue 3, 2003, Pages 207–213
Thawing should be done slowly at refrigerated temperatures (< 4°C). Thawing at this
temperature will allow for the ice crystals to dissipate with minimal structural damage
to the meat product. Also, at these temperatures, pathogenic and spoilage microbial
growth is minimized
Conclusions:
• The faster the freezing the better
• Even during frozen storage things happen
• Do not freeze fish again once it has ben
thawed
9
Fast Foods and Products
• A number of fast foods was chosen that busy parents
might give to their kids
• For fish products the respective raw products were
analysed (Alaska pollock, saithe, cod ...)
• Additionally for chosen products samples from every
processing step from raw to final product were taken
• Comparison of composition with food composition
tabels was performed
Fatty acid changes in fish
Cod
Crispy cod*
Fishfingers
Cod
Fishfingers
(white fish)
% Fat
0.62
7.8
9.3
7.6
SFA
24.3
47.4
26.6
13.4
MUFA
16.2
41.6
31.3
23.5
18:1n-9
6.72
40.6
30.2
21.6
18:2n-6
0.96
9.53
40.4
60.1
20:4n-6
1.65
nd
nd
nd
20:5n-3
13.4
0.36
0.39
1.05
22:5n-3
1.17
nd
0.02
0.08
22:6n-3
42.1
0.96
1.04
1.40
n-6
2.61
9.53
40.6
60.3
n-3
56.9
1.56
1.60
2.68
n-6/n-3
0.05
6.3
25.5
22.5
Fat and oils
-main fatty acids
SunRapeOliveflower Corn seed Palm Butter lard
oil Safflor
18:1 n-9 14-39 20-42 51-70 36-44 17-30 35-55 55-83 8-21
18:2n-6 48-74 34-65 15-30 9-12
1-3
4-12 3-21 68-83
18:3n-3
0.3
0-2
5-14 0-0.5
0.7-3
<1.5
0-1
-0.1
Conclusions:
• Fat content and fatty acid composition
in fish products is highly affected by
added fat or battering
• Depending on the used fat the n-3/n-6
balance willbe totally shifted
• The product will have a significant
changed untritional value
13
Fish- and liverpaté
Porkliver patés: various proportions of liver, porkmeat, pork fat,
Milkprotein, flour (rice, wheat) spices....
Fishpatés: 25-40% Fish, Milkprotein, potatoemash + potatoestarch,
Plantoil, etc...
Canned fish- lipid composition
Ratio!!!
Frying of carp in the traditional way,
using different fat sources:
• Fried plain and with a batter
• Frying oils (fat): Sunflower, butter, lard, rapeseed
• Fat content
• Fatty acids
• TBARS (lipid oxidation)
Fat content in carp fillets raw and after
frying
Changes in chosen fatty acids due to frying of
carp fillets
C14:0
35
30
C16:0
C18:0
C18:1n9
C18:2n6
C18:3n3
butter fried plain
butter fried in batter
lard fried plain
25
lard fried in batter
rapeseed oil fried plain
20
rapeseed oil fried in batter
sunflower oil fried plain
15
10
5
0
-5
-10
-15
sunflower old fried in batter
Conclusions
• Frying will increase the total fat content, frying
with a batter results in a three times higher fat
content
• The fatty acid composition of the used fat is
mirrored in the product after frying
• Use of n-6 rich oils (corn, sunflower) will
significantly change the nutritional value
• Recommend to use neutral oil or oil rich in n-3
(oliveoil, rapeseed)
19
Increasing nutritional value of traditional meat
products with an underutilized by-products
from carp processing
Aims:
• to develop innovative, novel products using so called carp
separate, an underutilized by-product from carp processing.
• to create attractive products and thereby promote and
increase the consumption of fish.
Method:
• Replace part of the meat with fish separate in 4 different
traditional meat products : Barbecue sausage, Vienna type
sausage, hotdog type sausage and liver pate
carp separate
barbecue sausages
hotdog type sausages
Fatty acid composition in commercial versus
novel products (%)
The amount of
combined EPA and DHA
was 74, 54, 109 and
77mg/100g in the novel
barbecue sausage,
Frankfurter type,
Vienna type sausage and
pâté respectively.
(22-31% of the minimal
recommended daily
intake by EFSA)
sausages with fish
min-max
commercial sausages
min-max
C14:0
1.37-1.46
1.33-1.88
C16:0
23.50-24.62
22.49-25.32
C16:1trans
0.09-0.43
0.33-0.46
C16:1
4.39-5.83
2.13-3.72
C18:0
10.41-12.30
7.95-15.29
C18:1n-9
42.62-44.96
37.83-43.71
C18:1n-7
0.87-3.41
2.33-3.37
C18:2n-6
7.53-8.30
7.01-19.91
C18:3n-3
1.06-1.15
0.59-1.68
C20:1n-9
0.48-1.25
0.54-0.90
C20:4n-6
0.41-0.44
0.24-0.40
C20:5n-3
0.22-0.36
n. d.
C22:5n-3
0.00-0.15
n.d.
C22:6n-3
0.14-0.31
n.d.
SFA
35.47-38.18
32.32-41.97
MUFA
51.41-53.15
44.83-50.83
PUFA
10.11-10.72
7.85-21.98
n-3
1.56-2.00
0.59-1.68
n-6
8.34-9.12
7.25-20.30
n-6/n-3
4.36-5.91
11.16-15.61
EPA+DHA
0.36-0.65
n.d.
Conclusions
• Fish by-products can be used in novel
combined meat-products and increase
their nutritional value
22
Fish marinated in various
berry concentrates
Treatment
 Marinating 24h in the chosen berry
concentrates
 Vacuum packaging, storage at 4 °C for 7 days
 Frozen storage at - 20 °C for 6 months
elderberry
cranberry
black currant
Lipid and protein oxidation
TBARS
µM/g
(MDA)
K= control
1=elderberry
2=cranberry
3= black currant
35
P=0.620
30
25
P=0.392
20
P=0.071
15
10
5
0
K
1
2
3
α-Tocopherol
µg/g
mM/g protein
Carbonyls
4.50
30
P=0.10
P=0.731
4.00
25
P=0.05
P=0.296
3.50
P=0.096
3.00
20
P=0.52
15
2.50
2.00
10
1.50
1.00
5
0.50
0.00
0
K
1
2
3
k
elderberry
cranberry
black currant
Volatile components, deriving from
lipid oxidation
ng/g
K= control
1=elderberry
2=cranberry
3= black currant
1-Penten-3-ol
(rancid flavor)
250
200
150
100
P=0.111
P= 0.087
P=0.105
50
0
K
1
2
10
9
8
7
6
5
4
3
2
1
0
P=0.048
*
K
3
7
Butanal
5
Hexanal
ng/g
1
P=0.036
*
P=0.061
2
3
2-Penten-1-ol
6
4
5
3
P=0.095
4
P=0.047
*
P=0.057
2
3
P=0.086
2
1
P=0.108
P=0.116
2
3
1
0
0
K
1
2
3
K
1
Colour…..
Conclusions
• Natural antioxidants from berry concentrates and
other novel additives protect fish against oxidation
and increase shelf-life
• A possible added value from the increased
proportion of antioxidants and polyphenols
• Possibility to design fancy healthy snacks with
natural ingredients….
Take home messages how to keep and
increase nutritional value of fish:
• Optimize preservation and storage conditions
• Use fat sources high in n-3 FA or ratio neutral fats in
processing
• Teach people to use right fat for preparation
• Evaluate the use of natural antioxidants for increase
shelf life and add value
• Communication through the whole production chain is
essential!