Transcript The biochemistry of fish processing

Esbjerg Campus, April 4-5, 2003
FISH
Global catch / harvest
Fish
Abt. 20.000 known species
Bony fish
Cod, plaice
Gristle fish
Ray
Shellfish
Shrimp, lobster
Bivalves
mussel
After Catch
Decomposition
Composition of a fish
Water
65 – 80 %
Fat
1 – 20 %
Protein
14 – 20 %
Vitamins
Minerals
Decompositon of fish
1) enzymatic spoilage
2) oxidative deterioration
3) bacterial spoilage
enzymatic spoilage (rigor)
Lactic acid produced
PH decrease
enzymatic spoilage (rigor)
Lactic acid produced
PH decrease
Muscle becomes rigid
Muscle becomes pliable
Species
trawled cod
Temper
ature
°F
in ice
37
42-44
62
rested cod from
aquarium
trawled redfish
trawled whiting
trawled plaice
trawled coalfish
trawled haddock
Time from landing on deck to Time from landing on deck to
entering rigor
end of rigor
hours
hours
2-8
20-65
4½-8½
54-64
5
2-5½
45
16-20
87
37
14-15
1½-2
72-96
in ice
in ice
in ice
in ice
in ice
53
22
1
7-11
18
2-4
2
120
20
54-55
110
37
24
oxidative deterioration
rancid odors
colour changes
Fatty acid composition of fish
Min. Max.
14:0
6
8
16:0 10
19
16:1
6
11
18:0
1
4
18:1
9
28
18:2
1
2
18:3
1
2
18:4
2
5
20:1
2
13
20:2 0,2
0,6
20:4
1
2
20:5
5
18
22:1
1
21
22:5
1
3
22:6
7
13
Oil = mainly triglycerides
Triglycerides → free fatty acids
peroxides
Free fatty acids → ketones
aldehydes
bacterial spoilage
TMAO  TMA + Formaldehyde
Decomposition of proteines
Amino acid composition, fish, g/kg
Lysine
Methionine
Cystine
Treonine
Tryptofane
Isoleucine
Leucine
Histidine
Fenylalanine
Tyrosine
Valine
Asparagine
Serine
Glutamic acid
Proline
Glycine
Alanine
Ornithine
Arginine
Hydroxyproline
12,3
4,7
1,5
6,6
2,0
7,0
11,2
3,6
6,0
5,1
8,4
14,3
6,9
20,6
5,7
8,2
8,8
0,1
8,7
0,7
Proteines → poly-peptides
Poly-peptides → free amino acids
Free amino acids → biogenic amines
Biogenic amines → TMA, DMA, NH3
Amino acid decomposition
Lysine
→ cadaverine
Histidine → histamine
Deterioration processes in fish
Lipids
Proteins
Chemical, bacterial and endogeneous enzyme reactions
Oxidation of fatty acids
Hydrolysation of lipids to free fatty acids
Hydrolysation of proteins to peptides and
amino acids
Deamination of amino acids
Decarboxylation of amino acids
THEREFORE:
Preservation
Preservation
Salting
Smoking
Cured Cod
Raw
Salted
Water % Fat %
78 – 83
0,1-0,9
33
0,5
Protein %
15-19
42
Smoked Haddock
Water %
Raw
79 – 84
Smoked
72
Fat %
0,1-0,6
0,9
Protein %
14-20
22
Preservation
Salted
Smoke
Heat
Cool
Preservation
Salted
Smoked
Heated
Cooled
Fermented
Dry
Fishmeal and fishoil production plant
Fishmeal and fishoil
Airdried
On the market
Quality changes
during preservation
Heated
Protein mink digestibility, in vivo tests
Fishmeal
A matter of time and temperature
Drying
temperature, °C
100
70
70 (5 seconds)
Mink digestibility,
%
88
91
94
Heated
Lipids
more or less unaffected
if proper manufactured
Otherwise risc of rancidity
Cool / freeze
Prolonged shelflife
Other preservation methods
Method
Salted
Proteins
No effects
Lipids
Might rancid
Smoked
No effects
Might rancid
Airdried
Might
deterioate
Proteins →
peptides ≈
bitter taste
Rancid
Fermented
Might get
rancid
Vitamins in fish
A
50 - 5.000 I.U./g
D
0 - 1.000 I.U./g
Pantothenic 1 - 20
μg/g
During heat processing
the vitamins will be destroyed
Depending upon the temperature
SUMMARY
Fishes are cold blooded vertebrates.
Fish muscle is biochemically similar to mammals.
Fish proteins breakdown more rapidly than mammals.
Fish muscle have certain associated problems like
endogenous enzymes, free amino acids and small peptides etc.
Lipids from fish contain high levels of polyunsaturated fatty acids.
The stability of fish lipids is short due to their
polyunsaturated nature.
SUMMARY
Most spoilage of fish is due to bacterial breakdown.
One spoilage characteristic found in fish and not in muscle foods
is trimethylamine formation.
This odoriferous amine is responsible for the fish smell associated
with spoiling fish.
fish meat has high level of polyunsaturated fatty acids,
which are unstable.
Chilling of fish immediately after harvest is very important
part of preservation.
The end
Hope you now have a better understanding of fish nature
Hope you understood my english
Hans Otto Sørensen
Laboratory manager
TripleNine Fish Protein
Denmark