2009_Book_FoodChemistry

632 13 Fish, Whales, Crustaceans, Mollusks
Table 13.12. Average chemical composition of processed fish
Product Moisture a Protein a Fat a NaCl a Edible portion b
Salted fish
Matje herring 54 18 18 10 68
Salt cured herring 48 21 16 15 68
Dried fish
Stockfish 15 79 2.5 3 64
Klipfish 34 45 0.7 13 99
Smoked fish
Buckling 58 23 16 3 62
Smoked sprats 62 17 20 2 60
Eel 53 19 26 1 73
Mackerel 61 21 16 1 70
Schillerlocken
(smoked haddock filet) 53 21 24 100
Semi-preserved fish
Bismarck herring 60 20 17 3 95
Bratherring (fried and
pickled herring) 62 17 15 4 92
Herring, jellied 56 29 13 55
Anchovies 69 13 5 1 100
Herring tidbit 62 15 10 3 100
a As % of edible portion.
b As % of the whole fish weight.
used for fishburgers and similar products. In comparison
with conventional freezing systems, the
food comes into direct contact with the refrigerant
(liquid nitrogen or liquid carbon dioxide) in
shock freezing. The spatial arrangement of the
freezing systems essentially corresponds to those
in air freezing.
During freezing of fish, problems associated with
drip or sap losses, discoloration and rancidity
due to lipid peroxidation and, consequently,
fish weight loss, poor visual appearance and
flat taste may arise and must be avoided by
suitable processing. Cold storage should proceed
at high air humidity (90%) and with stationary,
noncirculating air. Data on the storage
properties of some frozen fish are provided in
Table 13.13.
Thawing is carried out in a stream of air saturated
with water vapor at 20–25 ◦ Corbyspraying
with water. Fish must be processed immediately
after thawing because it loses juices rapidly
and decays. Fish muscle enzymes have noticeable
activity even at −10 ◦ C. Excessively long storage
or insufficient cooling, especially of fatty fish,
results in a rancid off-flavor and an unattractive,
Table 13.13. Shelf life of frozen fish, crustaceans and
mollusks as influenced by storage temperature
Product
Shelf life (months) at
−18 ◦ C −25 ◦ C −30 ◦ C
Fatty fish 4 8 12
Nonfatty fish 8 18 24
Lobsters, crayand
crawfish 6 12 15
Crabs 6 12 12
Oysters 4 10 12
yellow colored fish surface. Antioxidants and associated
synergistic compounds, such as ascorbic
and citric acids, are used to inhibit fat deterioration.
Changes in muscle texture are primarily due
to changes in protein solubility (Fig. 13.6).
13.1.6.3 Drying
Fish can be preserved by drying naturally in the
sun or in drying installations.