Food Chemistry

632 13 Fish, Whales, Crustaceans, Mollusks

Table 13.12.Average chemical composition of processed fish

Product Moisturea Proteina Fata NaCla Edible portionb

Salted fish
Matje herring 54 18 18 10 68
Salt cured herring 48 21 16 15 68

Dried fish
Stockfish 15 79 2 .53 64
Klipfish 34 45 0 .713 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
aAs % of edible portion.
bAs % of the whole fish weight.

used for fishburgers and similar products. In com-
parison with conventional freezing systems, the
food comes into direct contact with the refriger-
ant (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 station-
ary, 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 satu-
rated with water vapor at 20–25◦Corbyspray-
ing with water. Fish must be processed immedi-
ately after thawing because it loses juices rapidly
and decays. Fish muscle enzymes have noticeable
activity even at− 10 ◦C. Excessively long stor-
age 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, cray-

and crawfish 6 12 15

Crabs 6 12 12

Oysters 4 10 12

yellow colored fish surface. Antioxidants and as-

sociated synergistic compounds, such as ascorbic

and citric acids, are used to inhibit fat deteriora-

tion. 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.