FISHERIES AND MARINE SERVICE Translation Series No. 4334 ...

are generally not only evaluated differently but are also given very
different labels. In any assessment the fat content is of decisive
importance. This holds true for the designation as well as the stabi-
lity of the herring products, especially since herring oil (like other
animal fats and oils) has few natural protective substances and thus
easily undergoes oxidative fat changes under the influence of atmos-
pheric oxygen. Changes in fish oil also manifest themselves in fatty
peroxides but the changes are more easily detectable by a taste of
fish oil and a yellow to brown discoloration on the edges of the meat
and particularly by discoloration of the abdominal pieces. From this
it follows that the assessment of fish meat from the point of view of
food law is often based on results obtained by special techniques.
This will be discussed later in a different context.
For fresh herring the fat content of the meat can be determined
with sufficient accuracy via the water content from the fat—water—line
according to C.H. Brandes and R. Dietrich (1). This method is based on
the auount of fat obtained by acid decomposition and determination of
the water content of the fish meat by vacuum drying. The fat—water
line yields good results as long as one deals with fresh fish; however,
it no longer yields comparably good results with "fresh fish" from deep-
frozen herring. This holds true to a larger degree for herrings which
had been treated in other ways. Preservation by salting is one of these
methods. To evaluate the correlation between fat and water in herrings,
fat—water lines must be determined for all treatment steps. This too,
will be discussed later in a different context.
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