CHAPTER 29 



Analytical Methods 



Maurice E. Stansby 



In this chapter will be discussed only those aspects of methods for 

 analyzing fish where special considerations apply which are different from 

 those for other foods. No attempt will be made to give procedures for 

 all the various analyses. These can be found in standard analytical 

 chemistry reference works. Attention will be paid primarily to sampling 

 methods and to methods for determining freshness of fish. 



Sampling Fish for Analysis 



Owing to wide differences in composition of fish even within a small 

 batch (see Chapter 26) and to differences in spoilage rates of individual 

 fish from the same catch it is necessary, even in a fairly homogeneous 

 lot of fish, to use several fish to make up a composite sample to be repre- 

 sentative of the lot. A minimum sample size of six fish is necessary, even 

 in quite homogeneous lots of fish, in order to be at all sure that the 

 sample is representative of the lot. Where a large batch of fish involv- 

 ing several variables is involved, much larger samples are required. For 

 example, in a vessel load of fish some fish will have been stored from the 

 start of the catching period, possibly for several weeks, others perhaps 

 for only a few days. A representative sample for freshness determination 

 would then require at least six fish from each sub-lot, representing the 

 different storage periods. 



Similarly, if data on the proximate composition of fish are desired and 

 if these are to be representative of the species as a whole, then sometimes 



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