Rapid estimates of hypoxanthine concentration in muscle extracts by xanthine oxidase reaction agreed well with those obtained by ion‐exchange chromatography. Assay by precipitation as the silver salt was subject to some inaccuracy. Concentrations of hypoxanthine increased throughout the period of useful storage of a number of species. The increases correlated well with most evaluations of quality by taste panel.

Trimethylamine concentrations of fish muscle are used in research and industry as a quality assessment technique. An investigation of the Hoogland procedure for determining trimethylamine has been undertaken. Modifications to the procedure were introduced to improve (i) the stability of the extract during storage, (ii) the accuracy, and (iii) reproducibility when the method is used routinely on large numbers of samples.* Calculated as in Table 1.

Polyphosphates are widely used for treating fish, but little information is available on the amounts taken up by fish and the suitability of some commercial polyphosphate mixtures. Phosphorus assays were performed on extracts of fish muscle which had been treated or not treated with polyphosphate mixtures. Fish-to-fish variation in natural phosphorus content was so large that it was difficult to determine whether or not fish had been treated with polyphosphate. The amount taken up under the conditions of treatment adopted was equivalent to 50-100 mg P/100 g fish muscle.Earlier experiments showed that sodium tripolyphosphate and sodium pyrophosphate were the most active condensed phosphates for preventing drip in prepacked chilled fish. The commercial mixtures found to give the best anti drip effect contained a high proportion of one or both of these two phosphates.

Thin layer chromatography, gas liquid chromatography and colorimetric procedures were used to identify and determine amines present in standard solutions, cod muscle extracts, and in the toluene phase of a modified T M A procedure.These tests show that the use of potassium hydroxide solution to liberate TMA from formalized trichloracetic acid extracts of fresh or frozen cod is superior to potassium carbonate solution.

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