On post‐mortem changes in the nucleotides of fresh‐water fish muscle

Abstract
Summary. The post‐mortem changes in the nucleotides, and their relation to the phases of rigor and changes of quality in fish were investigated. the various compounds of the acid‐soluble fraction of the muscle were assayed on the basis of phosphorus content. Further, separate assays were made for adenylic radicals, changes in ultraviolet spectra and hypoxanthine; the latter was estimated as silver salt. At the same time, quality was evaluated in terms of odour, appearance and rigidity. the studies were mainly concerned with rainbow trout (Salmo irideus), although pike (Esox lucius) was also used in some experiments. the fish samples were kept at 4°C; the length of a complete storage period was 16 days.The total phosphorus of the acid‐soluble fraction displayed an increase which was initially rather steep. Labile phosphorus diminished, reaching a minimum in 25 hr and showing no change subsequently. A corresponding increase occurred in inorganic phosphorus during the same period. A drop in creatine phosphate occurred simultaneously with that of labile phosphorus. Some diminution was also noted in the adenylic radicals. A shift in the peaks of the ultraviolet spectra was noted after 12 hr, the maximum being shifted towards 250 mμ. No appreciable increase took place in hypoxanthine until after 7 days storage.