Studies on the Chemical Indexes and the Change of ATP and Related Compounds in Decomposition of Frozen Shrimps

Abstract

In order to obtain the chemical indexes for degree of decomposition in frozen shrimps, an organoleptic test and the measurement of pH, volatile base nitrogen (VBN) and trimethyl amine nitrogen (TMA-N) were performed on raw shrimps. At the stage of primary decomposition, the amounts of VBN and TMA-N increased to 30mg% and 3.9mg% respectively, but the exact index for pH was not obtained.From the above result and the experiment for imported frozen shrimps, the chemical index at the stage of primary decomposition was decided to be 30mg% in VBN. However, an organoleptic test should be also carried out with this index to confirm the degree of decomposition.It was assumed that the decomposition of imported shrimps occurred when they were exposured in the air before freezing, or thawed on account of some troubles of a refrigerator. Because any remarkable changes of pH, VBN and TMA-N were not observed in frozen shrimps stored at -23°C for 2.5 years, or in raw shrimps kept in ice over 10 days before freezing.As for the change of ATP and the related compounds in frozen shrimps kept at -23°C for 2.5 years, the amount of hypoxanthine and inosine increased and that of ATP decreased considerably. In addition, the improved method in thin-layer chromatography of ATP and the related compounds was established.