In the previous papers, it was reported that the fish muscle could be significantly lowered in freshness by autolysis rather than by bactrerial action during ice storage, and that post mortem changes of biochemical substances, especially of degradation products of ATP, should be more precisely elucidated in connection with freshness, as had already been shown by sever-al authors. From this point of view, the present communication deals with the changes in the concentration of free ribose and glucose in the plaice muscle during the ice storage.
At first, the recovery tests for added ribose and glucose were performed using the paper chromatographic determination method proposed by JONES. The recoveries were 51-74 per cent for ribose and 70-80 per cent for glucose, even when the aqueous solution of sugar was used as the sample (Table 1). On the other hand, the recovery percentage of 92 for ribose and 94 for glucose was obtained with the extract of muscle by applying FERNELL's method for simultaneous determination of pentose and hexose (Table 2). In this experiment inter-fering substances such as amino acids and nucleotides were removed according to JONES' de-scription.
The ribose content of plaice muscle increased almost linearly during the ice storage, and did not show any symptom of decrease even after 17 days' storage examined here (Fig. 1). It might be supposed that bacterial activity was not so high as to induce a significant decrease in ribose content, although the muscle was already much lowered in freshness at that time. And there was observed the stoichiometric relation between ribose and hypoxanthine accumu-lated during the ice storage (Fig. 2). Glucose was significantly increased for the first 9 days of storage and thereafter was gradually decreased.