Post-mortem breakdown of glycogen and accumulation of lactic acid in fish muscle.―I

Abstract

Following the work of Macleod and Simpson (1927) and Leim, Macleod, and Simpson (1927), Maopherson (1932) studied tire post-mortem changes in glycogen, free sugar, and lactic acid occurring in haddock muscle during storage at 0°C. It was found that glycogen disappeared far more rapidly than lactic acid accumulated without any change taking place in tire free-sugar value, and the concentration of lactic acid at its maximum was never more than equivalent to two-thirds of the glycogen loss. Efforts to show tire accumulation of certain possible intermediate substances (dextrin, trisaccharide) gave negative results. The present study was carried out in a similar manner to that of Smith (1929), attention doing paid to the effect of temperature on rate of change rather than to the actual relation between glycogen breakdown and lactic acid accumulation during storage after death. In frog's muscle Smith showed that during storage at low temperatures, the rate of lactic acid accumulation passed through a maximum at —2-5°C ., and thereafter decreased as the temperature of storage was lowered, until at —10°C. no accumulation of lactic acid took place. Further, a "critical" temperature of freezing occurred at —1 - 6°C. In muscle stored for 24 hours at any freezing temperature above —1-6°C., then thawed to 5°C ., the lactic acid which had accumulated in the frozen state disappeared until the normal resting level of 0.0 5% was reached. Muscle stored for 24 hours at temperatures below —1 -6°C. showed on tharwing to 5°C. further accumulation of acid until the rigor maximum was reached. Storage of frog's muscle therefore for 24 hours at trooping temperatures of —1.6°C. and below —1.6°C. caused irretrievable damage to the lactic acid recovery mechanism. In this paper results are given of a general survey of the effect of temperature on the rates of glycogenolysis and lactic acid production in fish muscle. It was found that as in frog's muscle the rate of change passes through a maximum at some temperature between 0° and —10°C.