Some Chemical Changes Exhibited in Sterile and in Contaminated Haddock Muscle Stored at Different Temperatures.

The bio-chemical changes which occur in fish tissues are due to two factors, autolysis and bacterial action. As early as 1903, Muller reported that changes due to autolysis took place when sterile fish tissues were incubated. More recently attention has been focussed on the relative importance of these two causes of bio-chemical change. Reed, Rice and Sinclair (1929) presented evidence that autolysis accounted for only a small part of the actual decomposition of haddock muscle, although autolysis was found to be an important factor in the decomposition of lobster and clam muscle. They also cited increases in pH of haddock muscle from 6.3 to 7 during the first twenty-four hours of incubation at room temperature, due to bacterial action. Gibbons and Reed (1930) made certain bio-chemical determinations on incubated sterile haddock muscle tissues which they inoculated with known types of bacteria, and observed that the introduction of bacteria caused an increase in protein decomposition products, such as ammonia and non-coagulable nitrogen. Hess (1932) reported an investigation of changes in haddock muscle and concluded that only slight autolytic changes took place in haddock muscle tissues held at temperatures between 300 and 360F. Bacterial decomposition was found to be about twice as great at 360F., as at 30'F. 1 Contribution No. 61 from the Department of Biology and Public Health, Massachusetts Institute of Technology, Cambridge, Mass.