Abstract
BROTZU(2) has defined the onset of putrefaction of calf meat in terms of its pH-value and amount of amino acids. TILLMANS and OTTO(3) have given that of fish muscle relative to the content of ammonia and amino acids. The present experiments were made with a view to obtain the relation between the pH-value an I putrefactive degree of fish muscle. Twenty-two kinds of marine fishes were used, their names and general chemical constituents being given in Tab. 1. All the fishes were in a condition shortly after rigor mortis. They were minced, put into flasks which were plugged with gum stopper in order to prevent invasion of microorganisms and evaporation of water. The flasks were then kept in thermostat which ran mostly at 17°C, but sometimes at 6.4°, 9.5° or 22°C. At intervals the material was taken out; the pH-value was estimated colorimetrically, and ammonia content was determined at the same time employing FOLIN'S method. The results of experiments are as shown in Fig. 1. It is seen that there is a linear relation between pH-value and ammonia-content irrespective of the temperature. The correlation coefficient was calculated : r=+0.875±0.0038 (Tab. 2). Putrefactive odour was emitted, as TILLMANS and OTTO reported, when the ammonia-content reached to 30mg. per 100 grams of muscle.
It is known from the regression line which was obtained in the calculation of correlation coefficient that the mean pH-value at the beginning of putrefaction for 22 kinds of fish is 6.5.
