Studies on the Effect of Food Additives on the Activity of Trypsin, using Cup and Disc Methods

Abstract

For the purpose of studying the effect of food additives on the activity of trypsin, the cup and disc methods were applied. Eight kinds of food additives, i.e., sodium benzoate, sodium dehydroacetate, dulcin, sodium cyclamate, sodium glutamate, glycine, Phloxine and Rose Bengale were tested. In each experimental run, one of these additives was dissolved in 20 ml of 1.5% agar solution (pH 7.6) which contained 0.5% of casein. The casein-agar medium which contained no food additives, was used as the control. These casein-agar solutions were poured into petri-dishes and solidified. Then, diluted trypsinsolutions were added through stainless cup or paper disc to the casein-agar plates in petri-dishes. The dishes were incubated at 37°for 24 hr. After incubation, transparent circles were formed in the plates by the action of trypsin on casein. The outlines of the digested casein circles became distinct by adding 9% trichloroacetic acid. After removal of trichloroacetic acid, the diameters of the circles were measured. The plot of the mean diameters of circles versus logarithm of enzyme concentration became linear. Thus the ratio of the enzyme activity in the presence of each food additive to that of control was calculated. The ratios were very small when dulcin, Phloxine and Rose Bengale were added to the reaction medium. These results showed that these three additives were inhibitory for the tryptic digestion of casein. It was also shown that other five additives had no effect on the activity of trypsin.