Use of Platelet Aggregometer to monitor the chymosin-initiated coagulation of casein micelles

Abstract

SUMMARYThe chymosin-initiated coagulation of casein micelles was followed by monitoring light transmission using a Platelet Aggregometer. The release of macropeptide by chymosin was monitored using fluorescamine. The lag period in the clotting reaction was proportional to clotting time and the reciprocal of enzyme concentration. The average rate of coagulation, which was approximately equal to the reciprocal of clotting time (Tc), increased in proportion to enzyme concentration at low enzyme concentrations and reached a limiting value at high enzyme concentrations. The percentage hydrolysis at the Tc was 47 ± 5% in the presence of 20 mM-CaCl2 and it was calculated that a 5-fold decrease in the speed of the enzyme-catalysed reaction would decrease this value at the Tc to 43 ± 5%. The possible uses and limitations of the Platelet Aggregometer for determining the influence of the chemical environment on the velocity of the chymosin-catalysed reaction and para-casein micelle aggregatability are discussed.