effect of thermal denaturation on the tryptic hydrolysis of glycinin

Glycinin, which represents the major protein of soya beans was subjected to heat denaturation at 87.5°C for 30 min. Using the pH‐stat procedure to measure the rate and gel filtration analysis to measure the extent of hydrolysis by trypsin at pH 8.0, it was found that there was a decrease in the initial rate of hydrolysis of the heat‐denatured glycinin by a factor of eight compared to the native or unheated glycinin. Molecular weight distribution analysis of the glycinin peptides provided evidence that the glycinin both before and after thermal denaturation produces peptide fragments in three well defined peaks, which can be broadly categorised as those above 30 000, those around 6000 and those below 5000 daltons. Chromatographic analysis of the soluble components of the tryptic hydrolysis showed no differences in molecular weight distribution between samples which had been heated and those which had not.