Proteolysis of Milk and Casein Fractions by Streblus asper (Kesinai) Extract

Whole milk (12.5% total solids) and casein fractions (1% w/v) were reacted with Streblus asper (Kesinai) leaf extract, Maxiren and Rennilase, separately. Their electrophoretic profiles were determined and compared. Close similarity in electrophoretic profile of milk coagulum and whey were observed for milk treated with Streblus asper extract and Maxiren. Rennilase hydrolysed more milk casein, resulting in comparatively higher amount of macro peptide bands in the whey fraction. Lower molecular weight macro peptides were formed by Streblus asper extract compared with Maxiren, when β-asein was used as substrate. Excessive proteolysis of β-asein was observed when Rennilase was used. However, no obvious difference between the electrophoretic profile of Streblus asper extract and Maxiren treated k-casein was observed. Rennilase on the other hand, hydrolysed k-casein excessively. Higher molecular weight macro peptides were obtained when k-casein was reacted with Streblus asper extract compared with Maxiren. Whereas Rennilase, resulted in excessive hydrolysis of k-casein. Casein loss studies showed that casein protein retained in coagulum after proteolysis was 1.2, 2.3 and 3.1 per cent for Rennilase, Streblus asper extract and Maxiren, respectively. Proteolytic activity at 5 per cent enzyme concentration was found to increase in the following order: Maxiren, Streblus asper and Rennilase.