Effect of buffer systems on the extent of enzymatic oligomerisation of milk proteins

The effect of borate, phosphate and tris buffer on the extend of enzymatic oligomerisation of sodium caseinate and whey protein isolate is described. The study revealed that buffer systems enhance the enzymatic oligomerisation of milk protein monomers by lactoperoxidase, lipoxygenase and β-galactosidase. Compared to water, higher amounts of protein polymers (>2×106 g/mol) using borate buffer and higher amounts of protein oligomers (2×104-2×106 g/mol) using phosphate or tris buffer were observed. Oligomerisation effects, which were originally attributed to the catalytic activity of enzymes, were shown to be in part the result of a complex interaction between buffer, protein and enzyme systems.