Effect of Modification of Amino Groups on Crosslinking of Casein by Micellar Calcium Phosphate

Abstract

Bovine αs1-CN was acetylated, succinylated, and citraconylated. Artificial casein micelles (αs1-κ-CN micelles) were prepared at a casein concentration of 2.5% with 20 to 50mM calcium, 17 to 27mM phosphate, and 10mM citrate, and crosslinking of casein by micellar calcium phosphate was examined by HPLC in the presence of 6 M urea. The content of casein aggregates that were crosslinked by micellar calcium phosphate in modified αs1-κ-CN micelles was lower than that in intact αs1-κ-CN micelles. Urea-insoluble calcium phosphate was present in succinylated αs1-κ-CN micelles, suggesting that it did not participate in crosslinking. The modified αs1-CN was less crosslinked by micellar calcium phosphate than intact αs1-CN, even when modified αs1-CN coexisted equivalently with intact αs1-CN in artificial casein micelles. The amino groups also affected crosslinking of casein by micellar calcium phosphate.