Chemical interactions among caseins during rennet coagulation of milk

Rennet milk curds were prepared under 4 different temperature and acidity conditions. The development of different types of inter-protein chemical bonds (disul-fide, hydrophobic, electrostatic, hydrogen, and calcium bridges) was monitored for 60 min after curd cutting. Hydrophobic inter-protein interactions originally present in casein micelles in milk were substituted by elec-trostatic, hydrogen, and calcium bonds throughout the curd curing period. Disulfide bonds were not disturbed by the experimental conditions employed in the study, remaining at a constant level in all studied treatments. Acidification of curds increased the availability of solu-ble ionic calcium, increasing the relative proportion of calcium bridges at the expense of electrostatic-hydrogen bonds. Although pH defined the nature of the interac-tions established among proteins in curd, temperature modified the rate at which such bonds were formed.

Automated summary

Rennet milk curds were prepared under different temperature and acidity conditions, and the formation of various types of inter-protein chemical bonds was monitored. The results showed that hydrophobic interactions were replaced by electrostatic, hydrogen, and calcium bonds, while disulfide bonds remained constant. Acidification increased the availability of soluble calcium ions, leading to an increase in calcium bridges and a decrease in electrostatic-hydrogen bonds. pH determined the nature of protein interactions, while temperature modified the rate at which these bonds formed.