Chemical interactions among caseins during rennet coagulation of milk

J.C Amaro-Hernández,G.I Olivas,C.H Acosta-Muñiz,N Gutiérrez-Méndez,C Rios-Velasco,D.R Sepulveda

doi:10.3168/jds.2021-21071

Abstract

Rennet milk curds were prepared under 4 different temperature and acidity conditions. The development of different types of inter-protein chemical bonds (disulfide, 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 electrostatic, 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 soluble ionic calcium, increasing the relative proportion of calcium bridges at the expense of electrostatic-hydrogen bonds. Although pH defined the nature of the interactions established among proteins in curd, temperature modified the rate at which such bonds were formed.

Highlights

Bovine milk gels under the action of rennet, forming a complex protein-based tridimensional arrangement (Sinaga et al, 2017; Lamichhane et al, 2018; Mehta, 2018)
An analytical technique reported by Van Camp et al (1997) and further developed by Keim and Hinrichs (2004) has been suggested as a feasible method to quantify the relative proportion of hydrophobic, electrostatic, hydrogen, calcium, and disulfide bonds in milk gels and other dairy products (Gonçalves and Cardarelli, 2019), providing a means to advance the knowledge in this field
The relative proportions of hydrophobic, electrostatic, hydrogen, calcium and disulfide bonds among proteins were measured on curd prepared from lactic acid bacteria-inoculated, and uninoculated milk, tempered at 30 and 40°C, resulting in 4 different treatments

Summary

Introduction

Bovine milk gels under the action of rennet, forming a complex protein-based tridimensional arrangement (Sinaga et al, 2017; Lamichhane et al, 2018; Mehta, 2018). After the onset of coagulation, some additional rearrangements of the structure occur (Lucey, 2014) External factors such as pH and temperature play an important role in determining the establishment of the various types of chemical bonds among caseins during this period (Corredig and Salvatore, 2016; Mehta, 2018). An analytical technique reported by Van Camp et al (1997) and further developed by Keim and Hinrichs (2004) has been suggested as a feasible method to quantify the relative proportion of hydrophobic, electrostatic, hydrogen, calcium, and disulfide bonds in milk gels and other dairy products (Gonçalves and Cardarelli, 2019), providing a means to advance the knowledge in this field

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Conclusion