Effects of sodium chloride salting and substitution with potassium chloride on whey expulsion of Cheddar cheese

摘要

A challenge in manufacturing reduced-sodium cheese is that whey expulsion after salting decreases when less salt is applied. Our objectives were (1) to determine whether changing the salting method would increase whey syneresis when making a lower sodium cheese and (2) to better understand factors contributing to salt-induced curd syneresis. Unsalted milled Cheddar curds were salted using different salting intervals (5 or 10 min), different salting levels (20, 25, or 30 g/kg), different numbers of applications when using only 20 g/kg salt (1, 2, or 3 applications), and salting with the equivalent of 30 g/kg NaCl using a 2:1 molar ratio of NaCl and KCl. Whey from these curds was collected every 5 or 10 min until 30 or 40 min after the start of salting, and curds were subsequently pressed for 3 h. Additional trials were conducted in which salted milled Cheddar cheese curd was immersed at 22℃ for 6 h in various solutions to determine how milled curd pieces respond to different levels of salt and Ca. The use of 10-min intervals delayed whey syneresis without influencing total whey expulsion or cheese composition after pressing. Lowering the salt level reduced whey expulsion, resulting in cheeses with higher moisture and slightly lower pH. Adding salt faster did not increase whey expulsion in reduced-salt cheese. Partial substitution with KCl restored the extent of whey expulsion. When salted milled curd was immersed in a 30 g/L salt solution, there was a net influx of salt solution into the curd and curd weight increased. When curd was immersed in 60 g/L salt solution, a contraction of curd occurred. Curd shrinkage was more pronounced as the salt solution concentration was increased to 90 and 120 g/L. Increasing the Ca concentration in test solutions (such that both serum and total Ca in the curd increased) also promoted curd contraction, resulting in lower curd moisture and pH and less weight gain by the curd. The proportion of Ca in the curd that was bound to the para-casein protein matrix changed with the Ca content of the test solution. Compared with test solutions containing 10 g/L Ca, at low Ca levels (i.e., 1 and 5 g/L) the proportion of bound Ca was lower, whereas at 20 g/L Ca, the proportion of bound Ca was higher. Both Ca and salt concentration influence the physicochemical properties of the protein matrix such that at low concentrations the curd expands, whereas at high concentrations the curd contracts and expels whey.