The effect of increasing the serum protein content of cottage curd on quality and yield

Abstract

When rennet type cottage curd was made from cheese milk pasteurized at 143°F. for 30 min. the heat labile serum proteins remained with the whey and represented a loss of approximately 15% of the total cheese milk protein. However, when higher heat treatments than pasteurization were applied, up to 65% of the serum proteins of cheese milk were denatured, rendered coagulable with the caseins and incorporated into the cottage curd. Similar results were obtained by blending high- and low- heat cheese milk. Composition and flavor quality of cards containing increased amounts of serum protein were closely comparable to curds made from conventional pasteurized cheese milk. The yield of curd was increased.

As the heat treatment of cheese milk was increased from 143 to 180°F., the denaturation of serum protein in drained whey increased from 0.0 to 60.01%, the percent of whey solids decreased 7.1%, pH at the A-C endpoint increased from 4.72 to 5.10, and time from setting to cutting decreased from 4.75 to 2.50 hr. When the percent of high-heat milk in blended cheese milks was increased from 20 to 95%, the percent of denatured serum protein in drained whey increased from 4.8 to 37.2%, the percent of whey solids decreased from 1.1 to 5.3%. pH at the A-C endpoint increased from 4.70 to 5.05, and time from setting to cutting decreased from 5.50 to 2.50 hr.

High quality curd comparable to the control was made from cheese milks receiving heat treatments up to 170° F. for 30 min. and from blonde containing up to 95% high·heat milk. Heat treatments over 170°F. slightly lowered the quality score of curd.

Pounds of curd per lb. of cheese milk protein was found to be the best procedure for calculating and expressing yield. When curd was made from cheese milk heated at 170°F. and from blends containing 85% high·heat milk, the curd yield was increased 16.22 and 9.61% above the control, respectively.