Date of Award:

1979

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Nutrition, Dietetics, and Food Sciences

Department name when degree awarded

Nutrition and Food Science

Advisor/Chair:

Dr. C. A. Ernstrom

Abstract

The study involves two different approaches to increasing cottage cheese yields by the inclusion of whey proteins in the curd. They were the use of high heat treated skim milk and ultrafiltered skim milk retentates for cottage cheese making. Increasing the pasteurization temperature of skim milk from 61.8 to 79.4 C for 30 minutes resulted in 15.6% increase in cultured cottage cheese yields. However, the high heat cheese exhibited variable quality and was generally inferior to the control. Cheese making from high heat skim milk was done by cutting at the A.C. end point and using 30 ml of rennet per 454 kg of skim milk. There appeared to be no relationship between the rate of heating to 79.4 C and the quality of cottage cheese produced. Skim milk was concentrated by ultrafiltration to 12, 16, and 20% solids. The 20% retentate was produced by concentrating skim milk 5:1 and then subjecting it to diafiltration with an equivalent volume of deionized water. The acidification of the retentates was accomplished by metering concentrated hydrochloric acid into the vortex of the centrifugal Culture growth in 20% retentates was inhibited below and soluble phosphate seemed to be an important factor in this inhibition. The yield trials indicated that the increase in yields over cultured cottage cheese made from skim milk was 12.4, 15.3, 5.6 and 1.6% for 16 % cultured, 16 % direct acid, 20% cultured and 20% direct acid cottage cheeses made from retentates. The lower yield increases from 20% retentates was because of the shattering of the curd while cooking, and the diffusion of the whey proteins. While the quality of cultured cottage produced by ultrafiltration was as good as the cultured cottage cheese from skim milk, the direct acid cottage cheeses were much inferior. Considering both high heat treatment of skim milk and ultrafiltration for increasing cottage cheese yields, ultrafiltration seems to be the better method owing to the much better quality of cheese produced. To obtain maximum benefits from ultrafiltration, problems of lactic culture growth in retentates must be solved and non conventional cooking methods have to be developed for handling curds from high solids retentates.

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