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Persistence of <em>Mucor Miehei</em> Protease in Cheddar Cheese and Pasteurized Whey and it's Effect of Sterile Milk Products

Whey from a commercial cheese plant, taken at draining on five separate days, from cheese made with a Mucor miehei coagulant was cooled within 1 h to 4 C. Portions were adjusted from pH 4.2 to 6.4 at .2 pH intervals and subjected to HTST pasteurization at 73.9, 76.6, and 79.5 C for 25 sec. Milk clotting activity in whey was determined before and after pasteurization. Resistance to heat in-activation increased with decreasing pH. All measurable activity was destroyed above pH 5.4 by pasteurization at 79.5 C, above pH 5.8 at 76.6 C and above pH 6.0 at 73.9 C.
Milk clotting activity in Cheddar cheese mad with Mucor miehei remained unchanged for 26 weeks.
Four commercial sterile liquid-milk-based consisting of infant formula, concentrated infant formula, nutritionally complete food, and diet food was aseptically inoculated with sterile Mucor miehei protease solutions to concentrations ranging from 5 x 10-3 to 1 x 10-7 chymosin units/ml of product. The samples were stored at 30 C. After 20 weeks there was no change in the nutritionally complete food. The diet food showed slight whey separation and thickening at 1 x 10-4 CU/ml and coagulation at higher concentrations. The infant formula showed definite whey separation and thickening at 1 x 10-4 CU/ml and coagulation and higher concentrations. The concentrated infant formula showed visible thickening at 1 x 10-3 CU/ml and coagulation at higher concentrations.

Identiferoai:union.ndltd.org:UTAHS/oai:digitalcommons.usu.edu:etd-6228
Date01 May 1977
CreatorsThunell, Randall Kirk
PublisherDigitalCommons@USU
Source SetsUtah State University
Detected LanguageEnglish
Typetext
Formatapplication/pdf
SourceAll Graduate Theses and Dissertations
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