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MODIFICATION OF MILK PROTEIN FUNCTIONALITY BY MECHANICAL SHEAR FOR LOWFAT CHEESEMAKING
Principal Investigator:MALIN E L
Associate Investigator:TUNICK M H; VAN HEKKEN D L
EASTERN REGIONAL RES CENTER
WYNDMOOR , PENNSYLVANIA , 19118
Sponsoring Organization:U. S. DEPARTMENT OF AGRICULTURE, AGRICULTURAL RESEARCH SERVICE
Start Date:941001
Completion Date:990930

Summary:OBJECTIVE: To enhance marketability of lowfat cheeses by studying effects of high pressure homogenization on milk protein structure as related to thermal, textural and flavor properties.

APPROACH: Effects of homogenization of cheese milk, both single strength and concentrated (for example by ultrafiltration), at pressures ranging from 0 to 3l,000 psi will be examined in terms of compositional variables and will be related to curd formation and structure, proteolysis, rheology, thermal characteristics, and flavor development. Because of the mechanical shearing action, opportunities for new protein-protein and protein-lipid interactions will permit development of novel lowfat cheeses with unique functional characteristics.

Summary:PROGRESS: Transmission electron microscopy and image analysis of low-fat and full-fat Mozzarella cheeses revealed that casein submicelles rearranged into clusters during 6 weeks of storage at 4 degrees C. Fast Fourier transforms indicated that average spacings between submicelles increased more than twofold. Observed changes in ultra- structure correlated well with improved texture and melting characteristics of lowfat Mozzarella brought about by proteolysis as determined by SDS- PAGE. Rennets from microbial sources degrade beta-casein as well as alpha-s1 casein, whereas degradation by natural or cloned calf rennet is usually confined to alpha-s1 casein. A method for detecting bovine milk adulteration of fresh water- buffalo Mozzarella is based on conversion of beta- casein to gamma caseins, followed by isoelectric focusing. The presence of bovinemilk is readily observed because of differences in the isoelectric points of bovine and water-buffalo gamma caseins. Differential scanning calorimetry can be used to detect the presence of bovine milk fat in fresh water- buffalo Mozzarella. These results provide the U.S. Customs Service with a means of detecting mislabelled imported Mozarella cheese.

Subjects:: LOW-FAT-CHEESE CHEESE HIGH-PRESSURE HOMOGENIZATION MILK-PROTEIN PROTEIN-STRUCTURE MECHANICAL-HANDLING SHEARING PROTEOLYSIS RHEOLOGY THERMAL-PROPERTIES FOOD-TEXTURE LIPIDS FOOD-FLAVOR FUNCTIONALITY ANALYTICAL-CHEMISTRY FOOD-PROCESSING FOOD- CHEMISTRY MILK DAIRY-PRODUCTS

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