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Activity of Four Enzyme-Based Cleaners for Ultrafiltration Systems Against Proteins in Skim Milk and Whey¹

Department of Food Science, University of Wisconsin- Madison 53706

ABSTRACT

Ability to hydrolyze proteins in skim milk and whey was determined for four commercial neutral pH enzyme-based cleaners for ultrafiltration systems. The four enzyme-based cleaners (A, B, C, and D) had a use strength pH of 7.0 to 8.4. Pasteurized skim milk and pasteurized sweet whey (adjusted to pH 8.0) were heated to 43°C, and 1 L of each was placed in Erlenmeyer flasks (A, B, C, D, and control). Flasks were placed in a waterbath at 43°C. Enzyme-based cleaners were added to give use strength concentrations and distilled water used to adjust for differences in amounts of cleaner added. Samples were taken over 24 h. Percentage of NPN by Kjeldahl and percentage of protein by dye binding were determined. Samples were taken after 8 h for gel electrophoresis. Samples containing enzymes A and D had increased percentages of NPN and decreased percentages of protein as measured by dye binding both in skim milk and whey. Enzyme A hydrolyzed whey proteins more effectively than enzyme D. Enzyme D, however, hydrolyzed casein more effectively than enzyme A. No changes in NPN or protein concentration were observed in skim milk or whey using enzyme B or C when compared with controls. Using SDS-PAGE to quantify the activity of four enzyme cleaners in skim milk and whey confirmed the action of enzymes A and D on whey proteins and casein and indicated no activity by enzymes B and C. Some commercial enzyme-based cleaners were ineffective in hydrolyzing casein or whey proteins. Other enzyme-based cleaners required extended times to hydrolyze whey proteins or casein to NPN.

¹ Research supported by the College of Agricultural and Life Sciences, University of Wisconsin, Madison, WI.