The effect of temperature and homogenization pressure on enzymatic activity in cheese whey

Abstract

Whey was homogenized by single and double stage homogenization at inlet temperatures of 12.8 and 35'C and at pressures up to 100 NTa. The proteolytic activity of the homogenized whey was determined by ninhydrin assay prior to homogenization and after homogenization at each pressure. The effect of homogenization on the protease activity was related to the final temperature of the whey when the homogenization pressure was greater than 50 NTa. The effect of heat at 57, 63, 67, 74, 78, 85 and 92'C on the proteolytic activity of a concentrated whey solution was determined after 0, 5, 15, 30 min. The proteolytic activity of the whey decreased with increasing temperature and increasing holding time. Heating the whey for 5 minutes at 57'C caused a 6% reduction in protease activity. After five minutes of heating at 63'C, the proteolytic enzymes retained more than 85% of its activity. Temperatures greater than 90'C were required for a complete inactivation of the proteolytic enzymes in the whey. Maximum proteolytic activity in the whey was found for whey homogenized at 50 NVa when the inlet temperature was 3 5'C. The maximum proteolytic activity of whey homogenized with an inlet temperature of 12.8'C was observed at homogenization pressures of 50 and 75 NVa.