Please read the abstract in the section, 00front , of this document / Dissertation (M Inst Agrar ( Food Processing))--University of Pretoria, 2008. / Food Science / MInstAgrar / unrestricted

This study is an observation of the various physicochemical changes that occur in enzyme-modified cheese (EMC) during the incubation step of production. The purpose of this study was an attempt to gain a better understanding of the changes that occur due to enzymatic reactions during EMC production. A standard EMC batch was prepared with the addition of two exogenous enzymes, a lipase and a protease (LP). Two additional treatment batches had either only a lipase (L) or a protease (P) added individually. Batches were prepared in duplicate with each replicate performed on different days. Each batch was incubated at 42±0.5°C in a water bath and was monitored for changes in pH, water activity, viscosity, water-soluble nitrogen, water-soluble free amino acids, titratable acidity, and visual observations, every two hours over a standard incubation time of 24 hours. Changes in pH showed little to no change in the P batches, while both the LP and L batches showed a decrease over time, very similar to each other. Changes in water activity showed a slight decrease over time in all batches from 0.98 to 0.94-0.97. However, because these changes were so small and a considerable amount of variation was found between replicate batches, water activity was likely a less practically significant method for measuring enzyme hydrolysis. Changes in viscosity were significantly different between all batches at different points and the L batches produced some very unique changes in viscosity. Changes in water-soluble nitrogen showed unexpected higher levels in the LP batches than the P batches. Changes in water-soluble free amino acids showed a significant impact that the protease had on the liberation of free amino acids. Changes in titratable acidity showed an increase in the LP batches and an apparent additive effect from both enzymes when combined. Monitoring these physicochemical properties in the different treatments indicated the changes that were brought about by the enzymes and may be repeated by manufacturers to identify production end-points.