Influence of NaCl and pH on intracellular enzymes that influence Cheddar cheese ripening
The influence of NaCl and reduced pH was determined for aminopeptidase, lipase / esterase and methanethiol-producing capability in selected lactic acid bacteria and brevibacteria in simulated cheese-like conditions. The observations on simulated cheese-like conditions were confirmed in 60% reduced-fat Cheddar cheese. The activity of each enzyme decreased with NaCl addition and when the pH was reduced to approximate Cheddar cheese conditions (5% NaCl, pH 5.2). Residual intracellular aminopeptidase activity was dominated by general aminopeptidase activity (aminopeptidase N and / or aminopeptidase C) in laboratory, simulated cheese-like conditions, and 60% reduced-fat Cheddar cheese curd. During cheese aging, total lipase / esterase activity peaked at 120 d then decreased, even though starter culture populations remained high. Methanethiol-producing capability occurred under cheese-like conditions in whole cells, but not in cell-free extracts. Met and Met-containing peptides induced methanethiol-producing capability for 2-3 generations and could be re-induced later in the growth cycle of Brevibacterium linens BL2. Aminopeptidase and lipase / esterase activity in reduced fat cheese were not correlated to an increase in Cheddar-type flavor, but a culture's methanethiol-producing capability was associated with higher cheese consumer preference scores. Results suggest that use of cheese-like conditions may aid in selecting cultures to increase desirable flavors for low-fat cheese manufacture. Additionally, data suggest that whole cells are important for proper flavor development in 60% reduced-fat Cheddar cheese.
Weimer, B., B. Dias, M. Ummadi, J. Broadbent, C. Brennand, J. Jaegi, M. Johnson, F. Milani, J. Steele, and D. V. Sisson. 1997. Influence of NaCl and pH on intracellular enzymes that influence Cheddar cheese ripening. Lait 77:383-398.