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\u27s 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