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 la ctic acid bacteria and brevibacteria in simulated cheese-like conditio ns. The observations on simulated cheese-like conditions were confirme d in 60% reduced-fat Cheddar cheese. The activity of each enzyme decre ased with NaCl addition and when the pH was reduced to approximate Che ddar cheese conditions (5% NaCl, pH 5.2). Residual intracellular amino peptidase activity was dominated by general aminopeptidase activity (a minopeptidase N and/or aminopeptidase C) in laboratory, simulated chee se-like conditions, and 60% reduced-fat Cheddar cheese curd. During ch eese aging, total lipase/esterase activity peaked at 120 d then decrea sed, even though starter culture populations remained high. Methanethi ol-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 cou ld be re-induced later in the growth cycle of Brevibacterium linens BL 2. Aminopeptidase and lipase/esterase activity in reduced fat cheese w ere not correlated to an increase in Cheddar-type flavor, but a cultur e's methanethiol-producing capability was associated with higher chees e 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.