Influence of NaCl and pH on intracellular enzymes that influence Cheddar cheese ripening

Abstract

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 NaCI addition and when the pH was reduced to approximate Cheddar chee se conditions (5% NaCI, 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 chee se aging, totallipase/esterase activity peaked at 120 d then decreased, ev en 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 flavar, but a culture's methanethiol-producing capability was associated with higher chee se consumer preference scores. Results suggest that use of cheese-like conditions may aid in selecting cultures to