Effects of variation in cheese composition and maturation on water activity in Cheddar cheese during ripening

Changes in the water activity (aw) of experimental Cheddar cheeses with different compositions were measured over a 270 d ripening period. The ranges of key compositional parameters were typical of those found in commercial Cheddar cheese: moisture (35.6–38.6%), fat (29.9–33.4%), salt (1.4–2.0%), salt-in-moisture (3.8–5.2%), moisture-in-non-fat substances (MNFS, 52.4–56.3%) and pH (5.0–5.7). Linear regression analysis indicated that at ripening times ≤30 d, the aw was inversely correlated with salt-in-moisture, while at 270 d it was positively correlated with levels of moisture and MNFS, but negatively with fat content. The aw decreased significantly (P < 0.001) during ripening, from a mean of ∼0.965 at 1 d to ∼0.956 at 270 d. The preponderant factor responsible for the decrease in aw was the increase in proteolysis, as measured using pH 4.6 soluble N and free amino acids.