Cheddar Cheese Flavor. III. Active Sulfhydryl Group Production During Ripening

The influence of incubation and heat treatment of milk on the active -SH group concentration in Cheddar cheese was determined. Eight-month-old cheese manufactured from nonincubated and incubated (37 C for 5 hr) raw milk exhibited average -SH values (lng cysteine tiC1 equiv./100 g of cheese) of 3.5 and 13.0, respectively. Concentrations of active -SH groups in cheese manufactured from raw milk or from milk heated at 143 F for 5 and 30 min, and 155 F for 15 min, were related inversely to the severity of the heat treatment of the milk. Active -SH groups appeared in raw-milk cheese after one week of ripening, reaching maximum values after one to three months of curing. Heating the milk delayed the appearance of active -SH groups in the cheese during curing. Generally, the intensity of characteristic Cheddar flavor was related to the concentrations of active -SH groups of the cheese but not to bacterial numbers.