Relation of Cheese-Making Operations to Survival and Growth of Staphylococcus aureus in Different Varieties of Cheese

SU]~[ARYTests were nmde to deternfine the effect of manufacturing procedures for specific varieties of cheese on the growth and survival of Staphylococcus aureus (MF31) organisms added to milk at the start of the process.The staphylococcal count was approximately 1 × ll)~/ml milk.Cheddar, Colby, Swiss-type, Liraburger, and Cottage cheese by two methods were made.Conditions of manufacture of each variety were favorable for the growth of S. aureus and significant increases occurred at specific stages.In general, the organisms were concentrated in the curd and increased in number until the cheese was salted.After pressing the curd, another increase might occur during the first 21 days of aging.A decrease would then take place, which generally continued throughout aging.At no time, however, did the S. a.ureus count become zero during aging.Staphylococci were not recovered from fresh Cottage cheese after it had been cooked at 130 F for 40 rain at pH 4.5.However, when the curd was stored dlT or creamed for ten days at either 40 or 50 F, viable S. aureus organisms were recovered.Nevertheless, the manufacturing procedure for Cottage cheese was the only effective one in destroying S. aureus.