The effect of the presence of penicillinase producing micrococci on the growth of cheese and yogurt starters in milk contaminated with penicillin

Abstract

SummaryCoagulase-negative micrococci isolated from the cow's udder, when cultivated together with cheese and yogurt starters in milk containing 0·3 I.U./ml of penicillin, contributed sufficient penicillinase to permit normal rates of acid production by the starters. Subcultures of such ‘mixed’ cultures also grew at normal rates in milk contaminated with penicillin at the same level.The possibility of using such micrococci to protect the starter organisms in both the preparation of bulk starters and during manufacture of cheese and yogurt is discussed.