Stability of Small Concentrations of Penicillin in Milk as Affected by Heat Treatment and Storage

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Abstract
The complete thermal inactivation curve for penicillin in milk has a Z value of 49.0. Five different kinds of penicillin varied in heat stability. Penicillin in milk developed smaller zones of inhibition than did the same concentration in buffer or water. Milk, phosphate buffer and water inoculated with penicillin were heated at various temperatures. The results revealed a direct relationship between heat treatment and extent of penicillin inactivation. Penicillin lost its potency in an increasing order in milk, buffer and water. On storage, the antibiotic lost its potency at a faster rate in milk and water than in buffer. Also, storage losses of the antibiotic were less in heated samples than in unheated samples. Within the limits studied, concentration of the antibiotic and degree of inactivation by heating or storage exhibited no relationship.

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