559. The inhibition of micro-organisms by raw milk: III. Distribution and properties of two inhibitory substances, lactenin 1 and lactenin 2

Abstract

1. The L 1 and L 2 contents of a number of samples of bulk milk and milk from separate quarters of cows with and without infection have been determined. The milk of cows sensitive to mastitis has about the same content as the milk from resistant ones. 2. The effect of heat on L 1 and L 2 has been observed for various combinations of time and temperature. Heat treatment corresponding to the legal standards of pasteurization destroyed 50% L 1 , but did not affect L 2 . 3. The inhibitory action of L 1 and L 2 has been observed on several micro-organisms. All the organisms tested were sensitive to lactenin in sterilized milk. Stimulatory substances have been shown to interfere with the inhibition by lactenin. 4. The action of lactenin on the growth of Str. pyogenes has been studied. The effect of hydrogen peroxide on lactenin has been compared with that of cysteine.