Inhibitory Activity of Acid and Rennet Whey on Propionibacteria

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Abstract
By disc assay techniques on heavily seeded lawns of 56 strains of propionibacteria comprising 8 species, several samples of whey made in the laboratory or collected from Swiss cheese vats (cooked up to 54[degree]C) were screened for antibacterial activity. Twenty-two propionibacteria distributed in 6 species were affected. Unaffected species were both pigmented - viz: R. [Rhodospirillum] rubrum and P. [Propionibacterium] thoenii. In broth cultures antibacterial effect of whey was determined by turbidimetric measurements at 650 mu. The inhibitory activity was quite stable when the whey was stored at room temperature and retained the potency up to 8 months at 5[degree]C. Heating at 100[degree]C. for 10 min. completely destroyed its suppressing potency; dialysis failed to remove the activity; treatment with Pronase (100 [mu]g/ml) at 45[degree]C for 60 min. appeared to destroy the antibacterial activity. The inhibitory principle(s) was found at the same concentrations in cold-separated milk as in whole milk indicating that it is not associated with butter-fat. The antibacterial effect did not appear to be similar to lysozyme when tested against Micrococcus lysodeikticus, or to agglutinins found in milk shown by reactions against agglutinin-sensitive lactic streptococci. Because of the wide-ranging activity of milk whey against propionibacteria, this phenomenon might have a direct bearing to the rate and extent of flavor and eye development in Swiss cheese.

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