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growth of contaminating microflora; this effect is particularly evident in proteolytic microorganisms. Destruction of milk protein (in culture media containing 3.4% skimmed milk powder), by Serratia marcescens and Bacillus subtilis, was studied at room temp. for 36 h of cultivation in the presence of tyramine (0.25 mg/ml). Proteolysis decreased with increasing tyramine content, and test microbes diminished in broth or died after 24 h. Tyramine had a bacteriocin-like effect on proteolytic microbes and consequently a protective effect on milk protein. Suppressed bacterial growth was not connected with changes in pH, since pH levels of culture media almost always remained approx. neutral (6.5-7.5). Based on these results, the use of tyramine-tolerant starter cultures in inoculated food products was proposed.