Antimicrobial activity of 235 natural flavor and fragrance materials was investigated using 4 bacteria and 2 fungi. Antimicrobial activity against bacteria and yeast was defined as percent inhibition of viable cell count after incubation with sample in phosphate buffer for 10min. Antimicrobial activity against mold was defined as percent inhibition of colony area on agar plate containing sample. Two hundred and three samples were very effective against at least one of the six test

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... . Samples consisting of chain terpene alcohols, cyclic carb onyl compounds, cyclic ethers and phenolic compounds as major components were very effective against S. aureus and/or P. aeruginosa. Minimum inhibitory concentration (MIC) was determined by agar dilution method. Samples which showed 100% of antimicrobial activity against B. subtilis, E. coli, P. aeruginosa and A. niger at 1000ppm gave a MIC of 2000ppm or over. Antimicrobial activities of samples were compared with that of p-hydroxybenzoic acid esters. Forty-eight samples were more effective than methyl p-hydroxybenzoate. The degree of antimicrobial activities of eight samples followed the same order as that of n-propyl p-hydroxy benzoate and n-butyl p-hydroxybenzoate.