EFFECTS OF SELECTED FOOD ADDITIVES ON GROWTH OF PSEUDOMONAS FRAGI

Tests were made of inhibition of Pseudomonas fragi in lactose-yeast extract broth by the food additives chlortctraeycline, nisin, bacitracin, chloramphenicol, lysozyme, ethylenediaminetetraacetic acid (EDTA), nitrofurazone, propyl-p-hydroxybenzoate, sodium benzoate, and potassium sorbate. The additives that proved effective in broth were tested in skimmilk and half-and-half. Nisin, bacitracin, lysozyme, and nitrofurazone were ineffective in broth; chloramphenicol increased the lag period prior to development of turbidity but resulted in chloramphenicol-resistant populations; and EDTA inhibited the organism slightly in broth but not in skimmilk or half-and-half. Propyl-p-hydroxybenzoate, chlortetracycline, and a mixture of lysozyme and EDTA were effective in broth but not in skimmilk or half-and-half, a difference attributed to metal ions in dairy products that react with chlortetracycline and EDTA. Sodium benzoate retarded P. fragi in broth, but only at low pH. Potassium sorbate was ineffective at pH 6.5 in broth, but at pH 5.5 and 5.2 inhibited growth of P. fragi in broth, skimmilk, and half-and-half. © 1969, American Dairy Science Association. All rights reserved.