Homologous Bacteriophage Control of Pseudomonas Growth and Beef Spoilage

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Abstract
The effects of homologous bacteriophages upon growth of a beef spoilage pseudomonad and the retail case life of beef were examined under conditions of simulated retail display. Initial studies with an aqueous extract of beef muscle showed Pseudomonas growth was significantly limited by phages for up to 3 d at 7°C. Subsequently, it was shown that the treatment of Pseudomonas-inoculated steaks with high titer phage lysates (108 PFU/ml) resulted in a 1- to 2-log reduction in the level of bacterial contamination and a 2-log increase in phage numbers after 4 d of retail display. These changes were accompanied by a marked decrease in steak surface discoloration and a concurrent improvement in retail acceptance. Steak case life was positively correlated with phage concentration within the range of 10 to 108 PFU/ml. At the highest concentration of phages tested (108 PFU/ml) steak case life was significantly increased from 1.6 to 2.9 d. It was concluded that phages could multiply on the steak surface and have the ...