Morphological characterization of a bacteriophage isolated from the Lactobacillus plantarum portion of a commercial meat starter culture showed that the isolate, phage fri, belonged to the Bradley group A bacteriophages. It had a regular six‐sided head (90 nm diameter), and a contractile tail (190 nm in length). Short tail fibres were observed at the distal end of the sheath. Fluorescent staining with acridine orange indicated that phage fri contained double‐stranded DNA. The resistance to high concentrations of either chloroform or ether showed that its lipid content was negligible. Heat lability was demonstrated by inactivation of a phage fri population within 10 min at 60°C and within 5 min at 70°C. It tolerated pH levels of 3.0–8.0 and exhibited greater stability in the acid region than did its host strain. The latent and rise periods were both 75 min, and the average burst size 200 pfu/cell. Sensitivity was limited to the Lact. plantarum strain of only one manufacturer of the commercial meat starters investigated.
The effects of phage fri, which was isolated from a commercial meat starter culture, on the growth of Lactobacillus plantarum and on pH development in broth culture were determined. The influence of this phage on pH development in laboratory sausages produced with the aid of four commercial starter cultures was also assessed.In the presence of a phage-sensitive starter culture, phage fri inhibited the growth of the organism and prevented the development of low pH levels when grown in broth culture. In laboratory sausage, the phage-sensitive, lactic-acid starter cultures produced sufficient acid for an acceptable product in the presence of phage frl. Results suggested that product failure in the fermented meat industry due to phage infection would not be common.
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