Microbial Spoilage of Fresh Refrigerated Beef Liver

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Abstract
The types and numbers of micro‐organisms involved in the spoilage of refrigerated beef liver were studied together with pH, hydration and organoleptic changes of the material. Fresh liver harboured a mixed population (c. 1 × 105 organisms/g) of Gram positive cocci, chromogens and non‐chromogens, sporeformers, presumptive coliforms and Gram negative rods. When samples were rejected organoleptically, after 7–10 days at 5°, the contamination attained levels of c. 7–8 × 107 organisms/g. Spoilage was due to souring; the pH fell from 6·3 (fresh liver) to c. 5·9. Lactic acid bacteria were predominant and Gram negative bacteria did not exceed 1·0 × 106 organisms/g. This type of spoilage is explained by the carbohydrate content of c. 5% in liver. The value of pH appears to be a reliable indicator of liver freshness, with a pH of 6·1 indicating incipient spoilage.