Abstract
Raw beef and chicken substrates inoculated with Staphylococcus aureus and two serotypes of Salmonella were subjected to severe temperature abuse at intervals during six months frozen storage at −18°C. A method was developed for enumeration of freeze-damaged Salmonellae in a mixed population. After 24 h S. hadar in chicken at c 20 or 27°C, increased by 2·87 and 5·40 log cycles respectively. In beef, S. typhimurium increased by 1·80 and 2·93 log cycles. Refreezing thawed samples reduced the Salmonellae by up to 99%. Growth of St. aureus during thawing was generally slight in comparison but there was little change in viable counts on refreezing. Substantial growth of St. aureus occurred in chicken at 27°C. Some samples were assayed for staphylococcal enterotoxin A but this was not detected in samples containing St. aureus at c 107 cfu.g−1. Growth of natural saprophytes had caused obvious spoilage by 24 h of thawing.