Injured bacteria in foods

Abstract

Food can contain a variety of micro‐organisms such as the bacteria Salmonella and E. coli and the yeasts and moulds. The presence of micro‐organisms in foodstuffs can affect both the safety and quality of the product. Consequently, food manufacturers have developed food processing treatments that help preserve foods, by destroying the micro‐organisms that are present or by injuring them and thus preventing their growth. There are many sites within a bacterial cell that can become damaged when the bacteria are subjected to these food processing treatments. These sites include the genetic material of the cell (DNA, RNA) and also the cell membrane. Some bacteria have developed ways to survive some processing treatments. These include the production of heat shock and cold shock proteins that help the cell function normally under higher or lower temperatures than normal. Some treatments will cause irreparable damage and the cells will be destroyed. However, sometimes the damage will be repairable and the cells are able to repair and recover. The micro‐organisms that are destroyed by processing will not cause subsequent food poisoning or spoilage, but organisms that are injured and become repaired could cause subsequent food spoilage or poisoning. The uninjured cells will be those organisms that are most easily detected and enumerated by current microbiological methods. The results gained from use of these methods are used to assess the risks of food spoilage and safety. However, the injured bacteria must also be accounted for. These organisms can also pose a food safety and/or spoilage risk as they can repair if the conditions become favourable. Therefore suitable test methods to detect bacteria within foodstuffs should be developed.