The Occurrence and Control of Clostridium botulinum in Foods

Abstract

Although outbreaks of human botulism in the UK are rare, the recent cases of botulism in Birmingham have provided a reminder that the potential hazards from foods contaminated with Clostridium botulinum cannot be ignored. Outbreaks of botulism in Europe and the USA are more frequent and have not always received the publicity given to the Birmingham outbreak. Data on outbreaks of botulism in Europe during the past 20 years have been collated and will be presented.

Spores oj Cl.. botulinum are known to occur widely in soil, freshwater mud and marine muds in many parts of the world. Contamination of foods and subsequent growth by CI. botulinum is therefore possible unless foods are adequately preserved. Some data on natural contamination of food material by Cl. botulinum will be presented.

Traditional preservation methods, including commercial sterilisation (e.g. in canning), use of low pH conditions (e.g. in acid fruits and pickles), restriction of available water (by drying or addition of humectants), and restriction of storage temperature (e.g. by chilling or freezing) are all used to prevent growth of both spoilage and foodpoisoning bacteria. Whilst the critical process conditions can be defined in some cases (e.g. the minimum botulinum cook (F₀ 3 min) for canned foods), in other situations insufficient data exist to quantify a ‘safe’ process with regard to CI. botulinum. This is particularly important where interactions of two or more preservation systems are required for safety and stability. Examples will be provided of the interactions between factors such as pH value and water activity (a_n.) in processed cheese and of those factors important in the safety and stability of pasteurised cured meats (e.g. salt, nitrite, other additives, thermal process value, pH value, storage temperature and time). The relative importance of these factors will be considered in relation to the establishment of a product risk evaluation system which could form the basis of a computer model.