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This research project aims to develop and validate a computer programme to predict growth of C. perfringens in meat during cooling using a range of cooking and cooling conditions.
Study Duration : September 2002 to August 2003
Contractor : University of Reading
C. perfringens is frequently associated with gastroenteritis in humans and between 1992 and 1999 13% of foodborne outbreaks in England and Wales were attributed to this organism, although this is known to be an underestimate of the true burden of illness. The organism is commonly found in low numbers in many foods, especially in meat and poultry. It is known to be associated with foods prepared in bulk where there are inadequate cooling facilities for cooked foods. Slow cooling may allow germination of spores that have survived cooking and rapid multiplication of the organism to an infectious dose. The Agency commissioned this research to further our understanding of the physiology and behaviour of C. perfringens .
The project aims to develop and validate a computer programme to predict growth of C. perfringens in meat during cooling using a range of cooking and cooling conditions. A mathematical modelling approach that works with any time-temperature profile and has been previously described will be used.
This project has produced a computer model that predicts the changing temperature profiles of different regions in a solid body as it is heated and cooled. The model was tested by heating and cooling large (14cm diameter) or small (6cm diameter) sausages containing either bacterial growth medium solidified with 'gelrite' or minced beef. The internal temperatures predicted by the model were compared with those measured using thermocouples inserted into the sausages at different positions within gelrite or minced beef sausages with a high degree of accuracy. The tests were conducted on sausages of different sizes with air-cooling and water-cooling. The temperature model performed well with beef of high or low fat content.
The Institute of Food Research in Norwich has developed the Perfringens Predictor model, which predicts the growth of Clostridium perfringens during the cooling of meats (Food Standards Agency project B14009). This model was tested by comparing the predicted extent of growth of C. perfringens with the experimentally measured growth in liquid growth medium supplemented with minced beef. The Perfringens Predictor provided good predictions under a range of changing temperature conditions.
Validation studies established that the predictive models for both temperature and growth performed satisfactorily, and that it was therefore valid to combine them in a model that would allow growth to be predicted in different regions of a solid body during heating and cooling. Preliminary validations of the model using solid food indicated that a combined model (temperature and perfringens models) gives realistic predictions.
A combined model would allow growth in different regions of a solid food to be predicted, and allows simulation exercises to be performed that illustrate the effects of changing product size and cooling conditions. The temperature model together with the Perfringens Predictor will provide the Food Standards Agency and Enforcement Agencies with a means of evaluating the risk of C. perfringens growth under different heating and cooling conditions.
The final report is available from the FSA Library and Information centre.
To obtain a copy, please contact the Enquiry Desk, Dr Elsie Widdowson Library and Information Services, Food Standards Agency ( tel: 020 7276 8181/8182 or email: library&info@foodstandards.gsi.gov.uk ).
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Email
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