290 Chilled foods Such systems could be used to interpret microbiological, processing, formula- tion and usage data to predict the microbiological safety of foods. However to be realistic, the models are only as good as the data input and at present there is both uncertainty and variability associated with the data available. Betts(1997) has also discussed the practical application of microbial growth models to the determination of shelf-life of chilled foods and points out the usefulness of models in speeding up product development and the importance of validating the output of models in real products. Modelling technology can offer advantages i terms of time and cost, but is still in its infancy(Pin and Baranyi 1998). Its usefulness is limited, as there is variation not only in the microbial types present in raw materials and products but also in their activities and interactions altering growth or survival rates or the production of metabolites recognised by customers as spoilage There are, not surprisingly, major differences between manufacturers in the degree of time or temperature abuse they design their product to withstand and hence the risks they are prepared to accept on behalf of their customers. This can result in major differences in the processes, ingredients and packaging used and the shelf-lives given to apparently similar products 11.2 Definitions Definitions are given below, firstly in order to avoid misunderstanding and secondly to introduce general comments and guidance for the design of processes which control microbiological risks adequately. They are discussed in the following groups: raw materials; Chilled foods, Safety and quality control Processes 11.2.1 Raw materials Undecontaminated materials These include any food components of the final product, that have not been decontaminated so that they are effectively free of bacteria prejudicing or reducing the microbiological safety or shelf-life of the finished product. Such arting materials should be handled in the factory so that numbers of contaminants are not increased and they cannot contaminate any other components that have already been decontaminated. For example, the layout of processing areas should be designed on the forward flow principle to prever cross contamination; uncooked material should not be handled by personnel also handling finished product (except with the appropriate hygiene controls and separation), or allowed to enter high care areas(see below). If it is anticipated that these materials may contain pathogenic microbes, the severity of the risks should be assessed Their handling, processing and usage should be controlled accordingly to prevent cross contamination or manufacture of products which may be accidentally harmful to customersSuch systems could be used to interpret microbiological, processing, formula￾tion and usage data to predict the microbiological safety of foods. However to be realistic, the models are only as good as the data input and at present there is both uncertainty and variability associated with the data available. Betts (1997) has also discussed the practical application of microbial growth models to the determination of shelf-life of chilled foods and points out the usefulness of models in speeding up product development and the importance of validating the output of models in real products. Modelling technology can offer advantages in terms of time and cost, but is still in its infancy (Pin and Baranyi 1998). Its usefulness is limited, as there is variation not only in the microbial types present in raw materials and products but also in their activities and interactions altering growth or survival rates or the production of metabolites recognised by customers as spoilage. There are, not surprisingly, major differences between manufacturers in the degree of time or temperature abuse they design their product to withstand and hence the risks they are prepared to accept on behalf of their customers. This can result in major differences in the processes, ingredients and packaging used and the shelf-lives given to apparently similar products. 11.2 Definitions Definitions are given below, firstly in order to avoid misunderstanding and secondly to introduce general comments and guidance for the design of processes which control microbiological risks adequately. They are discussed in the following groups: raw materials; Chilled foods; Safety and quality control; Processes. 11.2.1 Raw materials Undecontaminated materials These include any food components of the final product, that have not been decontaminated so that they are effectively free of bacteria prejudicing or reducing the microbiological safety or shelf-life of the finished product. Such starting materials should be handled in the factory so that numbers of contaminants are not increased and they cannot contaminate any other components that have already been decontaminated. For example, the layout of processing areas should be designed on the forward flow principle to prevent cross contamination; uncooked material should not be handled by personnel also handling finished product (except with the appropriate hygiene controls and separation), or allowed to enter high care areas (see below). If it is anticipated that these materials may contain pathogenic microbes, the severity of the risks should be assessed. Their handling, processing and usage should be controlled accordingly to prevent cross contamination or the manufacture of products which may be accidentally harmful to customers (see below). 290 Chilled foods