The microbial associations that developed in commercially produced sulphited and unsulphited sausages during storage for up to 8 days at a variety of temperatures were identified. Such associations were comprised of domiinant, e.g. Brochothrix thermosphacta, yeasts and lactic acid bacteria, or minor, e.g. Pseudomonadaceae and Enterobacteriaiceae, groups. A detailed analysis of numerous isolates of the previously-ignored Gramnegative microflora using computer-assisted numerical techniques revealed that sulphite concentratioin influenced the composition of the Enterobacteriaceae but not the pseudomonads. A method was developed for the assay of free and bound sulphur IV oxospecies in culture media or meat-based samples. It was superior to existing techniques and demonstrated limited irretrievable - by oxidation - and extensive reversible - by binding - loss of sulphite preservative from freshly manufactured and stored sausage. Selected micro-organisms isolated from sausage were tested for their tolerance of free and bound sulphur IV oxospecies in batch and "turbidometer" culture under various conditions. In general this technique reflected the elective/selective role of sulphite in sausage and allowed the microbial association to be defined more clearly in terms of tolerance of the active preservative. The incidence and level of contamination of sausage and its ingredients with Salmonella was established using a 'most-probable number' method. Despite a high incidence of contamination of most of the meat ingredients and finished product with these organisms, the level of infection - with the exception of mechanically recovered meat - was low. Thus the role of sulphur IV oxospecies in determining the fate of these food poisoning organisms in sausage or culture media was assessed by deliberate infection with rifampicinresistant Salmonella mutants. With a view to extending the shelf life of fresh sausage, a limited survey of adjuncts or alternative "preservatives" to sulphite using pilot-scale batches of sausage meat was done.
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