The effect of physical and microbiological factors on food container leakage

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Abstract
The effects of physical and microbiological factors on food container leakage was investigated in a container leakage model system (CLMS). The leakage of Acinetobacter calcoaceticus, Staphylococcus sp., Pseudomonas sp., Bacillus sp., a a coryneform, Staph. aureus, and two biotest organisms (Enterobacter cloacae NC1B 8151 and Ent. aerogenes MB31) was studied. The rate of bacterial leakage (log10 cells/channel/s) was greater in the presence of a partial vacuum of 51-305 mm Hg than at atmospheric pressure. Fluid flow (ml) through leakage channels was increased by the application of vaccuum. Leakage varied with vacuum, bacterial morphology, cell concentration, leakage channel size (0.78-120 .mu.m2) and channel shape (straight or convoluted). The number of leaked cells was not proportional to vacuum or channel size. The effect of channel shape varied with bacterial species. Increased container medium viscosity decreased bacterial leakage. Fluid flow through leakage channels was generally reduced by the most viscous solution. Cells from biofilms and monolayers of Ac. calcoaceticus or Staph. aureus attached to nylon (Hyfax) or stainless steel surfaces underwent leakage. Mixed bacterial populationss had characteristic leakage rates against vaccum different from the leakage pattern of individual species in the population. The composition of the leaked population was different from the original inoculum. The results indicated that container leakage is a complex process involving a range of interdependent factors.