Effect of reduced water activity on vegetative growth of cells and on germination of endospores of Sporolactobacillus.
Growth of vegetative cells and germination of endospores of Sporolactobacillus at reduced water activity (aw) values were studied with NaCl and glycerol as humectants, and compared with Bacillus cereus and Clostridium sporogenes. With NaCl the highest aw for complete inhibition of both growth of vegetative cells and germinated spores of Sporolactobacillus was 0.955. With glycerol, growth of vegetative cells was completely inhibited at 0.905 as compared to 0.880 for vegetative growth resulting from germinated endospores. The mechanism of this phenomenon cannot be explained yet. NaCl appeared to have a toxic effect, in addition to inhibition by reduced aw per se.
Public health implication of refrigerated pasteurized ('sous-vide') foods.
Food that upon pasteurization is stored in hermetically sealed containers at food temperatures not exceeding 3 degrees C could be designated by the generic term Refrigerated Pasteurized Foods of Extended Durability, REPFEDs. If not properly processed or protected against recontamination, or if temperature-abused, REPFEDs may present serious health risks. However, control is readily available. Sound microbial ecology, supported by expert risk assessment, allows the design and introduction of longitudinally integrated manufacture, distribution, handling by outlets and consumers and culinary preparation, which result in the assurance of the wholesomeness of the commodity as eaten. Recent progress, including intrinsic preservation by the incorporation of starter cultures, bacteriocins or particular enzymes, opens vistas for attractive future developments. Once microbiological safety has been built into the REPFED-line, monitoring can be limited to (i) real-time tests particularly applied to the factory environment; and (ii) rapid, simple examination for marker organisms of freshly manufactured products versus those approaching expiration dates. Such audits will allow rapid retrieval of incidental process failure and its rectification. It also serves to substantiate measurements of food temperature and spot checks on intrinsic inhibitory attributes. The application of scientific knowledge and technological expertise should primarily be entrusted to the industry itself, heeding Lord Plumb's strategy of "partnership along the food production chain from farm to fork." It should be supported and validated by Public Health Authorities. At all stages safety communication with the public should be ensured.
Thermal lysis of bacterial membranes and its prevention by polyamines.
SUMMARY: Protoplasts of Sarcina lutea and Streptococcus faecalis underwent thermal lysis when heated to 60° and above. [14C]Glycine was released from the internal pool of Strep, faecalis at 50°. Spermine, spermidine, cadaverine and Mg2+ partially protected protoplasts against thermal lysis.