Effect of Water Activities of Heating and Recovery Media on Apparent Heat Resistance of Bacillus cereus Spores
AUTOR(ES)
Coroller, Louis
FONTE
American Society for Microbiology
RESUMO
Spores of Bacillus cereus were heated and recovered in order to investigate the effect of water activity of media on the estimated heat resistance (i.e., the D value) of spores. The water activity (ranging from 0.9 to 1) of the heating medium was first successively controlled with three solutes (glycerol, glucose, and sucrose), while the water activity of the recovery medium was kept near 1. Reciprocally, the water activity of the heating medium was then kept at 1, while the water activity of the recovery medium was controlled from 0.9 to 1 with the same depressors. Lastly, in a third set of experiments, the heating medium and the recovery medium were adjusted to the same activity. As expected, added depressors caused an increase of the heat resistance of spores with a greater efficiency of sucrose with respect to glycerol and glucose. In contrast, when solutes were added to the recovery medium, under an optimal water activity close to 0.98, a decrease of water activity caused a decrease in the estimated D values. This effect was more pronounced when sucrose was used as a depressor instead of glycerol or glucose. When the heating and the recovery media were adjusted to the same water activity, a balancing effect was observed between the protective influence of the solutes during heat treatment and their negative effect during the recovery of injured cells, so that the overall effect of water activity was reduced, with an optimal value near 0.96. The difference between the efficiency of depressors was also less pronounced. It may then be concluded that the overall protective effect of a decrease in water activity is generally overestimated.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=92574Documentos Relacionados
- Effect of Ultrasonic Waves on the Heat Resistance of Bacillus cereus and Bacillus licheniformis Spores
- STUDIES ON HEAT RESISTANCE IV. : Sporulation of Bacillus cereus in Some Synthetic Media and the Heat Resistance of the Spores Produced1
- Effect of ultrasonic waves on the heat resistance of Bacillus spores.
- EFFECT OF DURATION OF HEATING, l-ALANINE AND SPORE CONCENTRATION ON THE OXIDATION OF GLUCOSE BY SPORES OF BACILLUS CEREUS VAR. TERMINALIS1
- Resistance and recovery studies on ultraviolet-irradiated spores of Bacillus pumilus.