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Mechanisms of heat inactivation in Salmonella serotype Typhimurium as affected by low water activity at different temperatures
Author(s) -
Aljarallah K.M.,
Adams M.R.
Publication year - 2007
Publication title -
journal of applied microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.889
H-Index - 156
eISSN - 1365-2672
pISSN - 1364-5072
DOI - 10.1111/j.1365-2672.2006.03054.x
Subject(s) - pasteurization , water activity , salmonella , food science , chemistry , sodium , serotype , heat resistance , microbiology and biotechnology , degradation (telecommunications) , biology , bacteria , materials science , water content , telecommunications , organic chemistry , computer science , composite material , genetics , geotechnical engineering , engineering
Aims: To determine the effect of reduced water activity ( a w ) on thermal inactivation of Salmonella serotype Typhimurium at different temperatures and its mechanism. Methods and Results: D ‐value determinations at a range of different temperatures showed that heating at reduced a w (0·94, produced by addition of glucose or sodium chloride to nutrient broth) was protective at temperatures above 53–55°C but sensitizing below this temperature. Using selective enumeration media to determine injury, it was shown that at lower heating temperatures cells survived at high a w with cytoplasmic injury whereas at low a w these cells were killed. At higher temperatures ribosome degradation was a more important cause of death and was inhibited by low a w heating media thereby providing greater heat resistance. Conclusions: The observed change in behaviour reflects the different reactions responsible for thermal death at different temperatures and their different response to reduced a w . Significance and Impact of the Study: This work qualifies the previous assumption that reduced a w is protective and suggests that the efficacy of low temperature pasteurization regimes may be increased by reduced a w .