The effect of prior heat shock on the thermoresistance of Salmonella thompson in foods

Abstract

The resistance of Salmonella thompson to heating at 54° or 60°C in tryptone soya broth, liquid whole egg, 10% or 40% reconstituted dried milk or minced beef was increased if cells were held at 48°C for 30 min before heating at the higher temperatures. Induction of thermotolerance by mild heat shock is thus not confined to cells grown and heated in broth systems. The heat shock phenomenon may therefore have implications for the safety of foods given marginal heat treatment.

Heat shock and thermotolerance of Escherichia coli O157:H7 in a model beef gravy system and ground beef

“…Previous workers have demonstrated the significance of the heat-shock response and induced thermotolerance of Yersinia enterocolitica in ground pork (Shenoy and Murano 1996), Listeria monocytogenes in a fermented sausage (beef and pork) mix (Farber and Brown 1990) and Salmonella thompson in liquid whole egg, reconstituted dried milk or minced beef (Mackey and Derrick 1987). Our findings illustrate the occurrence of the heatshock phenomenon with E. coli O157:H7 in beef gravy and ground beef where T 4D values at 60°C were increased 1·56-and 1·50-fold, respectively, over non-heat-shocked cells.…”

“…These studies, as well as the present study, clearly indicate that the thermotolerance response of bacteria depends upon the heating menstruum during the heat shock. Heat shock, in conjunction with the composition of the heating medium, conferred increased heat resistance on S. thompson (Mackey and Derrick 1987). Certainly, it would be difficult to predict the extent of induced heat tolerance in foods based on data obtained in media.…”

Spoilage and Preservation of Muscle Foods

“…This phenomenon has been reported in E. coli and Salmonella spp. (Mackey and Derrick 1987;Murano and Pierson 1992) Also, it has been reported that elimination of L. monocytogenes was not only dependent on the ultimate temperature but also on the rate ofheating; whole harns had to be heated to higher (pasteurization) temperatures than sausages to affect the sarne degree of thermal destruction. Due to slower heat penetration in the solid product, the potential exists for bacterial adaptation to otherwise lethal temperatures.…”

Induction of increased thermotolerance in Saccharomyces cerevisiae may be triggered by a mechanism involving intracellular pH

“…This stress response, more commonly known as the heat-shock response, may have implications for microbiological safety during food processing, particularly because the phenomenon is ubiquitous and almost certainly occurs in both foodspoilage and pathogenic organisms (Mackey & Derrick, 1987;Yamamori & Yura, 1982;Lindquist, 1986;Farber & Brown, 1990). In addition to the acquisition of thermotolerance, the stress response has been largely characterized by the expression and synthesis of a unique set of proteins: the heat-shock proteins (HSPs).…”