Combining heat treatment and subsequent incubation temperature to prevent growth from spores of non-proteolytic Clostridium botulinum

Abstract

. 1997. Refrigerated processed foods of extended durability rely on a mild heat treatment combined with refrigerated storage to ensure microbiological safety and quality. The principal microbiological safetj risk in foods of this type is non-proteolj-tic Ciostridiiint botultnum. In this article the combined effect of mild heat treatment and refrigerated storage on the time to growth and probabilitv of growth from spores of non-proteolytic CI. botulinum is described. Spores of non-proteolytic CI. hotu/iirum (two strains each of type B, E and F) were heated at 90°C for between 0 and 60 min and subsequent&-incubated at 5", 10" or 30°C in PYGS broth in the presence or absence of 17-sozyme. T h e number of spores that resulted in turbidit!. depended o n the combination of heat treatment, incubation time a n d incubation temperature the!-recei\-ed. Heating at 90°C for 1 or more min ensured a 10' reduction when spores were subsequently incubated at 5°C for u p to 23 weeks. Heating at 90°C for 60 min ensured a 10' reduction o\-er 23 weeks when subsequent incubation was at 10°C in the presence of added lysozj-me. The same treatment did not reduce the spore population by lo6 when subsequent incubation was at 30°C.

Effects of wet heat treatment on the germination of individual spores of Clostridium perfringens

“…In addition, inclusion of lysozyme in recovery medium plates can increase recoveries of wet heat-treated Cl. botulinum spores, perhaps by promoting spore germination (Duncan et al 1972;Stringer et al 1997), although this is not the case for spores of Bacillus subtilis (Coleman et al 2007). It appears possible then that analysis of specific germination defects in wet heat-killed spores may help to identify one or more spore proteins that are inactivated by wet heat treatment, and whose inactivation is associated with spore death.…”

“…However, the kinetics of germination of individual spores cannot be determined from these population measurements because of the heterogeneity in rates of germination of individual spores (Zhang et al 2010b;Kong et al 2011;Wang et al 2011a). A number of techniques have been developed for examining the germination of individual spores, including Raman spectroscopy to follow individual spores' CaDPA levels, DIC or phase-contrast microscopy to follow the germination of many hundreds of individual spores simultaneously (Zhang et al 2010b;Kong et al 2011), and measuring the time to generate measurable turbidity in microtitre wells containing growth medium and seeded with c. 1 spore/well (Billon et al 1997;Stringer et al 1997Stringer et al , 2005Stringer et al , 2009Stringer et al , 2011Smelt et al 2008;Ter Beek et al 2011). Raman spectroscopy is widely used in biochemical studies, as this technique has high sensitivity and responds rapidly to subtle changes in molecular structure (Wang et al 2011b;.When Raman spectroscopy is combined with confocal microscopy and optical tweezers, the resultant laser tweezers Raman spectroscopy (LTRS) allows the nondestructive, noninvasive detection of biochemical processes in physiological solutions (Zhang et al 2010b;Kong et al 2011).…”

Safety Evaluation of Sous Vide-Processed Products with Respect to Nonproteolytic Clostridium botulinum by Use of Challenge Studies and Predictive Microbiological Models

“…Recent research has identified combinations of mild heat treatment and subsequent refrigerated storage that, when combined with a specified shelf life, provide a defined safety margin with respect to nonproteolytic C. botulinum (10,15,46). Based on these research results, the Advisory Committee on the Microbiological Safety of Food (1) recommended certain procedures to ensure the safety of refrigerated processed foods of extended durability.…”

Study ofClostridium botulinumby Various Formulations of Salt and Preservatives in Persian Caviar

“…As storage temperatures increase, the time required for toxin formation is significantly shortened (Graham et al, 1997). The effects of different combinations of heat treatment, pH, and NaCl on the time for growth of type E in broth at different incubation temperatures have been reported (Graham et al, 1997;Stringer et al, 1997). The results of this study indicate that methyl paraben has had a more inhibitory effect than boric acid, borax, and NaCl and with decreasing storage temperature, the effects of the preservatives have been increased.…”