Behavioural pattern of vegetative cells and spores of Bacillus cereus as affected by time-temperature combinations used in processing of Indian traditional foods

Abstract

This study was undertaken to evaluate the behaviour of vegetative cells and spores of four potent native toxigenic food isolates of Bacillus cereus as affected by selected time-temperature combinations used in processing of Indian traditional foods. The vegetative cells of B. cereus when subjected to sublethal heat treatments, individually, in different heating menstra showed a sigmoidal inactivation pattern, with D-values in the range of 3.45 min at 60°C to 10.6 min at 56°C in saline. Accordingly, the zvalues recorded across the heating menstra ranged from 9.3°C in culture broth to 24°C in whole milk. Similarly, the inactivation pattern for spores for the same isolates was curvilinear with D-values ranging from 4.4 min at 95°C in whole milk to 19.45 min at 85°C in saline. The z-values for spores ranged from 16.6°C in saline to 38.4°C in whole milk. The thermal inactivation pattern observed for vegetative cells and spores indicate that the death rate was not constant during the process of heat treatment.

Impacts of sporulation temperature, exposure to compost matrix and temperature on survival of Bacillus cereus spores during livestock mortality composting

“…Effects of compost matrix and time in compost on mean and range in temperatures (°C) within sample retrieval pyramidsBased on the results of this study, thermophilic compost temperatures >55°C reduced survival of spores of both strains of B. cereus, while mesophilic compost temperatures (35-50°C) had little impact. Due to the overall lower survival of strain 805 both at room temperature and in compost, results of this study demonstrated that survival of spores of B. cereus in response to heat treatment was highly strain specific, in accord with previous studies of B. cereus and B. anthracis(Mazas et al 1995;Novak et al 2005;Desai and Varadaraj 2010). However, results of this study would be in contrast to those of…”

“…; Novak et al . ; Desai and Varadaraj ). However, results of this study would be in contrast to those of McCarthy et al .…”

“…All carcasses were exceedingly fat and on retrieval from compost, sample retrieval pyramids were coated in a layer of tallow. Fat has been shown to protect the viability of bacterial spores subject to heat treatment, possibly due to a reduction in water activity (Desai and Varadaraj ), although Mazas et al . () found B. cereus spores to be less heat resistant in media containing 20% fat.…”

“…All carcasses were exceedingly fat and on retrieval from compost, sample retrieval pyramids were coated in a layer of tallow. Fat has been shown to protect the viability of bacterial spores subject to heat treatment, possibly due to a reduction in water activity (Desai and Varadaraj 2010), although Mazas et al (1995) found B. cereus spores to be less heat resistant in media containing 20% fat. Leguerinel and Mafart (2001) demonstrated that an acidic pH decreased survival of B. cereus spores after heat exposure, although impacts of the acidic pH of sawdust compost may have been limited as low water activity of sawdust may have restricted translocation of H + ions.…”

Hydrothermal treatment for inactivating some hygienic microbial indicators from food waste–amended animal feed

“…This means that TPC was more sensitive to continuous temperature increase, but MY exhibited greater tolerance than TPC at each temperature (Figure 2). The difference of inactivation between MY and TPC by this hydrothermal process indicated that inactivation mechanisms varied among different indicators (Desai and Varadaraj, 2010). Generally, vegetative cells are more sensitive to heat when water evaporates, whereas spores are not (Rahman et al, 2004).…”