Influence of Sublethal Temperatures on Some Spore-forming and Vegetative Foodborne Bacteria and Impact on Hygienic Quality of the “Foléré” (Hibiscus sabdariffa) Beverage

Aims: “Foléré” beverage is a refreshing locally made drink much appreciated by the populations of the hottest parts of Cameroon. This paper aims at investigating microbial contamination of “Foléré” beverage and highlights impact of the sublethal temperatures on the hygienic quality the beverage.

Study Design: Design used for describing physicochemical and microbial profile is a random sampling and for impact of sublethal temperature on hygienic quality, we used food matrix simulations.

Place and Duration of Study: Samples: Local markets, between August 2018 and June 2019.

Methodology: The sample pH and soluble solids content were recorded using portables devices. Microbial analysis focused on total aerobic mesophilic bacteria, Escherichia coli, and spore-forming bacteria were determined according to accredited culture methods. Acidic “Foléré” beverage produced by an artisanal processing was sterilized and inoculated by Bacillus cereus T spores and Escherichia coli ATCC 25922 cells thermally stressed by pre-incubation at 10°C, 45°C, 50°C or 60°C for 45 min, 90 min and 180 min. The recovery method was used to determine acid pH resistance of both bacteria before and after sublethal thermal processing.

Results: “Foléré” beverage is of poor hygienic quality according to standards, despite its very low pH (2.01). Beverages at pH 2.01 and inoculated by each one of referenced bacteria indicated that the samples which contained thermally stressed bacteria were worse hygienic quality than the same ones which contaminated with unstressed bacteria. Some of recovery percentages of bacteria thermally stressed were significantly higher (P =.05) than those of same bacteria thermally unstressed after acid treatments. That phenomenon was called thermal-induced bacterial acid resistance.

Conclusion: it appeared that some sublethal cold and heat shock treatments (10°C/45 min, 45°C/45 min, 50°C/90 min and 180 min) could negatively affect food quality. So, the control of emergence and evolution of stress-resistant bacteria in food could help to improve food safety.