Effect of Food Matrix, Cooking and Preservation Modalities on the Outgrowth of Bacillus cereus Spores in Some Starchy Foods

Aim: Starchy products are very important in the fight against food insecurity in developing countries, where they are widely consumed. This study is aimed to assess the impact of cooking and storage methods on the spoilage of some cooked starchy products by spore-forming bacteria

Place and Duration: Department of Microbiology of the University of Yaoundé I between
June 2020 and September 2022

Methodology: In order to better understand the alteration of these foods by spore-forming bacteria, a survey was carried out among some households and restaurant owners in the city of Yaoundé to determine the cooking and preservation methods for cassava, maize and rice couscous. Then, cooking parameters and conservation modalities from the survey were simulated in the laboratory in order to assess the deactivation kinetics of Bacillus cereus.

Results: It emerged from this experiment that cooking time varies according to the foodstuffs, the most important being maize. The packaging is mainly done in non-food plastic bags, and the thermos is used more often than the fridge and the pot. Cassava flour was more contaminated in aerobic spore (1.105 spores/g) than maize and rice (5.103 and 9.103 spores/g) after cooking of different starchy food enriched with Bacillus cereus spores, their inactivation was more important in rice followed by cassava and maize couscous as indicated by the Weibull scaleparameters which were respectively 1.1; 0.52 and 0.08. It was also noted that increase in cooking time also reduced the time for spores to initiate outgrowth and this time was affected by the type of flour. These two parameters also affected the time of spore outgrowth to 5logufc/g.

Conclusion: Storage in the fridge is still the best way to store food, but the thermos flask is more often used. The use of electric thermostats set at temperatures around 60°C would increase the optimal shelf life and significantly reduce the risk of spoilage and foodborne illness.