Effect of Storage Temperatures on the Survival and Growth of Pathogens in Semi Preserved Foods

Abstract

The effect of storage temperatures on the survival and growth of pathogens in semi preserved foods was assessed using freshly prepared corn dough, dawadawa and cassava dough. Three pathogens, E. coli O157:H7 (Verocytoxigen-negative variant), Yersinia enterocolitica and Salmonella spp. were used. Pathogens were inoculated into 10g of samples in sterilized stomacher bags and stored at temperatures of 4, 15 and 30OC. Inoculated samples were sampled at regular time intervals and cultured on selective media. Predictive model was also used to assess how the pathogens will grow in the samples. The water activity (aw) and pH changes during the storage period were also measured. With the low aw of dawadawa (0.87), none of the pathogens could grow in it but growth was possible in corn and cassava dough. The survival and growth of the pathogens were affected not only by the water activity but pH, storage temperatures and time. However it is worth knowing that other physical and chemical properties of the samples which were not considered in the study might have also contributed to the extent to which the pathogens survived and grew in the samples. On the whole, the extent to which the pathogens did survived and grew in the sample depended on the water activity, pH of the sample and their sensitivity to temperature