Microbiological profile and modeling the survival of Escherichia coli ATCC 25922 in Amlou: A traditional Moroccan spread food

Abstract

This study was carried out to assess the bacteriological profile and to model the combined effects of physicochemical parameters on Escherichia coli ATCC 25922 levels in Amlou, a typical Moroccan traditional spread food made with argan oil, sweet almonds, and honey or sugar. Microbiological analyses of the samples (n = 44), collected from different traditional producers, included total viable count (TVC), total coliforms (TC), fecal coliforms (FC), E. coli, lactic acid bacteria (LAB), yeasts and molds (YM), Staphylococcus aureus, Salmonella, and Listeria spp. The results showed that 61% of samples met the Moroccan hygiene standards for vegetable paste spreads, with contamination levels of 4.21, 2.94, 2.38, 1.87, and 1.50 log cfu/g for TVC, YM, TC, FC, and E. coli, respectively. S. aureus was detected in 6.82% of Amlou samples, while Salmonella and Listeria spp. were not detected in any of the analyzed samples. On the other hand, the effects of water activity (a_w) (0.44, 0.50, 0.53), temperature (23, 30 °C), and pH (5.5, 6.5) on the kinetics parameters, inactivation rate (IR, log cfu/g/d), and shoulder period (SP, d) of E. coli ATCC 25922, were investigated. The survival curves generated under different conditions were fitted using the Baranyi model. Secondary modeling for the combined effects of a_w, temperature, and pH on the survival parameters was carried out using a polynomial equation. Finally, the goodness of fit was assessed for the survival kinetics of E. coli. Root mean square error (RMSE) and standard error of prediction (%SEP) obtained were 0.20 and 10.22% for IR and 0.24 and 40.01% for SP. These models can provide an estimate of E. coli inactivation in Amlou. Further studies should consider other factors such as argan oil concentration and amount of protein before being applied to ensure food safety for E. coli control in Amlou.