Aim:
Different heat inactivation techniques are used in the food industry to inactivate pathogens. These heat inactivation techniques need to be validated to estimate their actual heat inactivation of pathogens in the specific food matrix during the industrial process. This can be performed by using a non-pathogenic, surrogate strain that has the same heat resistance as the targeted pathogen. This non-pathogenic strain will be inserted in the industrial process and the inactivation after processing will be determined to provide information about the efficacy of the industrial process. This methodology will help to prevent recalls, leading to less food waste but can also lead to a reduction of the intensity of the process with less energy consumption. Therefore, it will help to obtain more sustainable production on an industrial scale.
Method:
The flour was inoculated with the different micro-organisms: three vegetative food pathogens Listeria monocytogenes, Salmonella spp., Escherichia coli O157:H7, and two surrogate strains: Enterococcus faecium strains. The flour was plated out on different media: selective, non-selective, and combination of both. The dough was prepared, standardized cookies were made and the heat resistance of the four food pathogen cocktails was compared with that of the two candidate surrogate strains during a baking process for 1, 2, 3, 4, 5, 7.5, and 10 minutes at 205°C.
Results:
The inoculation of the flour was optimized and resulted in an inoculum of 7.4 ± 0.3 log CFU/g in the cookie dough. The plating medium was also optimized and the overlayer method was used consisting of a layer of non-selective and selective media. E. faecium and the L. monocytogenes cocktail showed a similar heat inactivation curve. E. coli O157:H7 cocktail was less heat resistant and absent after 5 minutes of baking at 205°C. The Salmonella spp. cocktail followed a similar inactivation curve as the E. faecium.
Conclusion:
The selected E. faecium strains showed to be a good surrogate strain for the Salmonella spp. cocktail (most heat resistant pathogen) for this setup
