Ensuring process safety: validating industrial cookie and waffle production with a surrogate strain

Abstract

This study validated industrial baking processes for sugar waffles and cookies for the effective inactivation of vegetative pathogens. Although sweet bakery products are mostly perceived as microbial-safe, epidemiological data indicate foodborne outbreaks in flour and flour-related products caused mainly by Shiga toxin-producing Escherichia coli (STEC) and Salmonella spp. This study's first step compared observed inactivation of pathogen and potential surrogates during a lab-scale cookie baking process. Therefore, the flour was inoculated with one of the surrogates, i.e., Enterococcus faecium NRRLB-2354, Enterococcus faecium LMG11397, or Escherichia coli P1, or inoculated with one of the pathogenic strain(s), i.e., a Listeria monocytogenes cocktail, Salmonella Senftenberg, E. coli O157:H7 cocktail, or Salmonella spp. cocktail. Each dough was baked for 1, 2, 3, 4, 5, 7.5, and 10 min at 205 °C. The Salmonella spp. cocktail and E. faecium NRRLB-2354 showed the lowest observed inactivation and similar inactivation kinetics (remaining viable after a 10-min bake). Therefore, E. faecium NRRLB-2354 was chosen as the most suitable surrogate and used with the Salmonella spp. cocktail in a lab baking process for sugar waffles (195 s at 177 °C) to validate the surrogate in this food product. The reduction of E. faecium NRRLB-2354 was between 7.6 and 9.0 log CFU/g after the baking process of sugar waffles, which was similar to that of Salmonella spp. cocktail. Finally, the industrial baking processes of speculoos cookies and sugar waffles were validated with E. faecium NRRLB-2354, achieving a more than 7-log reduction in both processes, guaranteeing the absence of vegetative pathogens after baking.