Inactivation of refrigerator biofilm bacteria for application in the food service environment

Abstract

Refrigerator biofilm formation in food environments can result in spoilage and food safety problems. Biofouling of food contact surfaces are difficult to combat, and while there are significant risks involved with tolerating their presence, methods for their removal are not commonly available. In this study, biofilms were grown on plastic refrigerator trays. Cultures of mixed wild strains were started using kitchen scraps suspended in nutrient broth. Biofilms were allowed to mature with approximately 109 CFU per tray test area. Spoilage species identified included Pseudomonas putida, Sphingobacterium multivorum, Citrobacter freundii and Proteus vulgaris. A series of 39 different treatment interventions were trialed during three different biofilm test runs. Results obtained from treatments ranged from a less than 1 log10 reduction for light duty cleaning operations to over a 5 log10 reduction involving more complex treatment methods. The latter included combinations of hot soapy water (75 °C), scrubbing, treatment with high pH (12.0) cleaners followed by acetic acid (vinegar) exposure and included pre‐ and post‐treatment wiping with paper towels.

Identification of Household Bacterial Community and Analysis of Species Shared with Human Microbiome

“…Refrigerators in kitchens could be colonized by bacteria, and these bacteria might contaminate other stored foods or attach to and survive on the internal surface of the refrigerator, thereby posing risks of indirect, long-term contamination during subsequent food preparation activities [20–22, 30]. In this study, most bacteria detected were probably not pathogens or opportunistic pathogens, and genera belonging to common pathogens were detected in only a very small fraction of communities on the surfaces of refrigerators and toilets.…”

The incidence of significant foodborne pathogens in domestic refrigerators

“…Bacteria contaminating unwashed raw foods, leaking packages, hands, surfaces, etc. introduced to domestic refrigerators may directly contaminate other stored foods, or attach to and persist on the internal surface of the refrigerator posing risks of indirect longer term contamination during subsequent food preparation activities (Michaels, Ayers, Celis, & Gangar, 2001). Many domestic refrigerators are incorrectly adjusted, operating above the recommended temperature and are therefore capable of supporting sub-optimum but signiWcant growth of mesophilic organisms such as Staphylococcus aureus and Salmonella spp.…”

A psychrotrophicBurkholderia cepaciastrain isolated from refrigerated raw milk showing proteolytic activity and adhesion to stainless steel

“…This strain of Bur. cepacia showed capability similar to other recognized food spoilage bacteria like Pseudomonas putida, Citrobacter freundii and Proteus vulgaris , to form biofilms at low temperatures (Michaels et al 2003). Biofilms are formed in dairy processing lines despite cleaning-in-place procedures, representing a source of post-pasteurization contamination (Austin & Bergeron, 1995).…”