by Shira Kramer, PhD | Chief Executive Officer, Sterilex

It is now well established that bacteria, including foodborne pathogens, predominantly grow in biofilms, their natural habitat. Biofilms are comprised of dense, complex, multi-species populations of microorganisms that are irreversibly attached to a surface or to each other, and are embedded in a self-produced extracellular polymeric matrix. Within biofilms, bacteria of both the same and different species communicate and interact with each other, exchange genetic material, and are much more resistant to antimicrobials than they would be in a planktonic, or unattached state. Like humans and animals, microorganisms benefit from this community-based lifestyle for growth and survival. In food processing environments, biofilms represent a persistent source of product contamination and cross contamination through detachment or aerosolization of bacterial cells.

A wide range of food products are manufactured in low moisture environments, and these products are susceptible to contamination with biofilms and associated microorganisms. Although it may seem reasonable to assume that microorganisms and biofilms require some moisture for survival, they can, in fact, survive in a desiccated state. Once in this dried state, metabolism is reduced, and the cells and spores persist longer (months to years), and are more difficult to eradicate, than in a high moisture environment. Upon rehydration of low moisture foods or ingredients, conditions are favorable for the growth of the previously dormant microorganisms. The recent outbreaks of STEC 0121 and STEC 026, linked to flour in the US [1], and contamination of dry infant formula with Bacillus cereus and Cronobacter species[2] underscore the risks associated with biofilms in dry or low-moisture processing.

Studies have shown that dry surface biofilms are less susceptible to killing by heat treatment and high hydrostatic pressure than hydrated biofilms[3,4]. Typical cleaning and sanitizing methods, which are wet procedures, are not applicable in these low humidity, dry environments. Thus, steps should be taken to control biofilms and microbiological contamination in ingredients before the dry manufacturing process, which should include proper disinfection and sanitization of environmental surfaces and equipment associated with ingredient manufacturing. Various dry methods for cleaning, sanitizing, and disinfecting do exist, including dry powdered products, quick-drying sanitizers, and physical methods. Another important element in risk management is verification and environmental monitoring, including monitoring for biofilms.

There is much emphasis and activity focused on the development of microbial and biofilm control technologies for dry processing environments. Sterilex offers a variety of products to help dry processing plants with their microbial control efforts. Among these are Sterilex Ultra Step, a dry floor sanitizer that helps minimize the spread of microorganisms. For periodic deep cleaning, Sterilex Ultra Disinfectant Cleaner Solution 1 and Sterilex Ultra Activator Solution provide dry processing plants with a mechanism to remove biofilm and return plants to a microbial baseline.


[1] Crowe SJ, Bottichio L, Shade LN, Whitney BM, Corral N, et al. Shiga Toxin- Producing E. Coli Infections Associated with Flour. N Engl J Med 2017; 377:2036-2043.

[2] Centers for Disease Control and Prevention, National Center for Emerging and Zoonotic Infectious Diseases, Division of Foodborne, Waterborne, and Environmental Diseases. Page Last Reviewed October 17, 2018.

[3] Beuchat L, Komitopoulou E, Betts R, Beckers H, Bourdichon F, Joosten H, Fanning S, ter Kuile B. Persistence and Survival of Pathogens in Dry Foods and Dry Food Processing Environments. Report of an ILSI Europe Expert Group. November, 2011.

[4] Almatroudi A., Tahir S, Hu H, Chowdhury D, Gosbell IB, Jensen SO, Vickery K. Staphylococcus aureus Dry-Surface Biofilms are More Resistant to Heat Treatment Than Traditional Hydrated Biofilms. J Hosp Inf 2018; 98(2): 161-167.