As a fourth year Food Science major and someone who knows dirty dishes and stained counter tops far too well, I feel incredibly compelled to write this blog post. Truthfully, I have also been guilty of forgetting one or two (once eight) dishware in the kitchen sink for a day and overlooking some cleaning and sanitizing rules we should ALL abide by.
What happens if you leave your kitchen cabinet without cleaning and sanitizing it for too long? What ends up forming is a biofilm, otherwise a bacteria-laden aggregate of inorganic and organic materials that attach to surfaces. As more bacteria accumulates around and onto any surface such as a table, they continuously will bind to these surfaces and develop stronger bonds (van der Waals being the weakest bonds to hydrogen bonds being the strongest).With time and favorable conditions, these biofilms will allow some of their bacteria to contaminate other surfaces, even the air and water surrounding them!
The first layer that develops in a biofilm is the bacterial primer, also known as the conditioning layer made of proteins that aid in bacterial adhesion (1). When caught early, this attachment is reversible and can easily be eradicated by a biocide (2). However, with maturation, the second layer garners more adhesion and ability to spread. There are several factors that can encourage the rate of biofilm strengthening, such as:
pH (extremely high or low measurements can denature proteins*)
High contact surface temperature (denatures proteins*)
Low fluid flow rates
Increased surface hydrophobicity (enhances bacterial attachment) (i.e. stainless steel)
Extracellular polysaccharides that use a combination of chemical interactions (i.e. covalent bonds, hydrogen bonds, Van der Walls, dipole, and hydrophobic interactions)*= it is critical to understand protein denaturation since protein is responsible for structure and creating a barrier against bacteria sticking to the surface.
This maturation of the biofilm enables it to become more irreversible and contagious as it is able to disperse and spread throughout the environment. It spreads as more nutrient-deprived bacteria cells can approach these areas to garner nutrients and to create a conglomerate of a diverse array of bacterial species, chemical bonds, and degrees of resistance to heat and sanitizers (though resistance strengthens over time with the aging of chemical bonds). Biofilm development time varies depending on the environmental circumstances, but if conditions are generally favorable, biofilms can form as quickly as in just one hour (1). As more hours pass, more parts of a biofilm becomes irreversibly attached.
These horrific amalgamations of bacterial “cities” are often found on food production and environmental surfaces, food products, pipes, floors, walls, drains, and any cracks, dead spaces, crevices, pits, scratches, and nicks. The more difficult a certain part of a surface is to clean, the more probable it is to find a biofilm forming. The most common materials for biofilms are steel, glass, Buna-N, Teflon, nylon, and aluminum. Anywhere that involves food contact such as a cutting surface, conveyer belt, pasteurizer, gasket, a kettle, or blender, is more likely to allow for biofilm formation since they constantly contact nutrient sources and potential foods with extreme pH’s and polysaccharides.
How can you detect if a biofilm has formed? They are generally quite visible if the matrix is quite well-developed, but these techniques are useful in very early stages:
Plate counts allow for a “marginal or reject” value detected through ATP bioluminescence, a light energy form of detecting bacteria, for the first day (3). On the second day, the low total plate count and ATP bioluminescence value are calculated again. If the ATP bioluminescence value is in the “accept” range, a biofilm has formed.
Sponges to help recover a small proportion of total biofilm bacterial detection
Swabbing is used for plate counts, but recovers a very small amount of the bacterial biofilm analysis
Ultimately, the best strategies for removing biofilms encompass prevention. It is very similar to other aspects of life (use good form in exercise to prevent become injured and/or healthy lifestyle choices to prevent becoming sick)–hence, minimize cross contamination of dirty items on surfaces, be attentive to cleaning and sanitizing, and regulate temperature and time of exposure. Using bactericidal agents, solutions with optimal cleaning and sanitizing agent concentrations, and a good amount of forceful mechanical activity when scrubbing a surface will help in the early stages.
How often should you clean your kitchen? The answer is not exactly what most people want to hear, but it’s the truth: after each time you use a potential source of contamination (food, cutlery, surfaces, appliances, and more). This doesn’t mean you need to go around vacuuming, dusting, scrubbing, and sweeping the whole place, but any part where you set down a used rag or a plate of food must be cleaned and sanitized. The most feasible option would be to conduct a weekly deep cleaning of your kitchen to ensure the environment is spick and span. Use the proper type of soap for your surface and the nasties you want to drive off, warm water, and a sanitizing agent. Vacuum and/or mop the floors if necessary. You can also hire people to clean your homes for you and they will execute the exact same process. As long as the kitchen shines and sparkles afterwards, you are all set!
How often do you clean your kitchen? For me in San Francisco, not enough–I tend to avoid the kitchen area and just use the one at my workplace that’s cleaned every week; in my Los Angeles home, it’s cleaned basically every single day by my mother as well as housekeepers that come once a week, sometimes twice depending on the schedule!