Sources of contamination own-kitchen Nuno F. Soares article

More often than we realize, we seem to leave all that food safety mindset at work and make basic mistakes when we use our own kitchens. Most of us fall short on what we can do to bring awareness into our family or community to principles that should be implemented when we prepare food and cook.


As food safety professionals we are expected to apply and train others on basic principles of food safety. Among them are certainly preventing cross-contamination, monitoring kill steps, cleaning, sanitizing and science-based approach to processes. Strangely, more often than we realize, we seem to leave all that food safety mindset at work and make basic mistakes when we use our own kitchens. If that is not your case, then congratulations … but still most of us fall short on what we can do to bring awareness into our family or community to principles that should be implemented when we prepare food and cook.

Some weak habits that people are used to doing in the kitchen, most of the time are passed throughout generations and may be simple to change. One typical example of this is washing raw meat under the sink faucet. Washing or rinsing of raw meat is not recommended because bacteria can cross-contaminate other foods, utensils, and surfaces. Droplets have been shown to disperse up to 50 cm in front of a sink and 60 to 70 cm to either side of a sink where chicken was washed (Everis & Betts, 2003).

In a study published in August 2019, Food Safety Consumer Research Project: Meal Preparation Experiment Related to Poultry Washing (RTI International for USDA, FSIS, OPACE, Food Safety Education Staff) a control group washed the chicken 61% of the time. Meanwhile, participants who were informed that washing meat and poultry doesn’t destroy bacteria but spreads it, washed the chicken only 7% of the time.




Within a domestic environment, kitchens and bathrooms have high potential to function as “microbial incubators”, due to the continuous inoculation of new microbial cells, e.g. by food handling and direct body contact to domestic surfaces; the colonization success of these microbes then depends on the suitability of the environmental conditions, such as humidity and nutrient availability. Multiple use of the kitchen provides risky potential to introduce an array of pathogens which can contaminate foods, multiply and result in illness.

Thus, the need to focus on one of our favourite areas at home: The Kitchen.

As such … Love is in the Air and so is the Flu! So, wash your Hands properly.

Bacteria exist everywhere! They’re on you even now, and on the phone/tablet screen from which you probably are reading this article. Pervasive as they are, these  “invisible” microbial life forms are (usually) nothing to fear. You require to just fine-tune your kitchen food handling practices and you can keep your food safe.


“Within one linear centimeter of your lower colon there lives and works more bacteria (about 100 billion) than all humans who have ever been born. Yet many people continue to assert that it is we who are in charge of the world” –  Neil Degrasse Tyson


What do you think? Can you really eliminate most of the microbes in your house by only wiping down the counter surfaces, cutting boards, appliances and utensils with your soapy sponge or through the dishwasher appliance? The answer is No.

Figure 1 – Key pathogens found on frequently touched areas of the home kitchen (Adapted from Redmond et al. and Griffith)

Bacteria are attracted to warm, moist environments, which is why the kitchen is one of the germiest rooms in the house. A 2011 study by NSF International, a consumer safety organization, categorized the household objects with the highest germ count. They found sponges and dish rags were the dirtiest household items, followed by kitchen sinks, toothbrush holders, pet bowls, coffee reservoirs, faucet handles, countertops, stove knobs, and cutting boards.

To bring people’s awareness to this problem maybe you can share that, contrary to what they may think, the bathroom is not the dirtiest place in the house! It is precisely where their food is prepared that the study found more Coliform bacteria (an indicator of potential fecal contamination). In fact, Coliform was found in 75% of dish sponges/rags, 45% of kitchen sinks, 32% of counter tops, and 18% of cutting boards.




A) Sponge

Dr. Chuck Gerba, a professor of microbiology at the University of Arizona, who studies how diseases are transferred through the environment, agrees that the kitchen sponge or cloth is almost always the dirtiest thing in your house. His studies have shown that, compared with the average toilet seat, where there are about 50 bacteria per square inch (6.5 square cm), there are about 10 million bacteria per square inch on a sponge, and a million on a dishcloth.

If you are someone who repeatedly uses the same sponge to wipe your kitchen counters, dishes and table, replacing it every month or so, a study published in Scientific Reports on 19th July 2017 concludes that these sponges have massive colonization by Acinetobacter, Moraxella and Chryseobacterium species.  Kitchen sponges, due to their porous nature and water soaking capacity, represent ideal incubators for microorganisms (evident under the microscope).


B) Towels

There are more bacteria on towels as they are used for multiple purposes like drying hands, wiping utensils and wiping surfaces etc. Notice that is more common than you think to people use the same towel to wipe spills and then use it to dry just cleaned plates before laundering it! A better way is to have paper towels for cleaning the countertops and use dedicated towels to dry cleaned utensils or air dry cleaned utensils on a dishrack.


C) Kitchen faucets

When was the last time you cleaned your kitchen faucet?

The common metal aeration screen at the end of the kitchen faucet has a noble purpose for the environment, but can be a spot for bacteria growth which can even develop into harmful biofilms that stick to the screen.


D) Stove knobs

While not a place that many of us think about, stove knobs are in the top ten for common places for germs to hide. We do clean our stove tops but do pay a lesser or no attention to the stove knobs. As a Food Safety Professional, we should note that our hands constantly touch the stove knobs but do we ever think of cleaning these stove knobs ?

As per National Sanitation Foundation (NSF), stove knobs should be cleaned once per week (remove knobs, wash in hot soapy water, rinse well, let dry and re-install).


E) Drainage Pipes

Removing household wastewater is an important environmental health intervention for reducing disease. Poorly drained wastewater forms stagnant pools that provide breeding sites for disease vectors. Because of this, some diseases are more common in the wet season than the dry season. Drain cleaning and use of suitable disinfectants are important building maintenance steps.




If we put on our food safety professional glasses to look into our kitchen you will notice, like in any other step of the food chain, we will identify potential sources of biological hazards (e.g. Salmonella and Campylobacter in raw meat and poultry), chemical hazards (e.g. cleaning chemicals, lubricating oil from mixer grinders), and physical hazards (e.g. broken glass, rubber bands, brittle plastic, wire ties, staples from grocery bags, etc.).

Cross contamination of food occurs when bacteria or other potentially harmful microorganism are unintentionally transferred from one place to another i.e. from one food item to another. There are three ways of cross contamination in the kitchen:

  • Food to Food: e.g. raw meat touches cooked meat in storage
  • People to Food: e.g. food handler handles raw meat and then touches cooked meat with the same hands without proper hand washing.
  • Equipment to Food: e.g. food handler uses the same chopping board first to chop raw meat and then to chop ready to eat fresh salad vegetables. USFDA recommends replacing worn cutting boards as they wear out over time (i.e. indentations caused by knives cutting into the board are harborage sites for pathogens).


You should also assure that incoming products are safe, not only the more obvious like raw meat, fish, produce or eggs but also of the water used to cook, clean, make ice and rehydrate foods, for example. Additional content regarding proper storage and cooking time-temperature control will be added to this article and sent with the article’s PDF to all members of SKG (see below how to join).




Back in 2006, WHO published Five Keys to Safer Food Manual recognized the need to educate food handlers about their responsibilities for food safety. The introduction of Good Consumer Practices has been advocated by Sean Leighton, M.Sc., M.B.A., and William H. Sperber, Ph.D as a recognition that consumers should be responsible for the safe handling of their food and making real food safety from farm-to-fork.


There are special consumer advocates, the Food Safety Professionals. We have a higher responsibility, because we know better, and we not only have to walk the talk but also to educate first our families and of course everyone we can.


We would like to challenge you to take action! Who could you help bring awareness to this issue and teach one simple thing she/he could do differently to manage hazards in the kitchen? Write your comments as to what you will do today to make food safer at home.



USDA – Cutting Boards and Food Safety –

2011 NSF International Household Germ Study –

NFS – Cleaning the Germiest Home Items –

Cardinale, M., Kaiser, D., Lueders, T. et al. Microbiome analysis and confocal microscopy of used kitchen sponges reveal massive colonization by AcinetobacterMoraxella and Chryseobacterium species. Sci Rep 7, 5791 (2017).

Good Consumer Practices Are Necessary to Further Improve Global Food Safety (2015)

Quick, V.; Corda, K.; Byrd-Bredbenner, C. Determinants of safe food handling behaviours among middle school youth. Nutr. Food Sci. 2013, in press.

Kennedy, J.; Jackson, V.; Blair, I.; McDowell, D.; Cowan, C.; Bolton, D. Food safety knowledge of consumers and the microbiological and temperature status of their refrigerators. J. Food Prot. 2005, 68, 1421–1430.

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This article was written with Shuchi Arya – Food Safety Specialist (

Special thanks to Jocelyn Lee Lion for contributing and editing this article.


Disclaimer: The information contained on this article is based on research done in the last months and the authors personal experience and opinion. It is not intended to represent the view of any organization they work for or collaborate with. The authors will not be held liable for the use or misuse of the information provided in the article.

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