I know, those kitchen sponges are nice to use when they are new and clean, but after a few washes they become soiled, dirty, smelly and sometimes sticky. At some point you have to dump them, but did you know you can disinfect them and re-use them?
It is known that cross contamination in a household kitchen is common and can result in food borne illnesses. Chopping boards, knives, kitchen towels and kitchen sponges are common sources of cross contamination. There are approximately 70 million cases of food borne illness due to cross contamination in America every year.
Since kitchen sponges are common sources of cross contamination they require special attention as they are often left wet, creating a conducive environment for the growth of bacteria, molds and yeast and as a result can act as a vehicle of germs between washings.
Kitchen chopping boards and kitchen surfaces can be contaminated with different bacteria such as Escherichia coli, Staphylococcus aureus, Salmonella enteritidis, and Campylobacter jejuni. Using sponges to wipe them can transfer the bacteria to the sponges. Research has shown that these sponges can then transfer those bacteria to utensils including cooking pots and plates and eventually cause food borne illness.
A study of ten kitchens in the US showed that 33% and 67% of sponges tested positive for E. coli and fecal coliforms, respectively. It is therefore very important to limit the ability of kitchen sponges to transfers bacteria to other surfaces by disinfecting them effectively.
A study by Manan Sharma of Food Safety Laboratory of United States Department of Agriculture tested disinfection of sponges with a bleach (10%), lemon juice, microwave oven or dish washer.
In the study, kitchen sponges were soiled with minced meat slurry and the sponges were stored for 2 days at room temperature to allow the bacteria to grow. After 2 days the sponges were either treated with chemicals by dipping in half little of bleach (Sodium hypochlorite), lemon juice pH 2.9 or micro waved at full power in 1300 Watts microwave oven or cleaned in a dish washer without a detergent.
Microwave oven beat all the other methods by killing over 90% of bacteria and dish washer killed 85% while bleach and lemon juice killed only 5%.
On yeasts and molds, again, dishwasher and microwave emerged the winners by killing over 90 and 85 % respectively while the chemicals (bleach and lemon juice) killed only 5%.
Dishwasher was effective but it has a disadvantage in that it takes longer time, consumes more power and uses more water. Perhaps, a cheaper alternative to dishwasher is to sterilise the sponges by boiling them in water in a cooking pot.
It seems microwave oven emerges as the winner in disinfecting kitchen sponges because it is faster and uses less power. Next time you feel your kitchen sponge is a bit dirty, you know what to do, toss it in the microwave.
Arimi’s tip of the week: Disinfect kitchen sponge in a dishwasher or in a microwave oven.
Manan S., Janet E., Cheryl M. (2009). Effective household disinfection methods of kitchen sponges. Food Control 20, 330-313