Cleaning Sponges: What’s the best way?

You try to be a good housekeeper. You sponge down your counters and appliances and feel good about keeping a clean and sanitary kitchen. But you may be doing more harm than good by spreading bacteria, according to scientists with the USDA’s Agricultural Research Service (ARS).  

The sponge is a versatile kitchen aid because it absorbs liquid so quickly, wipes over a variety of surface types and is reusable. However, it harbors more than moisture. It may also hold food-borne pathogens, yeasts and molds.

The dirty sponges

Scientists for the ARS have tested several methods for reducing risks from harmful microbes hiding in reused sponges.  First, they soaked sponges at room temperature for 48 hours in a solution made from ground beef and lab growth medium.  This was to grow a high level of microbes to simulate a very dirty sponge.  After 48 hours, the sponges had 20 million microbes.

Cleaning methods tested

They tested five different cleaning techniques to determine which was most effective at reducing the microbes.  One sponge was soaked for three minutes in a 10% chlorine bleach solution, two sponges were soaked in lemon juice or deionized water for one minute, one sponge was heated in a microwave for one minute, and another sponge was placed in a dishwasher operating with a drying cycle. Researchers left one sponge untreated to use as a comparison against the five cleaning techniques.

Best cleaning method      

Findings indicated after soaking in the bleach solution, lemon juice or deionized water, enough bacteria still remained on the sponges to potentially cause disease. The microwave heating and dishwashing with a drying cycle proved to be the most effective methods for inactivating bacteria, yeasts and molds on sponges.

Microwaving sponges killed 99.99999% of bacteria present, while dishwashing killed 99.9998% of bacteria.  These simple and convenient treatments can help ensure that contaminated sponges don’t spread foodborne pathogens around household kitchens.

Cleaning vs. Disinfecting

Remember that cleaning and disinfecting are not the same thing. Cleaning removes germs from surfaces, and disinfecting destroys them.  Cleaning with soap and water to remove dirt and most of the germs is usually enough.  But sometimes, you may want to disinfect for an extra level of protection from germs.

You should clean and disinfect counters and other surfaces before, during and after preparing food – especially meat and poultry.  Follow all directions on the product label, which usually specifies letting the disinfectant stand for a few minutes.

Use paper towels that can be thrown away to keep bacteria from contaminating your sponge or dish cloth.  Another idea is a disposable sanitizing wipe that both cleans and disinfects. If you use a sponge, be sure to sanitize them regularly, either by microwaving for one minute, or running through the dishwasher using the drying cycle.


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