Your Kitchen Sponge Is Much, Much Dirtier Than You Think

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Your Kitchen Sponge Is Much, Much Dirtier Than You Think — Here’s What to Do About It

Fact: Salmonella, Staphylococcus aureus, and E. coli can live up to 16 days in it.

By Guy Martin

Published on July 21, 2024

https://www.foodandwine.com/how-to-clean-a-sponge-8679491

A soap sponge in a photo composite with Salmonella bacteria.

Photo:

Food & Wine / Getty Images

When laboratories want to grow salmonella or E. coli bacteria for research, they create warm moist environments with plenty of nutritious muck for the pathogens. Seen from the perspective of the bacteria, our kitchens are quite accurate copies of those lab environments: super-cozy rooms in which there’s plenty of bio-nourishment to feast upon — on our prep and cooking surfaces, in our sinks, on our implements, and most specifically, on and within our kitchen sponges.

The shortlist of bacteria that can bloom in an ordinary sponge reads like a who’s-who of pathogens that cause us serious problems: Salmonella, Campylobacter, Staphylococcus, E. coli, and Listeria.

The research from the American Society for Microbiology is even more pointed. Salmonella, Staphylococcus aureus, and E. coli can live up to 16 days on or in a kitchen sponge. The institute’s bacteria-growing experiments included microfiber dishtowels, which are almost as bad at 13 days.

FYI, Your Kitchen Is Probably Dirtier than a Toilet Seat

Turns out that hauling all of our grand comestibles into our kitchens and cooking beautiful meals with them is a dirty job. It’s not exactly breaking news that the world is full of bacteria riding right alongside us. The noble crusade of bacteria murder is a forever war. The “sponge problem” is the textbook example of, first, the need for vigilance and focus in the fight. Working against us is our innate laziness. On the long list of things that are of paramount importance, day in and day out, cleaning the sink-side sponge — as we’re tuckered out from the daily grind and have just gotten the kids fed — is not high on the list.

It should be.

The job of a sponge is to be your pots’ and pans’ garbage truck for bio-waste. From the point of view of the bacteria, who do not care about what use you have for the thing, the sponge is that special place in your kitchen that never dries out, is repeatedly made warm, and most dangerously, regularly has its food muck supply replenished every time you clean a pan or a dish or wipe a prep surface with it. In this sense, all human activity with and about the lowly sponge means that we cater to the bacteria as precisely and hospitably as Swiss hoteliers.

There are plenty of latter-day Hints From Heloise for shutting down the bacteria hotel, and we’ll get to those. But the first main step to take in the fight is to change the way we think about sponges. Kitchen-borne pathogens like being alive, which means that they will take any opportunity, to ensure their own survival, as all bacteria do. That, in turn, means that your own household Campylobacter and Salmonella attack squads will keep on battling for their survival when the kitchen has (according to you) been cleaned and you’ve retired to your Barcalounger.

So, here are seven simple hacks for cleaning your sponges and keeping them that way. They’re not labor-free but they are easy — and the point here is to get into the habit of doing them while you’re in the kitchen doing something else.

Dry them out.

First, a general tactical rule of the road: Don’t stack your sponges atop each other sink-side, and certainly don’t marinate them in a soap dish. Between uses, they need a shot at drying out. Got a dishrack? Store your sponges vertically in there as you finish the washing up and head for that well-deserved Johnnie Walker Black on the rocks.

Use baking soda.

Baking soda. Take a little bowl and make a paste from a couple of tablespoons of baking soda and a bit of water and swish your sponge around in it for a few minutes. Squeeze and let dry. Baking soda is a base or alkaline compound, which means it cleans by raising the pH. Note: A baking soda bath won’t completely disinfect your sponge, but it’s a good start in making them hostile to bacteria. Its crystals form an abrasive, which is why it’s also good for cleaning pans or surfaces without scoring them.

Vinegar works too.

Vinegar, which is acidic, will dramatically lower the pH in your sponge — and it’s more hostile to bacteria than baking soda. A full-strength white vinegar bath for five minutes in a dish or a small bowl is recommended. Estimates vary, but vinegar baths have been judged to kill some 99.6% of bacteria. As with baking soda, vinegar’s delightful edibility is key.

Bleach can be your friend, but make sure to rinse it out thoroughly.

A bleach bath, which researchers agree can kill just about anything, including you, is what we might call the nuclear option. As such, it’s a double-edged sword because it’ll take more than a few rinses to flush the sponge of bleach. Recommended is three-quarters of a cup of bleach in a gallon of water (or three-sixteenths of a cup in a quart), which is a fairly low intensity, but it does have a kill rate of 99.9%. Bear in mind that you’re using these sponges to clean the pans and the implements with which you cook. On balance, the effective difference between a vinegar bath and a bleach bath is three-tenths of one percent. Go for the vinegar.

You can go the microwave route.

Disclaimer: I’m not a huge fan of microwaves for anything, including thawing out frozen food, reheating leftovers, or actually cooking something that you would like to eat. But the U.S. Department of Agriculture research shows that radiation does kill an extremely high percentage of bacteria(99.9% to be precise). If you have the machine, by all means, don’t let us stop you from tossing your sponges in. Remember: No sponges with scouring pads containing metals attached! If you don’t have a microwave, please don’t use this as an excuse to run out to Costco and dump a couple hundred down the drain on one. There are better culinary uses for that money.

Hot water helps.

By itself, boiling your sponge for a few minutes reduces its bacterial load. The folks who did the microwave test note that, after you clear the people who have pacemakers out of the kitchen while the oven irradiates your sponge, you’re still confronted with the dead bacteria in the sponge when you pull it out. The point is that dead bacteria are, in fact, food (for bacteria). This is not a problem you face with the baking soda, vinegar, or bleach baths since you will be routinely rinsing and squeezing the sponges out.

The dishwasher is an option.

This is like boiling, but letting the machine do it for much, much longer. Some folks do love their dishwasher. Saves a lot of grinding and can even save water in the process of doing a big dinner party’s stack of scullery. And, used with the drying cycle at its hottest, it has a similarly high bacterial kill rate to the microwave, beyond vinegar baths, at 99.9%. But here again, your simple hand work on a sponge can come very close to the dishwasher’s accomplishment, while saving many multiples of time, energy, and water. Finally, there’s this simple fact: Your hand can squeeze the sponge as you rinse it to flush out the dead bacteria. Fancy as they have gotten — and they have gotten fancy — dishwashers haven’t yet been trained to squeeze dead E. coli from a sponge.