Tag Archives: sponge

What to do with the sponge

Posted on by
Reply

The kitchen sponge has been gaining a lot of traction lately in food safety media that stemmed from the recent German study that analyzed 14 sponges. Don Schaffner provided his expertise regarding the validity of the study on Barfblog earlier.

It is no surprise that sponges harbor bacteria, what is surprising is all of the conflicting messaging on what to do with them. Food safety messaging needs to be rapid, reliable, relevant and repeated. Unfortunately it is not just food safety messaging on social media, inconsistency exists within food safety Regulations in Canada compounding the problem further. But that’s a whole other blog.

A study conducted in 2007 evaluated different disinfection methods to reduce bacteria, yeasts and molds on kitchen sponges (1). Sponges were soaked in 10% bleach solution for 3 min, lemon juice (pH 2.9) for 1 min, or deionized water for 1 min, placed in a microwave oven for 1 min at full power, or placed in a dishwasher for full wash and drying cycles, or left untreated (control). The study showed that microwaving or placing the sponge in a dishwasher significantly lowered aerobic bacterial counts on sponges more than chemicals and control.

Doug Williams of the The San Diego Union Tribune writes:

As a longtime food safety consultant, teacher and inspector, Robert Romaine has seen plenty of disastrous and dirty commercial kitchens.
He knows the menacing microbes that make us sick and has seen the evils lurking in kitchen corners.
So, he has a couple of rules. One, avoid potlucks. Who knows how that chicken salad was prepared. And two, when invited to a friend’s house for dinner, put the blinders on.
“When I’m visiting someone, I try not to hang around the kitchen,” says Romaine, who owns Food Safety Consulting in San Diego. “Sometimes I know too much, and I just don’t want to know what’s going on in there.”
The dangers are many, from improper refrigeration to cross contamination. But recently, there’s been an added focus on kitchen sinks and counters and the way people keep them clean — or don’t.
Yet as Romaine notes, precautions can easily be taken in our home kitchens to lessen the dangers of contamination.
Take that disgusting sponge, for instance.
“If a person is careful and actually knows they got the sponge up to 180 degrees (when cleaning it), nothing’s going to live,” he says. The key is being certain the temperature is high enough, not just warm but lethally hot. Federal government guidelines suggest 165 degrees as the minimum temperature for killing bacteria. A food thermometer can be used to test that sponge after microwaving. Adds Joyce Wilkins, who taught food safety for years in San Diego through her business, Safe at the Plate: “Yes, the sponge is fairly disgusting. All bacteria, all organisms die at 165 degrees, so if you heat it up hot enough to burn you in the microwave, you will kill it.”

Wilkins, in fact, discourages the use of a sponge and suggests buying a pack of 10 dishcloths instead and using a fresh one every 24 hours. “The big issue is dampness,” she says. “Bacteria need water to survive, and if the cloth is dried out each time,” it helps prevent bacteria growth.

Romaine suggests using paper towels instead of cloths or a sponge for cleanup, especially after preparing meat or chicken. Paper towels can be thrown away so bacteria can’t be transferred. “Obviously, if you just cut up raw chicken, you don’t want to use a household sponge for that,” he says. “But if you’re just wiping up debris from cutting up bread or vegetables, that’s not very harmful.”

Wilkins also will use isopropyl alcohol to clean surfaces, along with a stiff-bristled brush instead of a sponge. A cutting board used to prepare chicken, for instance, will be scrubbed with a brush and hot, soapy water, then treated with some of the alcohol to kill remaining germs, rinsed and allowed to air dry. The same system can be used for countertops, where a brush can dislodge the bio film that can build up over time (and not be rubbed away with a sponge or cloth).
Instead of using a dishtowel to dry just-washed plates and utensils — a towel that may have been used to dry hands or wipe a countertop — allow those plates and utensils to air dry.

Do not use isopropyl alcohol to clean surfaces, washing with soap and water applying friction is good enough.

1. Manan Sharma , Janet Eastridge, Cheryl Mudd. 2007. Effective household disinfection methods of kitchen sponges. Food Control 20 (2009) 310–313

The attack of the kitchen sponge

Posted on by
1

This brings me back to my Kitchen Crimes days when we analyzed dishcloths and sponges from 13 Winnipeg homes and confirmed the presence of pathogenic microorganisms. Given that bacteria are all around us and providing a medium that is moist, porous and contains food particles left at room temperature, the following is not surprising.

Peter Dockrill of Science Alert writes

Scientists in Germany have conducted what they say is the world’s first comprehensive study of contamination in used kitchen sponges, and it backs up we already feared: these soggy, porous ‘cleaning products’ are positively teeming with living bacteria.
Researchers led by Furtwangen University ran genetic sequencing on samples from 14 different used kitchen sponges and ended up finding 362 different types of bacteria happily lounging within all that comfortable, springy foam.
Fortunately for you and me, the majority of this bacteria was in fact not harmful – but some of it was.
“What surprised us was that five of the ten [types] which we most commonly found, belong to the so-called risk group 2 (RG2),” says lead researcher, microbiologist Markus Egert, “which means they are potential pathogens.”
These included Acinetobacter johnsonii, Moraxella osloensis, and Chryseobacterium hominis – which the researchers say can lead to infections – plus Acinetobacter pittii and Acinetobacter ursingii.
Of these, bacteria in the family Moraxellaceae was the most dominant kind found, backing up previous research on sponges.
Since Moraxellaceae is also common on human skin, the researchers speculate that it might be people touching sponges that introduces this particular contamination.
It’s also that we insist on then wiping these dense bug-ridden colonies over other, potentially clean surfaces in the house, including bench tops, appliances, and kitchen sinks.

What I would find more interesting is how much of what is on the sponge actually transfers over to a dish after the application of a detergent followed by a warm water rinse.

In addition to the sequencing, the team was able to visualise the presence of bacteria in the samples in 3D using a technique called fluorescence in situ hybridisation coupled with confocal laser scanning microscopy (FISH–CLSM).
The visualisations reveal how the large surface area, moist foam, and scattered food matter within the sponge provide the perfect, incubating habitat for bacteria.
So much so, in fact, that it’s almost hard to differentiate where the sponge (blue) stops and the bugs (red) start:
“Sometimes the bacteria achieved a concentration of more than five times 1010 cells per cubic centimetre,” says Egert.
“Those are concentrations which one would normally only find in faecal samples. And levels which should never be reached in a kitchen.”

The authors recommend changing the sponge on a weekly basis. Dischloths are no better.

Killer dishcloths cycling through media spin

Posted on by
Reply

Press release before publication. Again.

And it seems to plague stories about dishrags or dishcloths or sponges or whatever they’re called; those things used to wipe up stuff in the kitchen.

In 1995, the front-page of Toronto’s Globe and Mail screeched, “Warning: your kitchen dishrag is a killer. … you probably handle an unimaginably dangerous collection of harmful bacteria" while going about your kitchenly chores, and that "90 per cent of food-related illness in the home could be prevented by using paper towels when preparing foods, especially meats."

That was Dec. 1995. The paper describing the research was eventually published in 1997.

Today, Safefood Ireland sent out a strinkingly similar press release with strikingly similar flaws.

And the Irish Examiner went with a similar lede.

A total of 27% of household dishcloths were found to contain the raw meat bacterium E. Coli, in a recent study.

According to research from Safefood, listeria was also present on 14% of cloths analyzed by scientists.

The research shows that although one-third of consumers who re-use dishcloths clean them in bleach and almost one in four wash them by hand, neither method is effective at removing the germs that cause food poisoning.

Safefood is reminding people that cloths must be cleaned in a washing machine on a temperature of least 30 degrees or else boiled for 15 minutes to effectively kill germs.

I’m not sure of the validity of those statements: Safefood cites some research, but it doesn’t appear to have been published anywhere; and if it has, PR 101 would be to include the reference on the press release.

Instead the PR contained this:

References:
1. ‘Assessment of the ability of dishcloths to spread harmful bacteria to other kitchen surfaces and determination of the effectiveness of various dishcloth cleaning regimes’. safefood/Prof David McDowell; University of Ulster; Jordanstown
2. ‘The microbiological status or household dishcloths and associated consumer hygiene practices’. safefood/ Eolas International, 2011

There’s lots of research out there, but the information presented in this press release is difficult to assess. What is the quantitative difference between rinsing a cloth or sponge before use, and the dishwasher? Were the numbers derived from self-reported responses or actual observation (people lie)? Can the actual risk of cross-contamination from such cloths be modeled in a risk assessment?

When I use a sponge or dishcloth, I habitually rinse it first, which does not eliminate but may reduce bacterial loads. Dish clothes and towels get swapped out 1-2 times a day, and sponges go in the dishwasher about every third day. When dealing with raw meat, the sponges or clothes are swapped out immediately. Pete Snyder makes similar recommendations.

The 1995 killer-dishrag story met the primary goal of its creators: to sell more sponges. Specifically, anti-bacterial sponges manufactured by 3M Co. of Minneapolis, Minn.

Dr. Charles P. Gerba, an environmental microbiologist at the University of Arizona in Tucson, was contracted by 3M to perform tests of household dishrags and sponges in five U.S. cities and compare the results to the 3M sponge. Dr. Gerba found about 100 times more bacteria in dishrags retrieved from households.

Then the public relations firm hired by 3M peddled the results, taking Dr. Gerba on a five-city tour to release the results. That was in Aug. 1995. Several stories appeared on the U.S. wire services. Why the Globe decided to run the story at the end of Dec. 1995 remains a mystery.

Some may argue the end justifies the means, that any message promoting the safe handling of food in the kitchen is good. Except that stories which overstate a risk have been shown to do more harm than good. It’s called the boomerang effect. If a message is oversold or overstated, people stop believing. With killer sponges, the message is more harmful than the bacteria; unless properly validated.