Washing the dishes is probably at the top of the list of chores that are bound to cause friction — who does it, how they do it and whether they can pile and leave them in the dish rack. And then there’s soaking, perhaps one of the most contentious parts of the process.
Does letting your dishes sit around with water actually make them easier to clean, or is it merely a ploy by the lazy to delay or evade the task at hand?
A recent Twitter thread got me thinking.
I’ve said it before and I’ll say it again. Leaving dishes to soak is the biggest con in the game.— Kim Severson (@kimseverson) September 10, 2021
Alas, the answer is not a simple yes or no. Read on, whether you’re ready to feel vindicated or willing to stand corrected.
Some background. Soaking is a go-to strategy when food becomes stuck to a pan in the natural course of cooking or, more likely, burning. As food is cooked, its water is driven out, says Melvin Pascall, a professor of food science and technology at Ohio State University. The molecules of the food get closer and closer to each other and the surface of the pot or pan. The food adheres to the cooking vessel.
High heat (and burning) can cause further chemical changes in certain foods, in which their molecules can polymerize, forming extremely powerful links that are very much like plastic. In some cases, other foods may undergo pyrolysis and charring, developing a blackened hue. “The more the food is burned, the more difficult it is to remove it,” Pascall says. Now you have to work extra hard to get it off. And this is where soaking can help.
What water does. “If you soak in water, then what you’re trying to do is reverse the process,” Pascall says. The water makes its way back in between the food and the pan, acting almost like a wedge to help lift the food from the surface. Warm or hot water is more effective at this, Pascall says.
How well soaking works depends in part on the type of food. Many of us recall at some point in our education being taught that water is the universal solvent. The reality is more nuanced. Water “has its limitations,” Pascall says.
It is very good at dissolving certain carbohydrates, especially residues from fruits, vegetables and, as anyone who has dabbled in caramel can attest to, sugar-based foods. (Starches from such foods as flour or oatmeal can actually be harder to remove once wet.) But not everything is water-soluble. Fats, or fat-soluble ingredients, can stubbornly resist being removed by water, much as oil and vinegar will separate in a salad dressing.
Many foods are not all fat- or all water-soluble. Some are naturally an emulsion, or a mix of water-soluble and fat-soluble components, such as dairy. In one study, Pascall found that the most difficult ingredient to wash away was burned buttermilk. Other foods are emulsions created in the kitchen, such as mayonnaise or cake batter. Water may only partially remove a food with fat- and water-soluble components, leaving behind a thin film of fat on the surface of a dish.
Thankfully, we have a few tools to help. Dish soap — really a detergent — includes surfactants, which can grab onto water and fat. So a squirt of dish soap in your soaking water will help lift off and wash away fats, though the soaking provides little advantage over just using soap to wash right away. For really burned-on messes, try soaking with baking soda. Pascall says that warm or hot water will activate the baking soda, triggering a reaction that results in carbon dioxide. As it fizzes, the carbon dioxide can help loosen food particles from the surface of the pan.
How the pan affects things. The material of the pot or pan impacts how much food might stick to it and how much, or whether, soaking will help. Metal pans, such as stainless steel and aluminum, have microscopic pits and grooves where food can settle and stick, as well as a high surface energy, meaning they will more readily bond with the food, causing it to adhere to the surface. That also means it will take more energy to break the bonds between the pan and the food, so you’re likely in for a combination of soaking and scrubbing.
Nonstick pans, well-seasoned cast iron, ceramics and glass (in enamel-coated cookware or something like Pyrex) are smoother with lower surface energies, which means they will clean easier. They may even require no soaking at all. The degree of heat plays a role, too, so even a nonstick pan may demand more effort or soaking time for blackened food. Plastic also has a lower surface energy, though its use as a cooking medium is limited (commercial nonstick coatings and cast-iron seasoning, however, are both plasticlike polymers).
When you should not do it. Certain materials should not be soaked in water. Wood is one of them, says Jason Bolton, extension professor and food safety specialist at the University of Maine Cooperative Extension. Soaking wood in water, whether that’s your cutting boards, wood-handled knives or spoons, can damage it and provide a nice little breeding ground for bacteria. Cheaper plastic may degrade with repeated soaking over time, Bolton says.
Another big no-no: Soaking cast iron. Even with well-seasoned cookware, you run the risk of causing the metal to rust. Stick with a quick wash of warm water and mild soap, which won’t remove the seasoning, and dry right away. For stuck-on messes, scrub with a chain-mail scrubber designed for the task or coarse salt mixed with a bit of water.
Dishes with large amounts of fat in them, such as a roasting pan from your Thanksgiving turkey, are not necessarily going to benefit from soaking, Bolton says. Since water alone won’t dissolve that fat, you may just end up with fat deposits interspersed in the water. Sending large amounts of fat down the drain is bad for pipes, too (see: fatbergs). Instead, pour off — ideally into a sealed container for disposal — and wipe out as much as you can before washing with soap and water.
Food safety considerations. If your primary argument against soaking is concern about turning the sink into a bacterial soup, here are a few things to put your mind at ease. While your food can conceivably feed bacteria as well, Pascall notes that some bacteria need free oxygen to survive, and those will not proliferate in water. And even anaerobic bacteria that do not require free oxygen should be eliminated by washing with soap, especially after just a brief soak.
Bolton’s main concern is cross-contamination, from the sink to the dishes or vice versa, as well as between different dishes. This is a particular concern if you’ve been working with raw meat. The sink is a hive of activity, including where you wash your hands and get a glass of water, situations where you would not want to be exposed to bacteria from a pile of dirty dishes under the faucet. To reduce the likelihood of cross-contamination between the sink and dishes, consider soaking them in a separate, clean basin or bowl in the sink or filling the dish with soapy water rather than filling the entire sink. Deal with dishes that have made contact with raw meat as soon as possible. Wash down the sink and dishes with soap and hot water. Bolton suggests sanitizing the sink with a diluted bleach solution as well. If you’re using store-bought cleaners, be sure to select one designated for kitchens (not bathrooms!) and follow the instructions.
Other considerations. Overloading a sink with soaking dishes can damage the sink as well as the equipment. You risk scratching or denting the sink and breaking or chipping your pots, pans and bowls. A pile of sudsy dishes can pose a safety hazard as well, if the water obscures sharp objects such as knives or box graters. And soaking skeptics are right about the mind-set — it is easy to procrastinate or ignore the task at hand once you fill the sink and walk away.
The bottom line. By now it should be clear that soaking can be helpful in certain, but not all, situations. “What I would say is in the first place, don’t burn the food,” Pascall says. But no one’s perfect, so the next piece of advice: “Clean your dishes as quickly as possible.” Let them soak just long enough to make the job easier and not any more — we’re generally talking under an hour. It’s the best way to take care of your equipment, your sink, your safety and, perhaps most importantly, your household relationships.
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