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If you notice an odor when you open your refrigerator, it might be time for a deep clean. But even immaculate shelves and crystal clear crisper drawers won’t save your fridge from that not-so-fresh smell if you frequently fill it with fancy cheese and fragrant leftovers.
For most people, the solution is a box of baking soda.
Known scientifically as sodium bicarbonate, baking soda is an incredibly versatile kitchen staple. A necessary component of airy baked goods, it can also be helpful for getting that perfect golden brown color on bagels, taming the acidity in tomato-based dishes, and quickly softening legumes. And when your refrigerator starts to reek of all of those things (or worse), you can just tear open a box of baking soda, stick it in the door, and wait for it to deodorize the stench.
It’s a housekeeping hack that has stood the test of time because it works. But contrary to the story we’ve all been sold, baking soda doesn’t make your fridge smell better by “absorbing” unpleasant food odors. In fact, according to Georgia Institute of Technology chemistry professor Anthony Rojas, the neutralization actually happens outside the box.
How baking soda makes your fridge smell better
The science behind baking soda’s deodorizing properties is an acid/base reaction. In this case, the food (no matter how bland) is the acid, and the baking soda is the base. To fully comprehend how this works in the fridge, it’s first important to understand that everything we eat is constantly in a state of flux.
As Rojas explained over Zoom, the microorganisms in food are always undergoing chemical processes that affect odor, appearance, and taste. At the same time, molecules are also traveling from the surface of those foods into the atmosphere, and the worst smells are often caused by the oxidation of those foods’ fatty acids. In other words: they’re the gaseous by-products of decay (and unless you have a live lobster or living basil plant in your fridge, everything in there is already in a state of decay).
Enter baking soda, which chemically speaking, is a base. If you happen to keep a box of it anywhere in your fridge, then there are microscopic sodium bicarbonate particles constantly rising up out of that box and moving around through the air, even if you can’t see them. Your refrigerator’s built-in fan gives them an added boost, as do you every time you open and close the door or rearrange a shelf, especially if you jostle the box.
And this is where the chemistry really happens, because those baking soda particles are attracted to the stinky food molecules…in a Fatal Attraction kind of way.
“Baking soda ‘attacks’ the molecule responsible for the smell,” Rojas says. “In doing so, it steals away an atom, thus chemically changing the structure of the odor molecule into one that smells differently.”
In other words, baking soda neutralizes food smells, and it does so in the air—not the box.
How to use baking soda more effectively in the fridge
Because microscopic particles can penetrate cardboard, you could put an unopened box of Arm & Hammer in the fridge and baking soda would still manage to escape and neutralize odors. Eventually. Venting the top or using a fridge-specific product with a larger, mesh-covered panel simply allows the process to happen much more quickly because when more surface area is exposed, more particles are able to escape at once.
If the contents of your refrigerator are extra pungent, or if you want faster results, think outside the box and place smaller containers of baking soda on every shelf. It will give the particles more opportunities to enter the atmosphere of your fridge, and they won’t have to travel as far to reach their targets, either.
So how often do you really need to replace the box of baking soda?
Baking soda has been the go-to for combating unwanted food odors since 1972, when Arm & Hammer launched a marketing campaign suggesting folks use their now-ubiquitous orange boxes to keep the fridge and freezer smelling fresh. To keep that momentum going (and the money flowing), the brand began instructing consumers to replace their box every three months.
Around 2008, the messaging was updated to encourage monthly swaps.
The “Change Every 30 Days” edict is now prominently featured on the back of the Arm & Hammer Fridge-N-Freezer box, along with a claim that doing so will result in “fresher tasting food.” In its online FAQ, the brand very clearly states that the recommendation is based on “continuing research efforts to understand the process of odor elimination and odor generation.”
But here’s a little secret Big Baking Soda doesn’t want you to know: Because sodium bicarbonate doesn’t really “absorb” odors, and the neutralization reaction happens outside of the box, you don’t actually need to replace it every month. Or even every three months.
As Rojas puts it, baking soda is only considered “used up” after it’s been part of a chemical reaction. So as long as you can still see the white powder in the container, it will continue to work as a deodorizer.
“Unreacted baking soda would wait in the wings for eternity, ready to jump into action,” he said.
So instead of spending your money on a new box of “fridge” baking soda every month, buy a few fun dispensers, fill them up once, and leave the rest to science. For a while, anyway.