If you found mold growing on a block of tofu in your fridge, throw it away. That mold is not safe to eat, and you cannot salvage the tofu by cutting the moldy parts off. However, if you’re asking about fermented “moldy tofu,” a traditional Chinese delicacy also called furu or sufu, that’s an entirely different product made under controlled conditions and is safe when produced properly.
The distinction matters because the word “moldy” describes two completely different situations: one is spoilage, the other is intentional fermentation. Here’s how to tell the difference and what you need to know about each.
Mold on Regular Tofu Means Spoilage
Tofu is a high-moisture food, which makes it an ideal environment for mold, bacteria, and other microorganisms. When mold appears on regular tofu that’s been sitting in your fridge, it’s a sign of spoilage. The fuzzy patches you see on the surface are only part of the problem. Mold sends root-like threads deep into the food it grows on, and in high-moisture foods like tofu, those threads can penetrate well below the visible surface. Bacteria also grow alongside the mold, spreading through the same moist environment.
This is why the USDA recommends discarding high-moisture foods entirely when mold appears. Unlike hard cheese, where you can cut an inch around the mold and safely eat the rest, tofu’s soft, porous texture gives mold and bacteria easy access to the interior. No amount of trimming makes it safe.
The mold species that colonize spoiled tofu can include strains that produce mycotoxins, toxic compounds that are harmful even in small amounts. Certain species in the Aspergillus family, for example, produce aflatoxins, which are classified as carcinogenic. These toxins are chemically stable and resist cooking. Research on heat treatments shows that boiling, frying, and even industrial processing typically reduce mycotoxin levels by 40 to 80 percent, but never fully eliminate them. Cooking moldy tofu does not make it safe.
How to Spot Spoiled Tofu
Fresh tofu should be white or off-white, with a mild, slightly sweet smell. Any of the following signs mean it’s time to discard it:
- Fuzzy spots in any color. White, green, black, or pink fuzz on the surface is mold growth. Pink mold in particular is a common sign of active spoilage on many foods.
- Slimy texture. A slippery film on the surface indicates bacterial growth, even if you don’t see visible mold yet.
- Sour or off smell. Tofu that smells noticeably sour, bitter, or unpleasant has started to break down.
- Discoloration. Yellowing, darkening, or any color change beyond the normal off-white suggests the tofu is past its prime.
- Bloated packaging. Gas buildup inside a sealed package means microorganisms are actively producing byproducts.
If the water your tofu is stored in looks cloudy or has an odor, that’s another red flag. Even if the tofu itself looks fine, contaminated water means bacteria have been multiplying.
What Happens If You Eat Spoiled Tofu
Eating tofu contaminated with spoilage bacteria or mold can cause food poisoning. Symptoms typically start within hours to a few days and include nausea, vomiting, diarrhea (sometimes bloody), stomach cramps, and fever. Most cases resolve on their own within one to three days, though the experience is miserable.
The timeline depends on which organism you ingested. Staphylococcus bacteria can trigger symptoms in as little as 30 minutes. Salmonella takes 6 hours to 6 days. E. coli typically causes illness in 3 to 4 days. In rare cases, food poisoning affects the nervous system, causing blurred vision, tingling, or weakness, which requires immediate medical attention.
People with mold allergies face additional risks. Inhaling mold spores from spoiled food can trigger sneezing, runny nose, itchy eyes, and coughing. For those with mold-related asthma, exposure can cause wheezing, shortness of breath, and chest tightness. In severe cases, mold exposure can lead to allergic fungal sinusitis or a rare condition called hypersensitivity pneumonitis, an inflammatory reaction in the lungs.
Fermented Moldy Tofu Is a Different Product
Fermented tofu, known as furu, sufu, or chao in various Chinese and Southeast Asian cuisines, is sometimes called “moldy tofu” because mold is a deliberate part of the production process. Producers inoculate blocks of tofu with specific, food-safe strains of mold from the Mucor, Rhizopus, or Actinomucor families. Over about four days, a dense white layer of mold grows on the surface, breaking down proteins and fats and creating the product’s characteristic creamy texture and pungent flavor.
The process is tightly controlled. Temperature, humidity, and the specific mold strains all matter. After the initial mold growth, the tofu is cured in brine, rice wine, chili paste, or other seasonings, which halt the mold’s activity and preserve the product. The result is a fermented condiment with a flavor profile ranging from mild and creamy to intensely funky, depending on the style.
Stinky tofu, a related street food, relies on a different microbial community. Its fermentation brine is dominated by bacteria rather than mold, with species that break down amino acids to produce its famously pungent smell. Fungal species make up only about 5 percent of the microbial community in stinky tofu brine.
Both products have long safety records when made by experienced producers. The key difference from accidental spoilage is control: the mold strains are selected for safety, the environment prevents harmful bacteria from taking hold, and the curing process adds an additional layer of preservation.
When Fermented Tofu Can Go Wrong
Homemade fermented tofu carries real risks if the process isn’t carefully managed. If the environment isn’t properly controlled, harmful bacteria can grow alongside or instead of the intended mold. Without the right temperature and humidity, you can’t guarantee that the mold growing on your tofu is a safe strain rather than a toxin-producing one.
If you’re interested in making fermented tofu at home, use a starter culture from a reliable source rather than relying on wild mold from your environment. Follow established recipes that specify temperature ranges and fermentation times. Any unexpected colors (green, black, or pink patches rather than uniform white fuzz), foul smells beyond the expected pungency, or slimy textures are signs something went wrong.
Commercially produced furu and fermented tofu products sold in jars at Asian grocery stores are safe to eat. These are made in facilities with standardized processes and quality controls. Once opened, store them in the refrigerator and use clean utensils to prevent introducing contaminants.
How to Store Tofu to Prevent Mold
Unopened tofu keeps until its expiration date when refrigerated. Once you open the package, submerge leftover tofu in fresh water in an airtight container and refrigerate it. Change the water daily. Stored this way, opened tofu stays fresh for 3 to 5 days.
Freezing extends tofu’s life to 3 to 5 months. The texture changes, becoming chewier and more sponge-like, which some people actually prefer for stir-fries and soups. Silken tofu doesn’t freeze as well as firm or extra-firm varieties.
If your tofu repeatedly develops mold before its expiration date, check your refrigerator temperature. It should be at or below 40°F (4°C). Tofu stored above this temperature spoils much faster, and mold thrives in warmer, moist environments.