The Dangers of Expired Soy Products

Fresh soybeans.
Raw soybeans should be bright green and firm. (Image: luknaja/iStock/Getty Images)

Soybean-based products are nutrient rich with high amounts of protein and a full amino acid profile, making them an excellent protein choice for vegetarians. Soy products that include tofu, soy milk and soy meats are healthful sources of protein that are easy to incorporate into your diet. The dangers of eating expired soy products are not as severe as those associated with meat, but expired soy can still make you sick.

Soy Sauce

This condiment, common in East Asian cuisine, is known for its dark, rich, salty flavor. Largely owing to its high sodium content, soy sauce shelf life is much longer than that of other soy products. If unopened, a bottle of soy sauce can last for years without going bad. While this is shortened to three months if it's opened, no dangers are associated with eating expired soy sauce.

Soy Milk

Similar to dairy-based milk products, soy milk has a relatively short fridge life once opened. Fresh for seven to 10 days after opening, refrigerated soy milk cartons begin to bloat once they begin to go bad. This bloating stems from the gas output of molds and bacteria feeding on your milk, causing it to change in color, become lumpy and smell sour.

Signs of soy milk expiration are similar to those of dairy milk, and drinking spoiled soy milk can cause reactions similar to those associated with spoiled milk. Although the side effects are not serious, drinking expired soy milk can lead to symptoms of food poisoning such as upset stomach, diarrhea, nausea and vomiting.

Soy "Meat"

With a taste and texture similar to that of meat, soy-based replacements for almost any meat product can now be found at grocery stores and vegetarian restaurants. Fortified with minerals similar to those found in meat products, soy meats are often made with wheat as a binding agent. To know when your soy meats have expired, look for a slimy texture and sour smell. These signs indicate that a mold is growing on, and possibly in, your soy meats.

The dangers of eating expired soy meats that contain wheat can be more serious than those of other soy products. Though rare, the presence of molds called mycotoxins, such as the potentially cancer-causing aflatoxin, can lead to serious stomach illnesses with chronic, long-lasting symptoms similar to those of food poisoning.

Soybeans and Edamame

Edamame is a Japanese snack made by boiling and salting entire pods of fresh soybeans. Similar to other fresh vegetables, beans and legumes, edamame has a short fridge life. Spoilage in edamame is indicated by a change in color and texture, with bruising and the development of a light fur on the surface indicating the presence of mold.

While dry soybeans only become soft and develop a poor taste after expiration, eating raw soybeans that have expired may lead to symptoms of mild food poisoning similar to those associated with drinking expired soy milk. Although such dangers are limited, you should never consume expired soy products if you think they've gone bad.

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