Tofu is a nutritious, lean source of protein. However, because it meets the criteria to be classified as a potentially hazardous food, certain precautions must be taken to prevent the growth of harmful microorganisms. Microorganisms may grow on tofu itself or in the water that tofu is packed in. Tofu can be safely enjoyed as long as proper refrigeration and storage techniques are followed.
Tofu is made with soy milk that has been treated with a coagulant or a jelling agent such as magnesium chloride or calcium sulfate, to form curds. The curds are pressed together to form blocks of tofu. Tofu is an excellent source of lean protein and is low in sodium, very low in saturated fat and free of cholesterol. Tofu that has been prepared using calcium sulfate provides 13 percent of the daily recommended amount of calcium in a four-ounce serving, according to a January 9, 1991, article in the "New York Times." While tofu has little taste on its own, it takes on the flavors of the ingredients it is mixed with—making tofu a very versatile ingredient.
Incidences of Food Poisoning from Tofu
Incidences of food poisoning from tofu have been rare. In 1982, more than 50 people reported signs of foodborne illness after eating a particular brand of tofu, according to the "New York Times." However, the bacteria had come from the water the tofu was packed in—not the tofu itself. In June 2010, another soy product manufacturer was shut down by the FDA due to improper storage of soy products—products were not being stored at a low enough temperature to prevent microbial growth, according to FoodSafetyNews.com.
Symptoms of food poisoning from foodborne pathogens can include gas, bloating, cramps, nausea, vomiting, fever, headache or diarrhea. Certain precautions can be taken in the store and at home to prevent the growth of foodborne pathogens in tofu.
Tofu can be bought in various forms of packaging. Packaged tofu that is packed in water has an expiration date, which should be checked to assure product freshness. Some stores sell tofu in bulk; blocks of tofu are found floating in large bins of water. This may pose a question of food safety—if the tofu is prepared on the premises, ask if it is prepared daily. Also ask how often the water in the bin is changed, as water can harbor foodborne pathogens. Aseptically packaged tofu has a shelf life of almost 10 months. Tofu sold in this type of packaging does not require refrigeration until after the package has been opened.
Tofu should be stored in the refrigerator below 45 degrees Fahrenheit in order to prevent the growth of harmful microorganisms. Aseptically packaged tofu has a shelf life of 10 months, but once it has been opened it should be refrigerated and used within two days. For tofu packaged in water, open the package, drain off the water, and replace the water with fresh water daily. This type of tofu should be used within a week of opening the package.
Tofu can also be stored in the freezer. If you choose to store tofu this way, it should be thawed in the refrigerator, not on the counter. Once tofu has been cooked, any leftovers should promptly be refrigerated.
Cooking and Serving
Most packaged tofu sold in stores has been pasteurized, packaged and refrigerated. Therefore, packaged tofu should be safe to use without cooking, as long as food safety precautions have been followed. Raw tofu sold in bulk bins poses a higher food safety concern. Since this product has not been pasteurized, it should be cooked to an internal temperature of 160 degrees Fahrenheit prior to consumption, according to Colorado State University Extension. This can be accomplished by cutting tofu into chunks and steaming or boiling it for five to ten minutes.