Black beans and red beans have tannic acid. Fruits such as apricots, cherries, peaches and dates also contain tannic acid as well. English walnuts, black walnuts and cashews also have tannic acid.
Certain berries, such as blueberries, blackberries and strawberries; chocolate, tea and coffee; spices such as cinnamon, cumin, oregano and turmeric; and apple juice all contain tannic acid. Tannic acid may also be present due to a flavoring agent, such as in beer due to the use of hops. Barley flour contains high levels of tannic acid, so certain bread products may have more of this chemical than expected.
The U.S. National Library of Medicine mentions that tannic acid has low nutritional value, but further studies indicate that certain cancers such as esophageal cancer are linked to tannic acid foods like herbal tea and betel nuts. However, other research shows that tannic acid is potentially anti-carcinogenic and antimutagenic. Tannic acid also has antimicrobial properties that combat microbe infections and fungus in fruits. Tannic acid can also serve as an agent in preserving the shelf-life of certain foods such as catfish fillets. Other properties have been documented in tannic acid, such as the reduction of blood pressure and the acceleration of blood clotting.