Fermented beans are those that have been dried and then fermented with various spices and salt. These types of beans are most commonly used in Asian cooking. Many different types of beans can be fermented, including soy beans, green beans, and black beans, among a number of others. All types of fermented beans have their own unique flavor and texture.
Nearly all beans are high in sugars and starch. When beans are fermented, bacteria — or, less commonly, yeast — convert the natural sugars and starch into lactic acid. This process increases the digestibility of the beans as well as their vitamin levels.
Often referred to as Chinese black beans or salted beans, black beans are actually made from black soy beans which have undergone the fermentation process. When purchased, these beans are most often sold in their dried form and must be rinsed before they are used due to their high salt content. They can be served whole or they can be soaked or mashed before they are used. Black bean sauce, a common ingredient in many Chinese recipes, is made from these fermented beans.
Fermented soy beans, which have undergone a slightly different fermentation process than Chinese black beans, are a rich brown in color and have a very strong scent. Popular in Japan, these beans are commonly referred to as natto. They are often served for breakfast along with sticky rice.
Dilly beans are green beans which have been pickled or fermented. These type of fermented beans have been soaked in a water and salt bath with spices added to it until they begin to oxygenate. This will be evidenced when the beans start to give off tiny bubbles of air signaling the fermentation process has begun. Dill is added to the water and salt solution, which is how these fermented beans get their name. Dilly beans are a popular addition to a bloody Mary cocktail in lieu of a stick of celery.
Yellow wax pole beans are also often fermented. Similar to the dilly beans, these beans are fermented in water and spices, usually including garlic. The garlic contrasts well with the flavor of the wax poll bean, which can tend to be a bit flavorless for some. These beans are often added to salads or they can be served in place of pickles along side a hamburger.