Farm Bulletin: To Soak or Not to Soak

When not wrestling with the great issues of our day (or digging turnips), you can find contributor Anthony Boutard and his lovely wife Carol at the Ayers Creek Farm stand at the Hillsdale Farmers Market. Indeed, they will be there this Sunday, Feb. 8, from 10 am till 1 pm. You can see and hear the two of them in action in a new video from Cooking Up a Story.

In the eight years we have been growing beans commercially, the most frequent and persistent question is whether they should be soaked before cooking. What follows is our answer given from a botanical perspective, a different way to look at the question.

The dry bean, when you first address it, is a living plant in deep dormancy. When you soak the bean, and most other vegetable seeds for that matter, the water breaks the dormancy and starts the physiological process of germination. Enzymes are activated and meristems are awakened. The enzymes start to break down the complex storage carbohydrates into simpler sugars that can be transported to the growth points, the meristem tissues in the root and shoot. Meristem tissues are the botanical equivalent of stem cells; they can be transformed into any type of plant tissue given the correct guiding stimulus.

If fresh, the bean is springing to life within hours. About four months after maturation, the bean begins a slow aging process, and the spring in its step gradually dwindles. In the storage section of the bean, you have a mix of proteins and carbohydrates. These are long, complex molecules, and after a while they begin to cross link and polymerize. As they become entangled, it hard for the enzymes to do their work. The bean won't germinate as quickly or grow as vigorously because some of the food supply is too tangled to use. The bean starts to turn grainy.

The human gut encounters the same problem as the bean's own enzymes; the indigestible stuff creates a touch of flatus in us. Old beans are dead, the germination process will never start, and they will never cook. In our experience, the third spring after harvest, the beans are pretty much worthless as seed.

During the soaking, seed will release various compounds that serve to attract beneficial fungi and bacteria, and ward off attacks by seed predators and pathogens. Most notably, black turtle beans will turn the soaking water inky black. In some beans, these compounds released from the skin are bitter, and detract from the flavor. Others are pleasantly flavorful. For example, we always retain the soaking water from black turtle beans, and pour off the water from pintos. Every variety of bean is different. That said, for most varieties we toss the soaking water.

It is worth noting that the raw garden bean is toxic. A raw bean is unlikely to kill you, but eat enough raw beans and you will suffer. They contain a class of proteins called lectins that cause severe cramping and diarrhea. Blood in the stools, real "House M.D." stuff. Lectins are unaffected by soaking; it takes about ten minutes of boiling to denature those proteins. That is why recipes call for ten minutes of cooking at high flame before turning down the heat and simmering.

Some nutritionists claim that soaking diminishes the beans' nutritional quality, the minerals in particular. Seeds are carefully constructed to assure their survival; leaking precious minerals into the surrounding environment defies logic. The minerals are part of the structure of the bean, and are needed for the growing embryo. The seed coat is not a leaky sieve; it is a very complex living membrane that has evolved to protect the nutritionally rich contents. When seeds exude compounds, as noted above, they have a specific purpose, and the process is active and controlled. It is unclear how soaking would wash out minerals, or deplete the bean in any significant way. We suspect, there is confusion between the soaking water and the cooking water. The heated bean is no longer living, and the cooking breaks down the tissues. The cooking water is a tasty and rich broth of nutrients, in some varieties distinctly sweet, and we always use it.

With this perspective, we generally soak our beans, especially after the New Year. We feel the beans are a bit sweeter and the soaking also improves the texture. The difference is subtle. With soaked beans, it is also easier to judge how much water they need for cooking. This is important because cooking dry beans in too little water leads a bitter flavor.