A note on hard beans

“Hard-seed” beans occur when temperatures are high, but humidity and water supply are low during the growing season. The outer seed coat gets very water-resistant. Hard-seed beans are smaller than normal and can be picked out before cooking.

“Hard-to-cook” beans are normal when harvested, but become resistant to softening when they are stored for a prolonged time (months) at warm temperatures in high humidity. This results from changes in the bean cell walls and interiors, including the denaturation of storage proteins and the formation of a water-resistant coating around the starch granules. There is no way to reverse these changes and no way of spotting them before cooking. Once cooked, they are smaller than normal and can be picked out.

Presoaking

Presoaking the dried beans in water can reduce the cooking time by more than 25%.

Heat penetrates a dry seed faster than water. If cooked directly from the dry state, much of the cooking time is spent waiting for water to get to the center. Meanwhile, the outer portions of the bean overcook and become fragile. Presoaking helps by allowing the water to reach the center first, before the heat cooks them.  

Soaking times depend on temperature. It is helpful to blanch the beans for 1.5 minutes in boiling water and then allowed to soak in the cooling water for two or three hours. Blanching rapidly hydrates the seed coat that controls water movement. If soaked in cool water, it takes 10-12 hrs before beans double in size.

Salt and baking soda speed cooking. Salt concentration at 1% (10g/l or 2 tsp/qt) speeds cooking greatly. Sodium displaces magnesium from the cell wall pectins and makes them more easily dissolved. Baking soda at 0.5% (1 tsp/qt) can reduce cooking time by 75%. It also contains sodium and its alkalinity facilitates the dissolving of cell-wall hemicelluloses. These additions, however, have an effect on the taste and texture of the cooked beans. Baking soda can give a slippery mouth feel and soapy taste. Salt reduces the swelling and gelation of starch granules within the beans, so the texture is mealy instead of creamy.

Cooking legumes

Fresh shell beans cook fairly quickly, in 10-30 min. Peas, lima beans, cranberry beans, and soybeans (edamame) are the legumes most commonly eaten fresh. Whole dried beans and peas take one to two hours to cook. Their larger size and water intake affect cooking time. Initially, water can only enter through the beans through the hilum, the little pore on the curved back of the bean. After 30-60 minutes, the seed coat has fully hydrated and expanded so that water flowing can pass across the entire seed coat surface, though the rate of flow is still limited.

The liquid in which legumes are cooked greatly affects both, the quality of the cooked beans and the time it takes to cook them. The greater the volume of cooking water, the more color, flavor, and nutrients are leached out of the beans, and the more they are diluted. Beans are best cooked in just enough water to soak up and to cook in.

Take into account the following:

• Boiling water speeds cooking, but damages seed coats and cause the beans to disintegrate.
• Temperatures below boiling (180-200 degrees F/80-93 degrees C) are gentler and better maintain bean structure.  
• Hard water with high levels of calcium or magnesium reinforces the bean cell walls, so cooking takes longer and may prevent the beans from softening fully.
• Acidity slows the dissolving of the cell wall pectins and hemicelluloses, so it slows the softening process but it helps maintain structure.
• Alkalinity does the reverse; it enhances the softening process.
• Sugar reinforces cell-wall structure and slows the swelling of the starch granules. It also helps maintain structure.
• Salt in the water slows the rate at which the beans absorb water, but it does get absorbed eventually. If beans are pre-soaked in salted water, they cook much faster.
• High altitude lowers the boiling point, so cooking dry beans is prolonged.

Note: ingredients such as molasses, which are somewhat acidic and rich in sugar and calcium, and acidic tomatoes can preserve bean structure during long cooking and reheating, such as in baked beans.

Legumes and flatulence

Many legumes contain large amounts of indigestible carbohydrates, such as oligosaccharides and cell-wall cements. The human body cannot break down these carbohydrates; therefore, they pass through the stomach in their complex form. Resident, symbiotic bacteria in the intestine break them down into absorbable forms. The increased growth and metabolism of the intestinal bacteria cause a sudden increase in gas production. 

Cooks can help minimize flatulence by manipulating legumes before consumption. Prolonged cooking helps break down much of the oligosaccharides and cell-wall cements into digestible single sugars. Oligosaccharides are also broken down during germination and fermentation, so sprouts, miso, soy sauce, and extracts like bean curd are less offensive than whole beans.

Legume structure and composition

Legume seeds consist of an embryonic plant surrounded by a protective seed coat. The embryo is made up of two large storage leaves, the cotyledons, and a tiny stem. The cotyledons are a transformed endosperm that provide the bulk of nourishment. The seed coat is interrupted at the hilum, a small depression where the seed is attached to the pod. It is through the hilum that the legume absorbs water.

Most beans and peas are mainly protein and starch, except soybeans and peanuts which have large contents of oil (between 25% and 50% respectively).

The colors of beans and peas are determined mainly by anthocyanin pigments in the seed coat. Solid reds and blacks survive cooking, while mottled patterns become washed out when their pigments leak into adjacent non-pigmented areas and into the cooking water. Color intensity is best preserved by cooking the beans in just enough water to keep them covered. It is best to add water only as needed to keep them barely covered.

Importance of legumes

Legumes have a high content of protein, two to three times that of wheat and rice. Their protein develops from a symbiotic relationship with species of the Rhizobium bacteria, which invade the roots of legume plants and convert nitrogen in the air into a form that is directly usable by the plant to make amino acids.

As a vegetable source of protein, legumes have been highly prized throughout history. No other food item has been so notably honored. Each of the four major legumes known to Rome lent its name to a prominent Roman family: Fabius (fava bean), Lentulus (lentil), Piso (pea), and Cicero (chick pea).

Legumes have been domesticated for thousands of years. Some date back to 3000 BCE. Today they make up staple ingredients in many food cultures.

Beans and other legumes

This week the topics are all about legumes. Topics include:

Legume overview
Common legumes
Cooking beans
Soybeans
Soybean products

Hope you join me!