Different varieties of beans and peas belong to the legume family. The dried legumes commonly used for food are navy, lima, kidney, soy, other varieties of beans, lentils, and dried peas. The dried legumes contain less moisture than the fresh ones. In cooking, the moisture lost by drying is replaced and water is absorbed. The legume is softened. This requires a longer period than for fresh legumes, so that the methods of cooking that shorten the cooking process are more important than for fresh vegetables. Effect of mineral content of the water upon cooking of dried legumes. Huenink and Bartow in trying to determine why the quality of canned products from some factories was always superior to those of others found that the mineral content of the water affected the softening of dried beans in cooking. Using a sirup and distilled water in canning beans, they found the product very tender and one that would grade strictly fancy on the market. When to the sirup, distilled water, and beans, calcium chloride was added, using lots with 100, 200, 300, 400, 500, 600, and 1000 parts per million parts of water, the hardness of the processed beans increased with increasing calcium chloride, the ones with 1000 being nearly as hard as uncooked beans. The series with 100 to 200 parts of calcium chloride were hard and tough and would grade standard on the market and be called underprocessed. Continuing their work they tried the following salts:

Calcium chloride CaCl2

Calcium sulfate CaSO4

Calcium bicarbonate Ca(HCO3)2

Magnesium sulfate MgS04 Magnesium bicarbonate Mg(HCO3)2

Sodium carbonate Na2CO3

Sodium bicarbonate NaHCO3

They found that the calcium and magnesium salts hardened the beans whether as chlorides, sulfates, or carbonates. The calcium and magnesium bicarbonates had a hardening effect but the results were not as consistent as with the other salts.

Both the sodium carbonate and sodium bicarbonate gave a softening effect, and with larger quantities the beans appeared over-cooked.

The National Canners Association has reported that calcium and magnesium salts harden beans and peas during cooking, having a greater effect upon the beans than on the peas. String beans and corn do not seem to be affected, nor are beets affected up to 350 parts of magnesium or calcium per million parts of water, but the salts of hard water combine with the soluble oxalates of the beet to give a white coat on the surface of the beet.

Van der Marel, investigating the effect of various salts, bases, and acids upon the softening during cooking of dried peas, has reported the following results. Using a "good cooking" variety of peas, and cooking for 1 1/2 hours he determined the percentage remaining hard at the end of the cooking period.

Table 18 Cooking Dried Peas (Fan der Marel)

Type of water and substance added

Percentage of peas remaining hard after cooking 1 1/2 hours.

Distilled water.....................


Amsterdam city water..............


Formic acid 0.01 M.................


Calcium chloride 0.01 M............


Sodium carbonate 0.01 M...........


With another variety of pea more difficult to cook he obtained the following results after soaking 24 hours and boiling 2 hours.

Table 19 Cooking Dried Peas (Van der Marel)

Type of water and substance added

Percentage of peas remaining hard after soaking 24 hours and boiling

2 hours.

Distilled water.....................


Amsterdam city water..............


Sodium carbonate 0.01 M...........


Ammonium hydroxide 0.01 M.......


Van der Marel decided that the softening effect was due to action on the pectic substances of the peas and that anything that made the pectic substances more soluble had a softening effect in cooking.

The results of Huenink and Bartow and of Van der Marel show why some waters are not desirable for cooking dry legumes. With increasing hardness of the water the hardening effect on the vegetable is more notice-able. Some housewives have found this out from experience. The writer remembers her grandmother's insisting that dried beans should be cooked in cistern water, because they cooked more quickly than in the well water which was permanently hard.

Hard water. Hard water contains salts of calcium, magnesium, and sometimes iron. Hardness of water is designated as temporary or permanent. Water containing calcium and magnesium bicarbonates is termed temporary hard water since the heating of the bicarbonates decomposes them and carbonates are formed which are deposited as crusts on the inner part of the tea kettle or cooking utensil. Such waters are rendered less hard by boiling. Permanent hard water contains the sulfates of magnesium and calcium. Some water is both temporarily and permanently hard.

Softened water, which is used a great deal at the present time, has the calcium and magnesium replaced by sodium. The author has noticed that, since softened water is used in the Home Economics building at Iowa State College, fresh green peas never become hard as they sometimes did with the old permanently hard water and that the difference between the time required for cooking dry beans not soaked and those that are soaked is very much shorter.

The pectic substances of bean coats. Snyder noticed that if the seed coat of pea or Great Northern beans was injured or scarified, the beans swelled in soaking and cooked in a shorter time. Next she noticed that entrance of water into the beans is not uniform over the entire surface of the bean but most of the water entered through the micropyle and germinal area. Substances that dissolved the pectic substances shortened the soaking and cooking time. Beans with very hard skins neither soaked nor cooked satisfactorily and contained a higher percentage of pectic substances than skins of beans that soaked and cooked easily. The major portion of the calcium of beans was found in the seed coat.

Snyder's results with calcium and magnesium salts, with acids, and with soda substantiate those of earlier investigators, with the exception that oxalic acid, which cannot be used in preparation of edible products, did not depress absorption of water. Oxalic acid would render the calcium salts insoluble.

Snyder found that 1/8 teaspoon of soda per pint of water was sufficient for soaking to shorten the cooking time, except with one very hard water. If the beans were soaked in water at 120°F. the maximum amount of water was absorbed in 6 hours. Molasses and tomato juice had an effect similar to that of acids but could be added without injurious effect after the beans were cooked. Beans that cooked rapidly on top of a burner also baked satisfactorily.