Pulses are edible fruits or seeds of pod bearing plants belonging to the family of the leguminous. Some of the major pulses which are used in food preparation on a daily basis are red gram dal, bengal gram dal, green gram dal etc. some are used as whole grams. Cow pea, rajma and dry peas also belong to a leguminous family.
Legumes play an important role as they have good dietary value. They maintain and improve the soil fertility through the ability to fix atmosphere nitrogen.
Pulses give around 340 calories per 100g which is almost similar to cereal calorie value. In a vegetarian diet pulses are important sources of protein. They give about 20-25% of protein content which is double the amount of protein given by cereals. They contain chiefly globulins and albumins. The protein in pulses are of low quality as they are deficient in methionine android gram is deficient in tryptophan also pulses are rich in lysine. A mixture of cereals and pulses is needed to supplement the protein requirements of the body. The most effective combination is 5 parts of cereal proteins to one part of pulse protein. In terms of grains amino acids like isoleucine, leucine, phenylalanine, threonine and valine.
Pulses contain 55 to 60% starch. Soluble sugars fibers and unavailable carbohydrates are also present. The unavailable sugars in pulses include oligosaccharides of the raffinose family which produces flatulence in man. These sugars escape digestion due to lack of alpha galactosidase activity and are digested by the microflora of the lower intestinal tract resulting in the production of large amounts of carbon dioxide, hydrogen and methane. Fermentation, germination, cooking, soaking and autoclaving reduce a considerable amount of oligosaccharide.
Pulses contain 1.5% lipids on a moisture free basis. They contain a high amount of PUFA. Apart from linoleic acid they contain a high proportion of linolenic acid. They undergo oxidative rancidity during storage resulting in a loss of protein solubility, off flavor development and loss of nutritive quality. oleic , stearic and palmitic acids are also present. They also contain calcium, magnesium, zinc, iron, potassium and phosphorus. In amounts used pulses do not contribute much to the total mineral intake. Legume seeds are a good source of B complex vitamins like thiamin, folic acid and pantothenic acid. They do not contain vitaminA or C but germinated pulses contain some vitamin C.
Among legumes chickpea has high digestibility. Other legumes including lentils have low digestibility. Rajma has low digestibility as it has a globulin fraction which is not easily digested. Pulse proteins have high molecular weight and compact molecules that reduce digestibility. Some proteins are complexed with phytin and decrease digestibility.
Milling or decortication of the seed coat tightly envelops the cotyledons through a layer of gum or lignin. The husk can be loosened and rendered brittle by controlling drying to a critical moisture level and easily removed by abrasion. Increased moisture content is needed for splitting the cotyledons. The dal obtained by the dry method is hemispherical in shape and softens rapidly on cooking. Dal prepared by wet method is usually flat and has a small depression in the center due to shrinkage and softens during cooking. The application of edible oil as a pre-treatment is for pigeon peas where the seed coat is tightly bound to the cotyledons. The advantages of milling are because protein digestibility is improved. Removal of hulls facilitates reduction of fiber and nutrients availability is increased. Dehusking the pulses also removes the anti nutritional factors of polyphenols. Keeping quality is improved due to the milling process.
Soaking many pulses like whole grams have a hard outer covering which needs soaking prior to cooking. During soaking water enters through the hilum or scar where the bean is attached to the pod. It seeps around the periphery of the bean and causes the seed coat to wrinkle. These wrinkles are eliminated when the cotyledons swell and fill the seed coat. Whole pulses are soaked in cold water overnight or in warm water for 4-5 hours. By rehydration the moisture content is increased from 10% to 60%. If there is hard water then the pulses can be boiled for two minutes and then soaked in warm water.
Thanks Giving
This article is written and submitted to The E Today by Shrushti Mehta.
We thank her for her research and analysis and hope to see the awareness about health and nutrition being spread ahead to larger mass of our citizens.