What are Pulses?
Pulses are the edible seeds of the legume family. They are edible seeds produced in pods. Pulse comprises all beans, peas and lentils, e.g.:
- baked beans
- red, green, yellow and brown lentils
- chickpeas (chana or garbanzo beans)
- garden peas
- black-eyed peas
- runner beans
- broad beans (fava beans)
- kidney beans, butter beans (Lima beans), haricots, cannellini beans, flageolet beans, pinto beans and borlotti beans
Composition of Pulses
The chemical composition of the edible pulse seed depends on the species. In general, their protein content is high and is more than twice that of cereal grains, typically around 20% of the dry weight of the seeds. The protein content of certain legumes, such as soybean, is as high as 40%.
- Pulse Proteins: Pulse are mostly globulins, but albumins are still found in a few animals. Pulse proteins are deficient in amino acid-containing sulphur, especially in methionine and tryptophan. Only soybean has tryptophan levels that are equivalent to the FAO pattern. Both pulses contain an appropriate amount of leucine and phenylalanine. The contents of lysine and threonine are poor only in groundnuts. Many pulse proteins have high molecular weights and are very small molecules, which decreases the digestibility of the native protein. Proteins also form complexes with phytin and polyphenols found in pulses, which contribute to their poor digestibility.
- Carbohydrates: Food pulses contain between 55-60 percent of total carbohydrates, including starch, soluble sugars, fibre and inaccessible carbohydrates. Starch accounts for the largest proportion of carbohydrates in legumes. The unavailable sugars in pulses include substantial levels of oligosaccharides of the raffinose family of sugars which cause flatulence production in man and animals. These evade digestion, as they are swallowed, due to the absence of alpha-galactosidase production in mammalian mucosa.
- Oligosaccharides: Oligosaccharides are not consumed in the blood and are digested by the microflora of inner intestinal tract, resulting in production of carbon dioxide, hydrogen and small volume of methane. Germination, soaking, cooking, autoclaving and fermentation eliminates significant amount of oligosaccharides.
- Lipids: Lipids constitute about 1.5 percent of dry matter in pulses except in groundnut, soyabean and winged bean. Most of the other pulse lipids contains poly- unsaturated acids. They experience rancidity during storage resulting in undesirable changes, such as reduction of protein solubility, off taste production and loss of nutritive content.
- Minerals: Pulses are essential sources of calcium, magnesium, zinc, iron, potassium and phosphorus. 80 percent of phosphorus in some of these pulses is available as phytate phosphorus. Phytin complexes with proteins and minerals and makes them naturally inaccessible to human beings and animals. Processing can decrease the phytin levels.
- Vitamins: Pulses contain small amount of carotene, the provitamin A. Many Pulses comprise 50-300 IU of Vitamin A per 100g. Thiamine content of pulses is nearly equal to exceeds whole of cereals, the average amount of thaimin being 0.4 -0.5 mg per 100 g of pulses. Pulses are high in niacin and low in riboflavin.
Toxic Constituents in Pulses
Some pulses contain chemical constituents that have toxic properties.
- Trypsin Inhibitors: Trypsin inhibitors are proteins that impede the activity of trypsin in the intestine and interfere with digestibility of dietary proteins and reduce their utilisation. They are present in red gram, Bengal gram, cowpea, double bean, soyabean and dry peas.
- Lathyrogens: Lathyrism is a nervous disease that cripples man. It is known to result from an excessive consumption of the pulse kesari dhal (Lathyrissativus). The symptoms of lathyrism are muscular rigidity, weakness and paralysis of the leg muscle.
- Haemagglutinins: These are proteins in nature and they exist widely in leguminous plants. Haemagglutinins decrease the food intake resulting in low growth.
- Saponins: These are found in soyabeans, Saponoins induce nausea and vomiting. These toxins can be reduced by soaking prior to cooking.
- Goitrogens: These compounds interact with iodine absorption by thyroid gland. They are found in soyabean and groundnuts. Excessive consumption of these foods can contribute to precipitation of goitre.
- Tannins: They have high amount of seed coat in most legumes. Tannins bind with iron irreversibly and interfere with iron absorption. Tannins also bind proteins and reduce their availability.
These toxic constituents may be separated during processing and cooking.
Cooking Pulses
- Combine pre-soaked pulses with water and seasonings in a large cooking pot or heavy saucepan. If available, you can add 5mL (1 tsp) of oil to avoid foaming.
- Use a large saucepan or boiling pot, as pulses double or triple in volume during cooking. (Dry pulses can yield approximately 2-3 times their original volume when cooked.)
- Bring water to a boil, cover tightly, reduce heat and simmer until pulses are just tender and not mushy.
- Simmer pulses slowly as cooking too fast can cause them to split or break open.
- Guidelines for cooking times will vary with the type and age of the pulses, as well as with the altitude and the hardness of the water. Follow the instructions on the package for best results.
- Tasting is the best way to check if pulses are done. Cooked pulses are tender, have no “raw” taste, and crush easily in your mouth.
Other Cooking Methods
Pressure cookers can dramatically shorten cooking times for pulses. Slow cookers make cooking without any focus. Follow the instructions on the box for best performance.
Storing of Pulses
Store dry (uncooked) pulses in a sealed container in a cold, dry spot. Pulses will hold forever. While the color can fade slightly during long storage, the taste will not change. Food protection specialists suggest that cooked pulses and cooked dishes containing pulses should spend no longer than two hours at room temperature because of their protein and moisture content. Refrigerate leftovers at 40 degrees Fahrenheit or below to consume leftovers within three days. Reheat leftovers to an internal temperature of 165 degrees Fahrenheit.
Health Benefits of Pulses
Cardiovascular Health
Having pulses in a diet reduces the risk of cardiovascular disease. Pulses are rich in fiber. For example, a 1 cup serving of cooked lentils contains more than 15 g of fiber, reaching 60 percent of your daily value. The fiber in the pulses supports heart health by lowering cholesterol levels. Pulses also are rich in potassium. Having potassium-rich foods in diet reduces blood pressure by counteracting the influence of sodium.
Reduces Risk of Diabetes
Pulses are a low-glycemic index food. The glycemic index rates food for how it influences blood sugar. Foods with a low glycemic index cause only a slight increase in blood sugar, whereas foods with a high glycemic index cause a surge in blood sugar. People who have more low-glycemic foods in their diet have lower rates of diabetes. For people suffering from diabetes, having pulses in their diet can make it easier for them to control their blood sugar.
High Protein Content
Pulses also make a safe and cheap source of protein. Many pulses do not have any of the essential amino acids, rendering them an inadequate source of protein. Although if grains and vegetables are added to our diet, we should be able to fulfill all of our amino acid requirements. Soy beans, though, are one of only a few plant foods that contain all of the essential amino acids, rendering it a complete source of protein like beef. A 1 cup serving of cooked soybeans contains 26 g of protein, while a 3 oz. portion of cooked chicken contains 24 g of protein.
Good Source of Folate
Pulses also are a good source of folate, a B vitamin required to grow and sustain new cells. Folate is particularly essential during periods of accelerated development, such as pregnancy and infancy. Women of childbearing age require sufficient intake of folate to limit their chance of having a child born with a neural tube defect. Folate content varies among the various pulses. For eg, a 1/2 cup serving of cooked black-eyed peas contains 105 mcg of folate, and the same size serving of cooked great northern beans contains 90 mcg.
