Pulses: A Potential Source of Valuable Protein for Human Diet

Abstract

Nutritional profile of pulses has significant importance in human diet with respect to protein and mineral quality and bioavailability. Protein energy malnutrition is widespread throughout the world especially among the developing countries. Pulses being rich in macronutrients such as protein from 20 to 26% and low in calories are most suitable for product development for target-oriented population. During last decade, the demand for pulse-based products with high protein and fiber, low glycemic index, and gluten free with more antioxidant showed increasing trend by the consumers. Drift of end-use application of pulses generated interest for research in all disciplines such as breeding, agronomy, food, and nutrition, etc. A great share of plant protein in human diet may be a critical step for reducing dependence on animal origin protein source. This chapter will review contribution or choice of plant-based protein from legumes or pulses with good-quality protein based on amino acid composition. Additionally, this overview can give insight into the development of new product with balanced nutritional quality and high protein contents as a potential protein supply for malnourished population.

1. Introduction

Pulses are dry seeds of legume family grown in pods in varying shape and size. These are member of the Leguminosae, family Phaseoleae, subfamily Papilionoideae [1]. Chronological, archeological evidences showed that legumes and pulses were domesticated and originated from America [2]. Now consumed in every part of this globe especially by people in the developing countries as well as developed countries [3, 4]. In some areas such as Mexico, south and central American, and African countries, these are being consumed as staple foods where per capita intake may extend up to 40 kg per year [5].

Oilseeds are excluded from this category, which are solely grown or harvested for oil extraction purpose. A variety of pulses are grown with various shapes and size throughout the world. Most commonly consumed pulses include chickpea (Cicer arietinum), field peas (Pisum sativum), lentils (Lens culinaris), mung bean (Phaseolus mungo), dry broad bean (Vicia faba), moth beans (Phaseolus aconitifolius), lupins (Lupinus albus) etc. In addition, there are a large number of minor pulses that are grown and consumed in different parts of the world [6, 7].

Pulses are most commonly consumed food in the Asian countries as a culinary staple since ancient times. However, its cultivation is not as increased as other staple crops such as wheat, corn, barley, etc., and mass production of pulses is restricted in underdeveloped countries where per capita consumption is increased up to 125–140 kcal as compared with western world such as the United States where per capita consumption is minimal, i.e., only up to 27 kcal [8].

Plant-based protein could be the best substitute for animal-based protein to overcome protein energy malnutrition. Legumes are considered as a good source of protein having 12–40% protein on an average. Although 60% share of global protein consumption is occupied by plant-based protein, and remaining 40% is fulfilled by animal-based proteins [8], however, pulse consumption has been increased to certain regions of the world. Currently there is a great concern for the sustainable, clean label product, pulses and legumes are best suited as these are environment-friendly with no carbon footprints or CO₂ emission. Ultimately substituting animal-based protein with plant-based protein would be beneficial from both environment and consumers’ health perspective. Similarly the consumers’ demand for plant-based protein can be met by advanced research and innovative processing technique with efficient availability of good-quality protein providing key amino acids that play a vital role in the development, reproduction, and support of the human body. Pulses in combination with cereals provide one of the best solutions to protein energy malnutrition being complementary to each other having lysine and methionine, respectively [11], and combination of both cereals and pulses is complimentary for product development with balanced nutritional quality and high protein contents. These products can be claimed as a source of potential protein supply for malnourished population.

This chapter covers the importance of nutrients of pulses (legume grains) especially protein and their importance and strategies for industrial application and processing industry for developing target-oriented protein-enriched products.

2. Nutritional importance of pulses

Whole and split pulses are a good source of complex carbohydrates, protein, and dietary fiber, having significant amounts of vitamins and minerals. Protein content in legume grains range from 17 to 40%, contrasting with 7–13% of cereals, and being equal to the protein contents of meats (18–25%) [9].

2.1 Micronutrients in pulses

Pulses are a good source of fat-soluble vitamins especially folate, riboflavin, and thiamin. Folate is an important micronutrient to reduce the risk of neural tube defects in newly born during pregnancy. Pulses are rich in vitamin A also but poor source of vitamin C. Pulses are also a good natural source of essential minerals including iron, zinc, selenium, phosphorus, calcium, magnesium, potassium, and chromium. These minerals play an important in human body during different physiological processes such as iron is required for hemoglobin synthesis and antioxidative activity, copper and zinc for lipids and carbohydrates metabolism, calcium is essential nutrient for bone health, copper for enzyme activity and iron metabolism. Pulses are lower in sodium content and helpful for decreasing the trends of different diseases especially hypertension. Pulses are high in iron content, but their bioavailability is low. However, legumes can be a good source of ion if consumed with vitamin-C-rich foods. Iron absorption increased in this way plays an important role in prevention and treating anemia especially in women because during menstruation, there is a high risk of anemia [10].

2.2 Carbohydrates in relation to pulses

Carbohydrates are energy-giving macronutrients, present in pulses up to 60% (dry weight). Leguminous starch is digested slower as compared with starch from cereals and tubers and considered as low glycemic index food for blood glucose control making them suitable for consumption by diabetic patients and those with an elevated risk of developing diabetes. Pulses are gluten-free, a very suitable option for patients suffering from celiac disease and persons who are sensitive to gliadin and glutenin proteins. Pulses are a valuable source of dietary fiber 5–37% including both soluble and insoluble dietary fiber. The monomers of dietary fiber present in legumes are glucose, galactose, rhamnose, arabinose, fucose, xylose, and mannose. Pulses also contain significant amounts of resistant starch and oligosaccharides, mainly raffinose, which have been reported to possess prebiotic properties. These are fermented to short-chain fatty acids by probiotics, helpful for improving colonic health and reducing the risk of colon cancer [11].

2.3 Dietary fiber in pulses

Pulses are an excellent source of dietary fiber and other complex carbohydrates. A wide variation is present in the amount of dietary fiber with a significant ratio of soluble and insoluble fiber. Depending on the specie, total dietary fiber ranges from 14 to 32% of dry weight [12]. Various types of dietary fiber present in pulses that include galacto oligosaccharides, long- and short-chain soluble and insoluble polysaccharides, and resistant starch. Insoluble dietary fiber is helpful in laxation while soluble dietary fiber is related to reducing the cholesterol levels and maintaining the post-prandial glucose level. Both types of fiber can act as prebiotics and are helpful in supplying nutrients to gut microorganisms. Fiber-rich fractions of pulses can be added to processed foods to increase their fiber content. Despite the nutritional and health-promoting effects, pulse fiber can also utilized to improve the textural properties by binding and retaining fat and moisture in food items [13].

Pulse fibers are important for individuals seeking a healthy, disease-free lifestyle. High-fiber and low-glycemic diets are important for preventing and treating many diseases/conditions including diabetes, constipation, heart complications, piles, and also some cancers. Furthermore, dietary fiber especially soluble dietary fiber has the ability to improve glucose tolerance and helps to lower the cholesterol by forming a gel lining along the intestinal wall that acts as a protective layer, thus decreasing the glucose and cholesterol assimilation into the blood stream while insoluble dietary fiber helps in increasing fecal bulk and stimulating normal laxation because it has low densities [14]. Pulses are an invaluable part of the human diet. Dietary fiber fractions of pules have found use in the bakery, meat, extruded products, and beverage industries as stabilizers, texturing agents, bulking agents, fat replacers, and emulsion stabilizers. Legume starch isolates have been employed as thickening agents in soups and gravies in the food industry [15].

2.4 Fatty acids composition of pulses

Pulses are generally low in fat, free from saturated fatty acids. The fat in pulses constitutes significant amounts of mono- and polyunsaturated fatty acids (PUFAs). The highest amount of poly unsaturated fatty acids of 71.1% in kidney beans and mono-unsaturated fatty acids of 34% in chickpeas are reported. The polyunsaturated fatty acids are present in legumes that include essential omega 6 linoleic acid and omega 3 alpha linolenic acid. These fatty acids must be included in diet because these are essential and cannot be synthesized in human body [16].

3. Antioxidant capacity of pulses

Pulses contain non-nutrient bioactive compounds such as phytochemicals and antioxidants include isoflavones, lignans, protease inhibitors, trypsin and chymotrypsin inhibitors, saponins, alkaloids, phytoestrogens, and phytates. Most of these chemicals are termed “anti-nutrients” and although they are nontoxic. Most of these anti-nutrients are heat-labile, and since pulses are consumed after cooking, they do not pose a health hazard. These anti-nutritional substances can be removed by different procedures such as boiling, soaking, de-hulling, steaming, roasting, fermentation, and sprouting before consumption.

Different studies have shown that many of non-nutrient components are phytochemicals that exhibit antioxidant characteristics, which play an important role in human body to protect from different diseases such as cancers, osteoporosis, heart diseases, and other degenerative diseases. The antioxidant capacity of pulses is helpful to prevent or stop the oxidative process that leads to many degenerative diseases. As such, the incorporation of pulses into human diets all over the world could offer protection against chronic diseases. Therefore, legumes, especially pulses, should be explored for the development of innovative, value-added products [17].

4. Pulse proteins

Pulses are well thought to be a good source having protein ranging from 20 to 40% d.m [18]. Proteins from different pulses vary in composition and structure and have different functional properties. The major proteins found in most pulses comprise globulins and albumins.

4.1 Globulins

Globulins are soluble in salt solutions, and albumins are soluble in water. Globulins accounts for 70–80% of seed protein. These are primarily storage proteins. These proteins are further divided into two types, i.e., Legumins and Vicilins, also called 7S and 11-12S globulins on the basis of their sedimentation coefficient. Molecular weight of legumins vary from 300 to 400 kDa. Legumins have higher amount of sulfur-containing amino acids (methionine and cysteine) as compared with Vicilins [19] Molecular weight of viciline is 145–190 kDa. These proteins are trimers of monomers either identical or nonidentical. This globulin does not have cysteine residue and thus lacks disulfide bond.

4.2 Albumins

Albumins are most nutritive proteins in pulse seeds in terms of amino acid composition. Albumins are primarily composed of metabolic proteins including enzymatic and non-enzymatic proteins. Only 10–20% seed proteins are made up of albumins. These proteins are generally low in molecular weight (MW; 5–80 kDa) and higher in cysteine and methionine content than pulse globulins [19] Albumins may also contain some anti-nutritional components such as trypsin or chymotrypsin inhibitors, amylase inhibitors, hemagglutinins, lectins, etc.

4.3 Prolamins and glutelins

Prolamins and glutelins are present in minor quantity. Prolamins are soluble in alcohol, and glutelins are soluble in dilute acid/base. Protamine has high concentration of proline and glutamine, and glutelins have high concentration of methionine and cystine. Globulin is the major fraction of embryo and cotyledons of pulses [20].

5. Amino acids in pulses

All proteins are created from 20 different amino acid building blocks. Out of these 20, nine amino acids are those that cannot be produced by the body and are called “essential,” and they must be obtained from food source. Each amino acid within the body is associated with specific function. Lysine and arginine are found to be associated with the release of growth hormone in young children. In the early years of age, protein intake is positively associated with height and weight. Hence children with lower serum level of essential amino acids particularly arginine, glycine, and glutamine lead to stunting and wasting. Pulses can provide potential ingredient for the intervention in such types of ailments. Branch chain amino acids (BCAA), e.g., leucine, are reported to play significant role in regulating signaling pathways of muscle protein, valine for repair, and isoleucine in muscle growth. Likewise each amino acid performs a specific function during different life stages, from infancy to elders [21].

Legumes containing relatively low quantity of methionine, essential amino acid, compared with egg, red meat, or poultry meat, are suitable as complimentary source with low lysine-containing cereals such as wheat. It can be source of good-quality protein. Protein quality is defined by Food and Agriculture Organization (FAO) as the capacity of a food protein source and diet to meet the protein and essential amino-nitrogen requirements [22]. Quality can be evaluated in terms of amino acid composition and protein digestibility. It is essential to have a good balance of amino acids in order to synthesize enough protein in the cells to keep the body healthy. Dietary intake of proteinaceous meal comprising sufficient quantity of balanced is essential for adults as well as growing children. If the dietary intake of amino acids is unbalanced, the amino acid that is most limiting becomes the bottleneck for the amount of protein synthesized.

Pulse consumption not only fulfills essential amino acid requirement within the body besides that lower methionine intake is responsible for reduction in oxidative stress by decreasing mitochondrial ROS generation and damage of the liver, which would ultimately increase longevity by this dietary manipulation. Amino acid composition of some common pulses is given in the table comprising essential and non-essential amino acids (Table 1).

Essential amino acids
Amino acids/type of pulse	Arginine	Histidine	Isoleucine	Leucine	Lysine	Methionine	phenylalanine	Threonine	Valine	References
White lupin	0.945	0.808	0.864	0.877	0.891	0.803	0.903	0.821	0.879	[23]
Lentil	0.831	0.36	1.75	0.180	0.723	1.18	0.88	0.990	0.971	[24, 25, 26]
Mung bean	0.945	0.808	0.864	0.877	0.905	0.803	0.908	0.829	0.841	[27]
Cowpea	0.750	0.311	0.453	0.778	0.756	0.224	0.756	0.385	0.506	[25, 28]
Green pea	0.724	0.245	0.456	0.745	0.817	0.113	0.524	0.385	0.5.9	[25]
Chickpea	0.488	0.296	0.425	0.759	0.600	0.290	0.789	0.389	0.554	[29]
Feba bean	1.048	0.306	0.373	0.646	0.634	0.060	0.242	0.346	0.454	[28, 30]
Non-essential amino acids
Non-essential amino acida/ pulses	Alanine	Aspartic acid	Cystine	Glycine	Glutamic acid	Proline	Serine	Tyrosine	Tryptophane
White lupin	0.954	0.849	0.808	0.851	0.904	0.831	0.852	0.882	—	[23]
Lentil	0.423	1.180	0.094	0.365	2.157	0.353	0.520	0.326	0.650	[24, 25, 26]
Mung bean	0.297	0.979	0.140	0.286	2.13	0. 429	0. 532	0.266	—	[27]
Cowpea	0.423	1.088	0.053	1.726	0.282	0.401	0.456	0.305	0.702	[25]
Green pea	0.524	1.106	0.183	0.451	1.750	0.383	0.564	0.373	0.505	[25]
Chickpea	0.497	1.104	0.606	1.730	0.373	0.385	0.546	0.280	0.0902	[29]
Feba bean	0.358	1.032	0.776	0.381	1.625	0.424	0.487	0.305	0.691	[28, 30]

Table 1.

Amino acid composition of some common pulses.

6. Application of pulses in processing industry

Pulses and legumes have been recognized as valuable since hundreds of years ago, as a low-cost source of high-quality protein products such as flour, concentrates, and isolates. However, the pulse flour application on an industrial scale is only limited to soybean proteins and to lesser extent pea protein products, owing to insufficient information regarding functional properties of other pulse flours. Being rich in protein, with essential amino acid composition along with dietary fiber and other micronutrients such as minerals, vitamins, and folates, pulses are best suited for the formulating and enrichment of food products [31].

Pulse flour as a whole or pulse flour fractions can be utilized in combination with staple cereals such as wheat, rice, barley, etc., to overcome the amino acid lysine deficiency, which is deficient in wheat (a most commonly consumed staple crop) and methionine deficiency in pulses, making complimentary to each other to overcome essential amino acid dearth. Due to low cost and comparative functionality, pulse and pulse proteins find their way in numerous industrial processing applications in cereal-based foods as well as in dairy and meat replacers’ food products having improved texture and finishing by increasing water absorption in dough and better.

Modification of protein through various methods of processing may reduce the protein denaturation and further value addition such as preparation of high-protein food supplements using defatted sesame seeds or flour, concentrates of mung bean, lentil, lupins, yellow pea utilized in baking as well as in dairy products. Application of heat, roasting, autoclaving, fermentation, frying, etc., brings more chances for further value addition [30, 32].

The enrichment of bread and other cereal-based confections with legume flours particularly in regions where protein utilization is inadequate has long been recognized [33]. Soybeans are most often modified into a paste, curd, or milk. Soy milk is suitable for lactose-intolerant consumers and emerges as a nondairy substitute for both milk and baby formula, who are unable to digest the lactose that naturally occurs in cows’ milk. Tofu, or bean curd, is prepared from curds of soy milk. A variety of other products such as soy cheeses, yogurt, sour cream, and other dairy spreads are prepared from this raw material. Chickpea, mung bean, yellow pea flours have great potential in dairy industry for preparing Imitation cream, ice cream, yogurt owing to their emulsifying abilities, and a host of other varieties. An ice cream–like desert called Tofutti is another well-known tofu product. These are especially welcome products for lactose-intolerant individuals as well as for those wishing to avoid the saturated fat in dairy products [34].

The growing interest in gluten-free, vegan, and vegetarian diets has resulted in an increase in pulse consumption. Bread, a traditional and economical product commonly consumable food throughout the word as a main component of breakfast, is a source of calories and of complex carbohydrates, with a modest amount of essential amino acids such as lysine and threonine. Pulses flour must be included in combination to wheat flour for cereal-based commonly consumed products such as flat bread, leavened bread, pasta, croissants, crackers, chips, cookies, etc.

In many countries, mung bean is used to make mini sweet desserts of different shapes such as vegetables and fruits. Mung bean noodles and breads are also common. Mung beans are prescribed for patients in the hospitals and served with bread. Green gram has good nutritive value, and on germination, it is free of flatulence-causing agents.

Dietary diversification strategy involves combination of more than one type of food source especially diverse plant-based food to improve nutritional health of people who are suffering from malnutrition such as protein energy malnutrition [35]. Pulses and legumes can therefore complement each other when blended at optimum ratio in providing good-quality protein [36].

7. Role of protein in human body

Protein is involved in almost all the body functions taking place such as development of muscle, bone, skin, hair, etc. It makes up the enzymes that trigger many chemical reactions within the body, e.g., the hemoglobin is responsible for carrying oxygen in the blood. Protein plays an important role in growth and muscle building. Protein requirements increase during illness, pregnancy, breastfeeding, and after surgery or an injury. Enzymes are also protein in nature that control metabolic processes within and outside the cell. These enzymes’ functions are critical during the process of digestion, blood clotting, muscle contraction, and energy production [37].

Some hormones are also made up of proteins; these are chemical messengers that conduct communication between cells, tissues, and organs. Some hormones are insulin, glucagon, human growth hormone, antidiuretic hormone, adrenocorticotropic hormone. Protein is helpful in maintaining the acid and base balance in body fluids including blood, gastric juice, etc. Proteins required to regulate body fluids as albumin and globulin are present in blood and are helpful to maintain body fluid by attracting and retaining the water. Protein is helpful in the formation of immunoglobulins or antibodies; these are necessary to fight against infections and play an important role in immune system. It also helpful in transporting nutrients, i.e., vitamins, minerals, blood sugars, oxygen, and cholesterol into cells, out of cells, and within cells. Proteins also play an important role in storing nutrients as ferritin is a form of protein that stores iron. Protein provides energy to body in the same amount as carbohydrates 4 g/kcal [38].

8. Outcomes of protein deficiency

Protein becomes deficit when intake of protein does not meet body requirement. According to an estimation, one billion people suffer from inadequate protein intake worldwide, protein deficiency is especially severe in Central Africa and South Asia, where up to 30% of children could not get sufficient amount of protein from their diet. Certain people in the developed countries are also at risk, who follow an imbalanced diet, as well as older people and hospitalized patients. Low protein consumption may result in compositional changes within the body that develop over a long period of time, such as muscle wasting. Kwashiorkor is the most severe form of protein deficiency. It often occurs in children in developing nations because of famine and lack of balanced diets. Protein deficiency can affect almost all aspects of body function [15].

Edema, characterized by swollen and puffy skin, is a classic symptom of kwashiorkor. Scientists believe it is caused by low amounts of human serum albumin and globulin, which is the most abundant protein in the liquid part of blood or blood plasma. When levels of albumin and globulin decrease in body, they are no longer able to regulate blood in blood vessels, and then fluid starts to build in spaces of cells, edema and swelling occur specially in stomach region [39].

Another common symptom of kwashiorkor is a fatty liver or fat accumulation in liver cells. Main cause of this is unknown, but some studies suggest that an impaired synthesis of fat-transporting proteins, known as lipoproteins, may contribute to the condition. Protein deficiency often leaves its mark on the skin, hair, and nails, which are largely made of protein as keratin protein present in hair. For instance, kwashiorkor in children is distinguished by flaky or splitting skin, redness, and patches of depigmented skin. Hair thinning, faded hair color, hair loss (alopecia), and brittle nails are also common symptoms [40].

Muscles are said to be body’s largest reservoir of protein. When dietary protein is in short supply, the body tends to take protein from skeletal muscles to preserve more important tissues and perform body functions. Over the time this lack of protein leads to muscle wasting. Even moderate protein insufficiency may cause muscle wasting, especially in elderly people. Bones gives support and shape to body, are also at risk when there is protein deficiency, and risk of fractures increases. One study in postmenopausal women found that a higher protein intake was associated with a lower risk of hip fractures. The highest intake of protein is linked to a 69% reduced risk of fractures [41].

Besides maintaining muscle and bone mass, protein is essential for body growth. Thus, growing age deficiency or insufficiency is especially harmful to children who require a steady supply of protein. In fact, stunting is the most common sign of childhood malnutrition. In 2013, an estimated 161 million children suffered from stunted growth that reaches up to 38.9 million during 2020. Stunted growth is also one of the main characteristics of kwashiorkor in children. Similarly the rate of wasting rises from 149.2 million to 203.6 million during this decade. A protein deficiency can also affect the immune system. Impaired immune functionality may increase the severity of infections. For instance, one study in mice showed that following a diet consisting of only 2% protein was associated with a more severe influenza infection, compared with a diet that provides 18% protein [42].

9. Role of pulses/legumes protein in human health

Pulses can play an important role in food systems to provide global food security and fulfill the nutritional needs in future. Food systems fail to provide safe, sufficient, nutritious food to all due to urbanization, climate change, and increase in population [43]. Leguminous family is highly appreciated as it is a cheap and safe source of nutrients especially protein. Compared with different maize, that is a staple in different regions of world, pulses are a better and effective source of protein and are rich in micronutrients such as iron, zinc, thiamin, folate, and niacin. Nutrient concentration varies in different varieties, locations, and between grains. Human nutrient consumption and status clearly depend on the bioavailability of nutrients. Furthermore, pulses are a good source of essential amino acids especially in lysine (∼64 mg/g of protein) and threonine (∼38 mg/g of protein), which are complementary to most staple foods, helpful to improve the quality of protein of diet. Pulses offer potential health benefits where future demand of nutritious and cheap food commodities is increasing because of lack of resources and undernutrition [7].

Protein requirements is not same for everyone; it depends on many factors including body weight, muscle mass, age, and physical activity. The recommended daily allowance of protein is 0.4 g per pound of body weight and 0.8 g per kg of body weight. Athletes required a greater amount of protein ranging from 0.5 to 0.6 g per pound of body weight (1.2–1.4 g per kg), required for muscle maintenance and training recovery. Pulses contain 21–25% protein and provide double amount as compared with cereals [44].

Protein is a most satiating macronutrient than fat and carbohydrates, and it is present in a high amount in pulses. Protein elicits the secretion of satiety-related hormones in the small intestine such as peptide YY, Glucagon such as peptide-1. Fiber and protein both are helpful to control satiety; pulses are rich in both fiber and protein and ideal to reduce caloric intake and managing obesity [45].

Pulses are recommended by Canadian and American government agencies as part of a healthy diet. Both Canada’s Food Guide (CFG) and the USDA MyPlate nutrition guides place pulses in the meat and alternative group. Animal protein is expensive and not acceptable for many people due to their beliefs and lifestyle. Pulse protein could be a great choice for vegetarian people and meet their essential requirements of amino acids for physiological processes and growth of children. Pulses supply a good amount of protein when consumed with cereals [46].

10. Protein digestibility of pulse-based diet

Protein digestibility can be defined as the percentage of protein or AA intake, absorbed by the digestive tract. It can also predict the estimated individual AA bioavailability [47, 48]. When protein-containing food is consumed, digestion begins from the stomach, and it triggers the release of the hydrochloric acid in the stomach by the partial cells of gastrointestinal mucosa of the gastrointestinal tract. Released acid activates the pepsinogen and converts it into active form, i.e., pepsin. This pepsin can break down the polypeptides into di- and tripeptides, which are ultimately broken down into amino acids; within the duodenum amino acids travel to the liver through hepatic portal vein and undergo de-amination. Amine groups are cleaved to form urea. The amino acids are simultaneously converted into non-essential amino acids or carbohydrate and fats or catabolized directly to energy. Since protein cannot be stored within the body, metabolism of amino acids is completed within few hours. If neither of these actions occurs, then it is released from the body in the form of urine or urea nitrogen contents (Figure 1) [49, 50].

Figure 1.

Catabolism of protein.

When we come to digestibility of pulse-based diet, it is evident that some type of anti-nutritional factors inhibit the digestibility and availability of protein to the body. These may be some types of protein inhibitor components such as trypsin and chymotrypsin inhibitors that arrest the functionality of proteolysis. Trypsin is a digestive enzyme, and the presence of this inhibitor interferes with normal protein digestion in humans. Presence of less digestible protein fractions, high levels of insoluble fiber, and high concentrations of anti-nutritional factors lowers the digestibility of protein. However, processing, cooking, and germination improve the digestibility of pulses. The preparation involves soaking, autoclaving, roasting, fermentation, and germination to reduce anti-nutritional factors (phytic acid, tannins, and polyphenols), which inhibit mineral absorption and protein bioavailability [50, 51, 52].

Starch present in pulse grains provides certain health benefits due to its high amylose content. It promotes the formation of resistant starch that cannot be hydrolyzed during digestion. Dietary fiber remains undigested in the small intestine; afterward, it is fermented by the microbiota in the colon that is helpful in controlling weight management, diabetes, and has cholesterol-lowering effect. Fruits and vegetables rich in promoter substances (ascorbate and beta-carotene) for mineral absorption should be taken to enhance micronutrient content and bioavailability. When processed, cooked, or heat-treated, the process of protein digestion by gastrointestinal enzymes as the inhibitory effect on proteolytic enzymes is inactivated [30]. Cooking or heat treatment increases the enzyme activity 2–3 times, chelating activity was also found to be increased in different legumes by cooking. Overall, the total antioxidant capacity values denoted the increased electron donating capacity of the legume seed proteins after digestion with GI enzymes, which could thus act as better radical chain terminators or free-radical stabilizers, when legumes and pulses are treated with heat application [53]. Overall the nutritional value and bioavailability of nutrients, proteins, minerals, phenolic or antioxidant capacity, are increased or improved by processing methods applied to grains as compared when consumed in raw form.

11. Conclusions

Pulses are becoming the corner stone of food and agriculture industry by the time as the awareness of plant-based protein over animal-based protein is revealed and global food security needs to provide balanced diet are publicized. The role of lentils, chickpea, beans, and other pulses becomes even more significant. Future projections suggest 23% global increase in consumption of high protein, high-fiber legumes. To satisfy this need, multidisciplinary approach is required toward research and development sector; efforts in increasing pulse production and consumption lead toward the sustainable food security goal in regional and national food system. Research is needed to identify pulse varieties and innovative processing approaches to develop complimentary food products with balanced available nutrients. Diet diversity and effective processing conditions can improve the nutrient availability and ultimately help to overcome malnutrition and protein deficiency.

Acknowledgments

No funding is provided by any institute or university for this publication.

Conflict of interest

The authors declare no conflict of interest.