J Food Sci Technol (March 2017) 54(4):853–857

DOI 10.1007/s13197-017-2537-4

EDITORIAL

Pulses: an overview
Narpinder Singh1

Published online: 14 February 2017

Pulses are an important source of nutrition for billions of sources of proteins including animal were considered
people around the world. The terms ‘‘legumes’’ and ‘‘pul- superior both nutritionally and functionally; however, uti-
ses’’ are interchangeable because all pulses are considered lizing animals as source of proteins raised many ethical
legumes but not all legumes are considered pulses. Pulses issues. Moreover, it cannot be continued to be used as a
belong to leguminoseae family and include those species sole source of protein to meet the growing need for proteins
that are consumed by human beings and domestic animals, due to increasing population. Therefore, interest in pulses
commonly in the form of dry grains and does not include due to their high protein content compared to cereal grains
groundnut (Arachis hypogaea) and soybean (Glycine max) is growing. These are second most consumed food crop
which are grown mainly for edible oil. The Food and after cereals in world. They are important food source for
Agriculture Organization of the United Nations has poor people especially those living in developing and under
declared 2016 as the International Year of Pulses with aims developed nations.
to enhance public awareness of the nutritional benefits of Pulses contain approximately 21–25% protein; however
pulses as part of sustainable food production. This was have limiting amount of essential amino acids such as
intended towards global food security and nutrition. The methionine, tryptophan and cystine (Tiwari and Singh
Year of 2016 was expected to generate a distinct oppor- 2012). The protein content and amino acid composition
tunity to encourage associations all over the food chain for vary with the variety, germination, environment and
better utilization of pulse-based proteins, increase global application of fertilizers. The protein content in pulses is
production of pulses, crop rotations and address the chal- almost double than that found in cereals. Pulse proteins
lenges in the trade of pulses. Pulse grains are an excellent were classified into two major fractions viz albumin and
source of protein, carbohydrates, dietary fibre, vitamins, globulin. Globulins are the major storage proteins in pulse
minerals and phytochemicals. Large number of people in seeds constituting 35–72% of total protein and the
the world consumes pulses as staple food in combination remaining protein fraction mainly consists of albumins.
with cereals and depends on them for meeting their protein Globulin proteins have higher amount of glutamine
requirement. The high lysine and folate content makes aspartic acid, arginine and lysine (Dahl et al. 2012).
pulses perfect for making the composite flours with cereals. Albumins usually have physiological role present in low
Pulses and cereal grains have similar total carbohydrate, amount than globulins constituting only up to 15–25% of
fat, niacin, riboflavin, thiamine and vitamin B6 contents. total seed protein (Casey et al. 1998; Machuca 2000). The
However, pulses has higher protein, folate, iron, magne- albumins have higher amount of cystine, methionine and
sium, potassium and zinc content that cereals. Traditional lysine contents as compared to globulin fractions in beans
(Marquez and Lajolo 1981). Globulins have highly packed
rigid structure due to the presence of disulfide bonds and
& Narpinder Singh hydrophobic interactions (Utsumi 1992). Among the four
narpinders@yahoo.com
major classes of protein in pulses, albumins are unique due
1
Department of Food Science and Technology, Guru Nanak to their solubility in water (Bean and Lookhart 2001).
Dev University, Amritsar 143005, India Because of solubility, albumins were capable of interacting

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and competing with starch for water. Pulse protein has poor undigested in the human intestine. The anaerobic fermen-
digestibility that is the major nutritional constraint in their tation of undigested carbohydrates led to the production of
utilization in weaning food formulations. Digestibility is H2, CO2 and traces of CH4. These gases caused abdominal
measured to determine the susceptibility of proteins to discomfort and excessive consumption of these carbohy-
proteolysis and is an indicator of protein availability. drates may lead to diarrhea (Sefa-Dedeh and Stanley 1979).
Highly digestible proteins are more desirable since these Pulses are rich source of many vitamins and minerals
provide more amino acids for absorption on proteolysis, (iron, zinc, calcium, magnesium). The deficiency of vari-
therefore, has better nutritional value than those of low ous minerals in different parts of the world led to cardio-
digestible proteins. Functional properties, such as foaming vascular disease and imbalance in majority of the
properties, water and oil absorption capacities, emulsifi- biological pathways. Pulses can provide adequate minerals
cation and solubility determine the suitability of proteins to required to fulfill nutritional requirement. Phenolic com-
be used as hydrocolloids in food formulations (Kinsella and pounds are grouped into phenolic acids, tannins and fla-
Phillips 1989). Globulins from lentils and horsegram were vonoids. Phenolic compounds and antioxidant activity also
shown to have better digestibility as compared to albumins varied among different varieties of pulses. Dark colored
due to presence of lower cystine content and hence less and pigmented pulses tend to have more phenolic content
number of disulphide bonds as compared to albumins. The as compared to light colored varieties. The presence of
digestibility of proteins varies with characteristics of phenolics and flavonoids in the grain especially in the hull
starch. An increase in protein digestibility of albumins and also vary with the color of grain. Interaction of these
globulins was observed in the presence of starch that was phenolics with different grain components (starch and
related to the opening of compact protein structure on protein) imparts different properties to grain and its prod-
binding to the surface of starch granules and forming new ucts. Polyphenols and flavonoids have anti-tumoral, anti-
bonds that resulted into easier access to the proteolytic platelet, anti-inflammatory and anti-allergic properties.
enzymes (Ghumman et al. 2016). They are highly useful for prevention of lipid peroxidation
Carbohydrate content in pulses is 60–65% and starch and scavenging free oxygen radicals due to their high
constitutes the major fraction of the carbohydrates. Pulse antioxidant activities thus improving the stability of foods
starch is consisted of amylose and amylopectin, and wide and protecting living systems against oxidative damage
variation in amylose content in pulse starches has been (Vazquez et al. 2008). Many studies have suggested that
reported (Tiwari and Singh 2012). Starches from various antioxidant capacity was positively correlated with phe-
pulses have different physicochemical, pasting and tech- nolic content of pulses, which was higher in lentil, black
nological properties (Singh et al. 2008). Pastes formed beans and red kidney beans (Xu and Chang 2008). The
from pulse starches were found to have high retrogradation ferulic acid was the most abundant phenolic compound
tendency and are hard to swell and rupture during cooking followed by p-coumaric acid and sinapic acid in common
as compared to cereal starches (Singh et al. 2008; Singh beans (Luthria and Pastor-Corrales 2006). Pulses are con-
2010). Their high stability towards mechanical shearing sumed as whole seeds and split-dehusked dhals. The phe-
and heat makes them useful in number of food application nolics compounds are concentrated in hull portion of the
and were considered to be a good alternate to replace cross- pulses. Milling of pulses to produce the dhals led to the
linked starches (Singh 2010). The tendency to retrograda- reduction in phenolic compounds. Pulses consumption are
tion in pulse starches dependent on the amylose content. especially recommended for reducing the risks of chronic
Higher retrogradation tendency of pulse starches make diseases such as obesity, coronary heart diseases, type-2-
them resistant towards the action of digestive enzymes diabetes, etc. The utilisation of pulses in the form of flours
resulting in the reduction of glycemic index (Singh 2010). has been reported to satisfy the nutritional requirements of
Hence, pulse starch is useful ingredient for developing a large portion of population in developing countries.
products for diabetic patients. Pulse grains hulls are rich Besides having lots of healths benefits, pulses are also
source of water-insoluble fibres and polyphenols (having have antinutritional factors such as phytate, enzyme inhi-
high antioxidant activities), while cotyledons contain bitors (trypsin inhibitors, chymotrypsin inhibitors, and a-
higher soluble fibres, slowly digestible and resistant starch amylase inhibitors), polyphenolics (including tannins),
as well as oligosaccharides (Singh et al. 2017). The pres- lectins, and saponins. These antinutrients impart hindrance
ence of oligosaccharides (raffinose, stachyose, verbascose in many biochemical pathways. Pulses were reported to
and ciceritol) in pulses also limits their utilization. These have low digestibility owing to the presence of anti-nutri-
oligosaccharides were known as flatus-producing carbo- ents which inhibit enzymes involved in digestion and
hydrates due to the presence of a-galactosidic bonds. The reduces bioavailability of nutrients. Among anti-nutritional
human body lacks the a-galactosidase that are required to factors, phenolic compounds interfere with the digestibility
break these bonds and hence these carbohydrates remained of the proteins in human body. They are considered to be

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highly reactive and bind reversibly as well as irreversibly (Hufnagel and Hofmann 2008). The variation in these off-
with proteins, leading to lower digestibility and bioavail- flavor contributing compounds in different varieties of
ability of amino acids. Tannins are mainly concerned with pulses grown in different agro-climatic conditions and soils
the defence mechanism in plants and have the capability to has not been studied in depth. Since, the pulses vary in
chelate with metal ions (Carbonaro et al. 1996) and protein, starch and fat composition, therefore, the retention
forming hydrogen bonds with proteins (Beebe et al. 2000). and adsorption in these may differ significantly. Various
Hence, reduces mineral absorption and digestibility of pulses are processed by different methods and their effects
proteins (Reddy and Butler 1989). Tannins also contribute on the retention and degradation of off-flavors cannot be
towards the reduction in nutritional value of pulses by ruled out. The detailed studies in this context are also
complex formation with starch or its digestive enzymes and required.
reduced palatability because of undesirable astringency The utilization of pulses is obstructed by the presence of
(Chung et al. 1998). Antinutritional factors in pulses also harder-to-cook (HTC) grains. The development of this
include phytic acid which is a potent chelator of metal ions defect was associated mainly with the prolonged storage in
and forms irreversible complexes with proteins and min- high temperature and humidity (Liu and Bourne 1995;
erals (Cheryan and Rackis 1980). Reyes-Moreno et al. 2000). HTC defect in grains led to the
Pulses are less acceptable due to the presence of typical loss of their ability to soften during soaking and made the
flavor, which is sometimes considered as off flavor by cell separation as well as starch gelatinization difficult
many consumers, that is inherent/produced during har- during cooking (Liu and Bourne 1995). Various factors
vesting, processing and storage (Roland et al. 2017). contribute to this defect including seed size, ripening
Generally, volatile off-flavor compounds in pulses belong degree, genetic factor and environmental factors while the
to the categories of aldehydes, alcohols, ketones, acids, most important is the storage of the grains in adverse
pyrazines and sulfur compounds. The off-taste also has conditions after harvesting (Prihayati et al. 2011). Different
been associated to the presence of saponins, phenolic hypothesis have been given for the development of HTC
compounds and alkaloids. No systematic studies have been defect in pulses which include (1) phytate-cation-pectin
performed on the identification of the off-flavor compounds model, (2) b-eliminative degradation of pectin and ligni-
present in pulses in relation to their contribution to the fications of cell wall (Liu and Bourne 1995). Interaction
overall perception of the pulses and their products. The between phytate, mineral cations and pectin was the most
major factor that limits the use of pulses as ingredient in acceptable hypothesis. This defect adversely affects the
food products is presence of off-flavor imparting chemi- nutritional quality along with high energy requirements and
cals. Many pulses impart flavor that are obstacle to the longer cooking duration that results in their constrained
consumption and utilization of pulses and pulse based acceptability by the consumer (Tuan and Phillips 1991;
products in different food formulations. For example, the Ruiz-Ruiz et al. 2012). Prolonged storage of black beans in
objectionable flavor of pea proteins hinders the wide adverse conditions revealed its negative relationship with
application in food products. The inherent off-flavor protein digestibility and solubility (Molina et al. 1976;
imparting chemicals in pulses are modified or eliminated Antunes et al. 1979). Both enzymatic as well as non-en-
during processing. The development of off-flavor can be zymatic reactions that contribute towards this defect,
diminished by implying appropriate processing to the simultaneously leads to the toughness in grains (Reyes-
pulses. The oxidation of unsaturated fatty acids also lead to Moreno and Paredes-Lopez 1993). Reports have also been
the development of off-flavor in pulses. The thermal found which includes the protein denaturation and pectin
degradation of phenolic acids and thiamine and formation insolubilization leading to the inability of grains to soften
Maillard products during heating of amino acids and sugars during cooking. Limited inter as well as intra-cellular water
also led to the formation of off-flavors (MacLeod et al. availability was also attributed of this defect (Hincks and
1988). Oxidation together with thermal degradation of Stanley 1987). b-eliminative degradation of pectin is also
cartenoids also contributes to the off-flavor development in one of the most important factor which results in the HTC
pulses. Lipoxygenase catalyzed degradation of polyunsat- defect. Being sensitive towards the increase in temperature,
urated fatty acids attributed to the off-flavor formation. The pectin undergoes degradation via breakdown of glycosidic
off-flavor development in pulses varies with storage con- bonds in the affinity of carboxyl group causing the for-
ditions, cultivar and growing locations. The saponin con- mation of low molecular weight products. To avoid the
tent was related to the bitterness of peas (Heng et al. 2006). development of this defect it is very important to store the
While, phenolics such as caffeic acid, vanillic acid, p- pulses in proper environment conditions. Protein concen-
coumaric acid and ferulic acid were reported to be trates, starch fractions and fiber rich fractions from HTC
responsible to the astringent character in pulses whereas grains can be produced using wet fractionation methods
ethyl esters of these phenolics were related to bitterness (Chel-Guerrero et al. 2002). These concentrates were

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