Hulless Barley: A new era of research for food purposes
Shaveta1, Harinderjeet Kaur,*1 Simarjit Kaur2 and Khushpreet Kaur2
1Department of Biochemistry, Punjab Agricultural University, Ludhiana 141004, Punjab, India
2Department of Plant Breeding and Genetics, Punjab Agricultural University, Ludhiana 141004, Punjab, India
*Corresponding author- Email: [email protected]________________________________________________________________________________________
Barley (Hordeum vulgare L.) is included in the family of grasses and is the fourth highly significant crop after maize, wheat and paddy. Barley is considered as important food ingredient because of the presence of vital biochemical constituents viz. ?-glucan (3-9%), starch (62-77%), amylose (25-30%), protein (10-15%) etc. Barley is usually classified as hulless or hulled types (presence or absence of hull adhering to grain). Hulless barley needs negligible processing and preserves maximum of the endosperm and germ which is once in a while lost during the time spent dehulling. As a result, it is highly suitable for human utilization as the entire grain can be specifically utilized to form a meal or processed into flour. Hulless barley has higher levels of starch and reduced fiber concentration, therefore have high digestible energy as compared to hulled barley. Because of the presence of dietary fibre, regular intake of barley contributes to maintenance of normal blood cholesterol concentration and also beneficial in preventing certain types of cancer like colon cancer. Barley has high ?-glucan content which helps in lowering of glycemic index and also causes the stimulation of bowel health. Barley ?-glucans are better in glucose and insulin responses compared to oat ?-glucan. ?-glucan soluble fiber is found throughout the whole barley kernel so, if these grains are processed, fiber will not get vanished. For this reason food industry is anxious about expanding the utilization of these cereals as nourishment fixings and henceforth more research is merited here.
Key words: Hulless barley, health benefits, ?-glucan, Amylose, Potential Uses
Barley (Hordeum vulgare L.) stands out amongst most significant cereal grain crop and positions fourth after maize (Zea mays), wheat (Triticum spp.) and rice (Oryza sativa) (FAO, 2011). It is diploid, self-pollinating crop having 14 chromosomes. The topmost barley producing countries are Russia, Germany, France and Ukraine (Table 1). Barley occupies 49.60 million ha area with 144.26 million tons production worldwide whereas in India it occupies 680 thousand ha area with 1790 thousand tons production (Anonymous, 2017). It is a Rabi season crop and in India, major barley producing states are Rajasthan, Punjab, Uttar Pradesh, Madhya Pradesh, Bihar and Haryana. Barley is highly adaptable cereal grain crop as it has ability to grow at higher latitudes and altitudes when contrasted with some other cereal grain species. Earlier, barley was considered as high energy food as it comprises eight vital amino acids and many potential antioxidants. Takahashi (1955) indicated by an examination that hulless barley is extensively dispersed, however its frequency significantly varied among locales. The distribution of hulless barley is skewed in the direction of East Asia as 95% of it grows in the plateaus of Japan, Korea, Nepal, Tibet of China and Bhutan. Hulless barley is comparatively grown in Ethiopia at low recurrence (Assefa and Labuschagne, 2004) and has been not really grown in Australia along with the western world. Hulless barley hereditary assets in China are richest throughout the world and it possesses 77% of the world’s aggregate hulless barley hereditary assets (Lu, 1995). Barley cultivars vary anatomically in the spike structure i.e., 2 and 6 rowed cultivars or in the growth pattern like between spring and winter-type barley genotypes. Hulled barley has the caryopsis covered with the hull. Hulless barley is rich in nutritional constituents like ?-glucan, limiting amio acids, starch and total dietary fiber as compared to its hulled types (Boros et al., 1996). Hulless barley has greater levels of starch and lesser fiber concentration therefore have greater digestible energy (Shon et al., 2007). There is a noteworthy rise in the production of hulless barley for the diets of non-ruminant animals who are not able to digest the fibrous hulls of the hulled barley and for the food thickeners, health foods and breakfast cereals for the human consumption because it has several nutritional characteristics (Edney et al., 1992). The two different forms of hulless barley are waxy and normal. The amylose to amylopectin ratio in the normal form of hulless barley is similar to the regular hulled barley (around 25% amylose and 75% amylopectin). The waxy form of hulless barley has higher content of amylopectin, starch and ?-glucans (about 95 to 100% amylopectin). Because of higher ?-glucan content, waxy barley is not easier to digest which makes it highly suitable for its use as thickening agents in various industries. Regular hulless barley cultivars possess higher ?-glucan content as compared to its hulled types. The ?-glucan inhibits rise in the LDL cholesterol levels in humans. Barley types differ considerably in starch, ?-glucan, grain test weight but not in the protein content, with hulless barley possessing significantly greater grain test weight and starch content as compared to hulled and malting barleys and significantly greater ?-glucan content as compared to malting barleys (Griffey et al., 2010).
Table 1. Top barley producers in the world during year 2016
Rank Country/Region Barley production
1 Russia 17.99
2 Germany 10.73
3 France 10.30
4 Ukraine 9.43
5 Australia 8.99
6 Canada 8.70
7 Spain 7.97
8 Turkey 6.70
9 United Kingdom 6.65
10 United States 4.33
Source: Food and Agriculture Organization Corporate Statistical Database (2016)
Barley was most probably used in food but progressed mainly into feed, malting grain due to the increase in eminence of rice and wheat. At present 94% of globally produced barley is used for the manufacturing of beer and only 2% is used in food. On the other hand, it is essential human nourishment in the areas where hulless barley is developed at much higher frequencies. As of late, it is pulling in signi?cant consideration as a nutritious human sustenance in non-conventional areas because of its higher content of ?-glucan, which go about as inhibitor in the synthesis of cholesterol (Berglung et al., 1993), its higher lysine (Bhatty, 1986), and protein content (Oscarsson et al., 1996) and owing to processing benefits without the removal of hull for the barley food trade (Bhatty, 1993; Newman, 1992). There are likewise ongoing increments in the utilization of naked barley in western nations. Therefore, hulless barley is now used in various kinds of food products and their consumption provides potential health benefits.
2. Structure of barley grain:
The most vital living tissue in the interior of a barley grain is the embryo. Duffus and Cochrane (1992, 1993) stated an inclusive review of the development and structure of the embryo. The productive portion of the barley seed is the embryo, which too contains lipids, proteins and starch. These biochemical constituents are utilized during the time-period of embryo development after fertilization and also as a primary sustenance source during the germination of harvested seeds. The feasibility and dormancy level of the embryo is thoughtful for the upcoming generation of seeds. There are various factors that can affect dormancy and feasibility comprising: i) environmental surroundings after anthesis and throughout the period of grain fill, viz. cold (frost) stress or heat (heat wave) stress; ii) harvesting conditions (viz. too much abrasions in the course of threshing in the harvester or pre-reap rain); iii) plant moisture (avoiding drought conditions); iv) storage circumstances (like too much heat during storage or higher grain dampness content can cause reduction in the germination potential).
The process of germination is commenced through the imbibition of water by embryo, from which initiation of course of biological reactions takes place. The only determination of the embryo is to produce a plant that will yield new seeds. The biological reactions start the breakdown of the stores in the endosperm to deliver amino acids, fats and sugars for the consumption by the growing embryo. These reactions initiate the advancement of complex enzymatic pathways (comprising the growth of hormones) that will causes the production of endosperm cell wall degrading enzymes, starch granules and storage proteins and consequent transport of these items to the embryo.
Barley grain primarily comprises of endosperm (75%), aleurone layer, germ and pericarp. Pericarp and seed coat provide protection to the seed against external injuries by completely covering the entire seed. The fundamental part of the barley grain is endosperm, the chemical composition which is straight linked to the malt quality. The endosperm tissue serves as the reservoir of starch granules whereas the aleurone layer primarily accompanies the significant portion of the barley grain. The aleurone layer is made up of the cells that comprise starch granules. It is few celled thicker and encloses the entire endosperm. The aleurone layer is just one cell thicker at the germ and in the crease its thickness is highly variable. The non-starch polysaccharides, arabinoxylan and ?-glucan are mainly located in the cell wall of aleurone layer. However, ?-glucan to arabinoxylan ratio is 25:75, which is opposite for the cell wall of endosperm. The higher the ?-glucan content thicker is the cell wall found in various cultivars (Zheng et al., 2000). The aleurone plays an important role in the expression of endosperm degrading enzymes during germination, comprising: i) ?-glucanases; ii) Limit Dextrinase (Sissions et al., 1992); iii) ?-amylase; iv) Proteinases and peptidases (Jones, 2005a); v) ?-glucosidase; vi) Inhibitors proteinases (Jones, 2005b), vi) limit dextrinase and trypsin (Macgregor et al., 2002; Stahl et al., 2007).
Fig 1: Barley grain structure
3. Barley grain classification and its composition:
Barley can be categorized into six row or two row type, spring or winter type, malting/feed/food type and hulled or hulless type. Based on the row of grain on spike when the heads of the stalks are seen from above barley can be categorized into two types: i) Hordeum vulgare: six rowed barley having a spike being notched on contrasting sides having three spikelets at each notch. Each notch has a flower or floret later developing into a kernel. ii) Hordeum distichum: two rowed barley with the central florets later producing kernels and having sterile lateral florets. Six rowed barley possess higher content of protein and enzyme when compared with two rowed barley (Table 2). Malt type barley is mainly used in brewing and malting industries, the feed type is majorly used in animal feed and the hulless type of barley is conspicuously utilized for human utilization. Hulled barley alludes to covered barley which is slightly processed so as to take off only the outer tough indigestible hull. Hulled barley might be bought in various forms comprising cut (grits), ground or flaked (flour or meal), kernels (berries). Hulless barley mentions to a kind of barley in which the intense inedible exterior hull is insecurely bound to the kernel. The exterior hull is so loose to the point that, it usually falls off during the harvesting time of the hulless barley. Processors frequently mention to this kind of barley as ‘hulless or naked’ barley. Hulless barley needs negligible processing to remove the outer tough indigestible hull. Since this product requires negligible processing, therefore most of the endosperm and bran is left undamaged and the germ is also present. Hulless trait of barley is mainly under the control of a single gene locus known as ‘nud’ (Taketa et al., 2008). The naked type of barley has a close resemblance with that of its hulled part in having the agronomic features except being poor in crop establishment for being sensitive to damage to exposed embryo (Choo et al., 2001). Hulless barley is considered as an excellent source of proteins, dietary fibre and fat fractions in contrast with hulled barley. The different forms of hulless barley are waxy and normal. The normal form of hulless barley has the amylose-amylopectin ratio similar to regular hulled barley (about 25% of amylose and 75% of amylopectin). The waxy barley is rich in amylopectin (95-100%), starch and ?-glucans. Being rich in ?-glucan, the waxy barley is difficult to digest which makes it better suitable for its use in industries as thickening agents.
Table 2. Difference between two row and six row barley
S.No. Quality Parameters Six-Row Two-Row
1 Plump Kernels (%) ;80.0 ;90.0
2 Germination (%) ?98.0 ?98.0
3 Extract (% dry basis) ;79 ;81.0
4 Total Protein (% dry basis) 9.0-12.5 9.0-11.5
5 Diastatic Power (degrees lintner) 160 120
6 ?-glucan (ppm) ;120 ;100
?-glucan is an important component which forms the cell wall in barley endosperm which accounts for 75% of the endosperm cell wall mass. Barley varieties with high ?-glucan content are digested more slowly than standard barley varieties and thus help in weight control programmes. ?-glucans are found to lower plasma cholesterol, to improve lipid metabolism, to reduce glycemic index and the threat of colon cancer (Ahmad et al., 2012). There is a genetic variation in the levels of ?-glucans in barley with levels ranging from ;3.0% to ;15.0%. Barley having the waxy gene showed higher levels of ?-glucans. ?-glucan content is affected by environmental conditions like an increase under dry and hot conditions and a decrease under moist conditions. Starch is the main carbohydrate in barley having having the range of 62-77% of the grain dry weight. It is composed of amylose and amylopectin. A higher percentage of amylopectin content leads to an increase in solubility whereas high amylose content lowers the digestibility of starch because the amylose content and the resistant starch formation are positively correlated with each other (Singh et al., 2010). Barley endosperm protein has high reserves of the prolamin (around 50%) storage proteins that have adequate nutritive quality with protein efficiency ratio ranging be around 2.04 with the three other proteins globulins, albumins and glutelins making up the rest of the protein. The synthesis of protein begins quite early after anthesis, in spite of the fact that there are distinctive reports on the definite timing of these protein constituents.
4. Potential Opportunities
Barley is a multi-purpose cereal crop grown for food, malting and general purposes (feed) throughout the world (Table 3). Whereas, relatively lesser amount of barley is utilized directly for food nowadays, it has incredible prospective to regain some of its importance as a food grain, mainly because of its high nutritive esteem. Barley grain offers lesser fat complex sugars primarily starch for energy, comparatively well-adjusted protein content to meet amino acid necessities, vitamins, mainly vitamin E, minerals and various other antioxidants, mainly polyphenolics, and soluble and insoluble fiber with general (quick passage of food in the colon) and definite health benefits. Barley is the main cereal used in the production of malt throughout the world because it contains numerous enzymes which are essential for transforming the grain starches into several types of sugars like glucose (monosaccharide), maltose (disaccharide), maltotriose (tri-saccharide), and the complex sugars known as maltodextrines. It also contains additional enzymes, for instance proteases, which causes the protein breakdown in the grain into different forms that can be exploited by yeast. Therefore malted barley grain is used in the production of beer, malted milkshakes, malt vinegar, whisky, confections like malsters and whoppers, flavored drinks like Horlicks, milo and ovaltine and some baked goods. For the ruminants barley is the third most readily degradable cereal after oats and wheat. So there are various potential opportunities of barley like malting, food and feed purposes and the prospective is great to progress barley for all these practices.
4.1 Malting/Brewing: About 10% of worldwide production of barley is utilized to make malt for preparing lager. The malting varieties incorporate two-row, six-row, hulled and hulless varieties, yet the hulled barley is favored because hull adds flavor and helps in filtration during the process of brewing (Gunkel et al., 2002). Malting barley varieties are for the most part produced for a particular market e.g. for trade or domestic brewing. The chemical, biochemical and physical properties of barley grain can largely affect the malting procedure and quality of beer. Kernel physical characteristics like germ growth, kernel maturity, germination percentage, size, frost damage and measure of seed borne maladies are factors that influence malting process. The measure of grain protein, ?-glucan, starch and their interactions during the period of grain filling influence grain hardness and yield of malt extract (Psota et al., 2007). Another factor that defines the quantity of malt extract is the level of alpha amylase. Soft barley varieties are usually preferred for malting (Gupta et al., 2010) with protein content ranging from 10.5-13.0% for six-row varities and 10.5%-12.5% for two-row types. Barley cultivars having higher protein concentration (;15%) are not used for malting because it requires long steeping time, produces low malt extracts and has erratic germination (Swanston and Molina-Cano, 2001). Bleached barley grain is additionally not suitable for malting because during the breakdown of phenolics, the production of undesirable flavors takes place in lager (Mussatto et al., 2006). An effective maintenance of malting barley trade market wants great determination of cultivars with suitable malting qualities.
4.2 Livestock feed: Barley is regularly utilized for animal feed in spite of the fact that nutritive value is lesser as compared to wheat or corn. Both six- and two-row hulless barleys are usually grown for the production of animal feed. The removal of the hull is required to result in uncertain increments in absolute nutrient levels of hulless barley when compared with regular barley. In practice, the nutrient composition of hulless barley often exceeds this expectation. That’s why the interest is growing towards the developing of hulless barley for the feed industry. Moreover, a substantial measure of hulled malting barley grain with insufficient malting characteristics entered into the animal feed market. This makes feed barley a non-homogeneous product with changing nutritive esteem. The six- and two-row hulless barleys produced for feed in Canada are moderately higher in protein content (14-15%), however the two-row barley grain is favored because it has a relatively higher content of carbohydrates (Fregeau-Reid et al., 2001) and is highly edible by monogastric animals like swine and poultry.
When the monogastric animals are fed with hulled barley they will not be able to digest the fibrous hull therefore to help in digestion, an ezyme named ?-glucanase is often supplemented with the diet of these animals (Mathlouthi et al., 2003). Other than hulls, an additional component of seed is phytate that adversely influence barley consumption as animal feed. Phytic acid effectively chelates polyvalent cations like copper, iron, calcium, magnesium, zinc and aluminium therefore making the minerals inaccessible for absorption (Adams et al., 2002). Zinc is one of the most vulnerable mineral to chelation by phytic acid. A decrease of phytic acid formation in barley genotype HB379 (Roslinsky et al., 2007) has multiplied the accessibility of zinc and phosphorous for broilers (Linares et al., 2007). Despite the fact that barley is prevalent as animal feed, barley grain possessing higher concentration of starch is not acceptable for ruminants. Quick fermentation of starch in rumen causes drop in pH, which ultimately decreases fiber consumption and causes various gastric disorders. Decrease in milk fat content is found when barley with high starch concentration is utilized as feed for lactating bovines (Larsen et al., 2009). For that reason it is essential to examine seed constitution while choosing barley grain for ruminants as well as non-ruminants.
4.3 Food: Commonness of lifestyle diseases is increasing step by step. For the most part the youthful age does not have much responsiveness about healthy nourishing supplements. Barley is a cereal grain that is rich in nutritive components with so numerous health welfares like weight decrease, declining blood pressure, blood glucose, blood cholesterol and prevention from colon cancer. It is effectively accessible and modest grain and it contains both insoluble and soluble fiber, protein, vitamin B and E, minerals like magnesium, iron and selenium, anthocyanins and flavonoids. Therefore, hulless barley is preffered nowadays in foods.
4.3.1 Cholesterol free or lower in fat content: Because of the presence of very lesser amount of cholesterol in hulless barley, doctors recommend to eat barley food to the heart patients. Although barley is cholesterol free but it also possess cholesterol lowering property and hence create hypocholestrolemic effects inside the body. Various studies have demonstrated that soluble fiber ?-glucan from barley and oat can bring down the LDL and total cholesterol level and therefore play an important role in both the anticipation and administration of cardiovascular ailment. The FDA established that every-day utilization of 3 g of soluble dietary fiber ?-glucan from barley or specific dry milled barley produces would create a similar cholesterol-bringing down impact as oat products (decreasing total plasma cholesterol level by 5–8%).
4.3.2 Contains several vitamins and minerals: Barley is also a principal source of various vitamins and minerals like niacin, thiamine, selenium, iron, magnesium, zinc, phosphorous and copper. The mineral content of barley kernel varies from 2-3%, depending on the genotype. The minerals present in the seed are mainly found in the aleurone, embryo as well as in pericarp tissues (Marconi et al., 2000). Minerals which influence the kernel nutritional value are mainly divided into macro- and micro-elements on the basis of their concentration in foods. The macro elements comprise calcium, calcium, magnesium, phosphorous and potassium. The others are sulphur, silicon and chloride. The nutritionally essential micro-elements present in the barley grain are zinc, selenium, iron, cobalt, copper and manganese. Phosphorus and potassium are the macro elements which are most plentiful and in terms of availability and nutritive qualities. Phosphorus present in barley kernel occurs in the form of phytic acid. The enzyme phytase is absent in monogastric animals for the consumption of phytic acid. The higher content of phytic acid chelates various monovalent ions like copper, zinc and calcium making them inaccessible. Comparatively lesser phytic acids are required for poultry feed as higher content causes sticky droppings.
Zinc helps to heal injuries and also works wonders for the skin whereas selenium plays a major role in reducing the risk of colon cancer. Selenium additionally plays an important role in various metabolic pathways: antioxidant defense systems, immune function and thyroid hormone metabolism. Selenium has been appeared to initiate DNA repair and amalgamation in damaged cells, to hinder the cancer cells proliferation, and to prompt their apoptosis, which is the the self-destruct sequence the body uses to remove worn out or abnormal cells. Copper is another trace element provided by barley, which is helpful in reducing the symptoms of rheumatoid arthritis. Phosphorous plays a vital role in forming the mineral matrix of bone and also helps in the formation of several life critical compounds comprising adenosine triphosphate (ATP: which is the energy currency of body). Phosphorous is the main component of nucleic acids which are the building blocks of genetic code. Copper is an important cofactor of crucial oxidative enzyme named superoxide dismutase (SOD). SOD deactivates free radicals produced in mitochondria.
4.3.3 Contains antioxidants and phytochemicals: Phenolics are one of the major class of phytonutrients and these are potent antioxidants that works in numerous ways to prevent diseases. Various compounds are incorporated in this category for example ellagic acid, curcumin, catechins, quercetin and many more. Barley grains comprise a varied range of phenolic acids that are either cinnamic acid or benzoic acid derivatives. In general, larger amounts of phenolic compounds were accounted for oat and barley contrasted with rye and wheat (Zielinski and Kozlowska, 2000). The phenolic acid which is present in large amounts in cereals is ferulic acid, signifying up to 90% of overall polyphenols (Sosulski et al., 1982). Similarly Naczk and Shahidi (2006) and Hernanz et al. (2001) stated that ferulic acid is the principal phenolic acid present in barley grain. Yu et al. (2002) examined the phenolic acids composition in thirty barley cultivars where they establish varying levels of cinnamic and benzoic acids. Phenolic compounds are thought to exhibit several roles like: reducing agent, free radical scavenger and prevents the formation of singlet oxygen and potential producer of pro-oxidant metals.
Anthocyanins present in barley and wheat are discovered either in the aleurone layer or the pericarp bring about blue and purple hues of grain colour, respectively. The black coloration of the pericarp and lemma of barley is depicted because of the presence of melanin-like pigment in them (Lundqvist et al., 1996) which might overlap additional pigments. The black colour of the kernel is because of melanin-like pigment is unidentified to wheat species.
Zeaxanthin and lutein are the two fundamental carotenoids recognized in barley (Panfili et al., 2004). They effectively functions as free radical scavengers because of the presence of electron rich chain (Cooke et al., 2002) and hinder the free radical propagation reactions for example lipid peroxidation. Zeaxanthin and lutein are accountable for the pigmentation of the macula lutea present in retina, which is the area of best visual sharpness. Therefore, dietary zeaxanthin and lutein are thought to provide protection against cataract and age-related macular deterioration (Beatty et al., 2000). Moreover, zeaxanthin and lutein probably act together with various other bioactive components against cardiovascular risk, cancer and different infections (Mares-Perlman et al., 2002; Calvo, 2005). Tocopherols or vitamin E are additionally present in noticeable amounts (Cavallero et al., 2004; Andersson et al., 2008). Another kind of phytonutrient rich in barley are plant lignans, which are converted by friendly flora present in digestion tracts into the mammalian lignans, comprising one called enterolactone that is supposed to provide protection against breast and various hormone dependent cancers along with heart disease.
Table 3. Proportionate utility of barley:-
VARIOUS FIELDS UTILITY (%)
1. Brewing purpose 50%
2. Food and feed purpose 25%
3. Distilled and whisky 20%
4. Syrup, Vinegar, Diuretics 5%
Figure 2: Hulless Barley
Figure 1: Hulled Barley
Table 4. Difference in Biochemical constituents in hulled and hulless barley:-
1. Calories 370 350
2. Protein 13g 10g
3. Carbohydrate 73.9g 78g
4. Fat 2.2g 1g
5. ?-glucan4.1% 3.9%
6. Crude fiber 1.4% 5%
7. Calcium 5% 2%
5. Health benefits:
A very higher content of fiber, minerals, vitamins, antioxidants, diabetes protection and heart health are some of the barley nutritive benefits that make it one of the best whole grain selections. Intake of whole grain barley with lots of fiber regulates blood sugar level. Consuming breakfast cereals comprising barley over weeks to months also helps to improve cholesterol levels and also glucose regulation. Therefore barley provide potential health benefits to human and they are listed below.
5.1 Hypocholesterolemic effect:
?-glucan positively affects the cholesterol levels because the fiber helps in the absorption and elimination of bile acids formed from the cholesterol present in the liver. The bile acids absorption activates the liver to make more bile acids from the cholesterol (Brennan, 2005) and the net impact is a decrease in cholesterol level of blood (Behall, 2004). Barley fiber is additionally an excellent source of vitamin B (niacin) that decreases platelet aggregations which are accountable for the formation of blood clots and declines the total cholesterol level, lipoprotein as well as free radicals that causes the oxidation of LDL cholesterol. Therefore, niacin secures against various cardiovascular diseases (Jood and Kalra, 2001).
5.2 Hypoglycemic effect:
Barley ?-glucan in their native form, are high sub-atomic weight polysaccharides that display higher viscosities at lesser concentrations (Ren Y et al., 2003). Intake of viscous polysaccharides causes an increase in meal bolus viscosity in the stomach, which ultimately reduces the blending of food with peptic enzymes and therefore delays gastric purging (Marciani et al., 2001). Greater viscosity also slows down the glucose absorption (Braaten et al., 1991; Panahi et al., 2007). In vitro digestion studies show that ?-glucan reduces the rate of starch degradation (Regand et al., 2011).
5.3 Antitumor activity:
Barley grains are great wellspring of phenols and contain high measure of total phenolics. Phenolic compounds are the secondary metabolites of plants possessing possible positive physiological effects (Peng et al., 2015). These phenolic compounds are the important bioactive components having high health promoting activity which are used in food products to increase dietary fiber levels and nutraceutical properties. They possess many biological properties like antioxidant, anti-carcinogen, anti-aging, inhibition of cell proliferation activity along with the improvement of endothelial function. These compounds are mainly located in the pericarp of cereal grains affecting their appearance, taste and odour in the plant foods. A wide range of pheolic antioxidant compounds were identified in barley like derivatives of cinnamic and benzoic acid, flavones, flavanones, chalcones, proanthocyanidins and flavonols (Hernanz et al., 2001). In cereals they can exist in free or bound form. Bound phenolic compounds are usually ester linked with the cell wall polymers present in the external layers of barley kernel. An important phenolic compound present in cereals in bound form is ferulic acid and its dehydrodimer derivatives (Kim et al., 2007). Ferulic and p-coumaric acids are the major phenolic acids in the cereals. Anthocyanins are the most studied water-soluble pigments in cereals.
5.4 Used as Prebiotic:
Prebiosis involves in the particular incitement of activity and growth of single or a restricted number of valuable micro-organisms in the gut microbiota, therefore increasing probiotic inferring medical advantages to the host (Mayo et al., 2008; Roberfroid et al., 2010). In addition, prebiotic properties have been identified with enhanced efficiency in immune functions, tumor prevention, intestinal functions and mineral absorption (Dass et al., 2007; Xiong et al., 2004; Artis, 2008). The gut micro-organisms include generally anaerobic bacteria that require fermentative substrates to get metabolic vitality for their activity and development. Non-edible food carbohydrates, containing fibres, resistant starch, oligosaccharides in addition to peptides or proteins that get away from human digestion, can be used by microbes as an energy source (Topping and Clifton, 2001; Lupton, 2004). Numerous food components, together with galacto-oligosaccharides (GOS) and fructo-oligosaccharides (FOS) have been presented to positively impact the metabolism and development of lactobacilli and bifidobacteria, along with the general composition of the gut micro-organisms, therefore playing out a prebiotic activity. Amongst dietary fibres, ?-glucans, accompanied by other indigestible food constituents such as lactosucrose, isomalto-oligosaccharides and soybean oligosaccharides, are presently being examined to assess their possible prebiotic impacts.
?-Glucans comprise the water-soluble portion of numerous cereals and these are present in the aleurone cell wall as well as subaleurone layer of sorghum, barley, triticale, rice, wheat and oat (Mayo et al., 2011, Holteljolen et al., 2006). Cereals (like barley and oat) with high ?-glucan level, the content of which lies in the range of 3–8 g and 2–20 g per 100 g of dry weight,trespectively. These cereal grain ?-glucans are linear polymers of D-glucose connected by ?(1,3) or ?(1,4) glycosidic linkages, for which individuals do not have enzymes to break these glycosidic linkages, and introducing side branches connected to the main chain by ?(1,2)- or (1,6)-glucopyranosyl units (El Khoury et al., 2012; Barsanti et al., 2011). In addition, ?-glucans have been appeared to be exceptionally fermentable by the intestinal micro-organisms of colon and caecum, and can improve the development rate and the production of lactic acid of micro-organisms sequestered from the human intestine (Blaut, 2002; Kedia et al., 2008).
5.5 Prevents osteoporosis:
Barley is considered as an excellent source of silicon, which is an important mineral in bone formation (Nielsen and Sandstead, 1974). High silicon content has been found in beer because of the processing of barley and hops. In 1970, Edith M. Carsile, Ph.D., in print a brief paper in discipline of science entitled “Silicon: a possible factor in bone calcification” (Carlisle, 1970). Silicon is bound to glycosaminoglycans and plays a major role in the development of cross-connects between proteoglycans and collagen (Carlisle, 1981). Silicon is found in all body tissues, but the most elevated silicon content was found in the bones and in various connective tissues like skin, arteries, hair and nails (Jugdaohsingh, 2007). In vitro studies have established that silicon activates osteoblast differentiation and the synthesis of type I collagen (Reffitt et al., 2003). Studies in rats have established that silicon at physiological levels increases the absorption of calcium in bone as compared to the rats that are silicon deficient (Seaborn and Nielsen, 2002). Therefore, silicon is an important element for formation the formation of bones. The precise sequence of mineralization is not known, however Carlisle established that silicon most likely acts by making the bone lattice more calcifiable (Carlisle, 1981). The concentration of silicon in osteoid is 25 times greater as compared to the surrounding regions and silicon concentration slowly decreases as calcification takes place (Carlisle, 1970). Additional investigation in postmenopausal animal models utilized elevated levels of supplementary dietary silicon (20 mg/kg/day) (Bae et al., 2008; Kim, 2009). These higher levels of silicon stimulate bone formation, decreased calcium defecation in the urine and increased bone mineral density.
5.6 Keeps Intestine Healthy:
Barley is an exceptional wellspring of fiber that keeps human body toxin free. Barley grass is lavish in dietary fiber which acts as an energy source to the benevolent bacteria present in our large intestine. The fiber present in barley is fermented by these bacteria and leads to the production of butyric acid which acts as principal fuel for cells of intestine. It is highly effective in keeping up a sound colon. By maintaining the intestine in good health, it helps to reduce the movement time of faeces and furthermore keeps the stomach hygienic. It significantly decreases the risk of colon malignancy as well as hemorrhoids.
5.7 Protects against gallstones:
Barley efficiently enables women abstain from developing gallstones. As it contains higher content of insoluble fiber, it really encourages people decrease bile acid discharge, in this manner escalating insulin sensitivity and decreasing the triglyceride amount. An article in the American Journal of Gastroenterology states that intake of a fibrous diet by women have 17% lesser possibility of gallstones development when compared with other women.
6. Current Research:
Much is known about the nourishing and medical advantages of barley intake but lesser is known about the usefulness of barley grain constituents in terms of processing and food product development. Considering the health benefits of barley ?-glucan and phenolic compounds, the human consumption of barley is encouraged by utilizing it in foods with attractive sensory characteristics. Efforts have been made to utilize barley in bread, cookies, chapattis and in noodles. Studies have also been undertaken to access transcriptome changes during the hulless barley grain development which is not surely understood yet.
6.1 To utilize hulless barley to enhance the nutritional value of biscuit and chapatti prepared from wheat flour: A great attention has newly ascended in the improvement of ‘functional’ foods, items that may offer health bene?ts further than the conventional supplements. Foods that contain high cancer preventive agents and a lower glycemic index (GI) can lower the threat of high postprandial oxidative stress, which is one of the components of the beginning of numerous long lasting diseases (Hou and Jimenez, 2013). Barley is considered as extremely nutritive cereal grain due to the presence of higher content of ?-glucan soluble fiber (Sullivan et al., 2013) as well as cancer preventive agents (Zhao et al., 2008). Studies additionally demonstrate that bread prepared with a combination of barley and wheat ?our has suitable sensory characteristics (Skendi et al., 2010). The ?-glucan present in barley ?our can improve the bread quality by altering the insulin and glycemic response (Gujral and Gaur, 2005). Barley is mostly being utilized to prepare beer and malt. Barley is moreover used in multigrain ?ours, ready to eat breakfast cereals, high ?ber biscuits, muesli, etc. At home, barley ?our can be effectively mixed with the wheat ?our keeping in mind the end goal to make more nutritive and healthy items for daily utilization.
Narwal et al. (2017) were made first effort to utilize a hulless barley genotype (BHS 352) for mixing with the wheat ?our (C306 & HS490) and making mixed chapatti and cookies. These foodstuffs were then evaluated for total phenolic, ?-glucan content and antioxidant activity to note the mixing effects. Their investigation has demonstrated that adding barley to wheat biscuit and chapatti can extensively improve the nutritive significance of these items in terms of high ?-glucan content, high phenolic content and antioxidant activity. Besides, hulless barley requires minimal processing when contrasted with hulled barley and therefore substantially more beneficial for blending motive at house hold level. Therefore, BHS 352, which is a hulless barley variety can be decent choice to enhance the health and nutritional bene?ts of wheat-based items. By integrating barley ?our into commonly utilized wheat-based items, it could help consumers to enhance their wellbeing.
6.2 To investigate transcriptome changes during barley grain development using Illumina-paired end
RNA sequencing: Hulless barley, with its exclusive nutritious esteem and possible medical advantages, has progressively pulled in considerations in current years. Though, the transcription changes during development of hulless barley grain are not surely knew. Tang et al. (2017) examined the transcriptome changes during development of barley grain of two Tibetan hulless barley varieties 08-1127(C2) and Zangqing 2000 (Q) with the different grain starch synthesis characteristics, and then relative transcription approach in these genotypes was accomplished by means of Illumina paired-end RNA-sequencing. Co-modulated and genotype-specific differentially expressed genes were recognized and functionally interpreted, and their expression levels accumulation in various KEGG pathways were additionally conducted. They further analysed the starch synthesis-related genes in these two phenotypes and authenticated by Quantitative real-time PCR. This investigation provides plentiful resources for identification of genes which are related to starch synthesis and are also essential for quality enhancement in barley.
7. Conclusions and implications
Hulless barley is known for its superior nutritional components like starch, protein, total dietary fiber, ?-glucan and limiting amino acids as compared to its hulled genotypes. The ?-glucan of barley prevents an increase in the LDL cholesterol levels and it also regulates glucose metabolism which helps in regulating type 2-diabetes. Due to the presence of high phenolics content in hulless barley, it serves as potential antioxidant and therefore doctors recommend the diet containing barley. In case of hulless barley minimal processing is required due to which it could be directly used for human consumption. Today around two third global production of barley is used for animal feed, one-third for malting purposes and near about 2% is used for human consumption. Currently hulless barley is used as feed as diet of non-ruminants as they are not able to digest fibrous hull of hulled barley. Utilization of barley in baked products such as cookies, chapattis and breads can also open a path to exploit the health benefits of barley in human foods.