Barley

Barley

Hordeum vulgare

Family- Poaceae

Barley is one of the oldest of cultivated cereals and is extensively used as food and cattle feed and for malting, brewing and pearling. The important producers of barley are Russia, USA, Canada, India and countries bordering the mediterranean. It has been cultivated since long time in northern India. It is grown in the plains as well as in the hilly regions of the Himalayas upto an altitude of 4200 m India-Gangetic area and the adjoining tracts of Madhya Pradesh.

History

Barley is supposed to have originated somewhere in the region between north west of India and Abyssinia. Several species of wild forms of barley still grow in various parts of the world, Palestine, Syria, the Euphrates Valley, Iran and further east and north-east in Afghanistan and Bokhara. According to Kornicke (1895) H. spontaneum, a wild form of barley, is particularly interesting in the history of agriculture. It is the oldest of our cultivated plants. It was the main crop of the Greeks. They called the baked barley bread as Alphita. Excavations conducted at Fayum, Cairo (Egypt), revealed grains of Neo Barley of Neolithic times (5,000-10,000 B.C.). From an early Iron Age settlement Fifield Bavant Down, Wills (England) grains of barley (as well as wheat and oats) were discovered in 1924 A.D. This grain was probably grown 2,000 to 3,000 years later than Fayum species. Barley is very frequently portrayed on ancient coins.

Botanical classification

The botanical classification of barley, as in most of the higher plants, depends on the form of the inflorescence. Linnaeus (1753) and the earlier botanists had recognised six species:

H. hexasticum

H. vulgare

H. distichum

H. zeocriton

H. coeleste

H. nudum

Cultivated barleys are divided into three groups based on morphological criteria and arrangement of spikelets. They are-

• Six rowed barleys: All the spikelets at a node are fertile. The spikelets are in six distinct rows and arranged at a uniform distance around the rachis. Hence the mature grains are in six rows upto the axis. H. hexasticum, H. intermedium, H. vulgare etc. belong to this group.
• Four rowed barleys: All spikelets at a node are fertile. The rows of grains are not at equal distance from each other on the axis. The lateral grains of one trio tend to overlap the lateral grains of the triplet on the opposite side of the rachis. This results in the formation of four rowed grains.
• Two rowed barleys: Of the triple of spikelets at each node, only the central one sets grain The lateral ones are imperfect. Hence, the grains are seen in two rows along the rachis. H. distichum, H. deficiens etc. belong to this group.

Botany of the plant

An annual erect, stout, tufted herb, 0.6-1.2 m high, resembling wheat in habit.

Leaves few linear, lanceolate, upper one close to the spike, sheath smooth, striate, ligules short, membraneous.

Spikes terminal, linear-oblong, compressed, 5-6 cm long, densely flowered.

Spikelets sessile, arranged in threes on two sides of a flattened rachis, all fertile (6 rowed type), or lateral ones barren and occasionally rudimentary (2 rowed type).

Glumes 2, small, narrow, short-awned, enclosing three spikelets, lemma lanceolate, fine ribbed, tapering into a long straight or recurved awn, palea a little smaller than lemma, with margins inflexed, lodicules 2, stamens 3, stigmas 2.

Fruit a caryopsis, elliptic, 9 cm long, short-pointed, grooved on inner face, smooth, free or adherent to palea or both to lemma and palea.

Ecology

Like wheat, barley does best in areas where winter is cool and the growing period lasts about five months. Areas that are always warm and moist are not suitable for this crop. The crop thrives well on well-drained and moderately rich loams.

Barley grain

  

The barley grain has a roughly spindle-shaped body, tapering at each end, with a shallow furrow running along the ventral side. In most commercial barleys the flowering glumes, (husk or chaff), adhere to the grain, but many varieties are known in which the naked or hulloes grain separates from the chaff. within the husk is the caryopsis a fruit in which the pericarp (the remains of the ovary wall) is fused to the seed coat (testa, tegmen). Within the testa the largest tissue is the starchy endosperm, bounded at the periphery by the aleurone layer, which is also part of the endosperm. At the basal end of the grain is the embryo. The embryonic axis consists of an apical meristem, three or rarely four embryonic leaves, usually two axillary bud primordial and tubular coleoptile with an apical pore. Below the shoot, are present the seminal root initials, each with a root cap.

Chemical composition

The average composition of Indian barley is as follows: moisture 12.5, protein 11.5, ether extra. 1.3, mineral matter 1.5, fibre 3.9, carbohydrates 69.3, calcium 0.03, phosphorus 0.23 percent, iron 3.7 mg/100g. Two-rowed barleys contain more starch than six-rowed types. The free sugars present in barley are sucrose and raffinose, with smaller amounts of glucose, fructose, maltose, glucodifructose and fructosans. Barley contains four classes of protein, viz., albumin, globulin, prolamin (hordein) and gluten (hordemin) free amino acids and protein intermediates are also present (Winton & Winton 1935).

The essential amino acids present are (calculated to 16.0 g.N) arginine 4.5, histidine 1.8, lysine 2.4, tryptophan 1.1, leucine 5.5, isoleucine 3.8, valine 5.1, phenylalanine 5.7, threonine 3.6 and methionine 1.0.

Uses

Barley grain can be used as a source of high amylose or high amylopectin starches. A proportion of barley grain is used to make malt which, with or without unsalted grain, is used to make beer, whiskey and some other products. By products of these processes, notably malt culms, surplus yeast, spent brewery grains etc. are used as animal feed. 

New Technology- Barley grain has a low protein content. For increasing the content of essential amino acids  and proteins, barley flour is added with buffer salts or urea and by culturing micro-organisms on the mixture. The filamentous mould Aspergillus oryzae or the thermo-tolerant basidiomycete and Sorotrichum pulverulentum have been cultivated on cereal flours, brans and cellulose for improving the quality of protein. 

Pearl barley- Barley grains from which the hulls and outer layers have been removed by a process of gradual abrasion are known in trade as Pearl Barley It is used in the food industry.

Malt and malt products

Malt is the name applied to cereal or millet grain which has been germinated upto a certain stage and then killed under controlled conditions. The purpose of malting is to activate the enzymes present in the resting grain and bring about certain desired physical and chemical changes in the kernel. Barley is the raw material favoured by the brewer for the production of malt.

Malting barleys are characterized by a high percentage of germination and relatively low nitrogen content. Most beers in Europe are brewed from malts prepared from 2-rowed barleys. 

Manufacture-

Selected and cleaned barley is dried in kilns at 37.4-48 degree C and stored for 60 days.

Steeping:

Stored grain is steeped in water at 9.9-1.5 degree C for 48-70 hours with frequent changes of water and intermittent aeration. A small quantity of lime water is often added to the first steep to inhibit fungus growth and to leach out undesirable hull constituents.

Germination:

The steeped water is drained out and the grain is (moisture content 44-45%) heaped (couched) on the germinating floor to a depth of 50-150 cm for 12-18 hrs. The couch is then broken and the grain spread on malting floor to a depth of 7.5-10 cm and a temperature of 13-15 degree C if maintained in the germinating shed. The germination is arrested after when rootlets develop and the plumule grows under the hull of the grain.

Kilning:

The green malt is air dried for 1-2 days. Then they are placed in a kiln through which hot air or flue gas is blown in. The moisture content is brought down to c. 6% by the gradual rising temperature to 65 degree C during 2-3 days and then rapidly to 87-100 degree C (curing)

Chemical changes during malting:

The chemical changes in the grain during malting are brought about by several enzymes such as cytases, proteases and amylases, elaborated or activated during germination primarily in the epithelial layer of the scutellum.

The cytases, consisting of several enzymes are activated early during the germination. They act on cell walls and render the endosperm permeable to other enzymes. Pentosans and pentoses are rendered soluble by the cytases and an increase in these compounds is an index of the degree of modification.

The proteolytic enzymes appear only during germination and include at least two peptidases. They act on the protein matter of the grain and solubilise 25-30% of total protein. The soluble products- amino acids, peptides etc., furnish the nutrients for yeast growth during brewing and they are also responsible for beer characteristics.

The amylolytic system comprises two major enzymes, namely alpha amylase and beta amylase. During germination, most of the beta amylase which occurs in a bond form in the raw grain is liberated and the alpha amylase is elaborated. The amylases diffuse from the scutellum into the endosperm and hydrolyse a part of the starch to soluble sugars. Only 8-10% of the starch is converted into fermentable sugars during malting, the major part of the conversion takes place during the mashy process.

Mashing:

Malted barley or a mixture of malted barley and malted wheat (2:1) is mashed with 10 times the amount of water at 37-50 degree C. The liquor is clarified by centrifugation and concentrated to 75-80% total solids at a temperature of 12.6 degree C under vacuum. This is called as malt extract.

In India malt is produced from barley, jowl and rage. 

 

Uses

Malt extract:

It has nutritive and laxative properties. It is rich in maltose (45-55%). Malt extract used as infant and invalid food is prepared by adding gelatinised wheat flour to a suspension of crushed barley malt. It is easily assimilable and is prescribed as a restorative in debilities of all kinds.

Malt sugar:

Malt sugar is a mixture of maltose and dextrin in varying proportions. It is used along with milk for feeding infants.

Malt enzyme:

It is used as a resizing agent in textile industry and is obtained by soaking ground malt in cold water and concentrating the extract under vacuum.

Malt flour:

It is obtained by grinding wheat malt and is used in the baking industry to improve the baking characteristics of wheat flour.

Diseases

Fungal diseases:

1. Covered smut- Ustilago hordei
2. Loose smut- Ustilago nuda
3. Black stem rust- Puccinia graminis
4. Yellow and stripe rust- Puccinia glumarum
5. Powdery mildew- Erysiphe graminis var. herdei
6. Seedling rot- Helminthosporium sativum
7. Leaf stripe- Helnminthosporium gramineum