Malt

The histology of the barleycorn is best studied by the examina tion of sections under the microscope. The grain consists of two main portions, the embryo or germ, and the endosperm, the store house of reserve materials for the growing plant.

Germination.

The barleycorn in its resting stage is in a stat e which may be described as one of dormant vitality ; it respires very slowly and thus loses weight during storage. The best and driest barleys are said to lose 1.3% of their weight in the first year, 0.9% in the second, and o.5% in the third. The loss is con siderably more with coarse and damp samples. When the grain is steeped this dormant vitality gives place to that complicated series of processes comprised under the general term germination. When germination begins enzymes are secreted, and these act on the re serve materials, starch and proteins of the endosperm, converting them into simpler compounds, capable of diffusing to various parts of the growing germ. Following this, starch and proteins are re formed, the former being deposited in the tissues of the germ and in the cells of the scutellum, which previously were almost free from starch; the protein matter deposited in the latter disappears to a considerable extent, and the protoplasmic content of the cells assumes a very granular appearance. The pointed mass of cells constituting the root-sheath is pushed forward by the root which protrudes through the base of the grain. It is at this stage that the barley is said by the maltster to "chit." After the first rootlet has broken through the ends of the sheath, it is followed by others. The cotyledonary sheath begins to elongate on the third or fourth day of germination and ruptures the true covering of the seed ; it then grows upwards between this and the husk and forms the acro spire or "spire" of the maltster.

Condition.—Barley is bought in the open market solely on the evidence of certain external signs, and judgment can only be acquired by very long experience. Immature barley feels cold to the hand, has a greenish-yellow colour, and, when dry, a starved wrinkled appearance. Over-ripeness in barley is distinguished by a white dead appearance of the corn. Mature or dry grains slip through the fingers more readily than unripe or damp ones. The contents of the endosperm should present a white friable or mealy appearance when the corns are bitten or cut in two with a pen knife. The condition of the grain may be determined by an ap paratus known as the diaphanoscope, which consists of a box fitted with a sliding tray, furnished with a certain number of shuttle shaped holes (usually 50o), each of such a size as just to hold a barleycorn longitudinally. Into the portion of the box below this tray an electric lamp is placed, and the corns are looked at from above. Thoroughly mealy corns are opaque, whilst steely corns are transparent. When certain portions of a corn are steely, these

present the appearance of lakes. By this means the percentage of mealy, steely or half steely corns in a sample may readily be estimated.

E. Prior points out that steeliness of barley is of two kinds, one of which disappears after the grain has been steeped and dried, and therefore does not necessarily influence the malting value of the sample, and the other which is permanent, and therefore re tards the modification of the corn. He proposed to determine what he called the coefficient of mealiness of a sample of barley by means of the formula :— in which A is the degree of mealiness, M is the percentage of mealy corns in the original barley, and is the percentage of mealy corns after steeping and drying the barley. Prior points out that, generally speaking, the degree of mealiness varies inversely as the protein content.

Munro and Beaven confirming Johansen point out that "Mealy grains have a lower specific gravity than steely grains, and contain a larger amount of interstitial air. The total nitrogen content of mealy grains is less than that of steely grains. Steely grains con tain a relatively high proportion of nitrogenous substances soluble (a) in 5% salt solution, and (b) in alcohol of specific gravity 0.9. Mealy barley modifies better than steely during germination. The process of drying damp and under-matured barley intact at oo° F produced an apparent mellowing or maturation. Other things be ing equal, maturation, which is physiologically a post-ripening process, is correlated with the mealy appearance of the endo sperm." H. T. Brown and his collaborators state that thin sec tions of steely corns when examined under the microscope no longer exhibit a translucent appearance, but show the mealy prop erties as completely as if they had been cut from a mealy grain, and they suggest that in a steely corn the whole of the endosperm is under a state of tensile stress which cannot be maintained in the thin sections. If, however, a thin section of a steely barley be cemented to a slide with Canada balsam and then pared away with a razor, steeliness may be preserved even in the thinnest sections. Brown and his co-workers determine the coefficient of mealiness of a barley as follows : Five hundred corns are cut transversely in a corn cutter and the percentage of mealy, half mealy and steely corns is noted. The number ioo is taken to represent complete mealiness, I complete steeliness, and so the intermediate class. If the percentage of each class be multiplied by its special value, and the sum of the products divided by ioo, the result is the coefficient of mealiness. By steeping and drying a very steely Scottish barley the coefficient of mealiness was raised from 29.7 to 87.1, whilst concurrently the specific gravity fell from 1.417 to 1.289.