MALT ; MALTING. Malt is made from all kinds of grain and from rice, but in England almost always from barley, for the use of brewers and distillers. It consists of grain which has become sweet and more soluble in water from the conversion of its starch into sugar by artificial germination to a certain extent, after which the process is stopped by the application of heat. The barley is steeped in cold water for a period which (as regulated by law) must not be less than 40 hours; but beyond that period the steeping may be continued as long as is thought proper. Here it imbibes moisture, and increases in bulk ; at the same time a quantity of carbonic acid is emitted, and a part of the substance of the barley is dissolved by the steep-water. The proportion of water imbibed depends partly upon the barley, and partly on the length of time that it is steeped. From the average of a good many trials, it appears that the medium increase is about 47 per cent. in weight, and 20 per cent. in bulk. The carbonic acid emitted while the barley is in the steep is inconsiderable; and it is probable, from the experiments of Saussure, that it owes its formation, at least in part, to the oxygen held in solution by the steep-water. The steep-water gradually acquires a yellow colour. The quantity of matter which it holds in solution varies from to of the weight of barley. This extractive matter is obviously derived from the husk of the barley, and is that substance to which the barley owes its colour. Accordingly grain becomes much paler by steeping.
After the grain has remained a sufficient time in the steep,the water is drained off, and the barley thrown out of the cistern upon the malt floor, where it is formed into a heap called the cowlz, about 16 inches deep. In this situation it is allowed to remain about 26 hours. It is th4n turned by means of- wooden shovels, and diminished a little in depth. This turning is repeated twice a day or oftener, and the grain is spread thinner and thinner, till at last its depth does not exceed a few inches. When placed in a couch, it begins gradually to abeorb oxygen from the atmosphere, and to convert it into carbonic acid, at first very slowly, but afterwards more rapidly. The temperature, at
first the same with that of the external air, begins slowly to increase ; and in about 96 hours the grain is at an average about 10° hotter than the surrounding atmosphere. At this time the grain, which had become dry on the surface, becomes again so moist that it will wet the hand, and exhales at the same time an agreeable odour, not unlike that of apples. The appearance of this moisture is called notating. A small portion of alcohol appears to be volatilised at this period. The great object of the maltster is to keep the temperature from becoming excessive, which is effected by frequent turning. The temperature which it is wished to preserve varies from 55° to 62°, according to the different modes of malting pursued.
At the time of the sweating, the roots of the grains begin to appear, at first like a small white prominence at the bottom of each seed, which soon divides itself into three rootlets, and increases in length with very great rapidity, unless checked by turning the malt. About a day after the sprouting of the roots, the rudiments of the future stem, called acrospire, may be seen to lengthen. It rises from the same extremity of the seed with the root, and advancing within the husk, at last issues from the opposite end ; but the process of malting is stopped before it has made such progress. As the acrospire shoots along the grain, the appearance of the kernel, or mealy part of the corn, undergoes a con siderable change. The glutinous and mucilaginous matter is taken up and removed, the colour becomes white, and the texture so loose that it crumbles to powder between the fingers. The object of malting is to produce this change : when it is accomplished, which takes place when the acrospire has come near to the end of the seed, the process is stopped by drying the malt upon the kiln. The temperature at first does not exceed 90°; but it is raised very slowly up to 140° or higher, according to circumstances. The malt is then cleared, to separate the rootlets, which are considered injurious.