All through the malting process meta bolic changes are proceeding in which both carbohydrates and pro teins are concerned. In its resting stage the embryo of a barley corn is generally free from starch ; as soon as germination sets in, however, starch appears in the scutellum, while the amount of sucrose there present increases, these being apparently formed from maltose originating from the action of diastase on the starch of the endosperm. Sucrose also augments in the aleurone layer, but starch is never formed in the aleurone cells. These changes occur when the malt is first loaded on kiln.
The fuel used for drying and curing malt is either an thracite or coke, and the greatest care is necessary in selecting it on account of its liability to contain arsenic, which is to a greater or less extent an invariable constituent of all coal. The fuel used for malting purposes should not contain more arsenic than grain per pound. Gas coke should on no account be used unless it has been proved to be sufficiently free from arsenic ; but the best oven coke frequently contains so little arsenic that it may be em ployed with perfect safety, especially if it be mixed with a pro portion (e.g., 5%) of milk of lime, which retains the arsenic as calcium arsenate. In Germany malt is, as a rule, dried and cured with hot air, whilst in Great Britain the products of combustion are passed through the malt, as it is believed that they exert a beneficial influence on the flavour.
Af ter the malt has passed through the curing stage it is generally heaped up for a few hours. This is believed to increase its flavour. The malt is then stripped from the kiln, and the rootlets, technically known as the coombs, are removed. Formerly this was effected by workmen treading the malt, who wore heavy boots for the purpose. At the present time, however, the rootlets are usually removed by machinery, special forms of which have been devised for this as well as for dressing and polishing the malt. It is the custom of some maltsters to store malt with the rootlets still attached; but this is an objec tionable practice, since malt coombs attract moisture, and the presence of more than 3% of moisture in malt produces the condition known as "slackness." When the malt is packed in bins it is often covered with a layer of coombs, which then prevent access of atmospheric moisture. Malt, to preserve its good qual ities intact, should be stored in bins made as nearly as possible air-tight, and it should never be placed in bin until it is quite cool. It is probably wrong to store malt in bins adjacent to the kilns, where it is kept at a higher temperature than that of the sur rounding atmosphere. During storage of the malt a kind of mellowing occurs, the mechanism of which is not understood. It is, however, known by practical brewers that the best results can not be obtained when new malt is used.
The tremendous amount of labour involved in the floor malting system has prompted many inven tions and developments to mechanize the procedure. The so-called Saladin system is best known of these and permits the germinat ing piece to be held in large rectangular boxes or bins. The grain
is then turned by means of vertical helices which traverse the length of the compartment. This mechanical turning has replaced practically all floor malting today.
Several years ago Galland suggested germinating barley in a drum, his idea being to do away with handling of the grain, and also to be independent of changes of atmospheric temperature. The latest development of this system, the so-called Galland-Henning process of pneumatic malting, has been improved by Mr. R. Blair Robertson. The drums are pro vided with a perforated channel for the passage of air through the malt, which is packed in the annular space between this channel and the outside wall of the drum. Each drum is capable of re volving on its axis, and there are arrangements for passing either moist, saturated or dry air through the malt. The system as now improved is capable of producing some of the best malt, especially if, after germination has been completed in the drums, the green malt is loaded on an ordinary kiln and the initial stages of kilning conducted in the usual way; the curing, however, may be carried out successfully in a special form of drum.
The malting process is attended with a certain amount of loss of dry substance of the barley, as fol lows:— In the steep ....... . . . 1.5 to 2.0% By respiration on floors and on kilns . . . . 3.o to 5.o% Coombs . . . . . • • • - 3.5 to 5.o% In addition to this, barley, as already mentioned, contains from 12 to 18% of moisture, whereas finished malt contains I to 2%. The total loss in weight which barley undergoes in the malting process may be put down at from 17 to 28%. Since, however, malt is lighter than barley (and the quantity of both was in for mer years measured exclusively by volume) it frequently hap pens that a given number of quarters of barley yield a large number of quarters of finished malt. When this happens it is usual to speak of an increase having been obtained. At the present time weight replaces measure for both barley and malt, and although it is usual to speak of the quantity of grain in terms of quarters, what is meant is not the measured quarter, but so many weighed standard quarters. The standard quarter for English malting barley is 448 lb. and for malt 336 lb. From this it will be seen that when a given number of weighed quarters of barley yields the same number of quarters of finished malt, the actual yield is 75%, and there is then said to be neither increase nor decrease. As a rule, in practical working the yield of malt varies from a 4% decrease to a o% increase, corresponding to an actual yield on the original barley of 72 to 82.5%. J. Bayer stock, an old writer, says that finished malt should weigh one-fifth less than the barley from which it is produced. This corresponds to a malting increase of about 7%, which is a high yield. As a rule, foreign barley will give a greater malting increase than Eng lish barley, because, on the one hand, the former usually con tains less moisture than the latter, and, further, because there is less loss on the floors by respiration and rootlet growth.