On Malt and Malting.
BY FRANK XAVIER MOERK, PH.G.
From an Inaugural Essay
(Mr. Moerk's thesis, presented to the Philadelphia College of Pharmacy, contains interesting investigations on barley and malt, but being quite voluminous, we deem it best to publish separately the different subdivisions or portions thereof.—EDITOR.)
Malt is described by the Pharmacopoeia as "the seed of Hordeum distichum caused to enter the incipient state of germination by artificial means, and dried."
The process which the barley undergoes is termed "malting," and has for its object the production of soluble albuminoids, diastase, from the insoluble albuminous bodies present. These albuminoids possess the property of converting, under suitable circumstances, the starch of the grain into maltose, a fermentable sugar, and dextrin, a body closely related thereto. The formation of diastase proceeds first in the same proportion as the development of the embryo, but after the young plant has arrived at a stage when respiration through the plumula and assimilation through the rootlets can take place, the amount of diastase stored up in the grain gradually decreases. It is, therefore, the aim of the malster to arrest the growth of the germ at the moment when most diastase is accumulated in the grain, i. e., before the future stem surpasses the length of the grain. This is accomplished by killing the embryo by drying and heating.
Malting consists of four operations: Steeping, Couching, Flooring, and Kiln-drying.
I. Steeping.—The barley is screened and sifted to remove broken or small grains, it is then let into a large cistern made of stone, iron, cement or wood. The water, temperature 10-13°C. (50-55°F.), is then added and allowed to cover the grain to a depth of 4 or 5 inches. The time required to steep the barley is about three days; the water is occasionally replaced by fresh water, in order to prevent putrefaction of the extracted matter.
II. Couching.—The barley, before it is thoroughly saturated, is thrown out of the cistern and put in large heaps on the couch. On thrusting the hand into the heap at the end of 24 hours, the length of time it is allowed to remain there, it does not feel moist. The grain, by this operation, has the benefit of a secondary steep with free access of air, the water adhering to the grain is mostly absorbed. The grain, when saturated, appears soft and flexible, and the husk will easily separate from the body, the latter, on pressing, becomes pulpy. The most characteristic indication of the penetration of the water is the appearance of a longitudinally split grain, the starchy body of which should be smooth and oily looking. The changes taking place while an the steep are as follows: Barley gains from 40 to 50 per cent. in weight and increases about 25 per cent. in bulk. About 1.5 per cent. is extracted, of which two-thirds is organic and one-third inorganic matter.
III. Flooring.—The barley is now thrown upon the floor to a depth of about 12 inches. The conditions required for a healthy germination are 1, the grain should have absorbed sufficient water while in the steep; 2, the steeped grain should be supplied with plenty fresh air; and 3, a certain, although only slight, amount of heat is required to introduce the activity of life into the grain. The first condition has been complied with in the previous operations. The second is fulfilled by turning the grain so that the portions in the centre and at the bottom are brought toward the top of the heap. This turning is made only once or twice a day for the first few days, but requires to be done oftener after the grain commences to germinate. The third condition is carried out by placing the grain to a considerable depth—12 inches—on the floor; by doing this, heat is generated after a time. The conditions having been complied with, oxygen is rapidly absorbed, and, in combining with part of the substance of the grain to form water and carbon dioxide, heat is generated which stimulates the growth of the young plant, after a time, to such an extent that the rise of the temperature in the mass of the growing grain must be checked. This is done by frequently turning the grain and laying it thinner every time it is turned. At the end of the fifth or sixth day, the grain covers the floor to a depth of 3 or 4 inches, and, as the grain then grows very slowly, it is necessary to stimulate the growth by gradually increasing the depth, so that at the end of this operation, the depth is about 9 inches. Very little change is noticed in the barley until it has been about three days on the floor. On thrusting the hand into the heap at this time, it feels moist. This is called "sweating" by the malster, and here germination commences. The grain is allowed to remain on the floor until the acrospire, plumula, creeping along under the husk almost reaches the other end of the grain; if allowed to pass this, the diastase rapidly disappears. This is the best indication of the progress made during flooring, and corresponds with the increase of diastase. The time required for this operation varies from 8 to 12 days. The best temperature is 10-13°C. (50-55°F.); if the temperature exceeds 15°C., it does not take so long a time, but there is a greater loss of substance. This loss, by oxidation, at 10-13° C., amounts to 5 or 6 per cent., whilst with a higher temperature it amounts to as much as 15 per cent. In this operation is produced the diastase, and also a modification of the starch, so that it is readily acted upon by diastase.
IV. Kiln-drying.—The further growth of the grain is now stopped by drying it at a temperature varying from 32-71°C. (90-160°F.). It is placed, to a depth of from 6 to 9 inches, on a perforated iron floor and heated air caused to pass through it. A temperature of 32° C. (90° F.) is most approved of to get rid of the greater part of the moisture; 52-57°C. (125-135°F.) for gradually drying the malt; and, 65-71°C. (150-160°F.) to produce an aromatic flavor and reduce the moisture to from 2 to 1 ½ per cent. By using still higher heats, the variously colored malts are produced. In consequence of the last operation the malt combes, rootlets, become very brittle and are easily removed by sifting.
The loss in malting may be summed up as follows:
|In steep||1.5 per cent.|
|Flooring||5. to 6. per cent.|
|Rootlets||2.5 to 3. per cent.|
|Total||9 to 10.5 per cent.|
The above description is taken from "Steiner's Principles of Malting," corrected by Mr. T. M. Perot, so as to agree with the preparation of malt at his malt house.
Barley and malt have been the subjects of many analyses; but the results differed in nearly every one. The presence or absence of sugar and dextrin, one or both, were the points to which these differences were due. Mr. G. Kuhnemann, in 1875, was the first chemist to prove that cane-sugar was present in barley and malt, the latter also containing another sugar capable of reducing Fehling's solution. On the other hand, he denied the presence of dextrin, this owing to his belief that dextrin reduced Fehling's solution. Researches made within the last few years, prove that dextrin, if pure, will not reduce the test solution, but commercial dextrin invariably reduces it, owing to the presence of more or less glucose. By repeatedly dissolving dextrin in water, precipitating by and washing with alcohol, glucose can be separated from the dextrin, and the latter will then not reduce Fehling's solution.
The American Journal of Pharmacy, Vol. 56, 1884, was edited by John M. Maisch.