In some instances the malt and liquor are mixed in the mash tun by stirring oars ; in others, by special machinery, afterwards to be described ; the object being to thoroughly mix the malt and water to prevent balling or lumps occurring. The mash at first is recommended to be made as stiff as possible, to 2 barrels of water a quarter of malt being generally used.
In determining the temperature of the water to be employed in the mashing, it is necessary to prevent the liquor being admitted at so high a temperature as to set, or lock up, the goods, that is, to cause the starch to run into a cohesive or pasty state. The proper initial temperature will depend upon the quality of the malt employed. When the malt is high dried, the liquor may be used at a higher temperature. Mashing is sometimes commenced at 71° (160° F.), and liquor subse quently added at a temperature that will give a wort ready to be drawn off at about 63° (145° F.). This method has its advantages. The malt is first softened, and the more soluble portions are extracted without loss of starch. Once the process is operating well, the addition of liquor at a somewhat high temperature does not offer great risk. There must also be taken into account the loss of temperature due to conduction and radiation of heat, and to prevent excessive loss it is advisable to heat the mash tun with hot water, before commencing mashing operations. Another alteration of temperature is caused by the mixture of the liquor with the malt. For instance, if a quarter of unmalted barley, at a temperature of 10° (50° F.), is mixed with twice this volume of water at 65° (150° F.), the mixture will have about a mean temperature of 38° (100° F.). But when malt is mixed with water, the resulting temperature is above the mean, and the difference is greater when the malt is more highly dried. With highly dried brown malt, the temperature would rise to as much as 5° above the mean. If the malt has become mellowed by the absorption of moisture from the atmosphere, the temperature is less ; this absorption is very likely to occur if the malt has stood long before grinding. The rise of temperature appears due to the chemical conversion of starch into sugar, and takes place during the first mash, when the conversion is most energetic.
During the formation of starch, a froth rises to the surface of the liquor in the mash tun, affording an indication of the conversion proceeding properly.
The theory broached above as to the action of diastase, that it converted the starch into dextrine, in the first place, and some of that dextrine into sugar, is due to Mulder. Schwarzer states that at temperatures above 60° (140° F.), the ratio of glucose to dextrine is as 1 to 3; whereas below that point, the ratio is as one to one, or equal. Sullivan states that neither dextrine nor glucose is formed, but that the sugar termed maltase, intermediate between grape sugar and starch, is the resulting product. Diastase is dissolved in greater quantities from the malt by a long digestion at low than at high temperatures ; and the action is most complete between 38° and 60° (100° and 140° F.). But the soluble matters of the mash suffer saccharine conversion more actively when the temperature is much higher.
From analyses that have been made of malt as well as barley, it appears that the available constituents of malt, as dried by ordinary means, amount to 78.3 per cent.; so that a quarter of good malt weighing 352 lb., will contain lb. of available constituents. The remainder con sists of water and husk. These available constituents are not all saccharine matter, but consist also of albumen and gluten, got rid of in after processes. The best practical results obtained, as measured by the saccharometers of Dring and Fage, give 243 to lb. available con stituents.
Of course the most important point with the brewer is to completely abstract the soluble substances from his malt, and to effect this with the least possible quantity of liquor, taking care to prevent the occurrence of acidity. In the opinion of Muspratt, too much water is used, and the diastase and gluten of the malt are considered to be capable of transforming a much larger quantity of starch into sugar than is present ; and the water used is sufficient to hold in solution a greater quantity of saccharine matter than occurs in the brewing operation. According to this view, the usual methods of brewing are defective, for the reason that an unnecessarily large quantity of liquor is used.