As the diastase is most active when the solution of malt is dilute, and when the tempera ture is between 71° and 77° (160° and 170° F.), by sustaining an equalized temperature and employing only a moderate quantity of water, the conversion of starch into glucose will be com plete almost in the first mashing, leaving nothing for subsequent sparging, except to remove the infusion absorbed by the goods. If this is accomplished with four to five barrels instead of with six to seven, there are the advantages that time and fuel employed in evaporation will be saved, as well as sounder beer produced, tendency to acetify being less with a strong wort than with a weak one. According to this view repeated mashes are to be avoided.
The English method of mashing employs a high initial temperature, and the following table by Graham gives the proportion per cent. of the constituents after three hours' mashing :— These figures show that the higher the initial temperature, the less is the proportion of sugar and unconverted starch contained in the extract.
Considering that one of the first necessities of the brewer is to prevent other fermentations being set up than that desired, cleanliness is one of the essentials. Any albuminous substanco tending to putrescence would communicate similar change to the wort. In no place is eleanliness moro required than in the mash tun, which should be carefully washed with lime water after every mashing, unless mashinge are made daily. This work should be eompleted on the day previous to that of the brewing, so that on the day of brewing operations may be commenced early in the morn ing, especially in hot weather.
The temperature of the atmosphere, thc quantity of the malt, and tho heats of the mashinga should he carefully noted ; Levesque has given the following practical example as a convenient illustration. For greater facility the example is reduced to one-quarter brewing, which can bo multiplied by any number that may be required. Tho total quantity of beer or liquor is technically termed the length.
All waste of liquor is to be duly accounted for, and this calculation is to be made for a fair quantity of boiling-room in the copper, which ought to be one-fifth part of the whole content. A quarter
of tender, well-made malt, thin skinned, of 44 lb. a bushel, or 352 lb. malt, as it is termed, will yield 2 bls. 0 fir. 3 gale. strong ale, of 10 lb. gravity a barrel, with 4 bls. 0 fir. 5 gals. liquor for the mashes, and 2 bls. 2 fir. more liquor for the return wort ; making in the whole 6 ble. 2 firs. 5 gals. liquor a quarter. This, previous to brewiog, is stated as follows :— Weight of Malt, 44 lb. a bushel, 352 lb. a quarter. Gravity 95 lb. a quarter. Malt I quarter, Hops 12 lb.
The malt should if possible be ground not longer than a day previous to mashing, and should never be kept for more than three or four days, because it absorbs moisture from the atmosphere, and becomes heated through internal decomposition of the saccharine constituents, which will make the beer bad in quality.
Mashing is performed in a vessel termed a mash tun, the contents being stirred either by hand with oars or by machinery. Different forms of mash tuns will be subsequently described.
After mashing the tub is carefully covered, to maintain the temperature of the mash and to exclude air from the wort. Allowed to rest for about two hours, it is drawn off to the copper. The following table, given by Levesque, which, like the preceding, has been calculated on the basis of Fahrenheit's thermometer, relates to the temperature and time of standing of the mash ; and shows reduction of the temperature of the air, the heat for mashing, at auy required temperature, in which the degrees and hundredths of a degree show how far calculation may be relied upon ; the hours and minutes for the standing of the mash, observing that when the air is higher than the given temperature, the time of the standing of the mash is to be diminished in ratio through the four classes of mashing heats. The heat of the tap is to be taken in the middle of the spending. For every shade of malt higher than the palest, a reduction of 5° must be made. If the liquor be cooled down in the mash tun to receive the malt, the liquor must be taken 8° lower than in the other method. In well-constructed breweries, the heats of the tap will correspond very nearly with the statement when the tun is mashed full or nearly so.