Consideration of the preceding principles will show that the season of the year materially affects the brewing process. In summer, the risk of using A highly saccharine wort is greater than in winter, but the proportion of this risk will depend upon the plant and arrangement of the brewery. The proportion of dextrine and sugar contained in the wort may be regulated practically during the process of mashing, in two ways. The proportion of sugar may be increased by prolonging tho mash as ith due regard to the maintenance of temperature ; or the same result may be obtained by keeping the drained or filtered wort at a temperature of 74° (165° F.) Ure in experimenting on the wort drained from the mash tun, and kept at that temperature, found the proportion of dextrine to augar, which was originally 16 to 3, to be changed to to 1.2, the conversion of dextrine into sugar being almost complete. The influence of variation in the proportion of dextrine and sugar in the fermentation of the wort, must be entered into in greater detail when treating of tho fermcntiog process.
It is necessary to be able to ascertain the proportion of dextrine or sugar contained in a wort. Ure describes two methods by which this can be done. The first consists in ascertaioing the amount of sugar in a given wort of determined strength ; and the second the amount of dextrine. It is more easy to determine the quantity of dextrine contained in a wort than the amount of sugar, but the proportion of augar can be ascertained with greater accuracy. This will be described later under Sacchometry.
To ascertain the quantity of dextrine, add to a given volume of strong wort, having the density of about 30 lb. a barrel, an equal quantity of alcohol, or ordinary spirits of wine, This addition will cause the whole of the dextrine to be precipitated ; and it is convenient to cause the precipita tion to occur in a graduated tube, by which the hulk of the precipitate thrown down may bo learned, and thereby its weight estimated. If the weight is less than 30 lb. n barrel, the proportion of alcohol must be increased ; but if the wort is stronger, a smaller quantity of alcohol will effect the precipitation. It will be found useful, in practice, to havo fixed to the tube a table, showing the relative proportion of alcohol required for worts of different strength.
The amount of sugar in a given wort may be ascertained by boiling 100 grains of the wort, with about 10 fluid oz. of the following solution : Sulphate of copper, crystals .. .. 100 grains.
Bitartrate of potash .. 200 Carbonate of soda, crystals . 800 Boiling water, 1 pint, or .. 8750 To make this solution, the sulphate of copper should be first dissolved, and the bitartrate of potash added. The carbonate of soda should then be added, and the solution filtered. By boiling
the wort with this solution, a red precipitate is obtained, which is to bo collected and weighed. Throe grains of precipitate indicate the presence of 1 graiu of grape sugar in the wort.
It is customary to indicate the strength of the wort by the excess in pounds of the weight of the barrel of it, above the weight of a similar barrel of water. For instance, the weight of a barrel of water being 360 lb., and that of the barrel of wort 390 lb., the wort is said to be of 30 lb. gravity. Brewers' saccharometers are graduated to show the gravity of the worts in this way ; a quarter of good malt generally yields sufficient extract with ono barrel of water for a wort of 90 lb. gravity, or sometimes even as much as 95 lb. gravity a barrel. Upon this fact is based the method of calculating the quantity of water or liquor, as it is termed, to be used in the mashing. Porter and stout, in which a considerable proportion of black or brown malt is used, allow of a lesser nmouut of extraot, or about that sufficient to make with one barrel of water, a wort of 84 to 86 lb. gravity. Those facts borne in mind, the quantity of liquor to be used in a given mashing may be thus calculated : If a mash of 50 quarters of malt be to be made and beer of 25 lb. gravity to be produced, the malt being of such quality as to yield 90 lb. a quarter, as estimated by the saccharometer, the quantity of beer produced will amount to 50 x590 = 180 barrels. If there were no losses during the 2 mashes and in the subsequent processes, 180 barrels would be the quantity of liquor to be used; but the several following allowances have to bo made. The goods, as the prepared malt is termed, retain by capillary action about barrel a quarter of matt mashed. The loss by evaporation during boiling in the copper has to be made up, as well as the evaporation during the cooling down from boiling point to the temperature when the beer is run into the fermentation tun. The last process generally incurs the loss of one-eighth of the total bulk, whilst the loss in the copper varies according to its evaporative effect. For 180 barrels, the total quantity of liquor may be calculated thus ;In addition to 180 barrels.
One-eighth for evaporation during cooling .. 22i For absorption.. .. .. .. 371 ,, For boiling .. . .. 8 68 There are several ways of distributing this quantity of liquor. It is preferred in some cases to make only one mash, and to spurge the remainder ; and in others as many as five successive mashes would be employed.