The firet two eeries give practically the same results, but with rapid increase of temperature there wae great reduction in the amount of extract, ae well as in the ratio of the sugar to the dextrine. Graham considers these experimeute to ehow that the more gradually the temperature ie raised, the more complete is the extract, and the higher the sugar-forming ratio, In Graham's experiments, the starch was broken up, not according to Mueculus' theory, but in the reverse ratio. There was a larger amount of sugar and a. smaller increase of dextrine, Referring to the experiments on the English infusion process at 60°, 33.5 per cent. of glucose is formed. As the temperature increases so the amount of sugar decreases, until a,t 77° the decrease is very great. These experiments prove that the higher the initial temperature, the less active the diastase ; a,nd the less extract in given time, the less sugar is formed. By etarting with a low initial temperature, and raising it in the course of a.n hour to the temperature indieated,main. taining that temperature for two hours, there is a gra.dual increment of sugar with a gradual incre. mut of total extract.
From this table, it will be seen that at 60° the percentage of glucose has risen to 37.5 per cent., indicating that a low initial temperature is best for the solution of the diastaee. But for a. given time, the diastase, when dissolved, attacks the starch most vigorously at a temperature of about 60° to 63°; and whilst thie temperature is adva.ntageous for the rapid conversion of starch into sugar and dextrine, experiruents have shown that the temperature of 74° to 75° was best for rapid con. version of dextrine into eugar. Graham makes the following deductione ae to the practical bearings of these facts.
Barley malt when well prepared contains an amount of albuminoue substances, or diastase, pro. duced in the germination process, greater than ie needed for the conversion of starch found in the malt. Time is an important element in the changes produced, and the longer the time at a low temperature, the more diastase is dissolved, and therefore in subeequent stages, the more starch converted and eager formed. The action of the diastase initially, when the mass of the diastase is small compared with that of the etarch, Ls to form dextrine into sugar in the ratio of 2 to 1. In malt, however, there ie so large an amount of diastase, that even in a ehort digestion an amount of sugar ie obtained greater than in this ratio. In the English infusion procees with its initial tem. perature varying between 60° and 68° (155° F.), but generally no higher than 66° (150° F.), there is an equal ratio of glucose and dextrine ; and this has been determined from worts obtained from four large breweries in different parts of England. As the initial temperature was raised above 66°, the total extract decretteed, as well as the ratio of sugar to dextrine ; and when the initial tem perature was decreaeed below 66°, within certain limits, the total extract increstsed, as well as the ratio of sugar produoed. The limite of theee varying ratios cannot exceed two of dextrine to one of eugar, or two of sugar to one of dextrine, and the ratios produced in any given time, in any particular maehing trial, depend on the varying conditions of the experiments ; upon the relative masses of starch and diastaee ; upon the temperature ; and on the qua,ntity of water. It has been well
authenticated that from 100 parts of starch not more than two-thirde can be obtained as sugar by the action of diastase; and this deficit is aecounted for by Sullivan, who has proved the formation of maltase, as previously referred to. Maltase has a peculiar setion on Fehling's copper solution, bv which thie teet solution represente only an amount of reduction equal to two-thirds of that which would occur if 100 parts of glucose were taken. Maltase formed in the mashing process, breaks np under the action of the potash and the copper solution into two parts of glucose and one. of dextrine. In the ordinary mashing process, there occur, it would appear from this consideration, two parts of dextrine and one of sugar ; and as the process continues, the ratio becomes more nearly equal, and ia reversed by the application of more heat and long-continued action, practically illuatrating the fact that the brewer may within certain limits vary the ratio of dextrine to sugar at will.
In order to increase the ratio of the sugar, the brewer may atart with a low initial temperature, and aecure the solution of a large amount of the active principle of diastase. Thia aolution obtained, the temperature of the mash may be raised to 60° to 65° (140° to 150° F.), either by adding hot piece liquor, or by steam driven under the false bottom of the mash tun, or by means of a heated coil, or by causing the wort to circulate through coils of pipea, delivering it finally to the top of the goods. After digestion for a certain period at thie temperature, the mash ahould be raised to 74° (165° F.), because at that temperature more augar can be produced than at 63° (145° F.), and because the higher temperature givea the additional advantage of a high tap heat. Upon the preaent plan of high initial temperatures, the brewer eau increase the ratio of augar by °imply adding it. Cane augar may be employed, and this can be converted into glucoae by the action of the diaetase, if added in the mash tun, or it can be converted partly into diastase by the action of the acids of the wort, by making the addition when the wort is boiled. If tbe cane sugar were to be added, without previous converaion, to the fermenting tun, it would require more yeaat than glucose, because the yeast would have to do a greater amount of work, to break down the complex atructure of the cane auger to the more aimple one of glucoae. Cane sugars are dangeroua, however, became they contain large amounts of albuminoua auhatancee likely to putrify, and it ia preferable to convert the cane sugar into invert sugar. Invert sugar is the sugar produced by the action of acida on cane sugar, dextro-glucoae, and la3vo-glueose. As glucose sugar can be made, not only from cane augar, but from starch, there ia nothing to prevent the brewer preparing his own grape sugar from etarch, by treating this with dilute aulphurie acid and afterwarda destroying the acid hy means of chalk. Although the process may leave about one-half per cent. of gypsum in the sugar, this is an advantage in the fermenting tun, rather than a disadvantage.