516 BREWING 



Schwarzer's researches, is perhaps the most valuable and precise of the present day, 

 and it would bo "well if every brewer wcro familiar "with them. 



In the Brewers' Journal, January 15, 1871, this information is fully detailed, but 

 as the number may not easily be obtainable, it is here reinserted : 



4 As a general rule, the larger the quantity of diastase and the greater the heat up 

 to a certain point, the more rapid is the transformation of the gummy portion of the 

 starch into sugar. 



'At a temperature of about 167 Fahr., and especially at 177 or 178, however, a 

 diminution takes place in the action of the diastase, which increases with the further 

 increase of the temperature ; and if tlio heat bo raised for a certain time to about 190, 

 the action of the diastase ceases altogether. 



4 If also an extract of malt be heated to 190 before the starch is added, a diminution 

 in the action occurs, which is the more determined according to the length of time at 

 which the heat has been maintained. 



' The quantity of diastase thus rendered inactive may be ascertained by comparing 

 the action of a certain amount of the overheated extract, with that of a like quantity 

 at the temperature of 145. Observation must be taken of the time which elapses 

 before all reaction ceases to be exhibited by the iodine test ; and the same test must 

 be applied to the action of the extract submitted to the lower temperature. 



' Two per cent, of an extract of malt, not weakened by heating, effects the trans- 

 formation more rapidly than four times that percentage kept at the heat of 178 for 

 one hour, or than twenty per cent, of the same extract maintained for the same period 

 at a temperature of 190. In the last case scarcely one-tenth of the diastase originally 

 developed in the malt remains in the extract. 



' With minute quantities of diastase the action proceeds more rapidly at first with a 

 temperature of 190, but afterward more slowly than at 145. 



' When the iodine test shows no discolouration, the saccharification is practically 

 terminated, and the continuance of the action of the diastase yields an infinitesimal 

 quantity of sugar. 



' If, in one hour, and until the iodine shows no discolouration/fifty per cent, of sugar 

 is formed, and if, during the next three hours, only two per cent, is produced, it is 

 certain that the iodine test shows practically the action is finished. 



' The cause of this feeble saccharification after the iodine test ceases to act, does not, 

 however, arise from the exhaustion of the energy of the diastase, because if a new 

 amount of starch be added, it will be rapidly transformed. 



4 At all temperatures from 167 to 32, even though employing very different pro- 

 portions of diastase, from fifty to fifty-three per cent, of sugar is invariably produced 

 from the starch in the extract. 



'Admitting that the starch is transformed into an equivalent of sugar, and an 

 equivalent of dextrine, analysis shows that the sugar to be obtained from the extract 

 amounts to 52'6 jar cent, of the extract. 



' The amount of sugar obtained in practice differs so little from this rate that the 

 small difference may fairly be supposed to arise from errors in the quantities and in- 

 terruptions in the action of the diastase. 



'At temperatures exceeding 167 the quantity of sugar produced falls off in pro- 

 portion. 



'At 190, after the iodine test ceases to act, the amount of sugar formed in the 

 extract may fall off to twenty-seven per cent. ; and even if the extract is heated to 

 that temperature before the addition of the starch gum, and the greatest care be taken 

 to prevent cooling during the experiment, very little change indeed will be observed 

 in the percentage. 



4 If all these facts be taken into account, it seems certain, that the action of the 

 diastase at temperature below 167 is very different from what it is under greater 

 heats. 



' The amount of sugar equal to twenty-seven per cent, which is the minimum value 

 at which the iodine test ceases to exhibit any change, agrees exactly with the trans- 

 formation of starch into an equivalent of sugar and an equivalent of dextrine. 



''A fact deserving of notice is, that between the temperatures of 167 and 190 the 

 difference in the amount of sugar formed is more than twenty per cent. 



4 In maintaining the extract of malt at 190 for a long period, it is so greatly altered 

 that when the heat is afterward lowered, the amount of sugar is not, or scarcely at 

 all, increased ; but if, on the contrary, a solution of starch which contains about 

 twenty-seven per cent, of sugar, be heated to ] 90, and afterwards submitted to the 

 action of diastase, not heated and enfeebled at a lower temperature, the percentage 

 may be carried to fifty-two per cent. 



4 During fermentation, the diastase continues to effect the transformation of starch ; 

 and it is not improbable that yeast acts in the came manner as the former.' 



