156 THE CARBOHYDRATES 



and develops but little reducing power : if now the mixture 

 be cooled to 50° and a fresh amount of malt be added, the 

 reducing power of the solution rapidly develops owing to the 

 saccharifying action of the second enzyme which was all but 

 inactivated at the higher temperature.* 



The process of saccharification is essentially hydrolytic, 

 whereby the starch molecule is successively broken down to 

 a number of substances of lower molecular weight such as 

 dextrins and sugars ; this change may be conventionally 

 represented as follows : — 



(QHioOs)!! + H,0-> (CeHioO,)x + CioH^Pn 

 Starch Dextrin Maltose 



though actually other sugars such as iso-maltose or glucose 

 may be formed according to the conditions. The production 

 of glucose for example was demonstrated by Ling and Baker f 

 by acting upon starch with malt diastase at 70° ; its pro- 

 duction has been attributed to the further hydrolysis of the 

 maltose by maltase contained in the diastase, but as maltase 

 is not active above 55° this is not possible, and, as Ling and 

 Nanji have shown, the glucose is actually produced from the 

 hydrolysis of jS-glucosido-maltose (see below). 



A detailed study of the action of diastase upon the two 

 constituents of the starch grain, namely amylose and amylo- 

 pectin, was undertaken by Ling and Nanji ; J these authors 

 find that the action of barley diastase at 50° upon amylose 

 is to convert it quantitatively into maltose without the pro- 

 duction of any intermediate substances. On the other hand, 

 amylopectin is first converted into aj8-hexa-amylose and the 

 further hydrolysis of this substance by malt diastase results 

 in the production of a series of maltodextrins, a trisaccharide 

 j8-glucosido-maltose, iso-maltose, maltose, and glucose depend- 

 ing on the conditions of the experiment. Thus malt diastase 

 acting at 70° upon aj8-hexa-amylose converts it into malto- 

 dextrin-a and thence into 2 molecules of a hexatriose ^- 



* Both saccharifying and Uquefying enzymes are destroyed at 80°. 

 t Ling and Baker : " J. Chem. Soc," 1895, 67, 702, 739. Ling and 

 Davis : " J. Fed. Inst. Brewing," 1902, 8, 475 ; " J. Chem. Soc." 1904. 



85, 16. 



X Ling and Nanji : id., 1925. ^27, 639. 



