CHAP. I.] ACTION OF DIASTASE UPON STARCH. 37 



diastase. He announced that one part of this body was able to 

 convert 2000 times its weight of starch into sugar. 



Early views Early in the century (1811) Kirchof discovered 



as to the that when starch is boiled with dilute sulphuric acid a 



action of sugar is formed, and that the same change occurs in the 



process of malting, by the action, as he thought, of the 



vegetable albumin upon the starch. 



It was soon found that in this process a gum-like body was 

 produced which was subjected to investigation by Biot and Persoz, 

 and, because of its optical properties, denominated by them dextrin. 



The latter body was discovered to be an isomer of starch, and the 

 sugar formed was supposed to be identical with grape-sugar, which 

 was considered to differ from starch merely by containing one molecule 

 of water in addition. The view which came to be generally enter- 

 tained was the following : that the first stage in the action either of 

 dilute acids aided by heat, or of diastase, consisted in the transforma- 

 tion of starch into its isomer, dextrin ; the second in the transforma- 

 tion of dextrin into grape-sugar. 



Researches The view that the sugar generated under the 



of Dubrunfaut action of diastase upon starch was an isomer of, 

 and O'Suiiivan an( j identical with, grape-sugar was contended against 

 in 1847 by Dubrunfaut 1 , who recognised it as a new 

 sugar, to which he gave the name of Maltose. Subsequent ela- 

 borate investigations of O'Suiiivan 2 established Maltose to be an 

 isomer of cane-sugar, possessing a very different crystalline form, 

 reducing power, and rotatory power to grape-sugar, and still more 

 recent researches have shewn that Maltose is generated not only 

 under the influence of diastase upon the starches but also of the 

 diastatic ferments of the saliva and pancreas 3 . 



Researches The assumed identity in the reactions which take 



of Muscuius. pl ac e when dilute sulphuric acid and when diastase act 

 on a warm solution of starch was shewn by Muscuius to be false. 



When diastase acts upon starch the process, according to Muscuius, 

 is one not of mere hydration but of decomposition, in which the 

 starch molecule, which he supposes to be of great complexity, splits 

 up into a dextrin and a sugar (which he afterwards admitted to be 

 maltose) ; a further action causes the dextrin formed to split up again 

 into a less complex dextrin and sugar, the process being repeated 

 until ultimately there result, as products of the reaction, a certain 

 amount of dextrin which has resisted the influence of the diastatic 

 ferment, though it is convertible into sugar by warm dilute acids. 



1 Dubrunfaut, Ann. Ch. Phys. Ser. 3, Vol. xxi. p. 178. 



2 O'Suiiivan, Journal of the Chemical Society, 2nd Ser., Vol. x. p. 579. 



3 V. Mering and Muscuius, 'Ueber die Einwirkung von Speichel- und Pancreas- 

 ferment auf Glycogen und Starke.' Zeitschrift f. physiolog. Chemie, Vol. i. (1878), 

 p. 395. Also ' Ein Beitrag zur Chemie der Starke.' Ibid., Vol. n. p. 177. 



