148 DIFFEEENTIATION AND SPECIFICITY OF STARCHES. 



glucose. The dextrin isolated by precipitation with alcohol was acted upon slowly by 

 barley diastase. At the end of 90 hours at 45 to 50 the product consisted of unaltered 

 dextrin, maltose, and glucose. Barley cUastase was found to be without action on mal- 

 tose; therefore the glucose must have come from dextrin. 



Ling (Jour. Fed. Inst. Brewing, 1903, ix, 446) noted that glucose is formed by the 

 prolonged action of diastase that had been heated to 65, and that the quantity formed by 

 a restricted diastase did not exceed 12 per cent of the total products of hydrolysis. He also 

 made the very interesting observation that upon continuing digestion the amount of glucose 

 diminishes. He believes that a reversion of the glucose occurred through a synthetic action 

 of the enzyme. Lintner's isomaltose, he suggests, may be a reversion product from glucose. 



Moreau (Ann. d. 1. Soc. roy. d. Sc. med. e. n. d. Bruxelles, 1903 xii, 117), by employ- 

 ing malt extract, saliva, pancreatic extract, blood serum, or dilute hydrochloric acid as 

 a hydrolyzer of starch and dextrin, found both maltose and glucose as sugar products. 



Both Rolfe and Geromanos (Jour. Amer. Chem. Soc, 1903, xxii, 1003) and Rolfe 

 and Haddock (ibid., 1015) record that through hydrochloric acid hydrolysis both maltose 

 and glucose are formed. 



Dierssen (Zeit. angew. Chem., 1903, xvi, 122), in experiments with oxaUc acid, found 

 glucose and levulose, and also a disaccharid, but ne\'er maltose, and he states that if maltose 

 is formed it must be converted immediately into glucose. The disaccharid corresponded 

 with the properties of Lintner's isomaltose, excepting that it, unlike Lintner's isomaltose, 

 is not converted by diastase into maltose. He does not believe it identical with Fischer's 

 isomaltose, because it is fermentable, while Fischer's is not. 



Gruters (Zeits. angew. Chem., 1904, xvii, 1169) also studied the products of oxalic acid 

 hydrolysis. According to him these substances consist of achroodextrins, maltodextrin, 

 maltose, glucose, and a small amount of levulose. He failed in attempts to prepare a 

 pure isomaltose, and found that mixtures of dextrin and maltose yielded osazones having 

 the properties of isomaltosazone. He states his disbelief in the "isomaltose theory." 



A comparison of the products of the decomposition of potato starch with starches from 

 cereals was made by O'Sullivan (Proc. Chem. Soc. Trans., 1904, xx, 65), who found that 

 the percentages of maltose and dextrin obtained from potato starch bear no quantitive 

 relation to those recorded in the experiments with cereal starches. This is in opposition 

 to his previous finding (Jour. Chem. Soc. Trans., 1878, ii, 1410), and his statement has 

 been shown by Ford and Guthrie (Jour. Soc. Chem. Ind., 1905, xxiv, 605) to be erroneous, 

 and due to errors of experiment (see page 193). 



The hydrolysis of maltose and dextrin was in\-estigatcd by Noycs and his associates 

 (Jour. Amer. Chem. Soc, 1904, xxvi, 266). They found that while the reducing power 

 of glucose is scarcely affected by heating with a 2.5 per cent solution of hydrochloric acid, 

 the products formed by the hydrolysis of maltose show a maximum reducing power after 

 about 1 hour at 100 or after 20 minutes at 111, and that further heating causes a decrease. 

 The maximum reducing power corresponded to a hydrolysis of 96 to 98 per cent. Hydro- 

 lysis seemed to be more complete in 2.2 to 4 per cent solution of product than in a 0.5 

 per cent solution. The rate of hydrolysis of dextrin was about half that of maltose. Jhe 

 hydrolysis reached 90 per cent in an hour. The reducing power of the products obtained 

 by the action of malt indicated a composition of 74 to 78 per cent of maltose and 26 to 22 

 per cent of dextrin. Such a mixture, from the results recorded, should, after 1 hour at 

 100, give about 96 per cent of the copper oxide, which would correspond to complete 

 hydrolysis. The amount actually found was 96.4 per cent for the 0.5 per cent solution, 

 and 97.1 for the 2 per cent solution. Practically, the maximum effect is reached in about 

 1 hour at 100. By dkect treatment of corn starch with 2.5 per cent hydrochloric acid 

 they obtained in a 0.5 per cent solution a hydrolysis of 97 per cent in 1 hour and 98 

 per cent in 4 hours. 



