ISOMALTOSE, MALTOSE, GLUCOSE, SACCHAROSE, ETC. 



Table 11. 



141 



Von AJlilm recommends a 2 per cent solution of acid, and that the glucose, if wanted 

 pure, be recrj'stallized from methj^l alcohol of a specific gravity of 0.816. 



Starch syrup was found by Sieben (Zeit. d. Vereins f. d. Rubenzucker-Industrie, 1884, 

 837) to contain 21.70 per cent of dexti-o.^^e, 15.80 of maltose, 41.96 of dextrin, 20.10 of water, 

 and 0.3 of ash. Incidentally it is of interest to note that genuine honey contains neither 

 dextrin nor maltose, and that Sieben found 34.71 per cent of glucose, 39.24 of levulose, 

 l.OS of saccharose, 19.98 of water, and 5.02 of non-saccharine matter, and total per cent 

 of sugar 75.02. 



Brown and Morris (Ann. d. Chem. u. Phar., 1885, ccxxxi, 72; Jour. Chem. Soc, 1885, 

 XLVii, 527), by the action of malt extract at 50 to 60, recorded at the end of digestion 

 80.9 per cent of maltose and 19.1 per cent of dextrin, and they hold that the properties 

 of tlie products of the diastatic digestion of starch can be fully accounted for by the pres- 

 ence only of maltose and a non-reducing dextrin. Lintner (Jour. f. prakt. Chemie, 1887, 

 XXXVI, 481) looks upon maltose as being the sugar-product of starch digestion by diastase. 

 Bourquelot (Compt. rend. 1887, civ, 71, 576) asserts that both maIto.?e and ghicose are 

 products of enzymic activity. 



An important discovery bearing upon the explanation of the presence or absence of 

 glucose among the products of digestion was made by Cuisinier (Chem. Centralbl., 1886, 

 XVII, 614; Moniteur scient., 1886, 718), who noted that since glucose is formed in both 

 normal barley and barley malt and in certain other cereals but not in others, there must 

 be a special enzyme present which forms glucose. This hypothetical enzjane he named 

 glucase. He found upon macerating corn-meal in water at a temperature of 50 that sugar 

 was formed, and in order to determine the nature of the saccharifying agent, and also the 

 character of the sugar, he carried out a series of experiments in which he found that corn 

 contains an enzyme which converts starch into dextrins and glucose, and that the dextrins 

 themselves are finally changed to glucose. He also showed that this enzyme converted 

 maltose into glucose, and that it acts upon starch-paste as weU as upon raw starch. It has 

 since been rendered evident that Cuisinier's enzyme was a mixture of diastase and glucase. 



The existence of such an enzyme as glucase was foreshadowed by the work of Brown 

 and Heron (1880), who found that while diastase gave ri.se to maltose, extract of the pan- 

 creas or of the small intestine not only formed maltose but also had the power of converting 

 maltose into glucose. Von Mering (1881) confij-med Brown and Heron's statement of the 

 action of extract of the pancreas. Bourquelet (1883) added further confirmation in experi- 

 ments with extracts carried on under aseptic conditions; and he also obtained proof that 

 the yeast plant and certain other low organisms secrete an enzyme which hydrolyzes 

 maltose into glucose. Since the announcement of Cuisinier, it has been shown that glucase 

 has probably a wide distribution in plant life. 



