AMYLODEXTRIN AND MALTODEXTRIN. 119 



siderable production of maltodextrin ; that all soluble starches prepared in the heat by acid 

 contain this substance; and it is to its presence, and not to the maltose or glucose, that 

 the copper-reducing power of soluble starches is due. This is proved, he states, by the 

 fact that yeast has no effect in reducing the amount of apparent maltose in a solution of 

 starch which on dialysis does not yield sugar but a body having the properties of amylo- 

 dextrin. He prepared soluble starch from arrowToot by Lintner's method, added water, 

 and dialyzed for 2 days. The dialysate was concentrated, and precipitated twice with 

 alcohol, and finally dissolved in water. The rotatory and reducing powers correspond 

 to {a)D aba = +189) 'ffab3 = 14.4, which are the values given by Brown and Morris for amylo- 

 dextrin. For practical purposes of diastasimetry the presence of amylodextrin in the 

 starch is of no importance, as it is equivalent to soluble starch. 



The degradation products of starch brought about by the action of oxalic acid were 

 studied by Griiters (Zeit. angew. Chem., 1904, xviii, 1169), who obtained achroodextrins I 

 and II, maltodextrin r, maltose, dextrose, and a small amount of levulose. He found that 

 the products of the action of oxalic acid are the same as those of diastase, except that the 

 maltodextrin r produced by the acid is replaced by maltodextrin /S by the diastase, the 

 latter showing different constants and behaving differently in the presence of diastase. He 

 beUeves, however, that both forms occur simultaneously, but in varying proportions. 

 He also notes that the divergent behavior of different isomaltose preparations toward 

 malt extract indicates an occasional preponderance of the more resistant maltodextrin r 

 as the lowest member of the dextrins present. 



By the use of chromic acid, Harz (Beiheft. z. botan. Centralbl., 1905; Woch. f. Brau, 

 1905, XXII, 721) prepared what he records as amylodextrin, and he found that (like the 

 original starch) it did not behave as a uniform substance, but seemed to consist of a number 

 of molecular groups which differ in complexity and density of internal structure. The 

 same composite character he noted in erythrodextrin II that he prepared by the action 

 of a 5 per cent alcoholic solution of hyckochloric acid on starch. Wlien, however, the 

 achroodextrin stage was reached the products seemed to possess homogeneity. 



Moreau (Ann. d. d. Soc. Roy. d. Sc. m^d. e. nat. d. Bruxelles, 1903, xii, 117; 1905, 

 XIV, 64), in following up his earlier work on the isolation of various products of digestion 

 by precipitants, separated the different products by precipitation by barium hydroxide 

 in aqueous or dilute alcoholic media, determining the progress of the reaction and nature 

 of the precipitated bodies by the iodine reactions of the filtrates. Amylodextrin and ery- 

 throdextrin were precipitated in aqueous solutions, while achroodextrin and sugar were 

 precipitated only in the presence of more or less alcohol; but the limits of precipitability 

 were sufficiently far apart to permit the separation of the several products by repeated 

 fractionation by barium hydi-oxide. By this means he determined, in support of Mittel- 

 meyer's theory of starch decomposition, that even in the earliest stages of digestion the 

 starch molecule is immecUately broken down into tln-ee forms of dextrin and sugar. De- 

 tailed directions are given for preparing pure amylodextrin from the dextrins of com- 

 merce. Such amylodextrin, as well as pure erythrodextrin, were found to be absolutely 

 devoid of reducing power in cupric solutions. 



The maltodextrin r, which was first described by Griiters, was further studied by 

 Rheinfeld (Woch. f. Brau., 1906, xxiii, 510), who finds that its position in the series of 

 disintegration products of starch is between the maltodextrin fi of Ling and Baker, or 

 the achi'oodextrin III of Prior, and maltose. He subjected starch-paste to the action of 

 diastase at a temperature of 70, and allowed the process to go on until a red reaction 

 with iodine no longer occurred. By a series of fractionations he obtained a form of malto- 

 dextrin which had the constants (a)D= +167.7 and R = G0.1 per cent of maltose. Based 

 upon glucose equivalents the constants were (a)D= +170-173 and i? = 61-64 per cent. 

 He calls attention to the fact that this maltodextrin was fermented to the extent of 50 



