192 DIFFERENTIATION AND SPECIFICITY OF STARCHES. 



(3) Tliis variation is exhibited toward all of the common cnzj'mic ferments studied, viz, dias- 



tase, ptjalin, pancreatin, and Taka-diastase, in the same relative order, with slight 

 exception. 



(4) This order, beginning with the starch which is most easily changed, is, for malt extract, 



sweet potato, potato, wheat, and maize; for saliva, potato, sweet potato, maize, rice, 

 and wheat; for pancreatic fluid, potato, sweet potato, and maize, with wheat and rice 

 imchanged; for Taka-diaslasc the potato was more quicklj^ changed than any other. 



(5) It seems reasonable to assume that the same relative degree of susceptibility exhibited 



by these starches in the experiments described would still obtain when they are sub- 

 jected to the action of the same enzymes in the process of digestion. 



Lindet (Bull. Soc. chim., 1902, xxvii, 634) records that the starch of stale bread is 

 less digestible than that of fresh bread. Roiix (Compt. rend., 1904, cxxxviii, 1356), in 

 his studies of reverted starch, states his beUef that stale bread may contam this substance, 

 and Day {loc. cit.) several years later reports its presence in the skin formed on boiled starch. 



Effront (Enzymes and their Apphcations, trans, by Prescott, 1902, 128) assumes 

 that both raw and boiled starches of different kinds differ in digestibility because of inherent 

 differences in the starch, which are owing to differences in the compactness of the layers. 

 He states that potato starch and barley starch are both composed of non-homogeneous 

 granules differing m degree of compactness of the layers which compose them. In the 

 granules of potato starch more resisting layers are found than in the granules of barley 

 starch, and from different kinds of starch there are obtained pastes which saccharify with 

 more or less difficulty. It must therefore be assumed that the difference in compactness 

 between parts of the same granule does not disappear when the starch gelatinizes. The 

 more coherent parts of the granules will form a jjaste more difficult to liquefy (see page 179). 



Liquefied starch was found by Fernbach and Wolff' (Compt. rend., 1905, cxl, 1067) 

 to yield a larger quantity of products of digestion than ordinary starch-pastes. The 

 pastes of cereal starches, they found, were more readily saccharified than the paste of 

 potato starch. In another contribution {ibid., page 1547) they state that the starch from 

 green peas differs from other starches by a high percentage of amylocellulose that is not 

 saccharified. They found that if the freshly boiled starch is at once subjected to diges- 

 tion, complete saccharification occurs, but if allowed to stand an unsaccharifiable amy- 

 locellulose is thrown down. Pea starch in its natural condition, they state, is analogous 

 to potato starch that has been coagulated by amylocoagulase. Roux (Compt. rend. 

 1906, 95) subjected starch-pastes prepared at 100°, 120°, and 150° to the action of malt 

 extract at 50°, and foimd that the yields of maltose from different starches were not the 

 same. Calculated on the basis of dry starch, the quantities were: Potato 83.0 per cent, 

 corn 83.3 per cent, wheat 87.1 per cent (prepared at 150°), rice 85.2 per cent, pea 83.8 per 

 cent, tapioca 81.5 per cent. The yields from starches prepared at 100°, 120° and 150° 

 differed but slightly from each other. Ling (Jour. Fed. Inst. Brewing, 1903, ix, 446) found 

 that soluble starches prepared under different conditions do not yield identical results 

 under the influence of diastase. 



In an investigation of soluble starch of various origins, means of preparation, and 

 properties, Ford (Jour. Chem. Ind., 1904, xxiii, 414) recorded that there is no doubt 

 that preparations of soluble starches do differ m certain physical characteristics, and that 

 he is of the opinion that when different specimens give different maltose productions with 

 diastase, it is not the starch which causes the variations, but the impurities present in the 

 specimen. Solutions of soluble starch, from whatever source, when equally pure, will 

 give the same maltose production when acted upon by equal amounts of diastase under 

 the same conditions of temperature, etc. The starches experimented with, except barley, 

 were bought commercially and purified by treatment with cUlute alkali and acid, being 

 well washed and air-dried. Portions of 15 to 20 gi-ams were gelatinized, and then liquefied 

 at 79° to 80° by means of a trace of precipitated diastase, boiled when limpid, and then 



