134 DIFFERENTIATION AND SPECIFICITY OF STARCHES. 



violet, and was then converted into maltose by malt extract at 63.7°. Seventy per cent 

 alcohol i)recipitated erythrodextrin from the filtrate. This dextrin was at first colored 

 light red with iodine, and then a brownish-red, and yielded 82 per cent of maltose. In the 

 filtrate achroodextrin was found, 95 per cent of which was converted into maltose. 



According to Pottevin, starch is changed into dextrin, and dextrin into sugar. He 

 explains the simultaneous presence of dextrin and sugar in certain stages of the reaction 

 by the fact that starch is composed of several constituents having varying degrees 

 of saccharifiability. He treated raw wheat starch with different portions of malt until 

 10 per cent of the original amount was left, and then prepared starch-paste from this, 

 and also from the normal raw starch, and found when both were treated in the same 

 manner with diastase that the former yielded only 44 per cent of maltose, while the latter 

 gave 75 per cent. 



In another contribution (Ann. d. ITnst. Pasteur, 1899, xiii, 728) Pottevin reports 

 on the non-homogeneity of starch-paste, and he states that the interior more labile parts 

 of the starch-grain are transformed almost instantly into dextrins which are wholly con- 

 verted into sugar, and which are soluble in 60 to 70 per cent alcohol, while the more resistant 

 portions of the grains jdeld dextrins that are only partially convertible into maltose and 

 which are insoluble in strong alcohol. He shows that the diffusibility of various dextrins 

 differs, and also that, owing to this, some of Brown and Morris's deductions regarding 

 their maltodextrins are erroneous. He prepared mixtures of a properly selected dextrin 

 and maltose which were absolutely identical with the maltodextrin of Brown and Morris, 

 which is claimed by them to be an individual, but which, however, do not exist in chemical 

 combination. 



Pottevin does not adinit the existence of Lintner's isomaltose, and he holds that this 

 body is merely a mixture of maltose and dextrin. In a third communication (Ann. d. I'lnst. 

 Pasteur, 1899, xiii, G55) he maintains *his statement in a former article that the starch- 

 grain and also starch-paste are not homogeneous; that the less dense portions are readily 

 converted into dextrin and this into sugar, while the more dense particles are converted 

 slowly and not comjiletely, and that there is always present at the end of saccharifica- 

 tion a residue of stable dextrin. Pottevin studied especially the different phases of the 

 reaction with reference to the properties of the enzyme used, and he holds that the enzyme 

 is to be regarded as being a mixture, dextrin-forming and sugar-forming, the one converting 

 starch into dextrin and the other converting dextrin into sugar. 



Stable dextrin in its relations to maltodextrin and soluble starch was studied by Brown 

 and Millar (Proc. Chem. Soc, 1899, xv, 13). They ascertained that when starch is trans- 

 formed by active diastase at a temperature of 60° the reaction goes on very rapidly until 

 a stage is reached when the rotatory power corresponds to {a)o = +153, and the reducing 

 value R = 80, at which time there is present maltose and a resistant dextrin having proper- 

 ties corresponding to {a)^ = +195.7 and R = 5.7 to 5.9. The reducing power they believe 

 to be inherent in the dextrin, as is indicated by the fact, as they state, that oxidation of 

 the dextrin gives rise to dextrinic acid, a polysaccharid acid; and they believe that both 

 the stable dextrin and the dextrinic acid are built up of Cg groups, and not C12 groups, 

 as in the case of maltodextrin. They state that the dextrin molecule may be regarded 

 empirically as composed of 39 CgHioOs groups in combination with a terminal C0H12O0 

 group, or, more correctly, as a condensation of 40 glucose molecules with the elimination 

 of 39 H2O. 



Petit (Compt. rend., 1899, cxxviii, 1176) supplemented the investigations above 

 referred to. He prepared dextrin by the action of a 1 per cent of malt diastase on starch 

 paste at 70°. The molecular weight of the dextrin he estimated to be 485, corresponding 

 to the formula (C(;Hio05)3. Its rotatory power was (a)D = +166.6, and its reducing power, 

 R = 18. Subjected to diastase at 50° to 55°, it was broken down into maltose and a residue 



