STARCH. 227 



granules which have a stratified structure and different shape and size 

 in different plants. Starch is considered insoluble in cold water. The 

 grains swell up in warm water and burst, yielding a paste. 



According to the ordinary opinion the starch granules consist of two 

 different substances, STARCH GRANULOSE and STARCH CELLULOSE (v. 

 NAGELI), the first of which turns blue with iodine and forms the chief 

 part of the granule. According to MAQUENNE and Roux x this is 

 not the fact. According to them the starch granule consists of two 

 constituents, of which the first, amylose, forms the chief mass (80-85 

 per cent) and the other, amylopeclin, forms only 15-20 per cent of the 

 granule. Amylopectin is not identical with v. NAGELI'S starch cellulose, 

 and the above investigators consider starch cellulose as only an insoluble 

 form of amylose. The amylose can occur in two forms; one, which is 

 soluble, is colored blue by iodine and is immediately transformed into 

 sugar by malt, the other is a solid substance, which is not colored 

 vdth iodine and resists the action of malt infusion. One modification 

 can be transformed into the other. 



In the paste, besides amylopectin, we also have soluble amylose, and 

 this can, by a process called retrogradation by MAQUENNE and Roux, be 

 transformed into the solid modification, " artificial starch." This 

 solid form occurs in the starch granule, and is identical with v. NAGELI'S 

 starch cellulose. As the starch granules are directly colored blue by 

 iodine they must, besides this, also contain soluble amylose. If the author 

 understands the above investigators correctly the starch granules con- 

 tain three constituents, namely, soluble amylose, which is colored blue 

 by iodine ( = starch granulose), insoluble amylose, which is not colored 

 by iodine ( = starch cellulose), and amylopectin. 



In the formation of paste the amount of amylose is not the essential 

 but rather the quantity of amylopectin. The amylopectin is a slime- 

 like substance, insoluble in boiling water and dilute alkalies, only becom- 

 ing pasty therein, and not colored blue by iodine. Accordingly the 

 paste is a solution of amylose made thick by amylopectin. The amylo- 

 pectin, unlike the amylose, is only slowly transformed into sugar with 

 dextrin formation. Starch is insoluble in alcohol and ether. On heat- 

 ing starch with water alone, or heating with glycerin to 190 C., or on 

 treating the starch grains with 6 parts dilute hydrochloric acid of sp. gr. 

 1.06 at ordinary temperature for six to eight weeks, 2 it is converted into 

 soluble starch (AMYLODEXTRIN, AMIDULIN). Soluble starch is also 



1 v. Nageli, Botan. Mittei]., 1863; Maquenne and Roux, Compt. rend., 138, 140, 

 142, 146, and Bull. Soc. chim. de Paris (3), 33 and 35. 



2 See Tollens' Handb., 191. In regard to other methods, see Wr6blewsky, Ber. d. 

 deutsch. chem., Gesellsch., 30; Syniewski, ibid. 



