102 DIFFERENTIATION AND SPECIFICITY OF STARCHES. 



of a number of observers, as already stated, that the degree of solubility is proportional 

 to the degree of comminution of the grains, and that complete comminution is equiv- 

 alent to complete gelatinization by heat in so far as the actions of digestive agents are 

 concerned. Fritzsche (Ann. d. Physik. u. Chemie, 1834, xxxii, 129), in his study of the 

 lamella; of the starch-grain, associates the greater density of the outer layer with the 

 insolubility of the raw grains in cold water, as he found that when the grains are crushed 

 some of the inner starch is dissolved in cold water. The solubility of a part of the raw grain 

 in cold water has been confirmed by Jessen, DelfTs, Knop, and others of the eariier investi- 

 gators (p. 28), and later by the investigations of BrowTi and Heron, Meyer, and Maquenne. 

 Uninjured raw starch-grains are as insoluble in vitro in solutions of amyloclastic enzymes 

 as they are in cold water, provided the actions of bacteria are prevented. Brown and 

 Heron (Ann. d. Chemie u. Phys., 1878, cxcix, 20G) found that starch-grains which 

 showed no change after a considerable time in the presence of malt extract were readily 

 digested after they were crushed. Meyer (Die StJirkekorner, etc., loc. cit.) noted that 

 perfect grains of the starch of the potato and of Dieffenbachia segvina are dissolved after 

 a time from within outwards in successive layers, but grains having clefts or fissures were 

 eroded with channels, pits, cavities, etc. Maquenne (Compt. rend., 1904, cxxxviii, 375) 

 compared the intensities of the digestive actions of diastase and dilute acids on raw 

 starch, crushed starch, and starch-paste. By means, for instance, of malt extract at 55° 

 he found the following percentages of soluble matter produced: Raw starch-grains, 2.8; 

 raw starch broken by trituration, 94.8; and starch-paste, 102.2, the percentages being 

 calculated on the quantity of original starch. 



The form of soluble starch that is obtained by simple solution of the comminuted 

 raw grains is doubtless the nearest derivative of natural starch, but a similar or identical 

 form may be prepared by the subjection of the grain to the temperature of complete 

 gelatinization; or by a sloiv solution of raw starch by amyloclastic enzymes, dilute acids, 

 etc., avoiding the formation of various decomposition products that are formed during 

 rapid action; or by the liquefaction of starch-paste by amyloclastic enzymes, dilute acids, 

 high temperatures, etc. The various products thus obtained are not to be regarded as 

 being of uniform composition, as will be evident by the context, and they may be further 

 individualized by modifications of certain of the methods of preparation. 



The form of so-called soluble starch that is made by boiling starch in sufficient water 

 to make a liquid preparation is so universally known as not to require special notice. 

 Starch-paste can be converted into liquid soluble starch without the formation of dextrin by 

 heating in the autoclave or by careful restriction of the actions of amyloclastic enzymes, 

 dilute acids, alkalies, etc., or by the use of modified enzymes. Syniewski (Ann. d. Chem. 

 u. Phar., 1899, cccix, 282; 1902, cccxxiv, 212) placed a 5 per cent starch-paste made 

 of potato starch in the autoclave, at a temperature of 140°, and obtained a clear solution 

 which gave a blue reaction with iodine. Tliis form of soluble starch is soluble in cold water 

 and is without reducing action on copper solutions. He also prepared soluble starch by 

 treating starch-paste for several minutes with malt extract. lintner and Diill (Ber. d. d. 

 chem. GeseUsch., 1892, xxvi, 2533) prepared soluble starch ("amylodextrin") by sub- 

 jecting potato starch to the action of air-dried malt at a temperature of 70°, and arresting 

 the action while iodine still yielded a blue coloration. Hot 40 per cent alcohol was added, 

 and the soluble starch that separated upon cooling was finally purified by repeated frac- 

 tionation with 30 to 40 per cent alcohol. Upon drying, a light white powder was obtained 

 which was only sUghtly soluble in cold water, but very soluble in hot water. It yielded 

 a blue reaction with iodine, but it did not reduce Fehling's solution. 



Pottevin (Compt. rend., 1898, cxxvi, 1218) found that when malt extract is kept at 

 79° to 80° for 15 to 20 minutes it loses its power of converting starch into sugar, but retains 

 its power of liquefying starch-paste and of forming dextrin. Petit (Compt. rend., 1905, 



