REVEKTED STARCH — ARTIFICIAL STARCH, ARTIFICIAL STARCH-GRAINS. Ill 



Soluble starch has also been prepared by the agency of sodium perborate (Slollc and 

 Kopke, and Fritsche, Chem. Abstracts, Amer. Chem. Soc, 1909, iii, 1105), by using 1 to 

 2 i)arts to 100 of starch and heating at 30° to 40° for 5 hours. It may also be made in like 

 manner by using a mixture of acetic and nitric acids instead of perborate. 



THE REVERSION OF STARCH-PASTE, SOLUBLE STARCH, AND AMVLODEXTRIN INTO COAGULATED AND INSOLUBLE 

 FORMS OF STARCH. "ARTIFICIAL STARCH" AND "ARTIFICIAL STARCH-GRAINS." 



The reversion of soluble starch to an insoluble condition was noted by Brown and Heron 

 (Ann. d. Chem. u. Phar., 1879, clxxxix, 266), who found that starch-paste upon standing 

 becomes opaque, owing to the formation of an insoluble form of starch. Salomon (Jour, 

 f. prakt. Chemie, 1883, xxviii, 82) observed the same phenomenon in preparations of what 

 he terms soluble starch (page 115). After precipitating and purifying, dissolving, and reduc- 

 ing to the consistence of a syrup, and setting aside over night, there was deposited a white 

 powder consisting of fine grains almost insoluble in cold water. A large part of the so-called 

 soluble starch separated from a concentrated solution as a white powder. (See page 192.) 



The phenomena of the reversion of dissolved starch into an insoluble form were inves- 

 tigated particularly by Rodenwald and Kattein, WolfT and Fernbach, Maquenne, Roux, 

 and Coombes. Rodenwald and Kattein (Sitzungsber. Kgl., pr. Akad. Wiss., Berlin, 1899, 

 XXIV, 628) prepared a form of soluble starch by means of iodine-potassium iodide in con- 

 junction with the autoclave, etc. (see page 109), which when hot is clear, or at most faintly 

 turbid, and which upon cooling deposits a white substance having the form of "artificial 

 starch-grains." Both the filtrate and these artificial grains give the blue reaction with 

 iodine. The grains when dried are insoluble in cold water, but are gelatinized upon boiling, 

 and swell and form a paste in the presence of potassium hydrate. 



Wolff and Fernbach (Compt. rend., 1903, cxxxvii, 718) coagulated solutions of starch 

 by means of amylocoagulase, an enzyme which they discovered in the green seeds of cereals 

 and associated with amylase in a large number of ripe seeds, germinating seeds, leaves, etc. 

 They found that 5 c.c. of a 10 per cent infusion of air-dried malt is sufficiently strong to 

 coagulate 100 c.c. of a 4 to 4.5 per cent solution of potato starch (prepared in the auto- 

 clave at 130° for 2 hours) in 20 to 30 minutes at 15° to 25°. The stronger the solution of 

 starch the quicker the coagulation and the denser and more coherent the mass. With weak 

 solutions the action of the amylocoagulase is hindered or prevented by the antagonistic 

 action of diastase. The coagulum never exceeds 30 per cent of the starch jiresent, and it 

 is readily soluble in hot water. Malt extract looses its coagulating property if subjected 

 to a temperature of 65° for five minutes. A solution of starch prepared by the restricted 

 action of diastase was found to be not so suitable for coagulation as that prepared in the 

 autoclave. Moreover, the reverted starches formed from the soluble starches prepared in 

 these two ways are not identical. 



The coagulum, or reversion product, or amylocellulose, as it has been termed, was 

 further studied by Maquenne, Fernbach, and Wolff (Compt. Rend., 1904, cxxxviii, 49), 

 who found that the formation of amylocellulose in the coagulum is more rapid when pre- 

 pared by the action of amylocoagulase on starch-paste heated at 120° for 15 minutes, or 

 at 100" for 30 minutes, or hquefied by heating in the autoclave at 130° for 2 hours, than 

 when amylocellulose is formed during the spontaneous reversion of starch-paste. The 

 coagulum immediately after its formation contains very little amylocellulose, but the 

 latter increases and may reach 50 per cent of the total coagulum. The amylocellulose 

 obtained by the reversion of starch-paste is saccharifiable by diastase, but not so with 

 that formed by the action of amylocoagulase. 



Additional observations were recorded by Fernbach and Wolff (Jour. Fed. Inst. 

 Brewing, 1904, x, 216) regarding the properties of amylocoagulase. They note again the 

 antagonistic actions of diastase and amylocoagulase, and that if the action of the former 



