CONVERSION OF STARCH INTO DEXTRIN. 99 



but also that serial actions may be or are due to independent actions of the several 

 component enzymes. Duclaux's conclusions received support in the investigations of 

 Pottevin (Compt. rend., 1898, cxxvi, 1218), who treated starch-paste with a malt extract 

 that had been heated to 79° to 80° for 20 minutes, and found that the greater part of 

 the starch goes over into dextrin without there being formed any reducing sugars. The 

 starch-paste he prepared by heating 10 grams of starch in 1 liter of water heated to 90° 

 for 30 minutes, and subsequently heated for the same length of time in the autoclave 

 at 120°. The paste thus obtained was sufficiently transparent to permit of the determi- 

 nation of its rotatory power, (a)j= +197.6. (See under Dextrins, page 120.) Pottevin's 

 results received confirmation in the investigations of Maquenne and Roux (Compt. rend., 

 1905, cxL, 1303), who converted amylopectin (see p. 112) by malt extract heated to 80° 

 into dextrins, one of which was non-saccharifiable. The investigations of O'SuUivan 

 (Jour. Chem. Soc. Trans., 1872, lviii, 579), Petit (La biere et I'industrie de la brasserie, 

 1896, 179), and Windisch and Hasse (Woch. f. Brau., 1892, xix, 192) also give confirmation 

 to Pottevin's results. Theu- studies show that heating diastase so alters its properties 

 that as the temperature is higher the proportion of sugar formed falls rapidly, and that 

 a point is soon reached at which dextrin continues to be formed, yet little or absolutely 

 no sugar. When the enzyme is heated to 71° to 75°, saccharification ceases, but not dex- 

 trinization. 



Schumann (Jour. Soc. Chem. Industry, 1888, vii, 335) and Berge (Jour. Soc. Chem. 

 Industry, 1892, ii, 448; 1897, xvi, 548) prepared dextrin from starch by sulphur dioxide. 

 Raw starch was set aside for 24 hours in 1 per cent acid. It was then collected and washed 

 with fresh water until free from acid. This washed modified starch was reduced by water 

 to a milk at 15° Baume, and boiled under a pressure of 3 to 4 atmospheres with a 0.5 per 

 cent of saturated sulphurous-acid solution until the fii'st trace of glucose could be detected. 

 The reaction was then stopped, the slight trace of sulphuric acid formed was fixed, and 

 the syrup filtered through animal charcoal and evaporated. Berge made use of either 

 gaseous or liquid sulphur dioxide. With the former a closed vessel is half filled with starch 

 and gaseous sulphurous anhychide passed in until the air is displaced, when the exit-tube 

 is closed and the temperature raised to 120° to 190°. When the conversion is complete 

 the gas is allowed to escape. He notes that below 80° the action on starch is almost nil, 

 but between that temperature and 115° soluble starch is formed. At 115° the soluble 

 starch, in the absence of moisture, is converted into a very pure dextrin. Berge ob- 

 tained a dextrin containing less than 1 per cent of sugar by heating diy potato starch 

 with sulphur dioxide at 140° for 7 hours in a revolving cylinder. With sulphurous acid 

 in solution the action is extremely slow below 45°, but at 100° saccharification to glucose 

 begins and is complete between 135° and 140°. In the case of potato starch granulose is 

 rapidly converted, but the starch cellulose quite slowly. Schumann (Jour. Soc. Chem. 

 Industry, 1889, viii, 295) prepared dextrin free from sugar by mixing starch to a thick 

 cream with cold water and treating with 1 per cent of its weight of sulphuric, hydro- 

 chloric, or nitric acid. After 24 hours the starch is washed free from acid. This prepared 

 starch is either dried or mixed with water to a cream, and heated to 160° or 170° on an oil- 

 bath or by means of superheated steam. 



Glycerine may be used to prepare sugar-free dextrins, as was done by Zulkowski 

 (Ber. d. d. chem. GeseUsch., 1891, xxiii, 3295). Starch dissolved in hot glycerol is con- 

 verted at first into soluble starch, but by continued heating it is completely broken down 

 into erythrodextrin, achroodextrin and a series of related bodies having increasingly 

 greater solubUity in alcohol as the decomposition proceeds. 



It is obvious from the foregoing that dextrin and sugar formation are independent pro- 

 cesses; that dextrin may be formed without an attendant production of sugar; that dextrin 

 may be produced under conditions unfavorable to, or impossible for, the occurrence of a 



