178 



DIFFERENTIATION AND SPECIFICITY OF STARCHES. 



Table 22. 



by Hammarsten (Jahr. ii. d. Fort. d. Thierchemie, 1871, i, 187), who writes that the variation 

 in the time required for changing starch-granules into sugar is due to differences in the 

 starches, and also according as to whether the grains were whole or broken or gelatinized. 

 Thus, in experiments made with human saliva, sugar 

 was formed from the raw starches as shown in table 22. 



Hammarsten states that since the use of starch- 

 paste made from these several starches showed no dif- 

 ference in the sugar-forming time, it may be presumed 

 that the unequal deposition of cellulose in different 

 starches presupposes unequal resistance to the influence 

 of the saliva and that it was therefore natural to ex- 

 pect that starch-granules, wliich in a raw state were 

 converted into sugar with difhculty, would react readily 

 if after being pulverized they were treated with saliva. 



This supposition was confirmed, inasmuch as finely powdered potato starch was found 

 to be rich in sugar after 5 minutes. Chewing starch-granules was then tried, with the 

 result that sugar was formed in all of the above-mentioned starches in 1 to 4 minutes. 

 The refractivity of raw potato starch to digestion was also noted by O'Sullivan (Jour. 

 Chem. Soc. Trans., 1878, ii, 125), who records that in the presence of fresh malt extract 

 the granules were unaffected after 24 hours. 



Baranetzky (Die starkeumbildenen Fermente in den Pflanzen, Leipzig, 1878, 40) 

 places the order of digestibility of raw starches as follows: Buckwheat, wheat, bean, 

 acorn, chestnut, potato, and rice. This does not accord with Hammarsten's records. Brown 

 and Heron (Ann. d. Chem. u. Phys., 1879, clix, 20G) ascertained that starch-grains in 

 the presence of malt extract do not undergo any change even after a considerable time 

 although when in situ in germinating seeds they undergo more or less rapid solution. 

 When, however, the grains were crushed by grinding in rough sand or broken glass, rapid 

 solution occurred. The marked solubility of the broken grains was noted by Hammarsten 

 and also by certain of the earlier investigators of starch. Recently Maquenne (Compt. 

 rend., 1904, cxxxviii, 375) found that fully comminuted grains yield as much soluble 

 matter by digestion at 55 with malt extract as starch-paste, and therefore that rupturing 

 the grains is as effective as gelatinization by heat in rendering the raw starch digestible. 



Lintner (Brau. u. Malzerkalender, 1890, xiii, 83) carried out a series of experiments 

 with various starches with diastase at different temperatures. In each experiment 2 grams 

 of air-dried starch were subjected to the action of 50 c.c. of malt extract for 4 hours. Each 

 preparation was then made to 100 c.c. by the addition of water, and then filtered to remove 

 the undigested starch. The filtrate was saccharified by weak hydrochloric acid, and the 

 sugar determined by Fehling's solution. From the sugar determinations the figures given 

 in table 23 were estimated as showing the percentages of starch digested. 



Table 23. 



