180 



DIFFERENTIATION AND SPECIFICITY OF STARCHES. 



Fcrnbach (Compt. rend., 1904, cxxxviii, 428) ascertained that the small, liglit grains 

 as compared with the large, heavy grains of potato starch contain a higher percentage of 

 phosphates, and he concluded that the grains consist of a nuclear portion relatively rich 

 in phosphorus, upon which are superposed layers free from phosphorus. In digestion 

 experiments he noted differences in the behavior of the grains and parts of grains in accord- 

 ance with this peculiarity. Wliole starch-grains were found by Maquenne (Compt. rend., 

 1904, cxxxviii, 375) to be but little affected by malt diastase. Only 2.8 per cent of the 

 raw starch was dissolved after treatment with malt extract at 55. The same amount of 

 starch after boiling and subjected to the same quantity of malt, the same temperature and 

 period of time, was completely saccharified. Under the latter conchtions of experiment, 

 finely comminuted raiv grains were saccharified to the extent of 94.8 per cent, or almost 

 equivalent to gelatinized starch. Day (U. S. Dept. Agriculture, Office Expt. Stas. Bull. 202, 

 1908, 24), in experiments with wheat, corn, barley, rice, potato, and arrowToot starches, 

 found that raw starch digests slowly; that the cracked grains digest more rapidly than the 

 solid grains; that the outer layer is less digestible than the inner; that the six kinds of 

 starch fall into two divisions according to digestibility, the starches of wheat, corn, barley, 

 and rice being more digestible than those of potato and arrowroot. (See pages 166, 189, 

 190, and 192 for further reference to the investigations of Day.) 



Hanausek (The Microscopy of Technical Pi'oducts, trans, by Winton, 1907, 37) 

 describes erosion changes in potato-starch grains such as may be obser\^ed in a sprouting 

 potato. The specimen examined he thinks had been acted upon by diastase. Some of 

 the grains were marked by clefts and fissures which passed through or radiated from the 

 hilum; others had an irregular sac-like nucleus; and others were corroded or finely pitted, 

 displaying cavities, channels, etc. In a specimen of wheat starch he found grains which 

 were partly eaten away, mostly on one side, but the appearance was different from that 

 of the sjirouted grain caused by diastase. He attributes the erosion to the action of acid 

 used in the preparation of the starch. Eroded grains in situ he states display delicate 

 concentric rings and more or less distinct central fissures. Often the rings in parts of the 

 grain (in the same radial direction) are very distinct, while in the intermediate parts they 

 are scarcely evident. After long-continued action of the ferments the grains become 

 hollowed in the center and show numerous canals resembling the bm'rows of insects. Han- 

 ausek also observed the grains from sprouted rye, which he states present a very different 

 appearance. The outer layers, he records, are radially striated, and separated from the 

 inner by a marked circular crack, while the central portion is irregularly fissured, the 

 original clefts about the lulum being enlarged. 



It seems to be generally believed that starch-grains of different sources undergo 

 erosion in specific ways peculiar to the plant source. If the character of erosion is peculiar 

 to each kind of starch, it indicates specific forms of non-homogeneity of the granules which 

 are attributable to peculiarities of the metabolic processes which give rise to the starch-grain ; 

 hence, is a matter of considerable importance in this research. 



