熱帯産澱粉のアミロペクチンの鎖長分布について

Abstract

The distribution of a-1, 4 chains in amylopectins from 4 kinds of tropical starches, i. e., from edible canna, arrowroot, cassava and sago, were examined. Potato and corn starches were used as controls. Each starch was debranched with isoamylase and then chromatographed on a Sephadex G-75 column. The eluates were fractionated into 3 peaks by measuring the reducing and total sugars and the iodine color reaction. Fraction I is thought to have been derived from amylose, and the content of fraction I agreed with the content of amylose by the amperometric iodine titration method except edible canna and corn starches. Fractions U and IQ are thought to have been derived from the long and short chains of amylopectin, and the average chain lengths of the combined II and Ilt fraction of potato and edible canna starches were approximately 18, while the values for the other four starches were approximately 16. The weight% values of fraction II of the potato and edible canna starches were 38.1 and 35.1%, respectively, and the mol% values were 16.2 and 14.8%. The weight% values of fraction II of the other four starches were 23.6-27.9% and the mol% values were 9.1-11.1% (refer to Table 2). These results show that potato and edible canna starches have more long chain branches than the other four starches. It is also shown that the edible canna, sago and corn starches were rich in branches, the chain length of which was longer than 10 and shorter than 20. In contrast, the potato and arrowroot starches were rich in short chains, with a chain length shorter than 10. The potato and edible canna starches showed X-ray diffraction patterns of the B type, while cassava, arrowroot, and corn starches were of A type, and sago starch of C type close to A. The relationship between the crystalline type and the average chain length of the amylopectins showed the tendency for the A type to have a shorter chain length than the B type.