Comparison of waxy potato with other root and tuber starches

The physicochemical properties of normal potato, waxy potato, yam and sweet potato starches were examined and compared. Normal potato and waxy potato starches displayed the B-type X-ray diffraction pattern, whereas yam and sw eet potato displayed the C-A- and C-type, respectively. X-ray patterns of N aegeli dextrins of normal potato and waxy potato remained the B-type, but t hose of yam and sweet potato changed to the A-type. P-31 NMR showed the pho sphorus contents of the starches to be primarily phosphate monoesters with no detectable phospholipid in any of the four starches. The chain-length di stributions of debranched amylopectins of the starches were analyzed using high performance anion-exchange chromatography equipped with a post-column amyloglucosidase reactor and a pulsed amperometric detector. Normal potato and waxy potato starches displayed lower proportions (13 and 14.8%, respect ively) of short branch chains of chain length dp 6-12 than did yam and swee t potato starches (17.1 and 19.0%, respectively). Normal potato displayed a larger proportion of long branch chains than did waxy potato amylopectin. The average amylopectin branch chain lengths of normal potato, waxy potato, yam and sweet potato starches were dp 28.6, 25.8, 25.8 and 26.3, respectiv ely. The Naegeli dextrins of all four starches displayed linear and singly branched chains, but no multiply branched chains. The Naegeli dextrins of n ormal potato, waxy potato, yam and sweet potato starches displayed ratios o f branched to Linear branch chains of 0.31, 0.36, 0.42 and 0.51, respective ly. The absolute amylose contents of the four starches were normal potato, 18.3%; waxy potato, 0%; yam, 17.7%; and sweet potato, 22.8%. (C) 1999 Elsev ier Science Ltd. All rights reserved.