Effect of Amylopectin Structure on the Gelatinization and Pasting Properties of Selected Yam (Dioscorea spp.) Starches

Abstract

AbstractThis study was aimed at elucidating the decisive structural parameters of amylopectin which govern the gelatinization or pasting behavior of yam starch dispersions, exemplified with four selected yam starches from Dioscorea alata and D. batatas with very similar amylose contents (32.2–34.6%). The results indicated that the yam amylopectins examined showed an average degree of polymerization (DP) of 3469–4474 anhydroglucose units (AGU), average chain length (CL) of 18.8–28.5 AGU, average exterior CL (ECL) of 11.8–16.4 AGU, average interior CL (ICL) of 6.0–11.1 AGU, and a noticeable proportion of extralong (> 100 AGU) and long (40–100 AGU) chains that gave the chain ratio r(el+l)/s (the weight ratio of extralong and long chains to short chains) of 0.88–1.40. Generally, the yam amylopectin with a lower DP and NC possessed a greater CL, ECL, ICL, and r(el+l)/s, associating with a higher blue value (BV) and maximal wavelength (λmax) for their complexes with iodine. D. alata amylopectins exhibited a lower DP, longer chain lengths and greater r(el+l)/s than the D. batata amylopectins. Statistically, r(el+l)/s was decisive for the BV and λmax; while CL and phosphate content were crucial for the gelatinization peak temperature and pasting viscosities of the yam starches examined. The role of swelling power or the volume fraction of dispersed remnants instead in governing the pasting viscosity was also mathematically explored.