Physicochemical, Morphological, and Molecular Properties of Starch Isolated from Dioscorea and Oxalis Tubers from Hidalgo State, Mexico

Starches are isolated from tubers of Dioscorea and Oxalis tuberosa (OT) grown in Hidalgo and surrounding areas. The starch particle sizes of Dioscorea bulbifera (DB) show a bimodal distribution, whereas those of Dioscorea mexicana Schidw (DM) and OT show unimodal distributions. The Dioscorea starch granules have a round shape, while those of OT have an elongated shape. Significant differences (p < 0.05) in pasting properties among the starches are observed, with DB showing the lowest viscosity value and DM showing the highest viscosity value. The peak and pasting temperatures show similar patterns, with higher values observed in the Dioscorea starches than in the OT starch. The gelatinization temperature values are low in the DB starch, compared to the DM and OT starches, which is consistent with the small granule size in DB. The interval in amylose content in the starches is 25.9% to 32.3%, classifying as normal starches. Molecular analysis reveals differences in molar mass and gyration radius between the amylopectin and amylose fractions of the starches, parameters that influence the physicochemical, pasting, and enzymatic hydrolysis characteristics of starches. The characterization of the tuber starches in this study reveals the potential of these under-used food crops.