Extraction and Characterization of Starches from Varieties of Oca (Oxalis tuberosa), a High-Andean Tuber.

Abstract

Oxalis tuberosa (Oca) is traditionally cultivated in the high Andean regions of Peru and represents a promising alternative source of starch with potential industrial uses, ranking among the most essential tubers after the potato. This study aimed to evaluate the physicochemical, morphological, techno-functional, and thermal properties of starch isolated from three specific varieties of Oca (yellow, black, and white) harvested at the Ccanccayllo production center in Andahuaylas, Peru. The isolated starches exhibited high purity, characterized by high luminosity (L* > 92.28) and a whiteness index exceeding 92.10. Moisture content ranged from 9.36% to 10.01%, correlating with low water activity (a_w = 0.44), indicating stability. Notably, the amylose content was significantly higher than that of other previously studied Oca varieties. This composition contributed to a favorable water absorption capacity, solubility index, swelling power, and viscosity, with the white variety displaying superior functional performance. Colloidal stability in aqueous media was moderate, as indicated by zeta potential analysis. Particle size analysis revealed granules ranging from 26.32 to 27.74 μm, with elongated and oval morphologies confirmed by SEM, displaying characteristic functional groups. Thermal analysis (DSC) demonstrated gelatinization temperatures between 52.73 and 53.12 °C and enthalpies ranging from 4.92 to 6.11 J/g, while Thermogravimetric Analysis (TGA) indicated thermal degradation up to approximately 74-80%. These findings suggest that the studied Oca starches possess significant potential for application in the food and pharmaceutical industries due to their distinct functional properties.