Comparative Characterization of Structural, Physicochemical, Thermal, and Functional Properties of Native Starches from Three Locally Recognized Oxalis tuberosa Materials

Abstract

Oxalis tuberosa (oca) is an underutilized Andean tuber with potential as an alternative starch source. This study compared native starches isolated from locally recognized yellow, pink, and black oca materials using compositional, structural, morphological, hydration, pasting, and thermal analyses. All starches exhibited B-type crystallinity but differed significantly in their measured characteristics. Black oca starch had the highest amylose content (28.1%), relative crystallinity (35.8%), median granule diameter (22.8 μm), and FTIR 1047/1022 ratio (1.36). Conversely, pink starch showed the highest swelling power at 90 °C (17.5 g g−1), peak viscosity (3900 cP), and gelatinization enthalpy (12.83 J g−1), compared with 10.9 g g−1, 2350 cP, and 7.61 J g−1, respectively, for black starch. The ordering of DSC parameters did not parallel XRD-derived relative crystallinity, indicating that relative crystallinity alone did not explain the thermal behavior. The contrasting functional profiles suggest that pink starch warrants further evaluation for applications requiring high hydration and viscosity development, whereas the lower RVA breakdown of black starch may be advantageous where resistance to viscosity loss during heating and shear is required. These findings demonstrate starch-level variation among the three local oca materials; however, application performance requires formulation-level validation, and broader multi-location and multi-harvest studies are needed to establish the stability of these characteristics.