Cultivar-dependent physicochemical, thermal, and crystalline functionality of native Oxalis tuberosa starches

Native starches obtained from underutilized Andean tubers have attracted increasing interest as sustainable biomaterials for food, pharmaceutical, and biodegradable applications. The physicochemical, thermal, optical, rheological, and crystalline characteristics of native starches derived from Oxalis tuberosa cultivars that are yellow, pink, and black were assessed in this work. All tested characteristics showed significant cultivar-dependent variations (p < 0.05). Greater hydration behavior and better storage stability were indicated by yellow oca starch’s maximum swelling power, water absorption capacity, solubility, and freeze-thaw stability. During heat processing, black oca starch exhibited the greatest peak viscosity, setback viscosity, and relative crystallinity, indicating a higher degree of molecular organization and enhanced rheological resistance during thermal processing. Pink oca starch, on the other hand, showed the maximum extraction yield along with decreased crystalline organization and a lesser tendency toward retrogradation. Thermal studies revealed that whereas yellow oca starch provided balanced thermal stability and hydration performance, black oca starch needed higher gelatinization temperatures and showed more retrogradation trend during storage. Black oca starch showed more particle clustering and optical heterogeneity, but yellow oca starch showed higher lightness and reflectance intensity, according to optical analysis. Significant variations in crystalline ordering across cultivars were verified by X-ray diffraction studies. The results show that native Oxalis tuberosa starches have unique structural and functional properties that may provide suitable physicochemical and structural characteristics for starch-based biodegradable materials, although biodegradation performance was not directly evaluated.