Thermo-structural and energetic characterization of flours obtained from the Andean tubers oca (Oxalis tuberosa) and olluco (Ullucus tuberosus)

Oca ( Oxalis tuberosa ) and olluco ( Ullucus tuberosus Caldas) are Andean tubers traditionally cultivated under extreme climatic and edaphic conditions and increasingly considered as alternative raw materials for functional food applications. In this work, the structural, thermal, and energetic properties of flours obtained from both tubers were systematically studied. The samples were characterized using ICP-OES, SEM/EDX, DSC, TGA, and combustion calorimetry. The empirical formulas of oca and olluco flours were determined as CH 1.83 O 0.96 N 0 . 03 S 0.0018 and CH 1.80 O 0.93 N 0 . 06 S 0.002 , respectively. The olluco flour exhibited significantly higher crude protein and fat contents, as well as higher concentrations of metallic and semi-metallic elements, compared to oca flour. DSC measurements revealed comparable gelatinization enthalpy for olluco (Δ H gel = 8.5 ± 0.5 J g −1 ) and oca (Δ H gel = 7.1 ± 0.5 J g −1 ) flours, although their gelatinization temperatures differed by up to 3K. TGA results showed that both flours display high thermal stability, with major degradation occurring between 573 and 873K and residual masses of up to 26%. Combustion calorimetry yielded standard massic-energies of combustion (− Δ c u °) corresponding to net calorific values ( q NCV ) of 16.8 ± 0.2 kJ g −1 (4000 ± 40 kcal kg −1 ) for olluco flour and 16.2 ± 0.2 kJ g −1 (3880 ± 40 kcal kg −1 ) for oca flour . These results highlight the relevance of Andean tuber flours as thermally stable, energy-dense materials with potential interest for food formulation and thermochemical studies.