Title : Synergistic effect of ultrasound and citric acid on physicochemical, structural and functional properties of oca starch
Abstract:
Oca (Oxalis tuberosa Molina), a starch-rich tuber, remains largely unexplored for industrial applications. This study evaluated the effects of individual and combined ultrasound and citric acid treatments on the structural, physicochemical, rheological, and digestibility properties of oca starch, as well as its performance as a fat replacer in reduced-fat white sauces. The starch was modified using ultrasound (SUS), citric acid esterification (SCA), and a combination of both treatments (SDual). The dual-modified starch presented the highest degree of substitution (0.42 ± 0.08), suggesting a synergistic interaction between the two treatments. Structural changes included ester bond formation, as confirmed by FTIR, and increased granule porosity. The modified starch exhibited improved techno-functional properties compared to native starch, including increased solubility, swelling power, and water retention capacity, while digestibility shifted toward a higher proportion of slowly digestible starch. In application, SDual sauces exhibited desirable pseudoplastic behavior, enhanced viscosity, improved structural stability, and higher sensory acceptability. These findings support dual-modified oca starch as an effective clean-label fat replacer for healthier food formulations.
