Enhancing the washing of harvested quinoa seeds with ultrasound-assisted hydration

Abstract

To improve the efficiency of harvested quinoa seed wash processing, this study comparatively evaluated the effects of ultrasound-assisted hydration (UH) and conventional hydration (CH) on hydration dynamics, saponin mass transfer kinetics, and pericarp structural changes in quinoa seeds. Moisture uptake was monitored using a gravimetric method, saponin content was determined through enzyme-linked immunosorbent assay, and pericarp structural changes were observed via scanning electron microscopy. The results showed that UH significantly enhanced the water absorption rate of quinoa seeds, with the Peleg model effectively fitting all hydration stages (R² > 0.93). The saponin content in the seeds decreased rapidly at first and then stabilized, with the most significant reduction occurring within the first 30 min of soaking. UH reduced the saponin content by 52 %–73 %, outperforming CH, which reduced it by 42 %–53 %. Fick’s diffusion model indicated that UH significantly increased the effective diffusion coefficient (D_eff) of saponins and reduced the activation energy (E_a from 21.83 to 18.15 kJ/mol). SEM images confirmed that UH accelerated the rupture and pore formation of the pericarp. All kinetic models showed good fitting performance, with the Weibull and two-term models providing the best fit under both CH and UH conditions, evidenced by the highest R² and lowest SSE, RMSE, and χ² values. These findings contribute to optimizing industrial quinoa processing, enhancing efficiency and sustainability, and provide valuable guidance for the application of ultrasound technology in grain-based food development.