Optimization of ultrasound-assisted dehulling for quinoa and comparison with conventional methods: Dehulling performance and physicochemical characterization

Abstract

Dehulling is an essential step in the post-harvest processing of quinoa. To address the limitations of conventional dehulling methods, including low processing efficiency, severe grain damage, nutrient loss, and environmental pollution, this study developed a novel ultrasound-assisted wet dehulling (UWD) method as an effective alternative. The feasibility of UWD for quinoa dehulling was investigated by examining the effects of processing time (20–60 min), processing temperature (20–60 °C), and liquid-to-material ratio (3–11 mL/g) on dehulling performance. The results indicated that the optimal processing conditions were 38 min, 40 °C, and 7.2 mL/g, achieving a dehulling rate of 84.74% with a grain damage rate of only 1.22%. Comparative studies between optimized UWD and conventional dry dehulling (DD), wet dehulling (WD), and mixed dehulling (MD) demonstrated that UWD achieved a better balance between dehulling efficiency and grain integrity, with a dehulling rate second only to MD (87.21%) and a damage rate slightly higher than WD (0.93%). For physicochemical characteristics, UWD exhibited the most favorable overall performance, with loss rates of protein, fat, starch, and dietary fiber ranging from 5.31% to 23.76%. The loss rates of macro-elements (K, Mg, P, Ca) and micro-elements (Fe, Zn, Mn, Cu, Co) ranged from 9.58% to 39.87%. Additionally, UWD-treated grains exhibited a cleaner and brighter appearance (L* = 77.12, a* = 4.36, b* = 20.75). Principal component analysis ranked the overall scores as: UWD > MD > WD > DD. The research results provide theoretical basis and technical support for new quinoa dehulling processing technology.