Ultrasound-Assisted Intermittent Hydration of Pumpkin Seeds: Improving the Water Uptake, Germination, and Quality of a Clean Label Ingredient

Abstract

This work investigated the ultrasound (US)-assisted intermittent hydration kinetics (1–4 cycles of 10 min, 38 W/L, 25 kHz, 25 or 45 °C) of pumpkin seed and its impact on the germination kinetics, as well as on the nutritional and biological quality of germinated flours. Sonication reduced hydration time (≤ 54.3%), decreased the germination lag phase (≤ 19.3%), and increased maximum germination capacity (≤ 5%) (p < 0.05). Furthermore, ultrasonic treatment led to greater rootlet length (≤ 19.4%) after germination. Regarding the flour quality, ultrasound increased protein and lipid content (≤ 23% and ≤ 8.4%, respectively), with the best result observed at 45 °C for 4 cycles of 10 min. Additionally, samples sonicated for 2 cycles of 10 min showed higher levels of reducing sugars (≤ 79%), phenolic compounds (≤ 81%), and soluble protein (≤ 19.8%) compared to non-US-treated germinated flour. These findings highlight the potential of ultrasound-assisted hydration, especially above two intermittent sonication cycles, for optimizing pumpkin seed germination and enhancing flour quality.