Drying kinetics and quality characteristics of ultrasound-assisted germination of quinoa grains: A study on functional properties, mineral content and bioactive compounds

Quinoa (Chenopodium quinoa Willd.), an Andean grain, has garnered attention from cereal-based industries as a functional ingredient. This study evaluated functional properties, minerals, bioactive compounds and structural properties of Pre-treatments assisted germination of quinoa grains JQ-778 including, Only germinated seeds (OGS), soaked germinated seeds (SGS), ultrasound at 28 & 40 frequencies (US 28 kHz & US 40 kHz) for 30 min in a Biochemical-Incubator of 96-hour period at 25 °C, 12/12 h dark and light circle, followed by drying at temperatures 50 °C, 60 °C, 70 °C & combined (70, 60, 50 °C). Midilli-Kuck model shows the best fits on drying data closely followed by Hii model, respectively. According to the thermodynamic parameters entropy yielded negative values while Gibbs free energy & enthalpy decreased as the drying temperature increased. Ultrasonic pre-treatments significantly altered functional properties, minerals content and bioactive compounds of quinoa grains (p ≤ 0.05). In US group, quinoa's magnesium, calcium, and potassium content increased from 124.17 to 143.59, 84.7-86.83, and 428.72-448.67 mg/100 g, respectively. Copper ranges from 0.77 to 1.04 mg/100 g, whereas iron 4.76-5.64, Manganese 3.09-3.51 and zinc 2.26-3.51 mg/100 g. Ultrasound assisted germination, especially US 28 kHz dried at 50 °C, showed the highest content of hydroxycinnamic acid, whereas US 40 kHz dried at 60 °C showed hydroxybenzoic acid of quinoa grains. US 40 kHz at 60 °C found rutin 22.62 µg/g, Quercetin 17.58 µg/g, while Kaempferol at 50 °C 24.51 µg/g, demonstrating a 2.5 to 4-fold increase in flavonoids and phenolic acid profiles in ultrasound pre-treated germinated quinoa grains. XRD showed no significant shifts in main peaks, although germinated samples showed intensity variations, suggesting crystallinity modifications. SEM pictures showed germinated quinoa aggregation at different temperatures, with a film-like substance covering and linking the aggregates, possibly a starch aggregates are coupled to lipids and incorporated in a protein matrix.