Ultrasound-Assisted Germination: Impact of Time and Frequency on the Physical, Chemical, Thermal Properties and Bioactive Compounds of High Andean Quinoa

Germination is a biological process that can enhance the nutraceutical value of Andean grains, but its efficiency can be optimized through emerging, sustainable technologies. This study evaluated ultrasound as a pretreatment for the germination of Collana black quinoa. A 23 factorial design was used to assess the effect of ultrasound duration, ultrasound frequency, and germination time on the content of bioactive compounds, antioxidant capacity, color, water activity, amylase, and reducing sugars. Two controls (C48 and C72) were included as additional data points. Subsequently, analysis of variance and multiple-range tests were applied to assess the significance of differences between treatments (Tukey’s test) and between treatments and the control (Dunnett’s test). The content of phenolic compounds and flavonoids, antioxidant capacity, amylose, and reducing sugars were quantified by UV–Visible spectrophotometry. At the same time, FTIR, DSC, and TGA were used to evaluate functional groups and thermal behavior. Ultrasonic treatments resulted in increases of up to 12% in total phenolics, 24.5% in flavonoids, and 15% in antioxidant capacity compared to quinoa germinated for 72 h without ultrasonic treatment, along with reductions in amylose and increases in reducing sugars. Prolonged germination was the most influential factor; however, ultrasound acted as an abiotic stimulus, increasing cell permeability and promoting phenolic biosynthesis. Thermal and FTIR analyses revealed subtle modifications in starch and protein structure, associated with greater thermal stability and molecular reorganization. These results demonstrate that ultrasound-assisted germination is a sustainable and effective strategy for integrating functional quinoa ingredients into modern food systems.