Impact of ultrasound-assisted intermittent hydration during pumpkin seed germination on the structure, nutritional, bioactive, physical and techno-functional properties of flours

Abstract

This study investigated the ultrasound (US)-assisted intermittent hydration of pumpkin seeds (2 cycles of 10 min, at 25 or 45 °C, 38 W/L, 25 kHz), followed by germination (3 days, 25 °C), evaluating the structure, nutritional, bioactive, color, and techno-functional properties of the obtained flours. US-assisted hydration produced flours that were more porous and lighter in color. Germination reduced starch crystallinity (≤14.3 %) and altered the flour's aliphatic hydrocarbons, amino acids and carbohydrates, particularly in the C-H and C-O bonds, as evidenced by Fourier transform infrared (FTIR) spectroscopy. US treatment did not affect the flours' mineral nor fatty acid profiles. On the other hand, sonication effectively increased the content of gamma-aminobutyric acid (GABA) (15.6 % and 13.7 %) and the antioxidant activities, measured both by 2,2′-azino-bis (3-ethyl benzothiazoline-6-sulfonic acid) (ABTS) (29.4 % and 9.7 %) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) (40.8 % and 2.4 %) methods compared to non-sonicated flours at 25 °C and 45 °C, respectively. US increased the water retention capacity, solubility index, foam capacity and foam stability by up to 49 %, 68 %, 143 % and 208 %, respectively. The enhanced nutritional and techno-functional properties suggest that germinated pumpkin seed flour hydrated under US, especially at 25 °C, is a promising and sustainable ingredient that can be used in products such as bread, cakes, cookies, and beverages.