Impact of Soaking on Physical and Morphological Characteristics of Browntop Millet: Kinetic Analysis of Polyphenol and Antinutrient Reduction

ABSTRACT This study investigates the impact of soaking conditions, temperature (25°C–45°C), and time (8–24 h) on the physical and morphological properties of browntop millet ( Brachiaria ramosa ), with emphasis on the kinetics of polyphenol and antinutrient reduction. A comprehensive analysis assessed hydration properties across soaking durations, alongside the dynamics of total polyphenols and primary antinutritional factors (phytate and tannin) to elucidate degradation kinetics. Morphological changes were examined microscopically, revealing notable alterations in surface morphology and endosperm structure with increasing soaking time. Results demonstrate that soaking improves hydration parameters and induces time‐dependent reductions in polyphenols and antinutritional factors, coupled with distinct changes in grain morphology. Degradation of polyphenols, flavonoids, and antinutritional compounds occurred at all temperatures, potentially affecting bioavailability and bioactivity. Within the first 8 h, polyphenol degradation reached 17%–25%, with more pronounced losses after 24 h. This trend is closely aligned with water absorption behavior. Flavonoid reduction was greater than polyphenols, with up to 97% loss at 45°C after 24 h. Phytic acid declined between 3.60% ± 0.09% and 22.53% ± 0.25%, while tannins decreased from 0.61% ± 0.004% to 16.65% ± 0.037%, depending on time–temperature conditions. Activation energy values were 13.21, 9.54, 1.79, 8.98, and 42.54 kJ/mol for water uptake, polyphenols, flavonoids, phytic acid, and tannins, respectively. Optimal soaking for bioactive retention and antinutrient reduction was 25°C–35°C for 8–12 h, minimizing excessive loss of beneficial polyphenols and flavonoids while ensuring substantial antinutrient reduction. These findings provide valuable insights for optimizing browntop millet pre‐processing to enhance nutritional quality and functional properties for food applications.