Impact of ultrasound as a pretreatment on the malting properties of Ragi and foxtail millet

Ultrasound pretreatment of cereal grains has been shown to have positive effects on their malting properties in the literature. As millets are highly nutritious and climate-resilient crops, this study focuses on using ultrasound pretreatment to enhance malting of Eleusine coracana (ragi) and Setaria italica (foxtail millet). Soaking kinetics and germination efficiency were evaluated after treating the samples with ultrasound using a 25kHz probe sonicator (6mm probe diameter) at amplitudes of 20% and 40% for 60s and 120s, respectively, with a pulse of 3s on and 6s off at 298K, corresponding to power densities between 597 and 1195 W/L^-1. Soaking kinetics were modelled using the Peleg, Page, Weibull, and Midilli empirical models, where the Midilli model gave the best fit (R² > 0.98). Ultrasound reduced soaking time by 20-30% compared to untreated control seed samples. This enhanced mass transfer can be attributed to the micropores created by ultrasound. Germination also improved with enhanced seed viability and germination capacity after ultrasonication. Ragi treated with a 40% amplitude for 60 seconds showed a maximum GR of 71.11% and dormancy of 28.89%. Similarly, foxtail millet also showed the best improvement, with a GR of 75.56% under the same treatment combinations. Among all the treatment conditions, moderate ones (40%, 60s) effectively enhanced soaking and germination compared to treatments of longer durations (120s). This validates ultrasound as a sustainable, non-thermal technology for improving the overall malting and functional qualities of millet grains, which require further research and investigation.