Optimisation of extraction parameters of millet-based non-dairy beverage: compositional and functional characterisation

Purpose The purpose of this study is to develop and optimise a lactose-free millet-based non-dairy beverage using response surface methodology (RSM) and to evaluate its physicochemical, functional, antioxidant and sensory characteristics for potential application as a sustainable dairy alternative. Design/methodology/approach Proso millet, pearl millet and little millet were used for the preparation of non-dairy beverages through controlled processing steps, including soaking, germination, grinding and filtration. The extraction parameters, namely, soaking time, germination time and millet-to-water ratio, were optimised using Box–Behnken Design of RSM. The developed non-dairy beverages were analysed for physicochemical properties such as protein content, total solids, yield, sedimentation index and titratable acidity, along with antioxidant activity, i.e. 2,2-diphenyl-1-picrylhydrazyl (%DPPH inhibition) and sensory acceptability. Advanced characterisation of the optimised formulation was performed using energy-dispersive X-ray spectroscopy and high-resolution mass spectrometry. Findings The results indicated that protein content ranged from 2.4% to 2.8% (p = 0.003), total solids from 7.6% to 8.8% (p = 0.0003) and yield from 68.0% to 78.0% (p < 0.0001). Titratable acidity varied between 1.1% and 1.6% (p = 0.0017), while the sedimentation index ranged from 1.0 to 1.1 g/20 mL (p < 0.0001). Antioxidant activity (%DPPH inhibition) ranged from 64.2% to 68.7% (p = 0.045), indicating significant radical scavenging potential. RSM optimisation predicted optimum conditions of 14.1-h soaking time, 24-h germination time and a millet-to-water ratio of 1:2, with a desirability value of 0.72. The experimentally validated formulation exhibited a yield of 73.3%, total solids of 8.2%, protein content of 3.4% and an overall acceptability score of 8.0 on a nine-point hedonic scale (p = 0.034). Spectroscopic and elemental analyses confirmed the presence of proteins, carbohydrates, essential minerals, fatty acids and bioactive compounds. Originality/value This study demonstrates the potential of millet-based milk analogues as nutritionally comparable and sustainable alternatives to conventional cattle milk as well as existing plant-based non-dairy beverages. The integration of RSM for process optimisation and advanced analytical techniques for characterisation provides a comprehensive approach for developing functional plant-based non-dairy beverages with improved quality and consumer acceptability.