Process optimization for development of jamun juice (Syzygium cumini L. ) fortified functional finger millet milk powder using spray drying and its characterization

The present investigation aimed to find the optimal conditions for the spray drying conditions of finger millet milk blended with jamun juice, with a novel approach of producing the powder without any additional carrier agents. A three-factor three-level RSM design was employed to optimize inlet spray drying temperature (T; 150-170 °C), ratio of millet milk to jamun juice (MJ; 1–3) and flow rate (FR; 150–250 mL/h) based on powder yield, color change (ΔE), total phenolic content (TPC), DPPH assay (DPPH) and solubility (S). The optimum drying conditions were determined as 150 °C inlet spray drying temperature, 212.89 mL/h flow rate and 1:1 MJ ratio, yielding a desirability of 0.995. Under these conditions, the product showed a powder yield of 34.07%, high total phenolic content (119.34 g GAE/100g), 80.13% DPPH, ΔE of 22.84 and solubility of 55.02%. Structural and molecular characterization of the optimal powder using SEM, XRD and FTIR confirmed amorphous morphology with retained bioactive compounds. The developed product contains the nutritional benefits of both finger millet and jamun, offering potential for use in the development of value-added food products.