Optimisation of Spray Drying Parameters for the Production of Soymilk Powder in Delta State

Spray drying is a widely used microencapsulation and powder production technology in the food industry, enabling the conversion of liquid food products into stable dry powders with extended shelf life. This study optimises spray drying parameters for the production of soymilk powder from soybeans cultivated in Warri, Delta State, South South Nigeria. The key spray drying parameters investigated were inlet air temperature (150 to 200 degrees Celsius), feed flow rate (8 to 16 ml per minute), and feed solid content (10 to 20 percent total solids) using a Box-Behnken experimental design with response surface methodology. Response variables measured include powder yield, moisture content, bulk density, solubility index, dispersibility, colour, and sensory reconstitution quality. The optimised conditions identified were 175 degrees Celsius inlet temperature, 12 ml per minute feed flow rate, and 15 percent total solids, achieving a powder yield of 82 percent, moisture content of 3.2 percent, and solubility index of 94 percent. Proximate composition and amino acid profile of the optimised powder were comparable to fresh soymilk with acceptable protein content of 38 percent on a dry weight basis. The study draws on recent spray drying literature for plant-based dairy alternatives. Findings provide a scalable protocol for soymilk powder production relevant to the Nigerian soybean processing industry and food manufacturing companies in the South South zone. Keywords: spray drying, soymilk powder, response surface methodology, optimisation, Delta State