Optimization of Fermentation and Spray-Drying Conditions for the Production of Oat-Based Postbiotic Powder

Postbiotics, a type of fermented functional food, are attracting attention alongside the more common pro- and prebiotics. The main production stages—fermentation, thermal inactivation, and drying—significantly influence the functional effects of these foods. This study investigated the impact of pH control during the fermentation of oat flour suspension and optimized spray-drying parameters to produce oat-based postbiotic powders. A Lacticaseibacillus paracasei CBA L74 fermented hydrolyzed oat suspension was analyzed at 37 °C for 24 h, with and without pH control. Both pH conditions produced similar bacterial growth (~109 CFU/mL) and lactic acid (~9 g/L). No significant differences were observed in polyphenols, flavonoids, or antioxidant activity, indicating that pH control did not noticeably improve productivity or the phytochemical properties. The best results—57.40% drying yield and 3.9% relative humidity—were achieved when the postbiotic suspension (diluted 1:4 with water) was mixed 1:1 with maltodextrins, and the spray drying process was conducted with 50 L/min air flow, 200 °C, 3.2 bar atomization pressure, and 5 L/min feed flow. These results support the possibility of scaling the production process from laboratory-optimized parameters and represent a first step toward a cost-effective and industrially feasible route for manufacturing stable oat-based postbiotic powders.