Processing effects on the characteristics of oat protein solutions: The role of enzymatic treatment and pH-shifting with mild heating

Oat milk has gained widespread consumer acceptance for its creamy texture, β -glucan content, and environmental sustainability. However, its relatively low protein content (typically 2–3 g/serving) presents a nutritional limitation, largely due to poor protein solubility. This study investigated how processing conditions influence protein content and functional stability in oat-based systems by applying two treatments: (1) α -amylase enzymatic hydrolysis, and (2) pH-shifting (from pH 7 to 12 and back) with mild heating (50 °C for 10 or 30 min). Oat protein solutions were formulated from two sources: oat flour (OF) and oat protein isolate (OPI). Results suggests that α -amylase pretreatment effectively reduced starch-driven viscosity in OF, facilitating better sample handling and centrifugation. Following pH-shifting and heat treatment, both OF and OPI solutions showed significantly improved protein solubility, with protein content increased from 2.0 to ∼6.5 g/serving. These changes were accompanied by reduced precipitation, smaller particle sizes, and more negative zeta potential values, indicating enhanced colloidal stability. SDS-PAGE analysis revealed the presence of low-molecular-weight protein fractions, supporting increased solubilization. Fluorescence microscopy confirmed the formation of smaller, more uniformly dispersed particles in treated samples compared to controls. However, noticeable darkening or browning occurred under high-pH heating, indicating potential challenges in color control. The findings provide useful information for future industrial applications and product innovation in the plant-based beverage sector.