Role of particle size and roasted degree modulating the stability of oat milk

This study evaluated the effects of sieving and roasting treatment on the stability parameters of oat milk. Compositional properties, centrifugal sedimentation rate, apparent viscosity, turbidity, droplet size, ζ-potential and stability kinetic index (SI) were measured in oat milk produced with oat flours with various particle sizes or different roasted degrees (RF). Results indicated that oat milk prepared from roasted oat flour exhibited more compositions (protein, sugars, and total solids) and greater homogeneity than that produced from raw (control) and sieved oat flour. The roasted samples displayed higher viscosity (16.00-17.50 mPa·s), larger droplet sizes (14.77-16.57 μm), significantly higher absolute ζ-potential values (-28.33 ∼ -30.90 mV), and better stability (SI = 0.07-0.10), with kinetics successfully fitted to a linear-quadratic rational model (R² > 0.95). Oat milk from RF-30 (oat flour produced from grains roasted at 30 % moisture content) exhibited the greatest stability, attributed to moderate roasting facilitating the glycosylation of oat protein and promoting the formation of protein-lipid complexes, thereby enhancing emulsifying property. Post-standing stability changes in all oat milk samples were primarily attributed to coalescence, with sedimentation manifesting as the dominant instability mechanism. This work can contribute to providing the conditions for raw material selection for producing oat milk with excellent stability.