Effect of roasting treatment on the micromorphology, gelatinization, structure, and digestibility of whole oat flour

Abstract

Roasting is the primary link in Chinese traditional whole oat food processing, but the role of roasting is rarely explored. This study aimed to clarify the effects of roasting treatment (160 °C, 0–60 min) of oat kernels on the characteristics of oat flour from the aspects of micromorphology, constituents, gelation, structure, and starch digestibility. Results showed roasting treatment disrupted the structure of oat kernels, promoted the release of lipids, and caused the aggregation and wrapping of oat flour particles. After roasting treatment, starch and protein content of whole oat flour did not change significantly, but lipid content increased and β-glucan content decreased. The roasted samples had better water absorption (25 °C, 2.41–2.69 g/g), swelling power (25 °C, 2.44–2.78), and solubility (100 °C, 25.40–28.11%), lower pasting viscosity (final viscosity, 1.84–3.61 Pa s), higher gel strength, and lower short-range order. Pasting viscosities and gel properties with roasting time conformed to the second-order polynomial model. Oat flour from roasting oat kernels for 40 min had the highest crystallinity (19.74%), the highest digestibility rate constant (k, 0.07), and lower product concentration (Cꝏ, 77.74%). These results will contribute to the application of roasting technology in the modification of whole oats.