The physicochemical and structural properties and in vitro digestibility of pea starch isolated from flour ground by milling and air classification

The fine, coarse and parent starches were isolated from pea flour by milling and air-classification. Their structural, thermal, physicochemical properties and in vitro digestibility were investigated. Particle Size Distribution showed the fine starch with the smallest unimodal distribution (18.33 and 19.02 μm) displayed higher degree of short-range molecular order and lower number of double helix structure. Scanning Electron Microscopy showed the morphology of the coarse starch granules as uniform in size and lacking protein particles on its smooth surface. Differential Scanning Calorimetry revealed the coarse starch had higher enthalpy changes while Rapid Visco Analysis showed higher peak, trough, and breakdown viscosities for the fine starch. In vitro digestibility featured the fine starch containing lower fast digesting starch contents, but with higher resistant starch content, indicating its resistance to enzymatic hydrolysis. The results could provide theoretical support for application of pea starch in functional foods and the manufacture of emerging starch products.