Impact of extrusion processing on the nutritional and physicochemical properties of intermediate wheatgrass (Thinopyrum intermedium)

Background and Objectives: Intermediate wheatgrass (Thinopyrum intermedium, IWG) is a perennial grain crop being explored for mainstream food applications. The impact of extrusion on the nutritional and physicochemical characteristics of IWG was investigated for the first time. Extrudates were produced using a corotating twin-screw extruder. Findings: Extrusion resulted in slight decreases in dietary fiber, fat, starch, and amylose contents of IWG, whereas protein and ash contents did not change. Significant increase in starch damage after extrusion led to significant increases in starch digestibility and hydration properties of IWG. Correspondingly, slowly digestible starches and resistant starches were significantly reduced after extrusion. Pasting profile studies showed significant decreases in all pasting parameters measured except for breakdown viscosity after extrusion. Higher antioxidant activity and phenolic acid levels, mainly due to ferulic acid, were observed even after extrusion. However, carotenoids content decreased significantly (up to 65.8% reduction in lutein and 50.4% reduction in zeaxanthin). Conclusions: These findings show that extrusion cooking can improve the antioxidant activity and maintain high protein and dietary fiber levels in IWG, but it may not be suitable for preserving carotenoids in IWG. Significance and Novelty: Extrusion cooking could potentially be used to produce extruded snacks from IWG with high protein and dietary fiber.