Effects of High-Moisture Extrusion Conditions on the Functionality and In Vitro Digestibility of Waxy and High-Amylose Barley Flours

This study assessed how high-moisture extrusion (HME) alters the structural, functional, and in vitro digestibility properties of two barley flours with contrasting starch architectures: waxy barley (Annapurna®) and high-amylose barley (Hilose®). The flours were processed at three moisture contents (50%, 60%, and 70%) and two screw speeds (100 and 150 rpm). Moisture content emerged as the main processing factor influencing the response of both barley matrices, although the magnitude and direction of the changes depended strongly on barley composition. At 50% moisture and 150 rpm, the higher specific mechanical energy was associated with increased amylose content and resistant starch formation, with Hilose® reaching 13.8% resistant starch. In contrast, processing at 70% moisture increased water absorption and rapidly digestible starch, which reached 69.6% in Annapurna®. Intermediate conditions (60% moisture, 100 rpm) favored β-glucan retention and were associated with higher slowly digestible starch, exceeding 40% in Hilose®. HME also induced matrix-dependent changes in in vitro protein digestibility and in starch and protein structural organization, as evidenced by FTIR analysis and protein molecular weight distribution. Overall, the results show that the functional and nutritional effects of HME depend on the interaction between processing conditions and the intrinsic starch architecture of the barley matrix, supporting the use of HME to obtain barley flours with differentiated technological and nutritional properties.