Extrusion pregelatinization improves texture, viscoelasticity and in vitro starch digestibility of mango and amaranth flours

Non-conventional flours from unripe fruits and pseudocereals have potential as functional ingredients given their high protein contents and antioxidant activity. Pregelatinized starch and flours are increasingly used in gluten-free foods and as fat substitutes. The present work aimed to address the effect of extruding pregelatinization in the viscoelasticity and in vitro starch digestibility of amaranth and mango flours. Differences in starch, protein, and lipid contents between these flours were shown, which impacted the characteristics of the extruded flours. The gelatinization degree was 51% (amaranth) and 56% (mango). FTIR analysis showed that extrusion disrupted the hydrated and short-range ordered starch structure. Amaranth flour presented higher content of slowly digestible starch (41.13% raw and 49.39% extruded flour), which can be due to its higher protein conten (18.3%) with the potential of forming complexes with starch. A principal component analysis revealed that extrusion had a strong effect on the properties of both flours.