Impact of low-moisture extrusion on carbohydrate constituents and antinutrients of a blend of a faba bean protein concentrate and a beta-glucan enriched oat fraction

Texturized vegetable protein (TVP) was produced using low-moisture extrusion (LME) from a blend of a faba bean protein concentrate and an oat beta-glucan-rich fraction. These ingredients are a possible source of antinutrients. In this work, the effect of LME (temperature in zone 6 of the extruder, feed rate (FR) and ratio between water feed rate (WFR) and the FR) on the concentration of certain antinutrients (i.e. vicine and convicine, trypsin inhibitors, phenolics, tannins, and saponins) and carbohydrate constituents was evaluated. Results showed that while extrusion did not significantly reduce vicine and convicine content in the explored experimental domain, the trypsin inhibitors of TVP samples exhibited a significant decrease (88-93 %). Moreover, the moisture content appeared to influence trypsin inhibitor activity (TIA), with higher moisture levels associated with smaller decreases in TIA. Saponin content decreased slightly (13-16 %) with LME at higher specific mechanical energy (SME). LME also impacted phenolic content, showing a slight decrease with higher moisture levels. Condensed tannins were not detected in either the original blend or the extruded TVP samples, due to previous dehulling of the faba beans. Regarding carbohydrate constituents, LME led to a decrease in reducing sugars due to Maillard reactions and an increase in soluble fiber. Overall, extrusion process has no important negative effects on the constituents studied. These findings provide insights into the changes induced by LME on the carbohydrate constituents and antinutrient composition of the TVPs, supporting the rational design of the best processing conditions to develop new alternative protein ingredients/products with improved quality.