New Gluten-Free Extruded Snack-Type Products Based on Rice and Chickpea and Fortified with Passion Fruit Skin: Extrusion Cooking Effect on Phenolic Composition, Non-Nutritional Factors, and Antioxidant Properties

The incorporation of pulse flour into gluten-free extruded snacks based on cereals improves the functional properties as well as the nutritional value of these types of products. The aim of this study was to investigate the changes induced by the extrusion process on the functional properties in terms of the concentration of total phenolic compounds (TPC), phenolic families (hydroxybenzoic acids, hydroxycinnamic acids, and flavonols), and non-nutritional factors (inositol phosphates and trypsin inhibitors) of extruded snack-type products developed from novel formulations based on rice-chickpea flours and fortified with different percentages of Fibersol^® and passion-fruit-skin flour. The in vitro antioxidant activity of the studied formulations was evaluated to explore their potential for developing sustainable snack-type products with added functional value. The results demonstrated that extrusion treatment caused a statistically significant (<i>p</i> < 0.05) decrease (12-30%) in TPC. Despite this reduction, the extruded formulations preserve an interesting content of these compounds, with hydroxybenzoic acids being the majority in the analyzed formulations. The extrusion process maintained or decreased the content of phytate and total inositol phosphates in samples fortified with passion fruit and Fibersol^®. A significant reduction (<i>p</i> < 0.05) of trypsin inhibitor activity (between 86.7% and 95.8%) was observed when comparing extruded samples to their raw counterpart. The antioxidant activity in vitro of the formulations was assessed. The results obtained by the Folin-Ciocalteu method indicated that extrusion caused a decrease in the antioxidant activity of 50% of the analyzed samples, while in the others, no changes were observed. DPPH and FRAP assays tended to demonstrate an increase in antioxidant activity. In general, the highest values were obtained by applying the DPPH method. Additionally, the effects of the ingredients used for fortifying the formulations were investigated. The results highlighted the complexity of the analyzed formulations, revealing that their composition is influenced not only by the presence of Fibersol^® and passion fruit but also by the interaction between these two ingredients.