Changes in the cocoa shell dietary fiber and phenolic compounds after extrusion determine its functional and physiological properties

The influence of different extrusion conditions on the cocoa shell (CS) dietary fiber, phenolic compounds, and antioxidant and functional properties was evaluated. Extrusion produced losses in the CS dietary fiber (3–26%), especially in the insoluble fraction, being more accentuated at higher temperatures (160 °C) and lower moisture feed (15–20%). The soluble fiber fraction significantly increased at 135 °C because of the solubilization of galactose- and glucose-containing insoluble polysaccharides. The extruded CS treated at 160 °C–25% of feed moisture showed the highest increase of total (27%) and free (58%) phenolic compounds, accompanied by an increase of indirect (10%) and direct (77%) antioxidant capacity. However, more promising results relative to the phenolic compounds’ bioaccessibility after in vitro simulated digestion were observed for 135°C–15% of feed moisture extrusion conditions. The CS’ physicochemical and techno-functional properties were affected by extrusion, producing extrudates with higher bulk density, a diminished capacity to hold oil (22–28%) and water (18–65%), and improved swelling properties (14–35%). The extruded CS exhibited increased glucose adsorption capacity (up to 2.1-fold, at 135 °C–15% of feed moisture) and α-amylase in vitro inhibitory capacity (29–54%), accompanied by an increase in their glucose diffusion delaying ability (73–91%) and their starch digestion retardation capacity (up to 2.8-fold, at 135 °C–15% of feed moisture). Moreover, the extruded CS preserved its cholesterol and bile salts binding capacity and pancreatic lipase inhibitory properties. These findings generated knowledge of the CS valorization through extrusion to produce foods rich in dietary fiber with improved health-promoting properties due to the extrusion-triggered fiber solubilization.