Impact of heat treatment and high moisture extrusion on the in vitro protein digestibility of sunflower and pea protein ingredients

This study aimed to evaluate the protein quality of sunflower and pea protein and how processing (fermentation, mild heating, and high moisture extrusion) would affect their digestibility. The protein quality was assessed by the amino acid profile (calculated scores) and in vitro protein digestibility via the degree of protein hydrolysis (DH) using the INFOGEST digestion model. The amino acid profile indicated that sunflower protein was deficient only in lysine (0.62) and leucine (0.86), while pea protein lacked tryptophan (0.83) and sulfur-containing amino acids (0.96). The blend of these materials (1:1) provided a complete amino acid profile reaching a score above 1 for all the essential ones. Fermentation and blending did not have a significant impact of the protein digestibility of the raw materials. The DH of sunflower protein concentrate increased from 33.6 to 46.9% (p < 0.05) after mild heat treatment (15% solids, 90 °C, 15 min) and up to 52.8% (p < 0.05) after high-moisture extrusion. Differently, the digestibility of pea protein or the blends was not affected by any of the heat treatments. The extruded sunflower protein had a similar DH than the beef reference (47.5%) and mixing beef with plant-based ingredients did not affect the DH. These results highlight the potential of sunflower as good protein source, especially when blended with pea protein or extruded into meat analogs.