Impact of high moisture extrusion and in vivo mastication on in vitro protein digestibility of meat analogs made from pea protein isolate

It has been unclear whether varying high moisture extrusion (HME) melt temperatures would differentiate protein digestibility of meat analogs made purely from pea protein isolate (PPI). This study examined whether the in vitro protein digestibility of three meat analogs made from PPI by HME at different temperatures, and a mildly baked PPI sample, differs from that of an animal protein -based counterpart (cooked chicken meat). Additionally, food microstructure, the impact of mastication in place of in vitro oral phase and consequent bolus properties were investigated. The degree of protein hydrolysis (DH %) was assessed after using the standardized, static in vitro upper intestinal digestion model (INFOGEST). The results show that the structure of the PPI analogs extruded at 125°C and 140°C resembled the fibrous structure of chicken meat, whereas the analog extruded at 90°C and the baked sample lacked this meat-like structure. All PPI-based samples had similar DH % to chicken meat. Differences in the measured properties – the shapes, sizes, and numbers of particles – in the masticated PPI-based boluses did not differentiate in vitro protein digestibility. Interestingly, the masticated chicken bolus showed a slightly lower DH % (p=0.05) than chicken subjected to the in vitro oral phase, but this cannot be explained by the measured bolus properties. As a conclusion, despite differences in food microstructure and bolus properties, protein digestibility was similar between cooked chicken and PPI-based meat analogs extruded in temperatures of 90–140 °C.