Structural-related properties, proteomics and nutritional benefits of insects (Galleria mellonella and Alphitobius diaperinus) proteins, and investigation of their role in mitigating oxidative stress and inflammation through static INFOGEST and transepithelial transport

This study explored insects (Galleria mellonella and Alphitobius diaperinus) as potential protein sources and bioactive peptides sources to encourage insect consumption. First, Galleria mellonella and Alphitobius diaperinus whole insects were ground to obtain flours and afterwards defatted to reduce the fat content and avoid proteins and lipid oxidation and saponification during protein extraction; then the proteins were extracted to overcome the shape of insects and produce protein ingredients. Extraction methods included alkaline solubilization coupled to isoelectric precipitation and Osborne fractionation, and their effects on the structural related properties and nutritional properties were studied as basis for development of insect protein application into food. With regards to nutritional and structural related properties, globulins (salt soluble proteins) are the most recommended for both Galleria mellonella and Alphitobius diaperinus. Also, a proteomics analysis was performed to identify the specific proteins present in Galleria mellonella and Alphitobius diaperinus protein ingredients. Then the proteins with the highest high protein content and highest recovery yield were selected for digestion and absorption experiments. The antioxidant and anti-inflammatory properties of digestates produced during in vitro gastrointestinal digestion were assessed and these showed a gradually enhanced bioactive potential with the digestion progression. However, the final gastrointestinal digestates did not show the best bioactivities in all the tests, concluding that beyond a certain level, further peptide hydrolysis may make some of the peptide sequences less bioactive. A good example is the iron chelating activity of the Galleria mellonella gastrointestinal digestates where the 1h digestates showed higher iron chelating activity than the final 2h gastrointestinal digestate. As for the anti- inflammatory effects, both insect digestates down regulated NF-kB signaling and mitigated ROS and proinflammation cytokines, while they up-regulated Nrf2 signaling to provide cell protection. The effects of the most effective peptides selected from digestates have effects on modulating the NF-kB pathway are predicted by molecular docking. In summary, based on the current results, both types of insects are demonstrated as potential future alternative protein sources with high nutritional value. In addition, based on the potential of peptides released during intestinal digestion, insect proteins have strong potential to mitigate oxidative stress and inflammation.