Effects of thermal processing on proteolysis of Silkworm pupae in the gastrointestinal tract of adults and seniors

Insects gain an increasing interest as a novel, nourishing and sustainable alternative food proteins. This study confirms high content of protein (40.40±0.07%w/w), lipids (29.56±0.08%w/w) and minerals, such as magnesium, potassium and calcium. In order to eliminate the insect appearance and improve its consumer acceptance, efforts seek to process insects but with limited insight into the ramifications to the chemistry and nutritional quality of the ingredients used. This study sought to investigate the plausible Maillard reaction between proteins and carbohydrates and their consequences to protein structure, techno-functionality and proteolytic breakdown during digestion.

SDS-PAGE analysis of gastrointestinal digesta of various thermally treated silkworm flour (SWF) revealed variability in the protein breakdown patterns. In-depth LC-MS/MS proteomic analyses show that baking in presence of fructose brought to a significant (p<0.05) reduction in the quantity of peptides in the gastric effluents. Bioinformatics mining against known bioactive peptide databases of the Arthropoda phylum revealed both cooking and baking in the presence of fructose brought to a reduction in the bioaccessible bioactive peptides (>70% homology). Analysis of the sequences by a predictive software (PeptideRanker) showed that processing may even lead to the generation of 14 potentially novel bioactive peptides (probability>80%) during digestion under the conditions of an elderly gut. Altogether, this study shows that process induced Maillard reaction interferes with SWF’s potential to generate bioactive peptides upon digestion but to a lesser extent in the gut of seniors compared to healthy adults.