Extraction, characterization and functional properties of soluble proteins from edible grasshopper (Schistocerca gregaria) and honey bee (Apis mellifera)

In our research soluble proteins from edible grasshopper (S. gregaria) and honey bee brood (A. mellifera) were exposed to defatting, alkaline, and sonication-assisted extractions. New nitrogen-to-protein conversion factors based on amino acid analysis were estimated for both insects: 4.5 for adult grasshopper, and 4.9 and 5.6 for pupae and larvae of honey bee respectively, in contrary to 6.25 commonly used for insects. All fractions were characterized by their composition, yield, color, protein solubility, and functional properties in comparison to whey protein concentrate. Besides an increase in protein content up to 57.5 and 55.2% for grasshopper and honey bee respectively, protein-enriched fractions showed improved foaming and emulsifying abilities. The highest emulsion stability after 120 min was determined for grasshopper powder extracted with sonication (85.5%) and whey proteins (89.8%). The protein-enriched fractions of both insects had significantly higher foaming stability (74.1% for grasshopper fraction after alkaline extraction and 55.5% for sonication-assisted honey bee fraction) than raw and defatted powder. All fractions obtained from honey bee brood showed significantly higher protein heat coagulation than grasshopper and whey proteins. Changes in protein functionality were found related to alteration in protein charge, surface hydrophobicity, and distribution of proteins according to their molecular weight. Therefore, our results showed that S. gregaria and A. mellifera have a potential for future applications for food, feed, or insect-based dietary supplements.