Characterization of protein isolates and hydrolysates from six edible insect species: Physicochemical properties and biological activities

This study was to prepare and characterize protein isolates and hydrolysates from six commercially available edible insect species in Thailand: house cricket, silkworm pupae, bamboo caterpillars, sago worm, mole cricket, and grasshopper. Protein isolates were prepared by alkali extraction, and protein hydrolysates were obtained by papain hydrolysis. The protein content of isolates ranged from 55% (bamboo caterpillars) to 79% (mole crickets), but protein hydrolysates improved solubility, obtaining >95% at pH 6-8. The functional groups and surface microstructure of the isolated proteins were analyzed using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), respectively. Thermal properties of isolates and hydrolysates were evaluated by differential scanning calorimetry (DSC), yielding denaturation temperatures of 78.8-93.1°C. Cricket protein hydrolysate exhibited the highest water absorption capacity (86%), and hydrolysates from most insects showed greater oil absorption than isolates. Grasshopper protein isolates had the highest antioxidant activity, whereas cricket and silkworm hydrolysates demonstrated enhanced antioxidant properties. All hydrolysate proteins exhibited in vitro inhibitory of dipeptidyl peptidase-IV (DPP-IV) (38–56%) and angiotensin-converting enzyme (ACE) (32–38%) activities, with silkworm pupae hydrolysate displaying the strongest in DPP-IV inhibition. These findings suggest that the potential of insect-derived proteins as functional ingredients is supported by their physicochemical properties and in vitro bioactivities, making them sustainable protein sources.