Functional Properties of Whole Tropical Banded Crickets ( Gryllodes sigillatus) Protein Hydrolysates
Entomophagy, or the eating of insects, is considered a cultural norm in over 113 countries worldwide , yet has only recently gained attention among western cultures. The nutritional quality and sustainability benefits of entomophagy make insects viable protein sources, while aiding in the world food-security problem . Cultural resistance to insect-eating among western cultures, however, has shifted efforts from traditional entomophagy towards insect-derived food products . To succeed on an industrial scale, the insect components utilized would need to show suitable functional properties such as solubility, foaming and emulsification, among others . The objective of this study was to develop cricket protein hydrolysates (CPH) derived from whole crickets and evaluate the protein functionality. Whole crickets (Gryllodes sigillatus) were hydrolyzed with alcalase at 0.5, 1.5, and 3.0% enzyme per substrate (E/S) for 30, 60, and 90 minutes. Degree of hydrolysis (DH), amino acid composition, protein solubility, emulsion activity index (EAI) and stability index (ESI), along with foam capacity (FC) and stability (FS) were evaluated. Subsequent analyses included quantification of: sulfhydryl groups, disulfide bonds, surface hydrophobicity, chitin, and antigenicity. Hydrolysis ranged from 26-52% DH, with increased E/S resulting in increased %DH. Increasing hydrolysis time did not have a significant effect on %DH. Compared with the control (unhydrolyzed cricket protein), hydrolysates showed improved functional properties. All hydrolysates displayed more than 30% protein solubility (p<0.05) at pH 3 and 7, and 50-90% protein solubility at pH 8 and 10. EAI ranged from 7-32 m2/g (was overall higher than the control), while the FC was higher (p<0.05) than control at 100-155%. In terms of emulsion stability, hydrolysate trials remained stable for 90 min, ranging from 13-60% ESI. Hydrolysates retained foam volume (22-55%) for up to 90 min, however the FS was lower than the control. Proteolysis had no significant effect on total and reactive sulfhydryl groups, but disulfide bond concentrations increased with increasing hydrolysis while surface hydrophobicity decreased indicating that the protein most likely aggregated with increasing hydrolysis. Hydrolysates also had decreased antigenicity, as detected by ELISA, compared with the unhydrolyzed crickets. The amount of chitin was negligent in the hydrolysates, showing that this would not be a concern in CPH. In conclusion, hydrolyzing whole crickets with 0.5 to 3.0% alcalase for 30 to 90 min, can generate cricket protein hydrolysates with improved functionality that will allow them to be used as ingredients in a variety of food applications. More studies are needed to establish optimal hydrolysis conditions, evaluate sensory characteristics and applicability in food systems (e.g. beverages, bread and fortified foods).
Liceaga, Purdue University.
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