Ultrasound-Assisted Enzymatic Processing of Grasshopper (Sphenarium purpurascens): Comparative Assessment and Characterization of Protein Hydrolysates

The increasing demand for sustainable protein sources has stimulated interest in edible insects such as the Mexican grasshopper (Sphenarium purpurascens). This study evaluated grasshopper flour as a substrate for producing protein hydrolysates by ultrasound-assisted enzymatic hydrolysis (US + EH). The flour was characterized for its proximate composition, soluble protein content, fatty acid profile, and antioxidant capacity. A 33−1 fractional factorial design was used to evaluate the effects of enzyme-specific processing conditions, enzyme-to-substrate ratio, and ultrasound treatment time on the degree of hydrolysis (DH) and antioxidant responses. Additional validation experiments enabled the selection of two representative hydrolysates for further characterization. TA, obtained under Alcalase-specific processing conditions, exhibited the highest DH (54.88 ± 1.72%) and ORAC activity (366.24 ± 23.55 µmol TE/g dry basis), whereas TB, obtained under bromelain-specific processing conditions, showed the highest ABTS activity (26.48 ± 1.10 µmol TE/g dry basis). Both hydrolysates exhibited higher soluble protein contents than defatted grasshopper flour and distinct amino acid, molecular weight, and structural profiles. Overall, US + EH effectively modified the compositional, molecular, antioxidant, and structural characteristics of S. purpurascens protein hydrolysates, supporting their potential as protein ingredients for future food applications.