Structural characterization and emulsifying properties of a novel cricket protein concentrate prepared via pepsin extraction-isoelectric precipitation

초록

Cricket (Gryllus bimaculatus) proteins represent promising sustainable ingredients. However, under conventional alkaline extraction, a portion of the protein fraction remains unexploited within the processing residue. This study aimed to recover a novel protein fraction from these residues using pepsin extraction-isoelectric precipitation (PE-IEP) and to compare its structural characteristics and emulsifying properties with those of a conventional cricket protein concentrate (CPC) prepared by alkaline extraction-isoelectric precipitation (AE-IEP). A pepsin-soluble cricket protein concentrate (PCPC) was obtained by pepsin extraction followed by isoelectric precipitation at pH 5.5. PCPC and CPC exhibited similar protein purities of 85.29 +/- 1.64 % and 85.36 +/- 0.58 %, respectively. However, PCPC consisted of lower molecular weight fractions and displayed significantly higher surface hydrophobicity, greater disulfide bond content, and reduced flexibility compared with CPC. PCPC also showed three-phase contact angles close to 90 degrees and pH-dependent zeta potential values distinct from those of CPC. Emulsions prepared with PCPC at pH 3 and 7 exhibited higher emulsifying activity and stability, smaller droplet sizes, and reduced creaming relative to emulsions prepared with CPC. Dynamic interfacial tension measurements confirmed that PCPC reduced the oil-water interfacial tension more rapidly and to a lower final value than CPC, consistent with faster interfacial adsorption driven by its lower molecular weight and higher surface hydrophobicity. Overall, these findings demonstrate that PE-IEP provides an effective strategy to valorize cricket processing residues by producing a structurally distinct protein concentrate with enhanced emulsifying functionality, suitable for use as a sustainable emulsifier in food and bio-industrial applications.

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