Composition, characterisation and emulsifying properties of natural nanoparticles in chickpea aquafaba for the formation of chilli oleoresin-in-water Pickering emulsions

Abstract

This study aims to assess the compositional characteristics of British Kabuli chickpea aquafaba (AF) by conducting a comprehensive analysis from raw chickpeas to centrifugation fractions of AF and its potential use in forming and stabilising capsaicin-loaded O/W Pickering systems by exploiting the presence of self-assembled nanoparticles and proteins, which act as natural-coating agent. To this end, chickpeas were soaked (16 h, 4 °C, 1:4 chickpea: water) and pressure-cooked (20 min, 113 °C, 10 psig, 1:5 chickpea: water). The dry weight-based (DWB) compositions included total carbohydrate (76.33 ± 4.20%), protein (16.29 ± 0.43%), total phenolics (7.05–8.77 mg/g) and saponins (39.95 ± 0.89 mg/g), thus confirming the leaching of these components from seeds to AF. SDS-PAGE electrophoresis analysis revealed the presence of low MW proteins (≤∼16 kDa). The monosaccharides comprised d-glucose, d-galactose, l-arabinose, d-xylose and d-fructose. AF's particle size distribution revealed the occurrence of a bimodal population of nanoparticles (D_h ≤∼1000 nm and D_h ≤∼100 nm), further characterised by SAXS and TEM imaging. O/W emulsions were prepared with three chilli oleoresin types (capsicum, chilli birds' eye, and chilli ancho) by high-pressure homogenisation. The emulsion with the highest capsaicin content (capsicum oleoresin) was the most stable while the emulsion with the lowest capsaicin content (chilli ancho oleoresin) was the least stable. The presence of incidental nanoparticles and denatured proteins in AF was reasoned to account for the formation and stabilisation of chilli oleoresin-in-water Pickering emulsions, a newly offered explanation for its interfacial properties that will be pursued further in future studies.