Nanobubbles were fabricated in aqueous solutions following a compression-decompression method with a mean hydrodynamic diameter of (332.8 ± 13.7) nm, a zeta potential of – (33.7 ± 1.2) mV, and a concentration of (1.58 ± 0.12) × 10<sup>11</sup> particles/mL. The effects of generated nanobubbles on the self-assembly behavior of 7S globulins isolated from pea proteins were systematically investigated. Various factors including pH, protein, and nanobubble concentrations were considered during the formation of self-assembled structures. We found that nanobubbles acted as a soft template to trigger the self-aggregation of 7S globulins adjacent to its isoelectric point (pI~5.5). Furthermore, we proved this process was concentration-dependent. An increase in protein concentration or nanobubble concentration resulted in a larger hydrodynamic diameter of formed nanoparticles, as demonstrated by the dynamic light scattering technique. However, in a low pH condition, the elevated nanobubble concentration destabilized the suspensions and thus nanoparticles were unable to generate. Results from transmission electron microscopy revealed that core-shell architectures were formed at both pH 4.0 and pH 6.0 when mixed with nanobubbles, whereas only solid spherical structures were observed without nanobubble treatment. The formed core-shell architectures at pH 6.0 maintained stable during 25-day storage at 4 °C, while the structures prepared at pH 4.0 gradually shrink within 25 days. The percentage of β-sheets and β-turns in 7S globulins increased, while the percentage of α-helix and intrinsic fluorescence intensity of 7S globulins at both pH 4.0 and 6.0 significantly decreased after the formation of nanobubble-induced nanoparticles. Our results provided a simple, novel, and non-thermal route for food protein self-assembly with a bottom-up strategy.

Compressible nanobubbles induced self-assembly of 7S globulins isolated from pea (<i>Pisum Sativum L.</i>)

ACS Spring 2022

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Compressible nanobubbles induced self-assembly of 7S globulins isolated from pea (Pisum Sativum L.)