Formation and Stability of Carbon Dioxide Nanobubbles for Potential Applications in Food Processing

Bulk nanobubbles (NBs) are ultrafine gas-filled cavities at nanoscale size possessing unique properties which can provide promising benefits to food product quality and processability. This work aimed to investigate the formation and stability of CO2 bulk NBs in water for intended applications in food processing. The NBs were generated by injecting CO2 gas at 300, 350 and 400 kPa pressures to deionised water pumped at 100 and 200 kPa through a commercial NB generator. Size measurement via dynamic light scattering (DLS) technique indicated that CO2 NBs generated were in the range of 200–500 nm depending on the gas pressures, gas and water flow rate used. Concentration of CO2 in water containing the NBs (~ 2000 ppm) also increased significantly. Zeta potential of the formed NBs varied from − 8 to − 19 mV, indicating their stability in the aqueous medium. Their existence lasted for more than 7 days with a good repeatability of size distribution density, and the pH values of CO2–NB solution were maintained below 4. These findings highlight some new fundamental understandings on the generation and physical characteristics of CO2 NBs, which can have potential applications in food processing that need to be further explored.