Comparison of stability of bovine serum albumin-stabilized emulsions prepared by microchannel emulsification and homogenization

Oil-in-water (O/W) emulsions stabilized by bovine serum albumin (BSA) were prepared by straight-through microchannel (MC) emulsification or homogenization. The emulsion samples with a similar average diameter were used in this study. We investigated how stability of the prepared emulsions is affected by thermal processing, freeze–thaw treatment, pH adjustment and NaCl addition. The coalescence of droplets was interpreted in term of increase in the average particle diameter of emulsions. The monodisperse emulsions with a BSA concentration between 0.5% and 2.0% prepared by MC emulsification exhibited good stability during thermal processing (30–80 °C for 30 min); however, it was unstable after heating for 30 min at 90 °C. In contrast, the emulsions with a BSA concentration of 1.0% prepared by homogenization became unstable at above 60 °C. Freeze–thaw treatment (−18 °C for 12 h/30 °C for 2 h) was strong destruction to the stability of emulsions prepared by both MC emulsification and homogenization. At pH 5, significant increases in the average droplet diameter and size distribution were observed in the emulsions prepared by MC emulsification and homogenization, suggesting extensive droplet coalescence. These increasing trends were more remarkable in the emulsions prepared by homogenization. All of the resultant emulsions showed good stability at NaCl concentrations lower than 150 mM. However, their remarkable coalescence occurred at NaCl concentrations at 200 mM for both MC emulsification and homogenization. Our results showed that the emulsion with uniform diameter prepared by MC emulsification had higher stability, being useful as the practical emulsions.