A New Method for Determining the Emulsion Stability Index by Backscattering Light Detection

Abstract

AbstractIn the present study, the Δbackscattering (ΔBS) method was developed as a simple and sensitive tool for determining the emulsion stability index (ESI) by backscattering light detection. The backscattering light detection method uses emulsion‐scanning technology to monitor physical behavior in an emulsion as a function of storage time. Emulsions were prepared by the homogenization (8,000 rpm for 2 min at 25C) of distilled water and perilla oil containing Tween 60, and the sample was quiescently incubated in a vial at 25C for 11 h. To confirm this new methodology, the sum of ΔBS at the clarified layer, obtained from the backscattering flux profiles over the storage period, was compared with the ESI determined by the volumetric method. Our backscattering light detection method was compared with the volumetric method based on the emulsifier content. The sum of ΔBS at the clarified layer decreased as the ESI decreased, with a correlation of 0.999, 0.993, 0.998 and 0.998 for emulsions stabilized with 200, 300, 400 and 500 μmol of emulsifier, respectively. Regardless of the emulsifier content in the emulsion, the R2 values for the fit curve, calculated by plotting the sum of ΔBS at the clarified layer against the ESI determined by the volumetric method, revealed strong linear relationship (R2 = 0.953). Our results suggest that the backscattering light detection method is a new tool for the quantitative determination of the ESI in an emulsion system.Practical ApplicationsThe acceptable way for the emulsion characterization is the determination of emulsion stability by measuring creaming rate and/or oil droplet diameter. Although the determination of oil droplet diameter provides the various information on the emulsion stability, it needs the expensive instruments based on dynamic light scattering or laser diffraction analysis. On the other hand, creaming is monitoring the change in the height of the boundary between the creamed and serum layers with naked eyes. In many cases, however, the condition of emulsions (such as their color, viscosity, and oil content, etc) prevents the clear reading of the boundary. The backscattering light detection described in this study could be a promising method which enables the accurate analysis of emulsion stability regardless of the limitations mentioned above.