Monitoring lipid oxidation in multiple emulsions by near infrared spectroscopy

Lipid oxidation has an impact on the quality and properties of fat-containing products that are commonly produced by cosmetics or coatings industries. In this study, a water-in-oil-in-water emulsion (48% w/w of pre-polymerized linseed oil stabilized with alkylpolyglucoside) was subjected to oxidation under accelerated aging conditions at 50°C over 15 days. After fat extraction from emulsion, peroxide, and p-anisidine values were measured using standardized methods. The application of near infrared spectroscopy (NIRS) in conjunction with chemometrics was investigated to assess the quality parameters of emulsions under accelerated aging within closed flasks. Significant variations were observed across the following spectral regions: 7541–5948, 5739–3657, and 3645–3637 cm⁻¹. Partial least squares regression discriminant analysis, possibly combined with multiplicative scattering correction preprocessing, proved to be a powerful method to classify the emulsions according to two oxidation levels defined by periods A and B. The performances of the prediction model were characterized by a precision of 85%, a predictive value of period A of 98%, a sensitivity of 99%, a specificity of 81%, and an accuracy of 90%. Thus, we demonstrate that NIRS is a suitable analytical method to discriminate emulsions according to their aging behavior.

Practical Applications: The PLS-DA method coupled to near infrared spectroscopy analyses is adapted to assess the chemical degradations of vegetable oil–based emulsions due to lipid oxidation. This tool is interesting for at-line or off-line monitoring of emulsions during their storage. As it is a fast and nondestructive method, the quality control of a formulation stored in a closed glass container is facilitated. This method could also be used to determine the effectiveness of an antioxidant or a drier in emulsions, respectively, prepared for cosmetics and coatings.