Storage Stability of β-Carotene in Model Beverage Emulsions: Implication of Interfacial Thickness

In order to evaluate the implications of the interfacial thickness of emulsions on the stability of encapsulated β-carotene, emulsions are prepared using polyethyleneglycol alkyl ether emulsifiers having various numbers of oxyethylene groups. At pH 3, β-carotene in emulsions having a thinner interfacial membrane formed with emulsifiers having less oxyethylene groups [0.050 day⁻¹ of degradation rate constant (k)] slowly decompose, compared with ones stabilized with emulsifiers containing more oxyethylene groups (0.068 day⁻¹ of k). At pH 3, iron molecules promote the degradation of β-carotene. Ferrous iron-mediated β-carotene degradation is faster in emulsions with a thicker interfacial membrane (0.113 and 0.165 day⁻¹ of k for emulsions stabilized with emulsifiers having the smallest and largest number of oxyethylene groups). Interfacial denseness is not an important determinant in β-carotene degradation (p > 0.05) when emulsions are stabilized by emulsifiers having the similar number of oxyethylene groups. Conclusively, the interfacial denseness and thickness of emulsions are important factors for inhibiting β-carotene degradation in emulsions. Practical Applications: β-carotene stability in emulsions is greatly influenced by their interfacial characteristics, depending on what is responsible for the β-carotene degradation. Therefore, when designing the emulsion-formed delivery systems it would be important to engineer the interfacial membrane of emulsion droplets to improve β-carotene stability therein. Interfacial thickness which is attributed by the hydrophilic group size (or length) of emulsifiers used is an important determinant in the chemical stability of β-carotene encapsulated into emulsions but sometimes it is not.