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

Abstract

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.