Adsorption of apple polyphenols onto β-glucan

Abstract

The adsorption of polyphenols from apples, a good source of polyphenols in the human diet, onto β-glucan, a soluble dietary fibre were studied. Polyphenols were extracted from the flesh and peel of two apple varieties (wild apple and Slavonska srčika) and adsorbed onto β-glucan for 16 hours. The adsorption capacities (mg/g) and equilibrium polyphenol concentrations (mg/l) were modelled with Freundlich and Langmuir isotherms. Polyphenols from the flesh and peel showed different behaviours - flesh polyphenols exhibited greater affinity and peel polyphenols greater theoretical adsorption capacity. The analysis of individual polyphenols with high-performance liquid chromatography revealed that the composition of the flesh and peel differed (flesh was rich in phenolic acids, peel in flavonols) which could explain the contrasting adsorption behaviour. This study shows that polyphenols from apples can be adsorbed onto β-glucan, that the flesh and peel exhibit distinct adsorption behaviours and that the polyphenol composition can affect the adsorption mechanism.

Keywords

• adsorption isotherms
• freundlich
• interactions
• langmuir