Pectin nanostructure influences pectin-cation interactions and in vitro-bioaccessibility of Ca2+, Zn2+, Fe2+ and Mg2+-ions in model systems

Abstract

This study explores the effect of pectin structure on mineral bioaccessibility in model systems. Commercial citrus and sugar beet pectin (CP and SBP, respectively) were demethylesterified by the action of carrot pectin methylesterase and characterisation of the resulting samples revealed different degrees of methylesterification (DM). Additionally, SBP exhibited a higher protein content, degree of acetylation, degree of feruloylation, degree of branching and molar mass compared to CP. In vitro-simulated digestion (stomach and small intestine phases) of mineral-enriched pectin solutions showed that decreasing pectin DM results in a decrease in mineral-bioaccessibility due to pronounced cation-pectin interactions. For a given DM, SBP digests exhibited higher mineral-bioaccessibilities than CP digests possibly due to structural differences of pectin in these sources. Furthermore, increasing the mineral-enrichment prior to in vitro-digestion resulted in a higher mineral-bioaccessibility while increasing the pectin concentration decreased the mineral-bioaccessibility. Generally, Mg2+-ions were the most bioaccessible followed by Ca2+, Zn2+, then Fe2+-ions.