Intermolecular binding of blueberry pectin-rich fractions and anthocyanin

• Published in: Food chemistry 2016-03, Vol.194, p.986-993
• Main Authors: Lin, Z., Fischer, J., Wicker, L.
• Format: Article
• Language: English
• Subjects: Anthocyanin; Anthocyanins - chemistry; Blueberry; Blueberry Plants - chemistry; Cyanidin-3-glucoside; Glucosides - chemistry; Intermolecular binding; Pectin; Pectins - chemistry
• ISSN: 0308-8146; 1873-7072
• DOI: 10.1016/j.foodchem.2015.08.113

•Anthocyanin binds pectic fractions at pH 2, 3.6 and 4.5, with least binding at pH 4.5.•Anthocyanin binds water soluble pectin the least.•Anthocyanin binds chelator soluble pectin 2 times greater at pH 2 and 3.6 than pH 4.5.•At pH 4.5, anthocyanin binds alkali soluble pectin more than other pectic fractions.•Binding mechanisms may be ionic interaction and anthocyanin intermolecular stacking. Pectin was extracted from blueberry powder into three fractions of water soluble (WSF), chelator soluble (CSF) and sodium carbonate soluble (NSF). The fractions were incubated with cyanidin-3-glucoside (C3G), a mixture of five anthocyanidins (cyanidin, pelargonidin, malvidin, petunidin and delphinidin) or blueberry juice at pH 2.0–4.5. Free anthocyanins and bound anthocyanin–pectin mixtures were separated by ultrafiltration. WSF bound the least amount of anthocyanin at all pH values. CSF had stronger anthocyanin binding ability at pH 2.0–3.6, while NSF had stronger anthocyanin binding ability at pH 3.6–4.5. The pectin and anthocyanin binding was lowest at pH 4.5 and higher at pH 2.0–3.6. Nearly doubling C3G pigment content increased bound anthocyanin percentage by 16–23% at pH 3.6, which favored anthocyanin aromatic stacking, compared to 3–9% increase at pH 2.0. Ionic interaction between anthocyanin flavylium cations and free pectic carboxyl groups, and anthocyanin stacking may be two major mechanisms for pectin and anthocyanin binding.