In this study, direct binding between blueberry pectin-rich
fractions and anthocyanins was demonstrated. All blueberry
pectin-rich fractions reduced the free anthocyanin pigment
content in C3G solutions, anthocyanin aglycone solutions and blueberry
juice. The binding is pH dependent, with the lowest amount
anthocyanin binding at pH 4.5. Nearly doubling C3G concentration
increased binding percentage by 16–23% at pH 3.6. Ionic interaction
between positively charge anthocyanin flavylium cations
and free pectic carboxyl groups and anthocyanin aromatic stacking
on bound anthocyanins might be the two major mechanisms for
anthocyanin and pectin binding. WSF had endogenous anthocyanins
and had relatively poor anthocyanin binding ability. CSF
had relatively strong anthocyanin binding ability at pH 2.0–3.6,
while NSF had relatively strong anthocyanin binding ability at pH
3.6–4.5. The pectin bound anthocyanins may have enhanced
bioavailability for colonic microflora fermentation and promotion
of colonic health.