Structurally modified pectin for targeted lipid antioxidant capacity in linseed/sunflower oil-in-water emulsions

- Pectin samples with distinct nanostructures were produced as a starting point.
- All pectins exhibited an antioxidant capacity in linseed/sunflower oil emulsions.
- The degree of methylesterification mainly determined the antioxidant capacity.
- Low demethylesterified pectin showed the highest antioxidant capacity.
- Pectin (0.1 and 1% w/v) caused instability of linseed/sunflower oil emulsions.

The present work explored the lipid antioxidant capacity of citrus pectin addition to 5% (w/v) linseed/sunflower oil emulsions stabilized with 0.5% (w/v) Tween 80, as affected by pectin molecular characteristics. The peroxide formation in the emulsions, containing tailored pectin structures, was studied during two weeks of storage at 35 °C. Low demethylesterified pectin (≤33%) exhibited a higher antioxidant capacity than high demethylesterified pectin (≥58%), probably due to its higher chelating capacity of pro-oxidative metal ions (Fe2+), whereas the distribution pattern of methylesters along the pectin chain only slightly affected the antioxidant capacity. Nevertheless, pectin addition to the emulsions caused emulsion destabilization probably due to depletion or bridging effect, independent of the pectin structural characteristics. These results evidence the potential of structurally modified citrus pectin as a natural antioxidant in emulsions. However, optimal conditions for emulsion stability should be carefully selected.