Functional properties of citric acid extracted mango peel pectin as related to its chemical structure

The objective of this work was to extract and evaluate some functional properties (gelling and emulsification capacity, acidified milk drink stabilization) of pectin extracted from mango peel using an acidic ion chelator (citric acid) (pH 2.5, 2h at 80°C). The novel extraction method resulted in a high yield of pectin (MPP - mango peel pectin) having a very high DM (78.1%), high neutral sugar to uronic acid ratio and a high average molecular weight (M_w). Those chemical structural characteristics had a large impact on the obtained functional properties of the pectin. MPP (0.8%) was able to stabilize 5% oil-in-water emulsion for 30 days similarly to pectin from apple that had a comparable DM but a much lower neutral sugar to uronic acid ratio and a much lower M_w. Despite the high M_w that was expected to provide good gelling properties, MPP did not form a strong gel even at high concentrations of pectin and sugar at acidic condition. Such a result is most likely due to high presence of neutral sugar branches sterically hindering the gel network formation resulting in a thickening effect. The large concentration of neutral sugars that might provide interesting health related activities seemed also to limit the utilization of MPP for acidified milk drink stabilization. The unique structural properties of MPP that include a high DM, high M_w and high branching with neutral sugars are responsible for the limitations and further opportunities of functionalization of this polysaccharide obtainable from the by-products of the fruit industry.