Biochemical characteristics and gelling capacity of pectin from yellow passion fruit rind as affected by acid extractant nature.

The effects of acid extractant type on the yield and characteristics of pectin from yellow passion fruit (Passiflora edulis flavicarpa) rind was investigated by using citric, nitric, or sulfuric acids at different concentrations (10 mM and 30 mM) and pH (1.8 and 2.5). The results showed that not only concentration, but also acid type influenced the extracted pectin yields (3-14%, w/w). The yield of pectin extracted with citric acid was the lowest. Acid type and concentration affected the molecular characteristics of pectin, notably, the degree of esterification (29-73), galacturonic acid to rhamnose ratio (14-35), weight average-molecular weight (100-250 kDa), gel strength (127-179), and setting time (841-1236 s). Citric acid-extracted pectin had a higher degree of esterification and weight average-molecular weight and better gelling properties. At 30 mM concentration, nitric and sulfuric acids solubilize pectins having a degree of esterification <50, contrary to citric acid. The results indicate that the latter acid exerts the least deesterifying action on pectin solubilization from the cell wall material. Citric acid-extracted pectin was closer to lemon pectin of similar degree of esterification in terms of gelling properties.