Effect of acid extraction and alcohol precipitation conditions on the yield and purity of soy hull pectin

Soy hull pectin was prepared by hydrochloride acid extraction, followed by alcohol precipitation, and the effect of extracting acid concentration and the pH of precipitating solvent on the yield and purity of pectin were investigated. Strength of acid used for extracting pectin from soy hull and the pH of precipitation had significant effects on the pectin yield. Highest yields of 26 and 28% were obtained when the acid strength was 0.05 and 0.1 N, respectively, and the pH of the precipitating solution was 3.5. Extraction of pectin with 0.2 and 0.3 N acid, or precipitation of pectin at pH 2.0, reduced pectin yield. Strength of acid used for extraction or pH of the solution during precipitation did not significantly affect the purity or degree of esterification of the product. Galacturonic acid content and degree of esterification of the products varied from 68–72% and 56–60%, respectively.