Relationship between softening and sourness of burdock roots prepared with enzymatic impregnation

Abstract

When plant foodstuffs were softened by freeze-thaw impregnation with macerating enzymes, it was often a problem that sourness was generated with the softening. In this study, we investigated the change over time in firmness and galacturonic acid content due to enzymatic reactions in burdock roots. As a result, more than 50% of the change in firmness occurred within 24 hours, but the galacturonic acid was produced in large amounts after 24 hours. A high correlation was observed between the pH value of burdock roots and the galacturonic acid included therein, indicating that the production of galacturonic acid during the enzymatic reaction process was one cause of the sourness. The results suggested that the promotion of softening using the enzymes with a citric acid-sodium citrate buffer can suppress excessive production of galacturonic acid and reduce the sourness.