Exo-polygalacturonase (exo-PG) activity was assayed in a 50 mL
diluted sample added to 2.0mL polygalacturonic acid (SIGMA, EUA)
in acetate buffer solution 0.1 mol/L (pH 4.0) at 35 C for 30 min.
Reducing substances were measured by Somogyi Method (1952).
One unit of exo-PG was taken as the amount that catalyses the
liberation of 1 mmol of polygalacturonic acid per minute, in the
reaction conditions