Following enzymatic treatment, the total protein content of the
above-mentioned samples was determined using the potassium
dodecyl-sulphate (KDS) protein precipitation followed by bicinchoninic
acid assay (Vincenzi et al., 2011). Proteins were precipitated
from 1 mL of juice by adding 10 mL of 10% (w/v) sodium
dodecyl-sulphate and 250 mL of 1 mol KCl and then quantified with
a bicinchoninic acid (BCA) protein assay kit (Sigma-Aldrich, Saint
Louis, USA) according to the manufacturer’s instructions.