For polyphenol oxidase (PPO) extraction, 1 g of
acetone powder was suspended in 0.05 m sodium
phosphate buffer (pH 6.8). The suspension was mixed
well for 20 min at 4 C. Then it was centrifuged at
9000 · g for 15 min and the supernatant (crude enzyme
extract) was separated. All the procedures were carried
out in triplicate and at 4 C.