As the counterpart to the phenolic compounds, the role of polyphenoloxidase (PPO) in (enzymatic) browning phenomena is very well documented and mainly contributes to a deterioration of plant product quality. Polyphenoloxidase, also known as tyrosi- nase, is a mixed-function oxidase possessing both monophenol monooxygenase activity (EC 1.14.18.1.) accompanied by an o-diphenoloxidase activity (EC 1.10.3.1./EC 1.10.3.2) (Mayer, 2006; Rawel & Rohn, 2010). These enzymes comprise a group of copper-containing proteins with binding sites for aromatic com- pounds and molecular oxygen, resulting in the insertion of oxygen