PPO activity
Extraction procedure of PPO was described by Rocha
& Morais (2001). The potato samples (20 g) were
homogenized with 0.2 M pH 6.5 sodium phosphate
buffer (extraction buffer) plus 2% polyvinilpirrolidone
(PVPP) for 3 min using a blender jar with external ice
bath, with 1 min intervals after each minute of homogenization.
The homogenates were centrifuged at 4∞C
for 30 min at 16000 r.p.m. (Sorvall RC-5C, Instruments
Dupont, refrigerated super speed centrifuge).
The supernatant was filtered through cheesecloth and
its volume determined for enzymatic activity assay.