The enzymes were extracted and determined using a spectrophotometric
method based on Cao et al.’s method (Cao et al., 2011). The increase
in absorbance at 420/470 nm for PPO/POD, respectively, was
monitored at intervals of 0.1 s−1 immediately after incubation using a
Cary 50 spectrophotometer (Varian Co. Ltd., Santa Clara, CA, USA),
which was equipped with a Peltier-thermostatted cell holder, a water
pump (Varian) to maintain the temperature at 30 ± 0.1 °C and a
built-in electromagnetic stirrer to mix the substrate and extracts together.
The slope of the first linear portion of the reaction curve was
considered to be the PPO/POD specific activity (abs. Min−1).