Stability of a polyphenol oxidase from the white-rot fungus Trametes versicolor in the presence of canola meal

The stability of a polyphenol oxidase (PPO) preparation from the white-rot fungus Trametes versicolor during a process for the enzymatic decrease of t he phenolic content of commercial canola meal (CM) was investigated. The ef fects of temperature, pH, protein origin and concentration, and meal partic les were considered. The results showed that the thermal stability of tl;le enzyme preparation was significantly increased in the presence of CM. The half-life times for the enzyme preparation, pre-incubated with CM at 50, 60 , 70 and 75 degrees C, were 45, 10.5, 3.5 and 1.5 hours, respectively; this represents an increase in the thermal stability of the enzyme preparation of up to four times in the presence of CM compared to the stability in the absence of CM. This effect was caused by the protective actions of both the CM particles and CM proteins, with the former responsible for 90% of the o bserved effect. The thermal stability of the enzyme in the presence of CM, from which 20% of the extractable proteins was extracted, was 5% lower comp ared to the stability in the presence of untreated CM. Changes in pH level from 5.0 to 3.2 resulted in a loss of stability comparable to that observed when the pre-incubation temperature was increased from 50 to 70 degrees C. A semi-empirical model describing the changes in the concentration of the a ctive enzyme pre-incubated in the presence and absence of CM at various inc ubation temperatures was proposed. A very good agreement between the model and experimental data was obtained. The proposed model, together with a gen eral set of model parameters, can be used as a tool for the optimization of a process for the upgrade of CM by enzymatically decreasing the meal's phe nolic content.