Effect of Polyphenol Oxidase (PPO) Enzymatic Inducing Factors on Non-enzymatic Browning of Apple Polyphenols
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Abstract:
In order to study the effects of apple polyphenol oxidase (PPO) enzymatic inducing factors on the non-enzymatic browning of apple polyphenols, chlorogenic acid and phlorizin were used as reaction substrates, and phosphate buffer was used as the model apple juice system to carry out enzymatic induction under controlled enzymatic induction conditions. Subsequently, the enzyme was deactivated, and the non-enzymatic polymerization in the model apple juice system was carried out at 60 ℃; L*, a*, b*, and △E* values were measured using a colorimeter every 24 h. The results showed that significant differences were found in the impacts of enzymatic inducing factors on the non-enzymatic browning involving chlorogenic acid and phlorizin. In the 3.5~6.0 pH range, the degree of browning in the model juice system containing chlorogenic acid and phlorizin increased with increasing pH values. When the temperature of enzymatic induction was between 20 and 60 ℃, the temperature of the inducing system had no significant effect on the non-enzymatic browning involving chlorogenic acid, while the degree of non-enzymatic browning in the model juice using phlorizin was higher at 40 ℃. A higher degree of non-enzymatic browning was achieved for the model juice using chlorogenic acid and phlorizin when the durations of enzymatic induction were 40 and 30 min, respectively. When the PPO activity was in the range of 14.25~171 U, the increasing enzymatic activity could accelerate the non-enzymatic browning involving chlorogenic acid and phlorizin. Meanwhile, the results indicated that non-enzymatic browning involving phlorizin was related to the haze occurring in apple juice, and the development of the haze in apple juice could be accelerated by increasing the pH, temperature, PPO activities, and duration of enzymatic induction.
