EFFECT OF SUGARS AND MAILLARD REACTION PRODUCTS ON POLYPHENOL OXIDASE AND PEROXIDASE ACTIVITY IN FOOD

The effect of glucose, fructose and sucrose aqueous solutions on polyphenol oxidase (PPO) and peroxidase (POD) activity was studied. Solutions with high concentrations of sugars showed a slight inhibiting effect on PPO while an activation was observed for POD. Glucose solutions, tested after sufficient heat treatments, showed an inhibiting action only on PPO activity. Maillard reaction products, obtained by heating a glucose/glycine solution, caused an unexpectedly strong inhibiting effect on both enzymes. The inhibition became more evident with increasing heating times of the glucose/glycine solution, reducing the activity of PPO and POD nearly to zero. Thus, the Maillard reaction products, already known for their antioxidant properties, were also shown to have a strong inhibiting effect on enzymatic browning.