Enzymatic Activity of Polyphenol Oxidase: A Laboratory Experiment in Flexible Learning

Polyphenol oxidases (PPO) are enzymes that catalyze the browning of fruits and vegetables when oxygen in the air reacts with the present phenolic compounds. This study demonstrates the enzymatic browning of food samples and the inhibition of its activity by common household materials. Fresh food samples were tested in different treatments of acidic and ionic solutions, and syrups. Observations from the students’ work showed that changes in pH, surface area for the site of reaction, and ionic conditions affect enzymatic browning. The deviation from the optimum working pH, introduction of ionic interaction, and alteration of the surface area led to the interruption of the interaction within the enzyme structure and between its active site and the substrate thereby inhibiting the enzyme function. Results of the experiment can also serve as a basis for further studies on the development of methods and products to inhibit PPO action and maintain the sensory value and nutritional quality of foods. Furthermore, experiments of similar nature can be crafted as practical activities and alternative teaching techniques designed for students to apply chemistry concepts and laboratory fundamentals to the conduct of an experiment suited for the flexible learning set- up.