Effects of hot-water and steam blanching of sliced potato on polyphenol oxidase activity

The worldwide potato production is considered the fourth-most important food sector due to the increasing use of potatoes as raw materials for high-convenience food. Enzymatic browning, due to polyphenol oxidase (PPO), is related to unacceptability by consumer. Among antibrowning agents, thermal treatments are viable alternatives. In this study, the efficacy of hot-water and steam blanching at 80-90 degrees C of potato slices (1-cm thick) was evaluated in terms of colour changes as well as PPO inactivation kinetics, substrate specificity and transition state parameters. In general, all treatments [1] bleached the slices, [2] inactivated PPO and [3] reduced its kinetic efficiency. Results from thermal inactivation kinetics promoted hot-water blanching at 90 degrees C for approx. 2 min as the fastest treatment to obtain enzymatic-stable potato slices. Moreover, steam blanching required more energy (53.93 +/- 1.24 kJ mol(-1)) than hot-water treatment (41.41 +/- 4.51 kJ mol(-1)) to reach the transition state and then to unfold the PPO enzyme.