Optimization of the process parameters of ultrasound on inhibition of polyphenol oxidase activity in whole potato tuber by response surface methodology

In this study, the polyphenol oxidase (PPO) activity of whole potatoes was inhibited by ultrasound. A 17-run Box-Behnken Design was used to optimize the ultrasound conditions for inhibiting the PPO activity. Three factors of ultrasound treatment including power, time, and temperature were investigated. Moreover, the effects of ultrasound treatment on the PPO activity of ultrasound-treated bruising damaged whole potatoes as well as on the micro-structure of the ultrasound-treated whole potatoes were evaluated. The adjusted coefficients of determination for models of Y-1 and Y-2 were 0.9980 and 0.9991, respectively. The p-values of two models for the responses were below 0.05, implying that the models can well represent PPO activities. The optimal ultrasound conditions were determined to be: ultrasound power 540 W, ultrasound time 15 min, and temperature 20 degrees C. Under these conditions, the mean PPO activities of the whole potatoes were 44.948 U/g, in accordance with the values predicted by the model. Besides, the PPO activity increases in the damaged whole potatoes. Nevertheless, the PPO activity of the ultrasound-treated whole potatoes was lower than that of untreated whole potatoes. Moreover, the power and time of ultrasound have a large impact on the micro-structures of the whole potatoes.