Heating Laws Of Solution And Inactivation Kinetic Of Potato Polyphenol Oxidase By Radio Frequency Heating

Enzymatic browning of fruits and vegetables makes a difference in the flavor and color and has a significant impact on the process. The staple food of potato will promote the rapid development of potato farming and processing industry. Enzymatic browning not only affects the quality of processed potato products, but also causes huge economic losses, and thusaffectsthe development of the potato industry.Traditional bleaching process is still an improtant mean of enzyme inactivation in the process of fruits and vegetables,with slow heating transfer, large nutrient loss, huge water consumption, difficult of sewage treatment and other shortcomings. As a new type of heating technology, radiofrequency(RF) heating not only heatrapidly, but also has deep penetration, good heating uniformityand otheradvantages. RF heatinghas a good prospect inblanching of fruits and vegetables.Inactivation of polyphenol oxidaseusing RF heating(PPO) was studied in this paper.RF heating laws of solution and inactivation of potatoPPO by RF heating were studied.Specific contents wereas follows:(1) The impaction of different electrode gaps, different diameter of the container, different height of liquid and locations of plastic container on the bottom plateon heating rate by RF.(2)Heating different solutions to acquirethe laws of RF heating according to RF heating model.(3)Inactivation kinetics of PPOsolutions under different conditions of RF heating and the most suitablet model for PPO inactivation by RF.(4)The purification of potato PPO andits inactivation by water bath and RFheating.The main conclusions wereas follows.(1)The electrode gap, diameter of the container and height of liquid allhave significant impacts on RF heating rate of liquid.The lower of electrode gap, higher of liquid height, smaller diameter of the container, the faster of heating upwas.Locations of plastic container on the bottom plate have little impact on the heating rate.(2)The closer of conductivity to 0.1S/m, the faster of heating up by RF was.Solutionshave good heating uniformity. There had a good consistency of experimental heating laws withtheoretical model. Different solutions have the same heating laws, which are universal.(3)The larger of electrode gap, the slower of heating up was. When the electrical conductivity was 0.1S/m, heating up speed was the fastest. The inactivating curve of PPO solution by RF heatingdid not comply with the first order kinetics. Log-logistic model provided the best fitness.(4) The optimal conditions of PPO activity measurement were 25℃, pH 6.5. The optimum conditions for potato PPOextraction were determined: extraction time 120 min, pH 7, ratioof solid toliquid1:20.Theinactivation curve of PPO by water bath heating complied with the first order kinetics.Log-Logistic model accurately fitted the inactivationcurve of PPO by RF heating.