Study On The Application Of Radio Frequency Heating Technology In The Production Of Frozen Sweet Corn Kernel Field: Emerging Technology Of Food Engineering

Sweet corn is one of the most widely grown and consumed grains in the world.It has a variety of nutritional and biological functions and is widely welcomed in Asian countries.At present,the biggest market demand is frozen sweet corn.Frozen sweet corn is faced with problems such as loss of nutrients and perishable deterioration during processing.Blanching inhibits the activity of enzymes such as peroxidase and lipoxygenase,and prevents deterioration during storage and after thawing.Therefore,blanching is an important process in the processing of quick-frozen sweet corn.Traditional blanching methods include hot water blanching,steam blanching,etc.,which easily lead to loss of nutrients in fruits and vegetables and cause water pollution.Radio frequency(RF)heating technology is a new type of electromagnetic wave heating technology.The radio frequency is smaller than microwave,and has the advantages of high frequency,large penetration depth,fast heating,and uniform heating.There are few studies on the application of radio frequency technology to quick-frozen fruit and vegetable blanching,which needs further study.This experiment studied the quality changes of RF blanching and traditional water(boiling water(BW);hot water(HW)blanching on sweet corn kernels and their frozen period after freezing.The main research contents are as follows: the dielectric properties of sweet corn with temperature and the law of frequency change;the influence of plate spacing,material weight,motor speed on RF heating uniformity and heating rate;RF blanching,BW blanching,HW blanching on the physical and chemical properties of sweet corn granules;RF blanching,The effect of BW blanching on LOX enzyme activity and cell microstructure of sweet corn kernels;quality changes and cell morphology changes of frozen corn kernels during cold storage after RF and BW blanching.The main findings of the study are as follows:(1)The dielectric constant(?')and the loss factor(?'')of sweet corn decrease with increasing frequency.As the temperature increases(25°C?85°C),the dielectric constant decreases.The loss factor increases first and then decreases as the temperature increases.At RF frequencies(13.56 MHz,27.12 MHz,40.68 MHz),the loss factor increases first and then decreases with increasing temperature;at microwave frequencies(915 MHz,2450MHz),the loss factor does not change significantly.The nonlinear regression analysis of the dielectric properties of sweet corn with temperature and frequency was carried out,and the quadratic regression model of dielectric constant and dielectric loss factor with frequency and temperature was obtained.(2)Using a variable speed motor to rotate the material to improve RF heating uniformity.The best conditions for RF heating uniformity of sweet corn kernels are: plate spacing 160 mm,material weight 120 g,motor speed 14 r/min.(3)RF,BW and HW blanching had significant effects on the weight loss,color,texture,Vc content and soluble sugar content of sweet corn(P<0.05).RF blanching can better protect material color and texture.,Vc and soluble sugar content.(4)The effect of RF and BW blanching on LOX enzyme were obvious.When the two methods were heated to 80 °C,the LOX enzyme was obviously inactivated,and the relative activity was reduced to 5% or less.The degree of RF blanching on sweet corn cells was less than BW drift.(5)The color,texture,Vc and soluble sugar content of RF hot-sweetened sweet corn were better than BW hot-sweetened sweet corn during the frozen storage period.