Study On Dielectric Properties Of Scallops During Microwave Sterilization

Scallop has high nutritional values, which is one of the most importantmariculture varieties in our country. Traditional processing methods of scallopadductors include dried scallop adductors, frozen fresh scallop adductors and instantscallop. It’s necessary for every processing methods to sterilize. Currently thetraditional sterilization,pasteurization and high-temperature sterilization, may destroythe nutrients or the properties of taste and color, as well as reduce aquatic product’svalue. As the customers improve the demand for food quality and taste, newsterilization technologies are stared. Microwave sterilization is a rapid andnondestructive sterilization technology, which can shorten the processing time andimprove product quality. The main parameters are dielectric constant ε’and dielectricloss factor ε”. Because of the new concept of high quality products based onmicrowave sterilization, the paper puts forth effort to study scallop’s dielectricproperties and quality change during heating processing in order to learn about thebehaviour of scallop in microwave field. In addition, the development of model foodof which dielectric properties coincide with scallop provide the theory basis forseeking cold spots of microwave sterilization device.The main contents include:1.The coaxial probe technology is used to measure the dielectric properties offour kinds of Xuejia island scallop, calculate the penetrate depth-dpat frequency of915and2450MHz, as well as built prediction equations of dielectric properties and dpas a function of temperature.The results show that:(1)As the frequency increases, bothε’and ε” of the four kinds of scallops decreases.(2)ε’and dpof scallop decreaseswith the rising temperature at frequency of915and2450MHz, while ε” increases. dpat frequency of2450MHz is higher than dpat915MHz. The trends of ε’, ε” and dparesimilar among the four kinds of scallop as a function of temperature andfrequency.(3)Predictive equations,Y=aX2+bX+c, for dielectric properties andpenetration depth of scallop as a function of temperature at915and2450MHz, which correlation coefficient(R2) is high,can be use to predict ε’、ε”、dp. In the chapter, thestudy on dielectric properties and penetration depth of scallop may provide basictheory for microwave sterilization.2.The change of scallop quality of four kinds are studied at different heatingtemperature and time.The results show that:(1)As the heating time rises, the lossweight of four kinds gains rapidly, then keeps going up slowly until reaches arelatively balanced state.(2)The parameters CIE L*、a*、b*can be used to analyze thecolor. The color of fresh scallop get whitening rapidly at first, followed by darkeningslightly with rising time.During the heating processing, the fresh scallop get red andyellow.(3)The Flexible goes through an increase-decrease-increase phase until reach abalance. The result shows that there are better qualities when the heating temperaturerange is from10to20℃. The objective of the chapter is to study the qualitychanges during thermal processing, to control and predict the quality change duringmicrowave sterilization, in order to choose a better sterilization procedure andimprove the process.3.The model foods fitting with dielectric properties of scallop at frequency of915and2450MHz are developed with WPC, D-ribose, gellan gum, NaCl andultrapure water. The change of dielectric properties of model food as a function offrequency, temperature, moisture, protein content, salt content are studied. The resultsshow that ε’ and dpof model food-B(WPC:12.5, NaCl:0.6) fits with frozen freshscallop at frequency of915MHz, while ε’and ε” of model food-F(WPC:17.5,NaCl:0.5) agrees with boiled scallop at frequency of2450MHz.The objective of thechapter is to provide information for looking the cold spots during microwavesterilization.4.The method of computer simulation combined with chemical marker is use toanalyze heating pattern of model food after microwave heating to locate the cold spotof microwave device.The relation between the value of F0and color differenceΔE isstudied. In addition, through the studying on heating pattern of model food, the coldspot location can be watched in right and down of model. The same results of three experiments proves that the microwave sterilization device has good stability.