Microwave Heating Characteristics Of Shrimp (Litopenaeus Vannamei) Surimi

Vannamei accounted for more than 70 percent of shrimp production, but most of them are sold freshly. Shrimp meat products are favored by domestic and foreign markets with its good taste. And it has become one of the most important deep processing products of shrimp. Compare with traditional heating methods, such as waterbath heating and steam heating, microwave heating has caught more and more attentions in meat products, because of high efficiency, low energy consumption and easy to industrial production.In this paper, three samples were made for the study: shrimp meat, shrimp meat with 5% soy protein isolate(SPI) emulsions, shrimp meat with 10% SPI emulsions. Firstly, the gel strength of the samples heated by waterbath heating and microwave heating was investigated. Arrhenius curves were plotted by calculating the gel-forming speed of the samples. The kinetics of the gel formation mechanism of samples were analyzed. Dielectric and thermal properties of the samples were measured in the temperature range from 10℃ to 80℃. The effects of temperature and SPI emulsions on density, specific heat, thermal conductivity, dielectric constant and dielectric loss factor were investigated. The electromagnetic fields and temperature fields in microwave heating were calculated by using COMSOL Multiphysics software. A mathematical model was established to predict temperature distribution in microwave heating of the three samples. Also the model was validated by experiments. The results were as follows:(1) The breaking strength of the samples increased with the addition of SPI emulsions by two different heating method. The gel-formation rate by microwave heating was much higher than that by waterbath heating. Also, the gel-formation rate reduced with the increase of SPI emulsions. The activation energy of the shrimp meat was higher than shrimp meat composite. The breaking force introduced by microwave heating was higher than waterbath heating if the samples absorbed the similar energy.(2) The results suggested that dielectric constant and penetration depth decreased as temperature increased, while loss factor increased with increasing temperature. The addition of SPI emulsions depressed dielectric constant at a given temperature and frequency, but had no significant influence on loss factor and penetration depth. Density decreased with increasing temperature, specific heat, thermal conductivity and thermal diffusivity increased as temperature increased. The addition of SPI emulsions also had an impact on the thermal properties. Density and specific heat increased with the concentration of SPI emulsions.(3) The electric field intensity showed uneven distributions at different locations and dimensions in the microwave oven cavity. Standing waves could be significantly observed. The temperature distributions of cylindrical samples were uneven during microwave heating, with the highest temperature at the bottom, the lowest temperature at the surface and the outside. Samples with different SPI emulsions showed differences on the temperature distribution after heating. The mathematical model established by COMSOL Multiphysics could predict the temperature distribution within the samples.