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Numerical Simulation With Radio Frequency Thawing Of Hairtail And Study On Its Quality

Posted on:2024-05-17Degree:MasterType:Thesis
Country:ChinaCandidate:H T JiangFull Text:PDF
GTID:2531307124496294Subject:Food engineering
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In recent years,as a new thawing method,radio frequency(RF)thawing has great application potential in the thawing and preservation of aquatic products.It has the characteristics of fast speed and large penetration depth.At present,the main objects of RF thawing are frozen fish and surimi products with single quantity and regular shape.However,the thawing performance and mechanism of non-cut frozen fish and irregular fish are not clear.In this paper,hairtail was selected as the research object.Based on the finite element analysis method,the electromagnetic thermal coupling model of the RF thawing process of hairtail was constructed,and the accuracy of the numerical simulation results was verified by experiments.In this study,the influencing factors of RF field energy distribution were evaluated by using indexes such as heating rate and temperature uniformity.and the direction of optimizing the thawing effect under the research scenario was analyzed.In addition,the effects of natural thawing,low temperature thawing and RF thawing on thawing efficiency and quality of frozen hairtail fish were further evaluated.The main research contents and results are as follows:(1)Numerical simulation of RF thawing of frozen hairtail and investigation of influencing factorsA numerical model with RF thawing based on the irregular geometry of hairtail fish was established.A RF machine(Rated power,6 k W)was used for the experiment.The effectiveness of the model was verified by comparing the experimental and simulated temperatures at multiple locations.The root mean square error(RMSE)values ranged from 1.51℃ to 2.41℃.At the same time,the surface temperature distribution was obtained by infrared thermal imager,which proved the high accuracy of the model.Three-dimensional numerical model was used to evaluate the thawing effect under different process parameters.The results showed that when the electrode gap was 15 cm,the thawing effect of single layer flat frozen hairtail fish was better.There was little difference in temperature between the individual in different material gap.In the process of thawing,the electric field intensity of hairtail in upright state was the largest,and the overall temperature difference was large(12.41℃).The hairtail placed flat on the bottom electrode had the best heating uniformity(UI=0.033)and moderate heating rate.As the number of stacked layers increased,the peak value of electric field intensity increased,the local thawing rate increased,and the temperature uniformity decreased.In addition,for complete fish as hairtail,better thawing uniformity can be obtained by placing it in the middle or slightly below the middle of two electrodes.(2)Effect of RF thawing on the quality characteristics of hairtailNatural thawing,low temperature thawing and RF thawing were carried out to compare the heating characteristics of the three thawing methods,and the effects of thawing completion and 24 h refrigeration after thawing on water retention,texture,color and other qualities of the hairtail fish meat were compared.The results showed that the thawing rate of RF thawing can be improved by about 24 times compared with that of low temperature thawing.The penetration depth of the hairtail fish in the 27.12 MHz RF system further confirmed the rationality of using5-layer hairtail fish for RF thawing.After the multilayer hairtail fish was thawed,the hot spot was always located in the corner area,and the temperature of the upper surface was obviously higher than that of the lower surface.The thawing loss(1.32±0.09%)was significantly lower than that of the other two thawing methods.At the same time,the hardness and chewability of the samples treated by RF thawing were the highest.After all samples were thawed and refrigerated for 24 h,the muscle L* value and W value decreased significantly,while the a*value and b* value increased significantly,and the texture quality deteriorated significantly.(3)Effect mechanism of RF thawing on quality characteristics of hairtail fish based on component analysisBased on the effects of RF field on the water distribution,protein oxidation and lipid oxidation of hairtail fish,the potential mechanism of quality change in the thawing process of hairtail fish was preliminarily analyzed.The results showed that RF defrosting reduced the fluidity of immovable water.The protein carbonyl content and TBARS in RF thawing treatment group were higher than those of low temperature thawing treatment group,and the protein solubility was significantly higher than that of the natural thawing group,indicating that the degree of fat and protein oxidation was weak.The above results fully indicate that RF thawing had little damage to the overall quality of products,and this new thawing method could be used as a potential method to improve the quality of fish.
Keywords/Search Tags:radio frequency, thawing, hairtail, computer simulation, quality
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