| With the improving of the people’s living standards,consumers gradually pay attention to a healthy diet,pay more attention to an indispensable part of the daily life of food quality and safety problems,especially for the rich in biological active ingredient of functional rice to form a rigid demand.In this paper,high-quality organic rice in cold black soil is used as raw material,and agricultural development is planned in accordance with the industrial thinking of"farming first,working last"and"grain first and eating last".The heat and mass transfer mechanism and mechanical characteristics of rice with low superheated steam are explored,and the combined technology of low pressure superheated steam wetting and drying of rice in the production process of GABA germ rice is developed to improve the mopping rate of high-quality rice.Increase the GABA content,increase the added value of rice science and technology,extend the rice industry chain to promote the industrialization process,and achieve the effect of helping farmers to increase income and promoting enterprises to increase efficiency.The main research contents and conclusions of this paper are as follows:1.Drying mechanism of rice under low pressure superheated steam and establishment of experimental platformon the basis of rice characterization of sex physical unit,based on the law of conservation of mass,the establishment of a low-pressure superheated steam drying rice heat transfer and mass transfer theory model.The results show that the mild drying characteristics of rice under the condition of low pressure superheated steam indicate that low pressure superheated steam drying has great potential to ensure the quality of rice.Fluent 2021 R1 software is used to conduct numerical simulation analysis of three kinds of drying oven structures,and determine the optimal structure parameters of drying oven.Establish the humidity in the low-pressure superheated steam drying process field,temperature field and stress field model,through the numerical simulation analysis of flow field test system rule,set the rice low-pressure superheated steam drying test rig,and development of PC data acquisition system.2.Experimental study on thin layer drying characteristics of low pressure superheated steam in rice(1)using the porous medium characteristics,analyzed the low-pressure superheated steam drying rice moisture migration mechanism,aiming at moisture content in drying process,analyses the initial moisture content,drying temperature,drying stress and drying time on comprehensive effects of moisture content in drying process change.The changes of moisture content,drying rate and moisture ratio of rice in the process of low pressure superheated steam drying were obtained.(2)Using SEM scanning electron microscopy and FTIR Fourier far infrared spectroscopy technology,by observing microscopic images and light wave absorption curve peaks,the internal microstructure and composition changes of rice under three drying methods of low pressure superheated steam drying,hot air drying and natural drying were studied,and it was determined that low pressure superheated steam drying could well maintain the starch and protein properties in rice.It can effectively inhibit the production of saturated fatty acids,effectively inhibit the aging of rice,and obtain better appearance quality and stress resistance.(3)The drying characteristics curves of 25 groups of rice under different conditions of low-pressure superheated steam drying are mathemtically fitted with the Henderson and Pabis model,Page model,Midilli model,Logaritmic model and Lewis model.Under the conditions of pressure and temperature determined separately,The above 5 typical drying models all had good fitting effects,among which the Midilli model was the best,with the maximum R~2value of0.9996 and the minimum R~2value of 0.970.The Lewis model had the worst fitting effect,and the minimum R~2value was only 0.7381.Aiming at 25 groups of drying characteristic curves,each typical model obtained 25 fitting equations with different coefficients.The 25 different equation coefficients were fitted respectively to determine the goodness of fit of each typical model to the overall test.The results showed that the maximum value of coefficient goodness of fit R~2was only 0.6177,and the minimum value was 0.0535.Therefore,the above 5 typical drying models could not well represent the water variation rule of low-pressure superheated steam drying rice.(4)according to five kinds of typical low-pressure superheated steam drying model is not suitable for rice moisture content variation law said,in this paper,using the regularized BP neural network and support vector machine(SVM)the establishment of the two kinds of machine learning way rice low-pressure superheated steam drying moisture change and the drying temperature,drying stress and drying time factors such as the laws of the model,the modeling results show that the By comparing R~2,RMSE and MAE of each model,the regularization BP neural network and support vector machine(SVM)were found to be suitable for modeling the variation rule of rice moisture content in low-pressure superheated steam drying,and the modeling effect was good.3.the biomechanical characteristics,low-pressure superheated steam drying of rice research(1)Through microscopic observation,the mechanism of crack generation and diffusion in rice grains was systematically studied and explained under three drying methods:low-pressure superheated steam drying,hot air drying and natural drying.Low-pressure superheated steam drying of paddy rice grain cracks produced far away from the kind of skin,with starch granular edge,no tear near the starch granule was observed.(2)using the universal material mechanics machine low-pressure superheated steam drying of rice under different drying parameters of rice grain pressure experiment,the article 1500 rice grain deformation curve.The typical force-deformation curves of rice grains were studied and explained in sections.According to Hooke’s law,the ratio of force to displacement and the ratio of force to displacement difference are analyzed.It is found that the ratio of force to displacement difference is a typical waveform image.By means of Fourier transform,filtering,normalization and spectrum expansion,the critical frequency domain point Frep of the sudden change of force-deformation curve is obtained.By regression analysis of the relationship between frequency domain point and drying temperature and drying pressure,the mathematical model was obtained:Frep=1634.7370×P+0.0363×T ~2.4.Effect of low-pressure steam enrichment-drying process on GABA content in rice(1)The internal p H value,glutamic acid decarboxylase activity,reduction potential and transcription level of rice seeds change under germination and environmental stress to produce a large amount of GABA.First,the mechanism of the influence of pressure,temperature,steam flow and time on GABA content in rice was analyzed through single factor experiment.Then,the mathematical model of the influence of various factors on GABA content in rice was established and optimized by the response surface.Enrichment of low pressure steam-dry production process was proposed,under the condition of laboratory,GABA content in rice is up to 104.161 mg/100 g,compared with the original process inventory product by about 50 mg/100 g.(2)The workshop comparison experiment was carried out.Under the new process,there was no good improvement in the emergence rate,transmittance and taste value,but there was obvious improvement in the indexes of increasing the rate of whole mished rice,reducing the rate of broken rice and startling grain,and increasing the content of GABA.The increase of whole mished rice was about 1.7%,the decrease of broken rice was 0.7%,and the startling grain was 9.3%.The whiteness was increased by 0.7%,GABA content was increased by 10 mg/100 g,and the enrichment-drying time was shortened from the original 10 h to 5 h by the new process. |
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