The Experimental Study On The Far Infrared Drying Properties And Quality Of Carrots

Carrots are crisp and delicious,nutritious,and have great food value,but they have a high water loss rate at room temperature and a short shelf life.Drying is the most effective way to increase shelf life and reduce post-harvest losses.Conventional drying methods include hot air drying,microwave drying,and vacuum freeze drying.However,the hot air drying is relatively polluting.Although microwave drying has a high drying rate and sufficient drying,the energy consumption during drying is relatively high.Although vacuum freeze drying can obtain high quality The dry products,but the equipment is expensive,has not been put into industrial production.Far-infrared drying is a kind of energy-saving and efficient drying method,and it is less applied in the food processing industry.In this paper,carrots were used as dry materials and single factor tests were performed under the same external conditions.In the range of parameters selected in this experiment,the moisture ratio decreased with the increase of drying temperature,with the increase as the increase,the drying rate increased with the increase of drying temperature,with the increase of the slice thickness and irradiation distance.cut back.The experiment shows that the drying effect of carrot is better when the drying temperature is 70°C,the slice thickness is 4mm and the irradiation distance is 240mm.On the basis of single factor experiments,the drying characteristics,water effective diffusion coefficient and drying activation energy at different temperatures,slice thicknesses and irradiation distances were studied,and a mathematical model of far-infrared dried carrot slices was established.The results showed that the drying process of carrot slices was slow drying,and the effective diffusion coefficient of water varied from 0.96919 to 3.5014 m²·s^-1.The dry activation energy of carrot slices calculated by Arrhenius formula was 43.96 kJ./mol.By evaluating the goodness-of-fit evaluation indicators such as coefficient R²,variance?SSE?and root mean square error?RMSE?,various dry models were evaluated,and the Gaussian model had the highest degree of fit and was able to predict well.The change law of moisture ratio of carrot slice in far infrared drying process.The effects of ultrasonic pretreatment on the drying properties of carrots and the microstructure of dried products under far-infrared drying conditions were studied.The results show that the quality of dry products is good when the ultrasonic time is 30min,the ultrasonic power is 60W,and the ultrasonic frequency is 40kHz.On the basis of single factor experiments,three-factor and three-level response surface optimization experiments were conducted.Based on response surface combination design theory,the effects of drying temperature,slice thickness,and irradiation distance on far-infrared drying process of carrots were investigated,and quadratic polynomials were established.Regression model.The results showed that the effect of the three factors on carrot index was:slice thickness>irradiation height>drying temperature;the best process parameters for far-infrared drying of carrot were:drying temperature was 72.4°C,slice thickness was 3.01 mm,The irradiation height was 239.99 mm,and the index values obtained at this time were 0.1932%/min,3.7370,and 19.2.Through the process verification test,color difference verification test and microstructure verification test,the reliability of the test data was verified,which provided a theoretical basis for the study of far infrared drying equipment and technology of carrots.