| Purple sweet potato,also known as the purple sweet potato or black potato,potato meat was purple to deep purple.Purple sweet potato not only had common sweet potato contained—protein,starch,pectin,cellulose,vitamins and amino acids,but also rich in selenium,iron and anthocyanins.It had high value and special health function.Fresh purple sweet potato with water content high,nutrient rich,susceptible to microbial infection,so storage was a large problem.Therefore,dehydration became an important means of purple sweet potato processing and storage.The Fujian cultivated purple sweet potato Liancheng No.1 were used as experimental materials,studied the purple sweet potato products non sulfur color protection technology by utilizing the solar assisted heat pump drying technology,discussed the drying process characteristics,analyzed the quality characteristics of drying purple sweet potato,and optimized the drying technology.1?In the non sulfur color protection process of purple sweet potato,the citric acid,phytic acid,L-cysteine and color retention time on purple potato products were studied in the test by single factor and orthogonal experiments.The results showed that the appearance quality of purple sweet potato was best when the concentration of citric acid,phytic acid,L-cysteine was 0.3%,0.25%and 0.1%,respectively,and color retention time was 90 min.2?The hot air drying,microwave drying,solar drying,vacuum drying and Solar heat pump drying technology were used to dry processing purple sweet potato,compared the sensory quality of purple potato products,evaluated by employing the fuzzy comprehensive evaluation method,the best quality of purple potato products through solar heat pump drying processing was picked out.3?The drying temperature,loading density,rotary speed and slice thickness on drying characteristics of purple sweet potato were mainly discussed.Among them,the temperature,loading density and slice thickness have great effects on the solar heat pump drying rate,while the rotary speed on drying rate has little effect.The experimental data was fitted,and the results showed that the drying process of purple sweet potato solar heat pump accorded with the Page model,the model predicted values and experimental values fit well.During the drying process of purple sweet potato by solar energy heat pump drying technology,the model can be used to accurately predict the change law of water.4?To in-depth understand the effects of different drying processes on the quality of purple sweet potato,four approaches of drying process,including hot air drying?microwave drying,vacuum drying and Solar-heat pump drying technology,were investigated by measuring the effects on physicochemical properties and microstructure of purple sweet potato.The results indicated that the low energy consumption and high efficiency drying technology-Solar-heat pump drying technology dried products had the best color and luster with micro-structural integrity.To sum up,Solar-heat pump drying technology is a novel and potential method in purple sweet potato drying.The results can provide reference for the industrial production of purple sweet potato products.5?In order to obtain the optimal drying process of purple sweet potato by solar energy heat pump drying technology in this paper,the load density X1,slice thickness X2,moisture content of conversion X3 were selected as variables,the three factor two quadratic regression general rotation was employed,and the drying time model of Y1,anthocyanin retention rate model of Y2,and energy consumption per unit model of Y3 were established respectively.Through the analysis of variables,the drying process was optimized by the evaluation function.The results showed the optimal parameters of purple sweet potato solar heat pump drying are loading density 3.68 kg/m3,slice thickness 5.84mm and moisture content of conversion 117.08%;the drying time 291.65 min,anthocyanin retention rate 86.21%,energy consumption per unit 18.582 KJ/g?... |
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