Study On Remove Of Moisture,Soluble Tannin And Nondestructive Testing Techology Of Dried Persimmon

Yue persimmon is known as "Chinese famous fruit".In 2015,the output of Guangxi was over 970,000 tons,and 30%of production was used for dried persimmon processing.The existing artificial dried persimmon shortens the drying time of dried persimmons and reduces the influence of weather and microorganisms.However,Dried persimmon processing still has raw material selection rough and non-standard,lack of theoretical basis for processing technology,residual astringency of dried persimmon,and determination of astringency only through sensory evaluation.Therefore,this paper studies the characteristics of dried persimmon processing materials,and establishes the dry kinetic model of dried persimmons,studies the removal of the astringency rules in artificial drying process,constructs a predictive model of soluble tannin in dried persimmon,and uses near-infrared technology to rapid detection of soluble tannin,in order to provide theoretical basis for optimizing the process of artificial dried persimmon.The main research contents are as follows:(1)Study on characteristics of raw materials for dried persimmon processingThe basic composition changes and appearance of different maturity raw materials and the dried persimmons were analyzed.It was found that the persimmons with maturity of 7-8 were more suitable for processing.Comparing the soluble tannins,sugar content and water content of different persimmons with different picking time and different origins,it was found that the tannin content and water content decreased with the picking time and the tannins,sugar content and water content of the persimmons with the same maturity in different producing areas were different.Comparing the basic physical parameters of raw persimmon,it was found that the physical properties of raw persimmon were significantly different,and the coefficient of variation the least was 2.21%and the highest was 48.22%.(2)Study on the drying kinetics of persimmon hot air:The effects of temperature,single fruit size and loading on the drying characteristics of dried persimmons were studied,and the drying curve equation was fitted.The results showed that the drying time of persimmon decreased with the increase of temperature;it increased with the increase of single fruit size and load;dried persimmon processing was divided into three drying stages:acceleration,first deceleration and second deceleration;According to the Fick's second law,the effective diffusion coefficient Deff of dried persimmon in the process of hot air drying is obtained,which increases with the increase of drying temperature;it decreases with the increase of single fruit size and loading.Comparing the different thin layer drying models,it is found that the Page model has the highest fitting degree,the verification coefficient is R2=0.99,and the root mean square error is RSME=0.03.(3)Study on removal of the astringency of dried persimmon:The effects of temperature,initial tannin content,drying rate and water content on the soluble tannin content of persimmon during the drying process were analyzed.It was found that the higher the drying temperature(35-55 ?),the shorter the removal of the astringency time.The lower the initial tannin content,the shorter the removal of the astringency time,but below a certain concentration,the removal of the astringency time is not affected by the initial tannin content;the drying rate has a promoting effect on the removal of the astringency,but too fast will cause the soluble tannin to be incompletely removed;the higher the moisture content,The shorter the removal of the astringency time,the less than 45%moisture content of the persimmon is not easy to removal of the astringency.Temperature,initial tannin content,time and moisture content were used as network input,soluble tannins were used as network output,and a 4-6-1 BP neural network model was established.The correlation coefficient of training set was 0.966,and the correlation coefficient of network model prediction was up to 0.93.(4)Near-infrared spectroscopy analysis of soluble tannins at dried persimmons:Firstly,the water content of dried persimmon was qualitatively determined by visible near-infrared diffuse reflectance spectroscopy.The cross-correlation correlation coefficient(1-VR)of the model was 0.913,the cross validation error(SECV)was 0.188,and the prediction accuracy of the prediction model was 85.50%.-95.65%.Dried persimmons with different water content have a clear spatial distribution in the PCA space.Therefore,a dried persimmon having a water content of 35%is preferred to establish a visible near-infrared quantitative qualitative model of soluble tannin.The correlation coefficient(1-VR)of the quantitative model interaction verification was 0.878,the cross validation error(SECV)was 0.105,the prediction coefficient was 0.865,and the prediction standard error(SEP)was 0.125.The correlation verification coefficient(1-VR)of the qualitative model was 0.83,the cross validation error(SECV)is 0.2036,and the prediction accuracy of the prediction model is 72.22%-88.89%.