Study On Extraction And Decoloration Processes Of Polysaccharide From Jerusalem Artichoke By Ultrasound-assisted Technology

Jerusalem artichoke polysaccharide has become an important functional food with definite molecular structure and physiological function.Jerusalem artichoke tubers are rich in polysaccharide,which accounts for 55%⁸0%of the dry weight.The polysaccharide industry of Jerusalem artichoke began posteriorly in China by studying mainly the process of cane sugar production at present.It was still inferior in processing technology,production automation and product quality.Especially,the pigment affects the quality of Jerusalem artichoke polysaccharide and production cost.In this work,ultrasonic technology to the extraction and decolorization of Jerusalem artichoke polysaccharide were studied,and the micro-optical fiber near-infrared spectroscopy technology to the in-situ real-time monitoring of the decolorization process was applied,which laid a foundation for the high efficiency and intelligence of the preparation process of Jerusalem artichoke polysaccharide.The main research work and its conclusions were as follows:?1?Study on ultrasound-assisted extraction of Jerusalem artichoke polysaccharide:Jerusalem artichoke polysaccharide was extracted from dry Jerusalem artichoke via six-frequency slit-shaped and five-frequency cylindrical divergent ultrasonic equipments to screen the optimal ultrasonic working modes.In the optimal operating mode,the optimal ultrasound-assisted extraction parameters of polysaccharide were determined by a single factor and then optimized by the orthogonal method.Through the mid-infrared spectrum technology,it was revealed whether ultrasound affected the structre of the polysaccharide.Results showed that all the ultrasonic working modes could significantly improve the extraction content of Jerusalem artichoke polysaccharide.The most effective ultrasonic mode was 28/35kHz using the five-frequency cylindrical divergent ultrasonic equipment.The optimal parameters of ultrasonic mode were:ultrasonic power density of 110 W/L,solid-liquid ratio of 1:15 g/mL,ultrasonic time of 20 min,ultrasonic temperature of55?.Under these conditions,the Jerusalem artichoke polysaccharide extraction ratio reached the maximum value 67.55%,while the extraction ratio of hot water extraction method was noly 49.24%.Five-frequency cylindrical divergent ultrasonic equipment could effectively improve the extraction ratio of Jerusalem artichoke poiysaccharide.The result of mid-infrared spectroscopy analysis showed that the absorption peaks of polysaccharides extracted from Jerusalem artichoke by hot water and ultrasound were consistent at 3362 cm^-1,2930 cm^-1,1031 cm^-1,930 cm^-1 and 832 cm^-1,indicating that ultrasound had no effect on its structure.?2?Study on screening and adsorption behavior of polysaccharide decolorizing resin from Jerusalem artichoke:In order to use the dynamic adsorption technology to decolorize the polysaccharide of Jerusalem artichoke,this paper firstly screened the optimal resin from six kinds of macroporous resins by static adsorption test,and further studied static adsorption kinetics,static adsorption model and thermodynamic parameters.Results showed that under the same experimental conditions,D301-G macroporous resin adsorbed pigment faster than other resins,meanwhile the loss rate of polysaccharide was the smallest.The decolorization rate of D301-G was 87.06%and the Jerusalem artichoke polysaccharide retention was 92.28%.The adsorption process fitted the pseudo-second-order model,which is mainly affected by particle diffusion resistance.Compared with the Langmuir isotherm model,D301-G macroporous resin used at 293 K,303 K and 313 K fitted better with the Freundlich isotherm model.Its adsorption of pigment molecules may be multi-molecular.The thermodynamic parameters were?H>0,?G<0,?S>0,indicating that the adsorption process occurred spontaneously,and the adsorption ability increased as the temperature increased.?3?Study on the dynamic decolorization process of Jerusalem artichoke polysaccharide by chromatography column:The effects of solution flow rate and the diameter high ratio of exchange column were investigated,and the effect of ultrasound on desorption of the resin was studied.Results indicated that the best conditions of D301-G macroporous resin for dynamic decolorization process was the speed of flowing of 2 BV/h and the ratio of diameter to height of 14:1.Under the optimal conditions,the single process load was 3.5 BV,and the percent of decolorization was 90.76%,and polysaccharide retention rate was 74.02%.Compared with the process of desorption of decolorized resin without ultrasound,ultrasonic treatment enhanced the desorption process of decolorizing resin.The preferred parameters for ultrasonic desorption process were eluent HCl of 5%,ultrasonic frequency of 20 kHz and power of 89.28 W.Under the conditions of adsorption,the ultrasonic desorption resin was used for 10 times and the decolorization rate was84.20%,which was close to that of the resin without ultrasonic desorption after 5times,which proved that the ultrasonic wave could improve the desorption effect of the resin.The refined Jerusalem artichoke polysaccharide with different degrees of decolorization were prepared.The yield of polysaccharide increased but the purity decreased with the decrease of decolorization rate.Considering the yield and purity of Jerusalem artichoke polysaccharide,the best decolorization rate was 89.82%,and the values were 26.69%and 94.09%,respectively.?4?Study on on-line monitoring the dynamic decolorization process of Jerusalem artichoke polysaccharide:The in-situ and real-time spectra were collected by near-infrared device and used for monitoring the parameters of effluent during dynamic decolorization process of Jerusalem artichoke polysaccharide.Four different preprocessing methods were used to deal with the original spectra.Synergy interval Partial Least Squares?Si-PLS?model for the decolorization rate and polysaccharide retention rate of the effluent in the dynamic decolorization process were established using the optimal spectral intervals.Results showed that Standard Normal Variate transformation?SNV?was the best preprocessed method.The optimal spectral intervals of the decolorization rate were 1051.12¹135.55 nm?2046.16²128.59 nm?2223.54²305.68 nm and 2311.99²400.3 nm.The optimal spectral intervals of polysaccharides retention rate were 1077.12¹174.45 nm?1899.98¹995.37 nm?2204.56²299.37 nm and 2305.68²406.61 nm.For the Si-PLS model,the correlation coefficient of the prediction set was 0.9694 and the RMSEP was 1.88%for the decolorization rate.For the Si-PLS model,the correlation coefficient of the prediction set was 0.9649 and the RMSEP was 5.92%for polysaccharide retention rate.This in-situ spectroscopy monitoring system,combined with the Si-PLS method,has a good predictive ability.It can realize in-situ real-time monitoring of the decolorization process,and provide technical support for the intelligent system design of the decolorization process.