| Stevia glycoside is a kind of glycoside extracted from stevia leaves. The purity of stevia glycoside and the proportion of stevioside and Rebaudioside A in it has a direct impact on the quality of product. At present, the processing of stevia glycoside was still at the start stage in the domestic. The prominent problems in the production process are the energy consumption, environmental protection and food security. The stevia leaves of ganxian of Jiangxi were used as raw material in this research, the optimize water extraction processing has been studied in the study, encironmentally material-PAC was used to flocculate the water extraction and ethanol was used to recrystallize the stevia glycoside to improve the product purity, which would offer theoretical support and data references for the industrial production.Through the discussion on determination of stevia glycoside, anthrone-sulfuric acid method was used for the determination of glycoside content:4mL3.3%anthrone-sulphuric acid reagent was joined in1mL liquid, the solution was immediately placed in an ice water bath after blending, after that, all samples were bathed in a boiling water for7min, then the samples were took out and were cooled in the ice water bath, all samples were detected the absorption at620nm. The conditions of determining a mixture of Stevia liquid chromatographic:Inertsil NH2column (4.6×250mm,5μm), Mobile phase acetonitrile:water (70:30), flow rate1mL/min, sampling20μL, room temperature operation. The simple ultraviolet detection method of Stevia was determined, it’s suitable for good decolonization and low protein content Stevia products to determine total glycosides.The optimal values for improved stevia glycoside yield were determined by one-factor and orthogonal experiment design methods as follows:extraction temperature70℃extraction time3hours, solid-to-liquid ratio1:15(g/mL).Under such conditions, a maximum stevia golycoside yield of up to97%was obtained.Comparing with the three conventional clarifiers in the water extracts from the leaves of the stevia plant. The suitable flocculent were determined by the yield of stevia glycoside loss,water extracts decoloration and lucency.Further research on the flocculation conditions of PAC,the optimal temperature,flocculant dosage and time of the flocculation were65℃,18mg/mL,and1h,respectively.Based on the single factor, recrystallization response surface model was established through the three levels of the four factors regression equation.The regression equations of the response value Yi were respectively:Y1(crystallization rate)=-282.71467+4.94347X1+0.92322X2+18.20933X3+11.45667X4-10-3X1X2-4×10-3X1X3-2×10-3X1X4-6.56882×10-16X2X3-1.66667×10-3X2X4+1.07692×10-14X3X4-0.02928X12-4.11111×10-3X22-2.172X32-0.543X42Y2(purity)=-420.08083+9.709X1+1.61417X2-6.93167X3+2.4725X4+1.6667×10-3X1X2+0.155X1X3+0.081X1X4+0.10417X2X3+0.010417X2X4+0.3X3X4-0.068X12-0.010816X22-2.02X32-0.50938X42Y3(RA/Total)=-14.54122+0.27694X1+0.046239X2+0.12993X3+0.23999X4+2.30496×10-4X1X2+3.06965×10-3X1X3-1.37227×10-3X1X4+3.00937×10-4X2X3+5.43917×10-4X2X4+2.01963×10-3X3X4-1.82752×10-3X12-3.60353×10-4X22-0.048684X32-0.010284X42The results showed that the influence degree on crystallization rate as follows: X1(dissolving temperature)>X4(water content in ethanol)>X3(liquid-to-solid ratio)>X2(recrystallization time)The results showed that the influence degree on product purity as follows:X3(liquid-to-solid ratio)>X2(recrystallization time)>X1(dissolving temperature)>X4(water content in ethanol)；The results showed that the influence degree on RA/Total content as follows:X3(liquid-to-solid ratio)>X4(water content in ethanol)>X1(dissolving temperature)>X2(recrystallization time)... |
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