| Nicotiana tabacum L. belongs to the Nicotiana of Solanaceae, and tobacco stem is its thick and hard vein. Nowadays, it is used to extract nicotin, solanesol, etc., while more tobacco stem is deserted. Because of considerable content in the tobacco wastes, it is worth to extract pectins from tobacco stem.Pectin is a natural water-soluble substance with a high molecular weight, which is present in a great number of many higher plants. Based on many special properties of pectins, especially the jelling ability to the aqueous solution, its application tends to become more and more varied and sophisticated. The main applications have been in the fields of food and others, such as Pharmaceuticals and cosmetics, where pectin has in recent years gained increasingly in importance.The pectin was extracted from tobacco stem by hydrochloride acid extraction, followed by molysite precipitation. In the extracting process, affecting factors selected were included: liquor-to-wood ratio, pH, temperature and duration, which were respectively provided with four levels in our experimental design.With jelly units (jelly units=yield of pectin viscosity of pectin solution) as evaluation criterion, experimental results of orthogonal experimental design (L16 (43)) were processed by visual analysis and variance analysis, and the same optimum program (P1) and its fiducialinterval range of engineering average at a = 0.10 were obtained. Furthermore, with the pectin yield and viscosity of pectin solution as the individual evaluation criterion, the other optimum program (P2) was got by dual target overall balance analysis. Through the comparison and verification of programs, which including P1, P2, P3 (maximal pectin yield in Li6 (45)) , P4 (maximal viscosity of pectin solution in L16 (45)) and P5 (maximal jelly units in L16 (45)) , the final optimum program was obtained under the selected factors and levels.Results showed that the most significant factors in extracting process were pH and liquor-to-wood ratio. To reduce their variation ranges, the experiment of single factor was respectively done. In addition, the effects of the inactivating process of pectase, decolourant ( absorbent charcoal ) ,dosage of chelator ( sodium hexametahposphate) on the yield and quality of pectin were studied as well in a systematical mode.In the precipitation process, affecting factors selected included: pH, molysite amount and temperature, all of which were respectively provided with three levels. With using the pectin yield as the evaluation criterion, our experimental data of orthogonal experimental design (L9(34)) was processed by statistic analysis. Furthermore, the effects of pH, molysite amount and stewing duration on pectin yield were separately researched.In the desalting process, the key parameters affecting the yield and quality of pectin were the mixture ratio of deferrization agent (acidic ethanol) and alkaline ethanol.Through the systematic studies on technology of acid extraction andmolysite precipitation, the obtained optimum technological parametersof extracting pectins from tobacco stem were as follows:(1) extracting process: pH=1.3~1. 6, liquor-to-wood ratio from 1:24to 1:30, at 70C for 80min, the ratio of absorbent charcoal amount(g) to fluid measure (ml) being between 0. 5% and 0. 7%, the ratio of sodium hexametahposphate (g) to raw material amount (g) being between 3% and 4%.(2) precipitating process: pH=3. 5~3. 9, concentration of molysite in precipitating liquid being between 0. 2% and 0. 3%, stewing duration over 4h at room-temperature.(3) desalting process: acidic ethanol mixed by HC1(10%) and ethanol(>95%) (HC1:ethanol(V/V) (2:3, 1:1)), the pH of alkaline ethanol(70%~80%) adjusted to 10?1 by Na0H(10%).According to the related standard in GBn246~85, the pectin sample obtained was identified and tested. It was shown in this work that the purity of pectin obtained in this technology is 90.9% and its content of methoxy group is 11.9%.
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