【作者】 宁海凤；

【导师】 童群义；

【作者基本信息】 江南大学 ， 制糖工程， 2010， 硕士

【摘要】 果胶是一类杂多糖,主要存在于高等植物的细胞壁中,具有良好的生理功能,广泛应用于食品、医药和化妆品等行业。豆腐柴是一种重要的野生果胶资源植物,其叶片中果胶含量高达30%-40%。本文主要研究了豆腐柴叶果胶的制备工艺及果胶产品的理化性质和流变学性质。以果胶提取率和果胶液透光率为指标,其中提取率为主要指标,分别采用热酸提取和混合酸超声微波协同萃取两种方法提取豆腐柴叶中的果胶。对于热酸提取工艺,分别考察了酸类型、酸的配比、pH、料液比、时间和温度对提取效果的影响,在此基础上进行正交试验,得出热酸提取豆腐柴叶中果胶的最佳条件为：料液比1：35(w/v)、pH1.5、提取时间1.5h、提取温度90℃,此条件下果胶的提取率为18.53%,果胶液透光率为92.70%。对于超声微波协同萃取工艺,分别考察了pH、料液比、微波功率和提取时间各因素对提取效果的影响,在此基础上进行正交试验,得出超声微波协同萃取豆腐柴叶中果胶的最佳条件为：提取时间500s、pHl.5、料液比1：15(w/v)、微波功率100W,该条件下豆腐柴叶中果胶的提取率为19.41%,果胶液透光率为92.50%。综合比较以上两种提取方法可以发现,超声微波协同萃取大大缩短了提取时间,而且一定程度上提高了果胶的提取率。因此本文后续试验选择超声微波协同萃取法提取豆腐柴叶中的果胶。对于果胶液的脱色工艺,以脱色率和果胶损失率为指标,选用S-8、X-5、AB-8、D3520和D4020五种大孔吸附树脂进行筛选试验。在此基础上进行大孔吸附树脂的动态吸附试验,选择最佳流速。试验结果显示X-5树脂在流速为56mL/h的条件下脱色效果最佳。在最佳脱色条件下,测定脱色前后提取液中蛋白质含量的变化。结果显示,在该条件下,蛋白质脱除率为80.32%,较理想。因此,本试验通过X-5大孔吸附树脂达到脱色及脱蛋白的双重效果。采用透析方法除去果胶提取液中的小分子。透析时间72h,每6h换一次水。采用乙醇沉淀果胶,以果胶沉淀得率为指标,分别考察原液浓缩比、乙醇浓度、沉淀时间对果胶醇沉处理的影响。试验结果显示原液浓缩比1/4、乙醇浓度80%、沉淀时间1.5h时沉淀效果最理想。乙醇沉淀后的果胶液过滤后取滤饼真空干燥(温度40℃,真空度0.1MPa),粉碎过筛得果胶产品。对经过以上工艺制备出的果胶产品的理化性质以及流变学性质进行了研究。流变学分析研究了果胶产品溶液的浓度、pH、钙离子浓度、蔗糖含量、处理温度、热处理时间对果胶产品溶液流变学性质的影响。结果表明：豆腐柴叶果胶产品溶液的黏度随剪切速率的增大而降低,表现为典型的假塑性流体；偏酸或偏碱环境都会导致果胶产品溶液黏度下降；果胶产品溶液的黏度随钙离子添加量以及蔗糖含量的增加而增大；热处理一定时间后,果胶产品溶液表现出理想的牛顿流体性质。更多还原

【Abstract】 Pectin is a family of complex polysaccharides mainly extracted from cell walls of higher plants.Because of its good physical function.pectin is widely used in industry such as food,medicine.cosmetic.The extraction technology of pectin from leaves of Premna Microphylla Turcz were studied in this paper. Then, the pectin has been prepared to study its physicochemical and rheological properties.As for the extraction of pectin from leaves of Premna Microphylla Turcz, the extraction rate of pectin and transmission of the pectin extract were utilized to evaluate two extraction methods, that is, acid water bath extraction and mixed acid ultrasonic-microwave synergistic extraction, while extraction rate served as the dominant indicator.For the water bath, the influence of type and ratio of different acids, pH, solid to liquid ratio, extraction time and temperature on extraction effect were studied.Based on single factor analysis,orthogonal test was designed to confirm the main factors and the optimum condition. The results showed that the optimum condition was as following:H3PO4 to H2SO3 ratio 1:2(v/v),solid to liquid ratio 1:35(w/v), pH1.5, extraction time 1.5h and extraction temperature 90℃. Under these conditions, the extraction rate of pectin and transmission of pectin extract were 18.53% and 92.70%, respectively.For the ultrasonic-microwave synergistic extraction, pH, solid to liquid ratio, extraction time and extraction temperature were chosen to assess the extraction result. The single factor analysis and orthogonal test were designed to confirm the main factors and the optimum condition.The results showed that the optimum condition was as following:pH1.5, extraction time 500s, solid to liquid ratio 1:15(w/v), microwave power 100W. Under these conditions, the extraction rate of pectin and the transmission of pectin extract were 19.41% and 92.50%, respectively.By comparison of the above two methods, ultrasonic-microwave synergistic extraction reached an ideal result, which was adopted in the following experiment.Concerning the discoloration of pectin extract, five types of macroporous resins, namely S-8,X-5,AB-8,D3520,D4020 were compared by their absorbing ability.The X-5 resin demonstrated an ideal result among various resins tested.Then, dynamic absorption process was adopted. Different flow rates were designed to optimize the discoloration process.Under optimized dynamic absorption condition (flow rate of 56mL/h), higher ratios of discoloration and pectin recovery for X-5 resin were observed.Then,the protein content before and after absorbing were tested and the result showed that ideal deproteinization effect was reached. Consequently, no additional deproteinization methods were utilized.Dialysis method was adopted to purify the pectin extract further.The water was changed every 6h in the process of 72h.Ethanol was used to precipitate pectin from the extract, several factors such as the concentration ratio of pectin solution, the concentration of ethanol, the precipitation time were used to optimize the precipitation process. The result showed that the optimized condition was as following:concentration ratio 1/4, concentration of ethanol 80%, precipitation time 1.5h. Followed by the above process, the physicochemical and rheological properties of pectin were studied. The influence of a number of parameters such as pectin concentration, pH, Ca2+ concentration, sugar content, temperature, different heating time on viscosities of pectin aqueous solution were studied. The result showed that the viscosity of pectin solution decreased with the increased shear rate and the pectin solution was a typical pseudoplastic fluid; the viscosity decreased under both acidic or alkaline condition; the viscosity increased with higher content of Ca2+ and sugar;the viscosity of pectin solution decreased and then become Newtonian fluid when heated for certain time.更多还原