【作者】 王海青；

【导师】 高忠良；

【作者基本信息】 河北工业大学 ， 化学工艺， 2003， 硕士

【摘要】 本文以蟹壳为原料，碱化法制备了壳聚糖，并考察了温度、碱浓度、碱化次数和微波场对壳聚糖制备的影响，并对壳聚糖进行了羧甲基化，制备了羧甲基壳聚糖和羧甲基甲壳素，考察了微波场和超声波场对合成工艺的影响，用均匀设计法对羧甲基化的工艺条件进行了优化。采用了低温溶胀、加入相转移催化剂等方法改进了合成工艺。本文还研究了壳聚糖和羧甲基壳聚糖对银离子吸附的作用，以及羧甲基壳聚糖在水果保鲜方面的应用。研究了壳聚糖先羧甲基化后降解制备低分子量羧甲基壳聚糖的工艺方法，并对其降解的动力学进行了探讨。 在壳聚糖制备过程中，采取了多次碱化法，及时补充新鲜的碱液，去掉反应过程中生成的乙酸钠等小分子，可制备高脱乙酰度的壳聚糖(脱乙酰度在90％～96％)。 在微波场中制备壳聚糖和羧甲基壳聚糖，可显著缩短反应时间，获得相同的脱乙酰度的壳聚糖和取代度的羧甲基壳聚糖，分子量下降基本上不超过2％～3％，这对减少能耗和改善产品性能有重要的意义。 通过先羧甲基化，后降解的办法，对壳聚糖进行降解，制备低分子量的羧甲基壳聚糖，平均分子量可降到8千左右。羧甲基的引进，使得羧甲基壳聚糖在中性条件下就能形成均一溶液，保持了溶液中自由氨基的数量，降解速度大大加快。 羧甲基壳聚糖比壳聚糖更能有效的吸附银离子，吸附平衡时间不超过15分钟，可作为银离子的天然金属螯合剂。 在对杏等水果的保鲜方面的研究中发现，不同取代度的羧甲基壳聚糖保鲜效果不同，常温下，取代度在0.4左右的羧甲基壳聚糖保鲜效果最好。其保鲜机理可能是羧甲基壳聚糖在杏的表面形成连续的具有选择通透性高分子膜，可使二氧化碳保存于膜内，并阻止氧气进入，但允许乙烯等气体从膜内逸出，从而使膜内能保持高浓度的二氧化碳，抑制其呼吸作用，延长其保鲜期。更多还原

【Abstract】 In this paper, we prepared chitosan from the crab shell, catalyzed by the NaOH. We studied the influence of the temperature ^ the density of the NaOH > the times of the basification and the microwave etc. to the preparation of the chitosan. At the same time, we got the CM-chitosan and CM-chitin. The influence of the microwave and ultrasonic to the reaction was studied, the preparation condition was optimizated. In order to improve the product technics, we dipped the chitosan in the low-temperature NaOH liquor before the basification and join the phrase-transmit catalysis. The adsorption to the Ag+ of the chitosan and CM-chitosan was researched. We use CM-chitosan as the antisepsis regents to the apricot. And finally we studied the hydrolysis dynamics of the CM-chitosan.In the preparation of the chitosan, we basified the materials repeatedly, and supplied the new lye and got rid of the impurities produced in the reaction and we got the high D.D. chitosan.(the 90% ^D.D. ^96%)The extinct characters of the microwave is to reduce the reaction time greatly, and so we can controlled the hydrolysis of the chitosan and CM-chitosan, it is important to cut down the energy exhume and improve the quality of the production.we studied the hydrolysis of the CM-chitosan, and the molecular weight was reduced to about 8000. The introduce of the carboxyl made the CM-chitosan resolved in the water when the PH was 7.0, so the -NH2 can be attacked easily. So the hydrolysis is high greater than the chitosan.Compared to the chitosan, the CM-chitosan were more suitable to adsorption of the Ag+ , the time was less than 15min when it became saturated.The antisepsis result of the CM-chitosan was different according to the different D.D. Through the experiment we find there was best antisepsis to the apricot when the D.D.was 0.4. The chitosan can made a membrane over the fruits, kept the O2 out side and restrained the breath, and kept the fruits fresh.更多还原