【作者】 刘巧瑜；

【导师】 张晓鸣；

【作者基本信息】 江南大学 ， 食品科学， 2008， 博士

【摘要】 为酶法选择性合成化学结构特定的麦芽糖酯,本文以麦芽糖和月桂酸为主要材料,在分离鉴定了酯化产物为麦芽糖月桂酸单酯和二酯的基础上,探讨了脂肪酶催化选择性合成麦芽糖月桂酸单酯的方法,确定了间歇式和连续化合成麦芽糖月桂酸单酯的工艺参数,系统研究了麦芽糖月桂酸单酯的热特性、水溶性、表面性质、乳状液的热特性和流变学特性、抗老化特性以及抑菌性,并和商品糖酯P1570作了对比分析。论文的主要结论如下:运用硅胶柱层析分离麦芽糖月桂酸酯,流动相为氯仿/甲醇(4:1, v/v),流速为18 mL/h。经MS、IR和NMR分析确定,Nov 435脂肪酶催化合成的麦芽糖月桂酸酯化产物中存在6’-O-麦芽糖月桂酸单酯和6,6’-O-麦芽糖月桂酸二酯。在间歇式反应器中脂肪酶催化合成麦芽糖月桂酸单酯的工艺条件为:20 g/L脂肪酶、25 mmol/L麦芽糖、75 mmol/L月桂酸和60 g/L的3A分子筛于5 mL丙酮中50℃反应72 h,麦芽糖月桂酸单酯的转化率和浓度分别可达92.7 %和23.35 mmol/L。反应温度对麦芽糖月桂酸单酯浓度的影响最大,麦芽糖浓度对麦芽糖月桂酸单酯转化率的影响最大。相同反应条件下,麦芽糖月桂酸单酯的转化率明显高于蔗糖月桂酸单酯的;麦芽糖单酯的转化率随脂肪酸碳链长度的延长而降低。连续搅拌反应器可实现麦芽糖月桂酸单酯的酶法选择性合成,优化后的工艺条件为:麦芽糖的初始浓度为50 mmol/L、月桂酸浓度为200 mmol/L、脂肪酶用量为40 g/L、不添加分子筛,每24 h补充16 g/L麦芽糖,反应器流速为0.15 mL/min,生产周期为10 d时麦芽糖月桂酸单酯的平均产量可以达到10.12 g/L·d。采用多次正己烷萃取-离心分离的方法分离纯化单酯产品,分离步骤为:25 mL反应液脱除丙酮后,沉淀用12.5 mL的正己烷一次萃取-离心分离,再用2.5 mL的正己烷二次萃取-离心分离和三次萃取-离心分离,产品中麦芽糖月桂酸单酯的含量为94.2 %(w/w)、回收率达到76.1 %。麦芽糖的月桂酸单酯、豆蔻酸单酯、棕榈酸单酯、硬脂酸单酯和蔗糖月桂酸单酯、豆蔻酸单酯、棕榈酸单酯可产生重结晶,重结晶体与新鲜糖酯的不同,是一种多晶体或结晶体和无定形体的混和物。月桂酸、豆蔻酸、棕榈酸和硬脂酸制备的麦芽糖单酯和蔗糖单酯的HLB值为16.1～18.2,可作O/W乳化剂。DSC分析发现,麦芽糖月桂酸单酯与n-癸烷和正丁醇(1.5:1:1, w/w/w)形成的模型乳状液体系可亲和16 %~20 %的水。麦芽糖月桂酸单酯和蔗糖月桂酸单酯水溶液为假塑性流体,豆蔻酸、棕榈酸和硬脂酸的麦芽糖单酯和蔗糖单酯溶液为牛顿流体。麦芽糖单酯和蔗糖单酯乳状液(石蜡油:水=8:2, v/v)为假塑性流体。0.09 %的麦芽糖单酯和蔗糖单酯可提高淀粉悬浮液的热稳定性、延缓淀粉糊贮藏过程中的老化;0.09 %的麦芽糖月桂酸单酯和蔗糖月桂酸单酯可有效抑制蜡状芽孢杆菌、凝结芽孢杆菌、枯草芽孢杆菌、嗜热芽孢杆菌、大肠杆菌和金黄色葡萄球菌的生长,两种糖酯的抑菌效果无明显差异。月桂酸单酯的表面性质和抑菌性整体上优于豆蔻酸单酯、棕榈酸单酯和硬脂酸单酯的,硬脂酸单酯的抗老化效果优于月桂酸单酯、豆蔻酸单酯和棕榈酸单酯的,麦芽糖单酯的表面性质、抑菌性和抗老化性略优于蔗糖单酯的。更多还原

【Abstract】 Sugar fatty acid esters have been widely used in foods, medicines and cosmetics by taking advantage of their particular properties, including nontoxic, biodegradable and great interficial properties. Sugar mono- and di- esters have obviously different physicochemical characterization and functional properties, so how to control the reaction condition to synthesize the production needed was a focus, difficulty and common problem. After the products focusing on maltose and lauric acid were purified and identified as monolauroyl maltose and dilauroyl maltose, the way to selective synthesis monolauroyl maltose was discussed, and the main parameters that need to be considered were ascertained. Water solubility, interficial properties, the thermal behaviour, rheology properties, anti-aging property and antimicrobial activity of monolauroyl maltose were studied and compared with other sugar esters. The main conclusion of this study included:Silica gel column chromatography with mobile phase of chloroform-methanol (4:1, v/v) for maltose ester at 18 ml/h was applied. The condensed products catalyzed by Nov 435 were analyzed by IR, MS ,1H NMR and 13C NMR, and then identified to be 6’-O-lauroylmaltose and 6,6’-di-O-lauroylmaltose.For monolauroyl maltose, the highest conversion of 93 % and concentration of 23.35 mmol/l were obtained in acetone when the condensation was carried out at 50℃for 72 hours with 20 g/l of lipase, 25 mmol/l of maltose, 75 mmol/l lauric acid and 60 g/l of 3 A molecular sieves in a batch reactor. Temperature was the major factor affecting the concentration of monolauroyl maltose, while maltose concentration was the major factor affecting the conversion of monolauroyl maltose. The conversion of monolauroyl maltose was obviously higher compared with monolauroyl sucrose at condition discribed above. The conversion of maltose monoesters was decreased when the fatty acid chain length increased. The activation energy of monolauroyl maltose enzymatic synthesis by Nov 435 was 23.07 kJ/mol.Monolauroyl maltose could be selectively synthesized in a continuous stirred tank reactor (CSTR). The highest concentration of monolauroyl maltose at 28 mmol/l in acetone was obtained when maltose was added at 4 g/d and the molar ratio of lauric acid to maltose was fixed at 4:1 at a flow rate of 0.15 ml/min effluent without supplement of fresh molecular sieve. The average yield of monolauroyl maltose was 10.12 g/l·d during 10 days operation. Several extraction-centrifuging were used to purify the product and recover the lauric acid unreacted, and which made it possible to prepare monolauroyl maltose in large scale. The separating process was as followed: after 25 ml effluent was concentrated, 12.5 ml hexane was added to the precipitation for the first extraction-centrifuging, then 2.5 ml hexane was added for the second and third extraction-centrifuging, the final product was purified to be 94% of monolauroyl maltose with 76 % of retention. HLB values of maltose monoesters and sucrose monoesters, were from 16.1 to 18.2, and could be used for the preparation of nonionic O/W microemulsions.The DSC revealed that the tested sugar esters could be recrystalized, except for monostearoyl sucrose. The recrystallization was a mixture of crystaline and amorphous state, and differred from the initial state. A model nonionic water-in-oil microemulsion system based on sugar monoester/1-butanol/n-hexandecane (1.5:1:1) could bound 16% to 20% with water.Emulsions (paraffin-water) produced by maltose monoesters and sucrose monoesters, water solution of monolauroyl maltose and monolauroyl sucrose were pseudoplastic fluid, while water solution of monomyristroyl maltose, monomyristroyl sucrose monopalmitroyl maltose, monopalmitroyl sucrose, monostearoyl maltose and monostearoyl sucrose were newtonian flow.The RVA and DSC showed that maltose monoesters and sucrose monoesters at 0.09% bulk concentration could improve the hot stability of starch suspension and prolong the starch paste aging during storage. Monolauroyl maltose and monolauroyl sucrose inhibited the growth of Bacillus cereus, B. coagulans, B. subtili, Geobacillus stearothermophilus, Escherichia coli and Staphylococcus aureus at 0.09% bulk concentration.Among the tested maltose monoesters and sucrose monoesters, monolauroyl maltose led to greatest interficial properties and antimicrobial activity, while monostearoyl maltose and monostearoyl sucrose had the greatest anti-aging property.更多还原