维生素E酯衍生物稳定性能及其在食品中的应用研究

为了研究维生素E酯衍生物的稳定性能及其应用注意事项，本文探讨了水分、温度、pH值、脂肪酶、血清等因素对维生素E醋酸酯化学稳定的影响，并比较了游离维生索E与维生素E醋酸酯在油脂抗氧化性能方而的区别。结果表明维生素E乙酸酯在较低温度含水溶液中基本不解离；在较高温的酸性或碱性含有水条件下，维生素E乙酸酯有一定程度的解离；而在含有脂肪酶的体系中，维生素E乙酸酯十分容易解离。维生素E乙酸酯和游离的维生素E的生理活性基本相同，但是在化学稳定性和抗氧化性能方面有着明显的区别。为了提高维生素E的使用效率，在食品或保健品的生产过程中，应根据生产或产品的实际需要添加适当形式的维生素E。     

纳米乳液改善多酚性能及在食品中的应用进展

国内外研究人员一直关注植物多酚促进人体健康的潜在作用,发现在实际应用中,多酚的稳定性差、溶解性差、生物利用率低等问题亟待解决。纳米乳液递送体系粒径小、稳定性佳,是极佳的多酚递送体系,应用前景广阔。经纳米乳液包埋后的多酚可改善稳定性,提高在体内的生物利用率,表现出更佳的生物可及性、抗氧化性及抗肿瘤活性,更适合应用于食品工业。该研究结合国内外研究者的成果综述了多酚的分类及作用;多酚纳米乳液制备新技术;纳米乳包载对多酚多种性能的改善效果与作用机制。基于多酚纳米乳液需解决的首要问题提出了乳液优化方案,并阐述了多酚纳米乳液在食品工业中的现状及潜在应用,对多酚纳米乳液未来的制备方向进行展望。     

Encapsulation of functional lipophilic components in surfactant-based colloidal delivery systems: Vitamin E,vitamin D,and lemon oil

The fabrication and stability of surfactant-based colloidal delivery systems (microemulsions and emulsions) suitable for encapsulation of lipophilic active agents (vitamins and flavours) was investigated. An emulsion titration method was used to study the influence of surfactant type (Tween 20, 60 and 80) and oil type (Vitamin E, vitamin D₃ and lemon oil) on the incorporation of lipophilic components into surfactant micelles. Oil-in-water emulsions were formed and then different amounts were titrated into surfactant micelle solutions. The influence of surfactant-to-oil ratio (SOR) and oil type on the formation of colloidal dispersions was examined using dynamic light scattering and turbidity measurements. SOR, oil type, and surfactant type had a pronounced influence on the nature of the colloidal dispersions formed. Microemulsions could not be formed using vitamin D or E in 1% Tween solutions, due to the relatively large size of the lipophilic molecules relative to the hydrophobic interior of the surfactant micelles. On the other hand, microemulsions could be formed from lemon oil at relatively high SORs. There was not a major impact of non-ionic surfactant type (Tween 20, 60 or 80) on the formation and properties of the colloidal dispersions. However, Tween 20 micelles did appear to be able to solubilise less lemon oil than Tween 60 or 80 micelles, presumably due to their smaller dimensions. This study provides useful information for the rational design of food grade colloidal delivery systems for encapsulating flavour oils, oil-soluble vitamins, and other functional lipids for application in foods and beverages.     

高压液相色谱法同时测定食品中的维生素A、D、E和K

本方法研究了应用反相高压液相色谱技术,同时测定食品中的维生素A、D、E、K。以C18柱为固定相(μ Bondapak C18,30cm×4mm),甲醇作流动相。在290nm下测定维生素A、E,在265nm下测定维生素D、K。样品的前处理分为两种,第一种皂化法,可同时测定维生素A、D、E。加标样品的回收率分别为:V_A97.2～110％,V_D92.3～102％,V_E96.6～110％。变异系数(CV％)分别为V_A2.29～3.15％,VD5.99～8.63％,V_E3.60～4.16％。第二种为酶解法,可同时测定维生素A、D、E、K四种,加标样品的回收率分别为:V_A87.62～98.01％,V_D90.23～102.7％,V_E86.18～91.09％,V_K80.15～85.07％。变异系数(CV％)分别为:V_A5.51％,V_D8.87％,V_E4.91％,V_K3.67％。     

不同形态硒、维生素E、紫萝卜提取物体外抗氧化协同作用研究

本文比较了不同形态硒（包括亚硒酸钠,SS;L-硒甲基半胱氨酸,L-Se-MSC;富硒酵母,SEY）、维生素E（V_E）和紫胡萝卜提取物（Ant）之间的抗氧化协同作用。分别建立DPPH、Fe³⁺和ABTS⁺·三种体外抗氧化模型,绘制清除率曲线,计算各物质的半抑制浓度(IC₅₀)。采用等辐射分析法,根据等效公式计算复配后的理论值(IC^50add),将其与实际测量值(IC^{50 mix})进行比较。结果显示,SS和L-Se-MSC的体外抗氧化性较弱,而SEY在体外具有较强抗氧化能力。同一模型中,不同复配比例的抗氧化协同效应不同。协同效应最佳的组合比例在DPPH模型中为:V⁽（Emix）∶Ant^mix∶SEY^mix=4∶1∶1,在Fe3+模型中为:V^Emix∶Ant^mix∶SEY^mix=1∶4∶1,在ABTS+·模型中为:V^Emix∶Ant^mix∶SEY^mix=1∶1∶1。因此,同一物质在不同模型中的抗氧化效应不同,SEY、V_E与Ant联用具有抗氧化协同作用,但同一组合在不同抗氧化模型中表现出的效应有所不同。      

皱褶假丝酵母脂肪酶CRL1在毕赤酵母中的高效表达及其催化合成维生素E醋酸酯

本研究将经密码子优化的皱褶假丝酵母脂肪酶(Candida rugosa lipase) CRL1基因克隆到毕赤酵母分泌型表达载体pHKA,构建得到重组菌株GS115/pHKA-CRL1;经摇瓶发酵并结合甲醇诱导120 h处理,该菌株对底物对硝基苯酚丁酯(p NPB)的水解活力达到39.73 U/mL。通过对AOX1启动子和α分泌信号肽同时进行改造,进一步获得重组菌株GS115/pHKA-AOX1m/αm-CRL1,其脂肪酶活力提高达到63.63 U/mL。发酵液上清液经超滤浓缩、硫酸铵沉淀后,再经脱盐和阴离子交换层析处理,获得纯化的重组CRL1。该纯化工艺的纯化倍数为5.41倍,回收率为33.81%。而纯化重组CRL1的比酶活为984.5U/mg。重组CRL1的最适温度为40℃,最适pH为7.5;经40℃保温6 h,仍保留52.99%的相对活力;在偏酸性环境中较为稳定。以摇瓶发酵、真空冷冻干燥后的重组CRL1为催化剂,在无溶剂体系中催化合成维生素E醋酸酯,在最适反应条件下(200 mg D-α-生育酚、1 mL乙酸酐、100 mg CRL1、反应温度60℃、转速200 r/min、反应时间9 h),D-α-生育酚的转化率在97.00%以上。     

维生素E乙酸酯制备方法与光谱表征

利用新型催化剂固体超强酸SO42-/TiO2合成VE乙酸酯,研究催化剂用量、反应物配比、反应时间、反应温度等因素对合成的影响,通过模糊数学模型确定了最佳合成条件。最优合成工艺:温度40℃,时间3h,乙酸酐与VE摩尔比1.2,固体超强酸SO42-/TiO2催化剂用量1.0g,反应酯化率为96.6%。利用IR、元素分析和1H NMR对产物结构进行表征,证明得到的产物为VE乙酸酯。     

解淀粉芽孢杆菌GSBa-1胞外多糖的发酵制取、流变学特性和应用

针对1株从传统酒曲中分离筛选得到的高产胞外多糖(exopolysaccharides,EPS)解淀粉芽孢杆菌GSBa-1,采用单因素试验和响应面法确定了菌株的最优产EPS发酵条件:培养基组成为胰蛋白胨10 g/L、酵母浸粉5 g/L、蔗糖40 g/L、氯化钠10 g/L;发酵温度35℃、发酵时间36 h、摇床转速160 r/min、接种量4%,在此条件下EPS产量为326.45 mg/L。对EPS的流变特性进行研究,结果表明,该EPS溶液的黏度较低,具有浓度依赖性和剪切变稠的特性,随着温度升高,黏度降低。采用激光光散射仪辅助测量EPS的分子形态:得到EPS在水溶液中重均分子质量为4.993×10~5 g/mol,回旋半径为48.34 nm,流体力学半径为64.62 nm,结构参数为0.748,该分子可能为紧密的球状结构。透射电子显微镜观察验证了EPS的球状结构。将该EPS加入到酸性乳饮料中,既不会增加其黏度,又具有良好的稳定特性,表明解淀粉芽孢杆菌GSBa-1 EPS可以作为一种新型的食品稳定剂,具有潜在的应用价值。     

Inactivation kinetics of inoculated Escherichia coli O157:H7, Listeria monocytogenes and Salmonella Poona on whole cantaloupe by chlorine dioxide gas

The objectives of this study were to examine inactivation kinetics of inoculated Escherichia coli O157:H7, Listeria monocytogenes and Salmonella Poona inoculated onto whole cantaloupe and treated with ClO(2) gas at different concentrations (0.5, 1.0, 1.5, 3.0 and 5.0 mg l(-1)) for different times (0, 2.0, 4.0, 6.0, 8.0 and 10.0 min). The effect of ClO(2) gas on the quality and shelf life of whole cantaloupe was also evaluated during storage at 22 degrees C for 12 days. A 100 microl inoculation of each targeted organism was spotted onto the surface (5 cm(2)) of cantaloupe rind (approximately 8-9 log CFU 5 cm(-2)) separately, air dried (60 min), and then treated with ClO(2) gas at 22 degrees C and 90-95% relative humidity for 10 min. Surviving bacterial populations on cantaloupe surfaces were determined using a membrane transferring method with a non-selective medium followed by a selective medium. The inactivation kinetics of E. coli O157:H7, L. monocytogenes and S. Poona were determined using nonlinear kinetics (Weibull model). A 3 log CFU reduction of E. coli O157:H7, L. monocytogenes and S. Poona were achieved with 5.0 mg l(-1) ClO(2) gas for 5.5, 4.2 and 1.5 min, respectively. A 5l og CFU reduction of S. Poona was achieved with 5.0 and 3.0 mg l(-1) ClO(2) gas for 6 and 8 min, respectively. A 4.6 and 4.3 log reduction was achieved after treatment with 5.0 mg l(-1) ClO(2) gas at 10 min for E. coli O157:H7 and L. monocytogenes, respectively. Treatment with 5.0 mg l(-1) ClO(2) gas significantly (p<0.05) reduced the initial microflora (mesophilic bacteria, psychrotrophic bacteria, and yeasts and molds) on cantaloupe by more than 2 log CFU cm(-2) and kept them significantly (p<0.05) lower than the untreated control during storage at 22 degrees C for 12 days. Treatment with ClO(2) gas did not significantly (p>0.05) affect the color of whole cantaloupe and extended the shelf life to 9 days compared to 3 days for the untreated control, when stored at ambient temperature (22 degrees C).