膳食纤维对蛋白包裹型乳液油脂消化的影响及其机制

发布时间：2018-01-05 23:35

本文关键词：膳食纤维对蛋白包裹型乳液油脂消化的影响及其机制　出处：《西北农林科技大学》2017年博士论文　论文类型：学位论文

【摘要】：乳液递送系统可有效包被、保护并靶向递送饲料及食品行业中的诸多脂溶性成分(如脂溶性维生素、类胡萝卜素、植物甾醇、类黄酮等)。这些生物活性分子的生物可给性和利用度通常取决于乳液油脂消化的速率和程度。在胃肠道中,膳食纤维对乳液油脂消化过程的影响取决于其本身的分子及理化特性。本研究借助全自动酸碱滴定仪(pH-stat),对体外胃肠道(GIT)消化模型的相关参数(滴定液浓度、离子强度度、脂肪酶及胆盐浓度、温度、转子转速)进行了标准化,建立并完善了单级和多级GIT消化模型。在这两种体外消化模型的基础上,选择三种不同类型和浓度水平的膳食纤维(带正电荷的壳聚糖、带负电荷的海藻酸钠、呈电中性的刺槐胶),测定其在体外GIT消化模型的不同生理阶段(初始阶段、口腔、胃、小肠)对乳液理化性质(粒径、ζ-电位、表观黏度)和微观结构的影响。假设每个三酰甘油分子可释放2个自由脂肪酸分子(FFAs),通过实时记录用以中和FFAs所消耗的氢氧化钠(NaOH)溶液的体积,可计算出被脂肪酶水解的三酰甘油在初始脂肪乳液样品中所占的比例(即消化率)。随后,对消化曲线进行LOS(logarithm of slope)分析,可得到油脂消化过程中的反应动力学参数。各试验内容及结果如下:1.选取三种带有不同电荷属性的膳食纤维(壳聚糖、海藻酸钠、刺槐胶),按比例与β-乳球蛋白(1 wt%)乳化形成的纳米乳液混合,使乳液-多糖复合体系中的膳食纤维浓度分别为0、0.1、0.2、0.4 wt%。含有膳食纤维的乳液在体外小肠消化模型中的消化时间为2 h(37℃),消化体系中钠离子和钙离子的摩尔浓度分别为150 mM和10 mM,脂肪酶浓度为1.6 mg/mL,胆盐浓度为5 mg/mL。测定消化前后乳液样品的粒径、PSD、ζ-电位和流变学参数。研究显示,膳食纤维对消化前后乳液液滴理化性质及微观结构的影响各不相同,且取决于纤维类型和浓度:0.1-0.4%的壳聚糖可使乳液液滴平均粒径从0.206μm增大至170-240μm;低浓度的海藻酸钠(0.1-0.2 wt%)对粒径影响不明显,但高浓度组(0.4%)可使乳液平均粒径增大到约54μm;刺槐胶(0.1-0.4 wt%)可诱发乳液液滴形成絮凝体(粒径约1至11μm)。通过PSD、ζ-电位和激光共聚焦图像可推断:(1)低浓度的海藻酸钠和刺槐胶诱发乳液液滴絮凝或聚集的原理为排空效应,且内部作用力相对较弱,因此结构相对不稳定;(2)高浓度的海藻酸钠可与人工小肠液中的钙离子结合形成凝胶体系,且可包埋乳液中的部分脂肪液滴;(3)而带正电荷的壳聚糖则是通过静电桥连作用引发液滴聚集,且结构相对紧凑。2.通过记录用以滴定乳液油脂消化产物FFAs所消耗的NaOH滴定液(0.1 M),可计算乳液油脂消化所释放的FFAs在初始乳液样品总TAG中所占的比例,进而得到反映乳液油脂消化的动态曲线。当乳液中含有较低浓度水平(0.1-0.2 wt%)的膳食纤维,自由脂肪酸的初始释放速率排序为:对照组≈刺槐胶组≈海藻酸钠组壳聚糖组,但各处理组最终油脂消化率(≈82%-88%)差异不显著(P0.05)。当膳食纤维的浓度水平增高至0.4 wt%时,海藻酸钠和壳聚糖显著抑制了乳液油脂消化过程,油脂消化速率和程度如下:对照组≈刺槐胶组(≈83%-87%)壳聚糖组(≈72%)海藻酸钠组(≈60%)。3.以1 h为限,于FFAs释放曲线中取13个消化数据点,在前10 min内取8个样本点,其后,每10 min取1个样本点。将所得数据点进行LOS分析,根据R2寻求最佳线性回归方程。结果表明,不同类型和浓度水平的膳食纤维影响乳液油脂消化的潜在反应动力学机理也存在差异:含不同膳食纤维的乳液油脂消化动态曲线存在一阶和二阶反应的差异,表现为存在单个或两个伪一级反应速率常数,其大小取决于膳食纤维的类型和浓度水平。4.在多级GIT消化模型中,调节消化前乳液-多糖混合溶液中膳食纤维的浓度至1.6wt%,以使单级和多级GIT模型的小肠阶段膳食纤维浓度保持一致(0.4 wt%)。通过对比消化率和伪一级速率反应常数,得到以下结论:海藻酸钠在单级GIT模型中的油脂消化率约为60%,在多级GIT模型中提高了23%;壳聚糖组在单级GIT模型中的消化率≈72%,多级GIT模型处理后消化率提高至83%;空白组和LBG组乳液样品在多级GIT模型中未见显著提升(P0.05)。分析伪一级速率反应常数可推断:多级GIT消化模型中人工唾液和胃液对乳液-多糖混合溶液的预处理,可改变油脂与脂肪酶结合的比表面积或界面特性,进而提高乳液油脂消化率。综上所述,我们在此提出构化设计准则:通过控制膳食纤维的类型和浓度水平,即可控制乳液液滴在胃肠道中的理化性质(粒径、ζ-电位、黏度)和微观结构,最终可有效调控特定乳液-多糖结构体系在胃肠道中的油脂消化速率和程度。同时,经过标准化的单级和多级消化模型可用于筛选饲料或食品级的功能性乳液递送系统
[Abstract]:Emulsion delivery system can effectively protect package, and targeted delivery of feed and many fat soluble components in the food industry (such as fat soluble vitamins, carotenoids, phytosterols, flavonoids). These bioactive molecules bioavailability and utilization degree usually depends on the digestion rate and oil emulsion degree. In the gastrointestinal tract, and the physical and chemical molecules depends on dietary fiber effects on oil emulsion digestion process to its own characteristics. This study uses automatic titration instrument (pH-stat), gastrointestinal tract (GIT) on the in vitro digestion model parameters (titration concentration, ionic strength, lipase and bile salt the concentration, temperature, rotor speed) was standardized, establish and perfect the single stage and multi-stage GIT digestion model. Based on these two models on the in vitro digestibility of dietary fiber, choose three different types and levels of concentration (positively charged chitosan And negatively charged sodium alginate, locust gum electrically neutral), measured at different physiological stages of in vitro digestion GIT model (initial stage, oral cavity, stomach, small intestine) on the emulsion properties (particle size, zeta potential, viscosity) effect and microstructure. Assuming each three - 2 glycerol molecules can release free fatty acid molecules (FFAs), through the real-time recording to counteract the FFAs consumption of sodium hydroxide (NaOH) solution volume can be calculated by lipase hydrolysis of three glycerol for fat emulsion in the proportion of initial samples (i.e. digestion rate). Subsequently, LOS (logarithm of slope) digestion curve analysis, can obtain the kinetic parameters of oil in the process of digestion. The experiment contents and results are as follows: 1. selected three kinds with different charge properties of dietary fiber (chitosan, sodium alginate, locust gum), according to the proportion and beta lactoglobulin (1 wt%) emulsion type The nano emulsion mixture, the digestion time of in vitro digestion in the small intestine in the model to make dietary fiber polysaccharide composite emulsion concentration in the system was 0,0.1,0.2,0.4 wt%. containing dietary fiber emulsion was 2 h (37 C), the molar concentration of sodium and calcium ions in the digestive system were 150 mM and 10 mM, lipase the concentration of 1.6 mg/mL, bile salt concentration was 5 mg/mL. measured before and after digestion emulsion sample size, PSD, zeta potential and rheological parameters. The results show that dietary fiber on digestion before and after the emulsion droplets microstructure and physicochemical properties of varies, and depends on the fiber type and concentration: 0.1-0.4% shell chitosan can make the emulsion droplet average particle size from 0.206 m increased to 170-240 m; low concentration of sodium alginate (0.1-0.2 wt%) on the particle size effect is not obvious, but the high concentration group (0.4%) the average particle size of the emulsion is increased to about 54 mu m; locust gum (0.1-0.4 wt %) can induce the emulsion droplets to form flocs (diameter of about 1 to 11 m). Through PSD, zeta potential and laser confocal images can be inferred: (1) low concentration of sodium alginate and locust gum induced emulsion droplet flocculation or aggregation principle for emptying effect, and the internal force is relatively weak. So the structure is not stable; (2) a high concentration of sodium alginate with calcium binding to artificial intestinal juice in the formation of gel system, and can be embedded in the emulsion part of fat droplets; (3) and positively charged chitosan is caused by electrostatic droplet aggregation bridge even, and the relative structure compact.2. by recording with NaOH titration solution in the titration of oil emulsion digestion products consumed by FFAs (0.1 M), can be calculated by the release of the FFAs oil emulsion digestion for initial milk samples in total TAG ratio, and then obtain the dynamic curve of oil emulsion reflect digested. When the emulsion contains a Low concentration (0.1-0.2 wt%) of dietary fiber, initial free fatty acid release rate as follows: control group group group is about locust gum sodium alginate chitosan group, but all final fat digestibility (= 82%-88%) had no significant difference (P0.05). When the concentration of dietary fiber levels increased to 0.4 wt% when sodium alginate and chitosan significantly inhibited the lipid emulsion process of digestion, fat digestion rate and extent of control group is as follows: Locust gum group (about 83%-87%) chitosan group (= 72%) group (.3. = 60%) of sodium alginate is limited to 1 h, in the FFAs release 13 data points in the digestion curve, 8 take the sample points in the first 10 min later, every 10 min from 1 samples. The data were analyzed by LOS, according to R2 for the best linear regression equation. The results showed that different types and levels of dietary fiber digestion effect of emulsion oil potential reaction dynamics There are also differences: physical differences between one order and two order reaction dynamic curve with different oil emulsion digestion of dietary fiber, there is a single or two pseudo first-order reaction rate constant, its size depends on the type of dietary fiber and the concentration level of.4. in multiple GIT digestion model, multi - emulsion before regulation of digestion the sugar in the mixed solution of dietary fiber concentration to 1.6wt%, with the intestinal dietary fiber made of single-stage and multi-stage GIT model was consistent (0.4 wt%). By comparing the digestion rate and the pseudo first-order reaction rate constant, get the following conclusion: sodium alginate fat digestion in the single stage GIT model in the rate is about 60%. In the multilevel GIT model is improved by 23%; chitosan group in single stage GIT model the digestion rate is about 72%, the multilevel GIT model after treatment digestion rate increased to 83%; control group and LBG group in milk samples in the GIT model did not significantly improve the multi-level (P0. 05). Analysis of the pseudo first order reaction rate constant can be inferred: pretreatment of emulsion polysaccharide in the mixed solution of artificial saliva and gastric juice digestion multistage GIT model, can change the oil with lipase combining with the specific surface area and interface characteristics, and then improve the digestibility of fat emulsion. In conclusion, we propose the design criteria: the type and concentration level control of dietary fiber, the physicochemical properties of the emulsion droplets can be controlled in the gastrointestinal tract (particle size, zeta potential, viscosity) and micro structure, can effectively control the specific emulsion polysaccharide structure in the gastrointestinal tract of the fat digestion rate and extent. At the same time, through standardization the single stage and multistage digestion model delivery system for functional screening of emulsion feed or food grade

【学位授予单位】：西北农林科技大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：S816

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