复合界面对食品乳液中脂肪消化的影响

以中链甘油三酯为油相制备乳液,将天然高分子与小分子表面活性剂复配,构建阿拉伯胶(gum arabic,GA)或乳清分离蛋白(whey protein isolate,WPI)与吐温80(T80)的复合乳液界面。采用逐层添加或混合添加的方式,调控界面组分的吸附次序,构建不同界面结构的乳液体系。采用体外模拟小肠消化模型和界面流变技术等手段剖析乳液界面结构对脂肪消化速率的影响。结果表明:对于GA、WPI和T80形成的单一乳液体系,GA和WPI的界面弹性模量高于T80界面,黏弹性好。三者抗胆盐取代和延缓脂肪消化能力依次为GAWPIT80。在大分子GA或WPI与小分子T80形成的复合乳液体系中,由T80吸附占主导的界面,其延缓脂肪消化和界面抗胆盐取代的能力优于GA或WPI与T80共同吸附的界面结构。     

Investigating the effect of surfactants on lipase interfacial behaviour in the presence of bile salts

It is known that non-ionic surfactants and phospholipids provide large protection in emulsions against lipase-induced destabilization as compared to proteins, even in the presence of bile salts. In relation to this, the aim of this study is to probe the ability of two surfactants of industrial interest, poloxamer Pluronic F68 (non-ionic) and Epikuron 145V (phospholipid), to modify the adsorption of lipases at an oil–water interface under the physiological conditions existing in the duodenum. We have designed an experimental procedure by means of a pendant drop film balance equipped with a subphase exchange technique, which allows sequential adsorption of the compounds. This allows the investigation of the interfacial behaviour of lipase in the presence and absence of surfactant. According to this experimental approach, the lipase is added directly into the subphase only after the surfactant has been adsorbed onto the oil–water interface. We have used interfacial dilatational and shear rheology techniques to characterise the interfacial layers. The results suggest that Pluronic F68 reduces the interfacial activity of lipase more efficiently than Epikuron 145V. Furthermore, it seems that Pluronic F68 affects the accessibility of the lipase to the oil–water interface, even in the presence of the bile salts. These results may have applications in the development of novel strategies to rationally control lipid digestion in the diet.     

表面活性剂对T1脂肪酶活力的影响

本文研究了非离子型、阳离子型、阴离子型以及两性离子型表面活性剂对T1脂肪酶活力的影响。采用不同浓度的表面活性剂对T1脂肪酶进行处理,再以对硝基苯酚月桂酸酯作为底物,测定处理后的酶活变化。研究发现,低浓度的非离子型表面活性剂对T1都有激活作用,使其相对酶活提高50%到150%。当非离子型表面活性剂的浓度超过其临界胶束浓度,T1的活力受到不同程度的抑制,其中吐温80的抑制作用最为明显。阳离子型(CTAB)、阴离子型(N-L与SDS)和两性离子型(SB3-14)表面活性剂都对脂肪酶的酶活有强烈的抑制作用,可能是因为离子型表面活性剂的带电基团与蛋白质表面的带电氨基酸产生强烈的电荷相斥作用,导致蛋白变性而失去活力。T1脂肪酶是一类具有工业应用价值的耐热脂肪酶,研究不同类型的表面活性剂对其活力的影响,对于在不同目的下选择使用适合的表面活性剂具有重要意义。     

Fabrication,characterization and lipase digestibility of food-grade nanoemulsions

The behavior of nanoemulsion-based delivery systems within the gastrointestinal tract determines their functional performance. In this study, the influence of particle radius (30–85 nm) on the in vitro digestion of nanoemulsions containing non-ionic surfactant stabilized lipid (corn oil) droplets was examined using simulated small intestine conditions. Nanoemulsions were prepared by a combination of high-pressure homogenization and solvent (hexane) displacement. Lipid droplets with different sizes were prepared by varying the oil-to-solvent ratio in the disperse phase prior to homogenization. The fraction of free fatty acids (FFA) released from emulsified triacylglycerols (TG) during digestion was measured by an in vitro model (pH-Stat titration). Nanoemulsions exhibited a lag-period before any FFA were released, which was explained by inhibition of lipase adsorption to the oil–water interface by free surfactant. After the lag-period, the digestion rate increased with decreasing oil droplet diameter (increasing specific surface area). The total amount of FFA released from the emulsions increased from 61% to 71% as the mean droplet radius decreased from 86 nm to 30 nm. The incomplete digestion of the emulsified lipids could be explained by inhibition of lipase activity by the release of fatty acids and/or by interactions between lipase and surfactants molecules.     

膳食脂质消化行径及其影响机制研究进展

膳食脂质是肌体能量、必需营养物质和生物活性成分的重要来源或载体,其在体内的消化行径往往受到消化场所及存在形态差异的影响.本文通过对膳食脂质在胃肠道内不同阶段的消化行径进行综述,分析膳食脂质在各阶段消化过程中的变化,阐明了膳食脂质在机体代谢过程中与脂肪酶、胆盐的亲和机制,以及小肠内的微生物菌群与膳食脂质在消化吸收中的相互...     

Digestibility and β-carotene release from lipid nanodispersions depend on dispersed phase crystallinity and interfacial properties

The influence of interfacial structure and lipid physical state on colloidal stability and digestibility of solid lipid nanoparticle dispersions (SLN) and canola oil-in-water emulsions (COE) stabilized with the non-ionic surfactants Poloxamer 188 (P188) and Tween 20 (T20) were examined and the release of encapsulated β-carotene (BC) under simulated gastrointestinal conditions determined. While the SLN and COE were all stable during exposure to gastric conditions (mean diameter ～115 nm), more destabilization was observed for the COE than SLN during the duodenal phase. ζ-Potential measurements indicated rapid adsorption of bile salts (BS) and phospholipids (PL) to both solid and liquid interfaces, with greater surfactant displacement observed for the COE. Compared to the SLN, significantly more lipolysis and BC transfer to the aqueous phase was observed for both the COE-P188 and COE-T20 (p < 0.05). The properties of the colloidal structures present in the aqueous phase, which are important in terms of the uptake of lipolytic products and lipophilic bioactives, depended on non-ionic surfactant type, the extent of lipid digestion, as well as the presence of BS and PL.     

Interfacial design of protein-stabilized emulsions for optimal delivery of nutrients

Proteins are often used as ingredients in food emulsions, as their amphiphilic structures provide electrostatic and steric stabilization. Significant attention has recently been directed at understanding how the composition and structure of oil-water interfaces change during digestion and how these can be manipulated to enhance the delivery of nutrients contained within the oil droplets. These efforts have necessitated the development of more sophisticated in vitro digestion models of greater physiological relevance and increased efforts in research to identify the role of the various digestive parameters on interfacial dynamics. The changes occurring at the oil-water interface will affect the adsorption of gastro-intestinal lipases and, ultimately, affect lipid digestion. The composition of a protein-stabilized oil droplet changes continuously during digestion, because of proteolysis and the formation of peptides with different affinities for the interface. In addition, natural bio-surfactants such as phospholipids and bile salts, other surface- active molecules present in foods, and the products of lipolysis (i.e. mono and diglycerides, lysophospholipids), all compete for access to the interface, and contribute to the dynamic changes occurring on the surface of the oil droplets. A better understanding of how to tailor the composition of oil droplet surfaces in food emulsions will aid in optimizing lipid digestion and, as a result, delivery of lipophilic nutrients. This review focuses on the physico-chemical changes occurring in protein-stabilized oil-in-water emulsions during gastric and small intestine digestion, and on how interfacial engineering could lead to differences in fatty acid release and the potential bioavailability of lipophilic molecules.     

表面活性剂对大肠杆菌产L-鸟氨酸的影响

系统研究了表面活性剂种类(Tween-40、Tween-60、Tween-80、曲通-X-100(Triton X-100)、十二烷基硫酸钠(SDS)、十六烷基三甲基溴化胺(CTAB))、表面活性剂添加浓度以及表面活性剂添加时间对大肠杆菌BW25113生长和发酵产L-鸟氨酸的影响。研究结果表明,发酵0h添加浓度范围为0.1g/L 2g/L的表面活性剂时,Tween-40、Tween-60、Tween-80、Triton X-100和SDS对大肠杆菌BW25113的生长和L-鸟氨酸的产量均无影响,而CTAB对L-鸟氨酸生物合成有一定的促进作用。CTAB的作用效果因CTAB的添加浓度和添加时间的不同而有所差异。发酵8h添加与0.1g/L为CTAB最适添加时间和最佳添加浓度。在该条件下,添加CTAB对大肠杆菌BW25113发酵产L-鸟氨酸的促进作用最大,L-鸟氨酸产量可达743mg/L并且几乎不影响大肠杆菌BW25113的生长。与不添加CTAB的对照组相比,L-鸟氨酸产量提高1.25倍,发酵周期也缩短10h。     

膳食脂质肠道消化及吸收的研究进展

膳食脂质作为人类生活中一种必不可少的营养物质来源，为机体提供所需的必需脂肪酸和能量，维持人体正常的生理活动，其中肠道作为脂质最主要的消化场所及特定吸收场所，发挥了重要的作用。该研究在基于脂质肠道消化途径的基础上，从脂质自身形态、蛋白质与脂质相互作用下的形态、脂质构型变化、胆汁盐分泌、胰脂肪酶以及共脂肪酶等多角度论述了影响脂质肠道消化的主要因素，分析了影响脂质消化关键行为的界面作用，从转运因子调节、分子吸收路径以及肠道微生物间接调控吸收三个方面阐述了膳食脂质的肠道吸收机制，为深入开展膳食脂质的功能化修饰、高值化利用、创新性研发提供了理论依据。     

Factors affecting lipase digestibility of emulsified lipids using an in vitro digestion model: Proposal for a standardised pH-stat method

The control of lipid digestibility within the human gastrointestinal tract is important for the development of many functional food and pharmaceutical products. The influence of product composition and microstructure on lipid digestibility is typically studied using in vitro digestion methods. This article focuses on the impact of various experimental factors on lipid digestion in oil-in-water emulsions, using a pH-stat method that simulates the small intestine. The rate and extent of lipid digestion were found to increase with: increasing lipase (from 0 to 4.8 mg/ml), decreasing bile extract (from 20 to 0 mg/ml), increasing CaCl₂ (from 0 to 20 mM), decreasing lipid (from 2.5 to 0.1 wt.%); decreasing droplet diameter (from d = 800 to 200 nm), and decreasing fatty acid molecular weight (medium chain triglycerides versus corn oil). These affects are interpreted in terms of the surface area of lipid exposed to the aqueous phase, and factors affecting the accumulation of reaction products (fatty acids) at the oil–water interface. Based on our own and others’ work, we propose a standardised in vitro digestion model to test emulsified lipids, based on pH-stat titration. This study has important implications for designing and testing delivery systems that control lipid digestion using the pH-stat method.