微生物脂肪酶催化合成中长链脂肪酸结构脂的研究进展

中长链脂肪酸结构脂(medium-and long-chain triacylglycerol, MLCT)是一种根据脂质在体内消化和吸收特点所设计的一种特殊结构脂质，由天然油脂改性而来，甘油分子上同时结合着中链与长链脂肪酸，因其具有独特的代谢方式与特殊的生理功能，在食品与医药方面展现出丰富的应用潜力。针对酶促合成MLCT的生物催化剂(固定化微生物脂肪酶)、合成方法、MLCT的生理功能及应用等研究现状进行综述，并对比了各种方法的优缺点及适用方向，对MLCT的研发前景进行了展望，以期为进一步研究MLCT及其他相关功能性结构脂的开发应用提供理论指导。     

中长链脂肪酸结构脂质及其制备工艺研究进展

中长链脂肪酸结构脂质(MLCT)是指甘油骨架上同时含有长链脂肪酸和中链脂肪酸的结构甘三酯,因其在人体中独特的代谢途径和在免疫系统中所起的积极作用等优势成为油脂领域研究的热点,在食品工业和医疗行业崭露头角.本文针对MLCT的发展历程、生理功效、制备工艺以及实际应用等研究现状进行了综述,以期为MLCT及其他相关功能性结构脂...     

酶法合成中长碳链甘油三酯

以椰子油和富含1,3-二油酸-2-棕榈酸甘油三酯(OPO)和1-油酸-2-棕榈酸-3-亚油酸甘油三酯(OPL)的油脂为原料,NS40086脂肪酶为催化剂,酶法合成中长碳链甘油三酯(MLCT)。确定反应体系并探究底物摩尔比、反应温度、加酶量和反应时间对产物中MLCT含量的影响,并采用分子蒸馏纯化产物。结果表明:在底物摩尔比0. 8∶1、反应温度65℃、加酶量8%、反应时间6 h、无溶剂体系条件下,产物中MLCT的含量为70. 44%;分子蒸馏后产物中甘油三酯含量达97. 22%;通过UPLC-Q-TOF-MS分析甘油三酯组成,结果表明酯交换反应生成了与人乳脂结构相似的MLCT,具有代表性的有OPLa、LPLa、OLaO、LLaO、OPCa、OMLa、LLLa、OLaLa、LLaLa等。     

Lipozyme TL IM催化合成中长链脂肪酸甘油三酯的工艺优化

为探索高含量中长链脂肪酸甘油三酯(MLCT)和低成本的酶法催化合成MLCT工艺,以一级菜籽油为原料,采用脂肪酶Lipozyme TL IM酶法催化酯交换合成MLCT,采用单因素试验研究了底物配比(菜籽油与中链甘油三酯质量比)、反应时间、反应温度、酶添加量对酯交换反应的影响,在此基础上,通过正交试验对MLCT合成工艺条件进行优化。结果表明,最佳的MLCT合成工艺条件为底物配比3∶1、反应时间4 h、反应温度50℃、酶添加量8%(基于底物的质量),在此条件下MLCT含量达到87.50%。优化的MLCT合成工艺具有MLCT含量高,反应时间短、反应温度低的优势,可降低能耗及减少酶失活,从而降低了生产成本。     

母乳中长链甘油三酯研究进展

母乳中甘油三酯的结构对于婴幼儿的脂肪消化吸收具有重要影响。作者所在团队前期研究结果显示,母乳脂肪天然富含中长链甘油三酯（MLCT）,是母乳中含量最丰富的一类甘油三酯,其质量约占总甘油三酯的30%,主要结构是一个中链脂肪酸和两个长链脂肪酸构成的单中链型甘油三酯（MLL）。母乳中几乎不含中链甘油三酯（MCT）。作者综述了母乳脂肪中MLCT的含量、组成、影响因素以及母乳与婴幼儿配方奶粉中甘油三酯的差异,总结了MLCT的消化特性,以及MLCT型母乳替代脂的研究进展,为新型配方奶粉脂肪的开发提供理论依据。     

月桂酸酸解棕榈硬脂合成中长链脂肪酸甘油三酯的工艺优化及其理化性质分析

为制得富含月桂酸的MLM型中长链脂肪酸甘油三酯（MLCT）,以月桂酸酸解棕榈硬脂合成富含1,3-二月桂酸-2-棕榈酸甘油三酯（LaPLa）的MLCT。以LaPLa含量为指标,比较了固定化脂肪酶AO IM、RM IM、TL IM的催化性能,同时对反应温度、酶载量、底物摩尔比、反应时间进行优化,对合成的MLCT的理化性质进行了测定。结果表明,固定化脂肪酶AO IM具有良好的催化性能,在反应温度65 ℃、底物(棕榈硬脂与月桂酸)摩尔比1∶ 10、酶载量10％、反应时间2.5 h的条件下,LaPLa含量可达到40.59％。与棕榈硬脂相比,纯化后的MLCT酸价(KOH)（0.19 mg/g）降低,过氧化值(4.85 mmol/kg)升高,碘值(I)（37.35 g/100 g）降低,结晶起始温度（17.58 ℃）和熔融起始温度（23.97 ℃）都有所降低。该MLCT具有潜在的结构和功能优势,为开发新型MLCT提供了研究思路。     

基于核桃油的中长链甘油三酯的酶法制备及纯化北大核心CSCD

利用脂肪酶催化中链甘油三酯(MCT)与核桃油发生酯交换反应,利用分子蒸馏脱除产物中的游离脂肪酸(FAA),再用乙醇萃取MCT制备高含量中长链甘油三酯(MLCT)的结构脂产品。对酶催化酯交换反应条件进行优化,对乙醇萃取条件进行优化,并对结构脂产品的脂肪酸组成及分布进行测定。结果表明:最佳酯交换反应条件为以Novozym 435为催化用酶,加酶量10%、MCT与核桃油摩尔比2∶1、反应温度55℃、反应时间9 h,在此条件下反应并通过分子蒸馏脱除FAA后所得产品的MLCT含量为76.2%,MCT含量为14.3%,长链甘油三酯(LCT)含量为9.5%;最佳乙醇萃取条件为乙醇体积分数85%、底物(分子蒸馏脱除游离脂肪酸后产物)与乙醇溶液的比例1∶3,在最佳条件下所得产品的MLCT含量为85.4%,MCT含量为3.7%,LCT含量为10.8%,产品得率为80.8%。制备的产品中MLCT含量高,富含亚油酸与亚麻酸,其含量比值为5.8,可作为消化系统缺陷患者补充必需脂肪酸的油脂来源。     

中长链甘油三酯对大鼠肝脏脂质代谢的调节作用

为研究中长链甘油三酯(MLCT)在短期内对大鼠肝脏脂质组成及脂代谢的影响,选取雄性SD大鼠随机分为空白对照组、中长链甘油三酯组(MLCT组)、中链甘油三酯组(MCT组)、高油酸菜籽油组(HORO组),每日以1g/100g体重的剂量灌胃相应脂质2周。结果显示:与HORO组相比,MLCT显著降低大鼠血浆中甘油三酯(TG)和总胆固醇(TC)的含量,且降低低密度脂蛋白胆固醇(LDL-C)的含量;MLCT显著抑制大鼠肝脏质量的增加,降低肝脏中TC、TG含量,使载脂蛋白A1/载脂蛋白B比值显著性升高。各组大鼠肝脏中甘油三酯、磷脂(PL)的脂肪酸组成变化显著,说明摄入不同脂质可导致肝脏脂肪酸组成的改变。MCT组大鼠肝脏中激素敏感性脂肪酶(HSL)、环磷酸腺苷(cAMP)和蛋白激酶A(PKA)水平最高,脂肪甘油三酯脂酶(ATGL)水平最低。相反,HORO组的HSL、cAMP和PKA水平最低,而ATGL水平最高。MLCT组上述脂质代谢相关酶水平均介于MCT、HORO组之间,且均高于对照组。本研究表明,MLCT在2周内可有效改善大鼠体内脂质代谢,提高肝脏中脂质代谢的效率,从而降低脂代谢以及相关疾病的发生风险。     

天然油脂抗氧化剂及其产业化应用研究进展

动植物油脂是食品工业中应用极为广泛的一类调味品配料,而油脂氧化是影响食用油脂品质的重要问题之一,天然抗氧化剂对预防油脂氧化效果显著。对近年来天然油脂抗氧化剂的研究进行了总结与综述,重点阐述了天然抗氧化剂的种类、抗氧化机理及在各类油脂中的应用效果,旨在为抗氧化剂在油脂产业化中的应用提供理论指导。     

硅胶柱层析精制中长链结构甘油三酯

为探究硅胶柱层析在中长链结构甘油三酯（MLCT）精制方面的应用,以亚麻籽油和中链脂肪酸甘油三酯为原料合成MLCT粗产品,采用硅胶柱层析进行精制,优化精制工艺条件并对硅胶柱层析精制前后MLCT的质量指标进行了测定。通过硅胶薄层层析确定硅胶柱层析的洗脱剂,通过洗脱曲线确定洗脱液收集体积,以甘二酯脱除率和产品回收率为评价指标,确定洗脱流速和上样量。结果表明：以正己烷-无水乙醚（体积比5∶ 1）为洗脱剂,等梯度洗脱,洗脱流速2.0 mL/min,上样量4 g,硅胶40 g,收集洗脱液500 mL条件下对MLCT粗产品进行精制,所得产品甘二酯脱除率达到99.40%,MLCT回收率为95.07%。精制后产品酸值（KOH）和过氧化值显著降低,分别为0.04 mg/g和0.00 g/100 g,色泽变浅,色值为R0.0,Y0.1。硅胶柱层析具有同时脱除副产物,降低酸值、过氧化值、脱色等综合效果,在MLCT精制方面有良好的应用前景。     

Enzymatic Synthesis of Medium- and Long-Chain Triacylglycerols (MLCT): Optimization of Process Parameters Using Response Surface Methodology

The main objective of this study was to understand the effects and relationship amongst four factors, which are reaction temperature, reaction time, enzyme load, and substrate mole ratio with the purpose of producing healthy functional cooking oil for long-term dietary treatment. Lipozyme RM IM lipase-catalyzed esterification of medium- and long-chain triacylglycerols (MLCT) from glycerol and mixtures of capric and oleic acid was optimized using response surface methodology (RSM) with a five-level, four-factorial design. Reaction temperature, reaction time, and substrate mole ratio strongly affected MLCT synthesis (P < 0.01). However, enzyme load did not have a significant (P > 0.01) effect on MLCT yield. Comparison between predicted and experimental value from central composite rotatable design optimization procedures revealed good correlation, implying that the reduced cubic polynomial model with backward elimination statistically expressed the percent MLCT yield obtained. The optimum MLCT yield was 59.76% by using 10 wt% enzyme load, reaction temperature of 70°C, reaction time of 14 h, and substrate mole ratio of 3.5:1. Experiments to confirm the predicted results using the optimal parameters showed an MLCT yield of 56.35% (n = 2). The choice on the types of fatty acids used in MLCT optimization work greatly influenced the physical and chemical properties of MLCT oil produced. The refined MLCT oil characteristics study showed this oil is suitable to be used for cooking/frying purposes as a high-value added product.     

Deep Frying Performance of Enzymatically Synthesized Palm-Based Medium- and Long-Chain Triacylglycerols (MLCT) Oil Blends

The main aim of this work was to assess the frying strength of the enzymatically synthesized palm-based medium- and long-chain triacylglycerols (MLCT) oil with the aid of different antioxidants under deep-frying conditions. Palm-based MLCT oil in the presence of synthetic or natural antioxidants showed significantly better (P < 0.05) thermal resistance and oxidative strength than refined, bleached, and deodorized (RBD) palm olein throughout the five consecutive days of frying. Rancimat induction period, free fatty acid content, anisidine value, E^\text1% _1\textcm E^{{\text{1\% }}} _{1{\text{cm}}} at 232 and 268 nm, color, percentage of oil uptake, and viscosity measurement can be used as oil quality parameters to indicate the degree of oil deterioration under continuous stressed frying conditions. No significant changes (P > 0.05) in the saturated/unsaturated fatty acids ratio across frying periods indicated good oxidative stability of the palm-based MLCT oil. Due to the polarity of medium- and long-chain triacylglycerols in palm-based MLCT oil, total polar compounds determination may not be a suitable oil quality measures. Sensory evaluation of fried chips showed no significant differences (P > 0.05) between chips fried in RBD palm olein and palm-based MLCT oil over the 3-month storage period.     

Oxidative stability of palm‐ and soybean‐based medium‐ and long‐chain triacylglycerol (MLCT) oil blends

BACKGROUND: Medium‐ and long‐chain triacylglyerols (MLCT) enzymatically esterified using Lipozyme RM IM lipase has very low oxidative stability as it does not contain any antioxidants. The aim of this work was to study the ability of various antioxidants to increase the oxidative stability of palm‐ and soybean‐based MLCT blends which assist to bring up the oxidative stability of both MLCT blends. In this study, the effectiveness of rosemary extracts, sage extracts, tert‐butylhydroquinone (TBHQ) and mixtures of tert‐butyl‐4‐hydroxyanisole (BHA) and tert‐butyl‐p‐hydroxytoluene (BHT) in protecting against oxidation of various MLCT blends was investigated. RESULTS: Blending of MLCT oil with either palm olein or soybean oil improved its smoke point values and oxidative stability. TBHQ addition to both palm‐ and soybean‐based MLCT blends increased oxidative stability. Combination of BHA and BHT showed no significant improvement (P > 0.05) in ability to protect blends from oxidation compared to natural antioxidants such as sage or rosemary extracts. CONCLUSION: Blended oils with 500 g kg^?1 MLCT and 500 g kg^?1 palm olein (MP5) were the most suitable for use at high temperature based on the fatty acid composition of the MLCT blends, which subsequently had an effect on thermal oxidative stability. In general, addition of either natural or synthetic antioxidant assisted in improving the antioxidative strength of both MLCT blends. MLCT blends with added TBHQ showed the highest thermal oxidative stability among the antioxidants used. Copyright © 2008 Society of Chemical Industry     

Dietary Intake of Structured Lipids with Different Contents of Medium‐Chain Fatty Acids on Obesity Prevention in C57BL/6J Mice

Three medium‐ and long‐chain triacylglycerols (MLCT) with different contents of medium‐chain fatty acids (MCFA) (10% to 30%, w/w) were prepared and evaluated for their anti‐obesity potential in C57BL/6J mice. The group fed with a high fat diet of MLCT containing 30% (w/w) MCFA showed significantly decreased body weight and fat mass (P < 0.05) relative to the control mice fed an obesity‐inducing high fat rapeseed oil diet. In addition, serum parameters including triacylglycerols, total cholesterol, glucose, high‐density lipoprotein cholesterol, low‐density lipoprotein cholesterol, apolipoprotein A1 and apolipoprotein B in the treatment group fed with 30% (w/w) MCFA were close to those of mice fed with a low fat rapeseed oil diet, but significantly different (P < 0.05) from those of the obesity control group. Moreover, the intake of MLCT with high content of MCFA reduced the size of adipocytes. In addition, the visceral fat and liver weights, as well as the liver triacylglycerol for 3 treatment groups were lower than those of the obesity control group. These results demonstrate the great potential of MLCT with high content of MCFA in weight loss.     

Chemical transesterification of flaxseed oil and medium-chain triacylglycerols: MLCT yield,DAG content,physicochemical properties,minor compounds and oxidation stability

A type of medium- and long-chain triacylglycerols (MLCT) rich in α-linolenic acid (ALA) was produced by chemical transesterification of medium-chain triacylglycerols (MCT) and flaxseed oils. Under the optimal substrate conditions of 60%, catalyst loading of 0.3% at 60 °C for 15 min, the product contained MLCT (74.06%), ALA (37.26%) and diacylglycerol (DAG) (11.25%). After that, changes in fatty acid (FA) composition, physicochemical properties and minor compounds after chemical transesterification (CTE) were investigated. The correlations analysis results of these factors on oxidative stability showed these factors could be divided into positive and negative groups. Although DAG appears to be beneficial in slowing down oil oxidation, it is critical to avoid its mass production because it would decrease MLCT.     

HPLC-ELSD和GC-FID测定中长链甘油三酯含量比较研究

采用间接法定量,建立了HPLC-ELSD外标法和GC-FID内标法测定中长链甘油三酯含量的方法,并对两种方法进行比较。结果表明:两种方法在各自的质量浓度范围内均具有良好的线性关系,HPLC-ELSD外标法测定辛癸酸甘油酯和大豆油的平均加标回收率分别为101.0%和99.5%,RSD分别为1.58%和1.62%,得到酯交换产物中中长链甘油三酯含量为72.8%±0.80%;GC-FID内标法测定辛癸酸甘油酯和大豆油的平均加标回收率分别为99.4%和99.6%,RSD分别为1.24%和2.03%,得到酯交换产物中中长链甘油三酯含量为72.5%±0.84%。说明两种分析方法均具有良好的精密度和重复性。HPLC-ELSD外标法的分析时间为43 min,GC-FID内标法分析时间仅需12.7 min。     

Physicochemical Properties and Sensory Attributes of Medium- and Long-Chain Triacylglycerols (MLCT)-Enriched Bakery Shortening

Six binary formulations of medium- and long-chain triacylglycerols (MLCT) fat and palm stearin and four ternary formulations of MLCT fat, palm stearin, and palm olein were produced. MLCT fat and palm stearin were mixed in ranges of 40–90% with 10% increments (w/w), while for the ternary formulations, 10% and 20% palm olein were substituted to palm stearin in MS 46 and MS 55 formulations. The solid fat content (SFC) by pulsed nuclear magnetic resonance and heating profiles using differential scanning calorimeter of these formulations were determined. Results obtained from SFC and heating profiles found that all the formulations melted completely at 55 °C. The high complete melting temperature is due to the stearic acid content in MLCT fat. Generally, increasing % MLCT fat (40–90%) in the formulations lowers the SFC curves at the measured temperatures (0–60 °C). The binary samples of MS 73, MS 82, and MS 91 showed SFC between 15% and 25% at room temperature (25 °C), which indicated that these formulations were suitable for shortening production. As the production cost of MLCT fat is high (approximately USD 3/kg), an attempt to reduce the proportion of MLCT fat in the shortening formulations was done by developing the ternary formulations. Shortenings formulated with 40:40:20 (MSO 442), 50:40:10 (MSO 541), and 50:30:20 (MSO 532) of MLCT fat/palm stearin/palm olein formulations had similar SFC% at 25 °C, and they were subsequently chosen to produce shortening. Using multivariate analysis, taste attribute showed positively and highly correlated to the melting temperature and SFC at 25 °C of the MLCT-enriched shortenings. In acceptance test, high correlation (R ² = 0.98) was only found on cakes made from MSO 442 and MSO 541 shortenings. Both untrained and trained panelists rated the Madeira cakes made from MSO 532 shortening the highest for overall acceptability.