乳脂肪球膜的特性、开发及在模拟母乳脂肪球结构中的应用

乳脂肪球膜（milk fat globule membrane,MFGM）是包裹在天然乳脂肪球外部的3 层膜状结构,然而牛乳基和大豆基婴儿配方奶粉缺少MFGM,脂肪球结构与母乳存在较大差异,因此添加外源MFGM以及制备与母乳脂肪球结构接近的婴儿配方奶粉成为了近期的研究焦点。本文综述了MFGM的相关特性和生产开发途径,以及牛乳MFGM在仿母乳脂肪球结构乳液和婴儿配方奶粉中的应用。体外模拟婴儿胃肠道消化实验以及啮齿动物体内实验结果表明,仿母乳脂肪球结构乳液和婴儿配方奶粉能够促进婴儿脂肪消化并且改善脂质代谢过程。     

人乳与市售婴儿配方乳粉脂质比较研究

目的 研究不同市售婴儿配方乳粉中脂质的结构、含量和组成特征,并将其与人乳对比分析,为婴儿配方乳粉的改进和发展提供参考。方法 分别挑选了甲、乙(添加乳脂肪球膜)和丙3个品牌的婴儿配方乳粉,利用激光共聚焦显微镜对人乳和乳粉中的中性和极性脂质进行显微结构观察,并依靠气相色谱和拉曼光谱,分析脂肪酸组成的差异。结果 各乳粉复溶后脂质呈现球状结构,和人乳状态相似;各乳粉极性脂质碎片化存在,不同于人乳;观察到乙乳粉脂肪亮斑较少,其脂肪含量也较低,为16.3 g/100 g,其脂肪球粒径显著大于其余乳粉。在脂肪酸组成上各种乳粉和人乳也有明显不同,乙乳粉的单不饱和脂肪酸含量较为接近人乳,含有较高DHA、AA;拉曼光谱显示各乳粉脂质流动性较为接近。结论 目前市售的婴儿配方乳粉的脂质存在状态与人乳存在差异,优化脂肪球的脂质微结构,使其状态更加趋近于人乳可能是未来婴儿配方乳粉的重要方向。     

乳脂肪球膜及其配料的科学共识

目的:富含乳脂肪球膜的乳清蛋白粉是婴幼儿配方乳粉的配料之一。有关专家在综合分析乳脂肪球膜对婴幼儿营养健康作用的研究文献基础上,形成《乳脂肪球膜及其配料的科学共识》。方法:组织科技界和产业界的相关专家,通过文献检索分析与研讨的形式开展研究。结果:乳脂肪球膜是包裹在乳脂肪液滴表面,由极性脂质、胆固醇和蛋白质等组成的复杂的3层磷脂蛋白膜,而鞘磷脂和神经节苷脂为乳脂肪球膜配料的特征性指标,其安全性和耐受性在临床试验中得到证实。现有研究表明在婴幼儿配方乳粉中添加“富含乳脂肪球膜的乳清蛋白粉”,可促进婴儿大脑认知发育,增强婴儿免疫力。目前乳脂肪球膜原料生产企业尚无统一的质量标准体系,乳脂肪球膜相关配料的组分复杂,且因获得方法不同而存有较大差异。对原料和终产品的检测方法,特别是对膜蛋白的检测方法尚不成熟,应加强乳脂肪球膜配料及主要特征成分检测方法、产品质量控制、营养功能与临床研究。政府有关部门、食品科技界及产业界也应加强对乳脂肪球膜及其配料的认知,助推我国婴幼儿配方食品产业健康发展。     

母乳脂质对婴儿肠道功能影响研究进展

婴幼儿出生后免疫系统不成熟,依赖先天免疫系统进行保护,肠道是先天免疫的重要执行者.母乳提供了婴幼儿足够数量的脂质和最适宜消化吸收的脂质结构,脂质以乳脂肪球的形式存在并被乳脂肪球膜所包裹.母乳脂质的结构、组成也直接影响对婴幼儿肠道功能的调节.本文对母乳中饱和脂肪酸、长链多不饱和脂肪酸和脂肪球膜以及复合脂质在婴儿肠道发育和...     

母乳脂质的研究及其作为婴幼儿乳粉特种油脂的应用

母乳是婴幼儿喂养的黄金标准,母乳脂质的深入研究不断推进脂质代用品的发展。母乳提供了婴幼儿足够数量的脂质和最适宜消化吸收的脂质结构,这些脂质以乳脂肪球的形式存在并被乳脂肪球膜所包裹。母乳脂质的组成、结构和性质直接影响婴幼儿对脂质的消化吸收。与此相对应,母乳脂质代用品也经历了从脂肪酸组成接近向三酰基甘油结构接近的转变。本文对母乳脂质研究近年来的新进展进行了回顾,并对这些新知识如何推动脂质代用品特种油脂的发展进行了探讨。     

乳脂消化吸收及其功能研究进展

乳脂肪球是由甘油三酯为核心的小球组成,周围有三膜结构,即乳脂肪球膜。乳脂肪球膜含有复杂的脂质和蛋白质,具有营养、免疫、神经和消化功能。然而,这些功能和胃肠消化之间存在的联系及其影响乳脂胃肠消化的因素未得到充分的研究。文章综述了乳脂成分及其结构、乳脂功能特性、乳脂胃肠消化概况及其影响乳脂消化吸收的因素,旨在为婴儿配方奶粉的消化研究提供参考。     

乳脂肪球膜功能特性的研究进展

乳脂肪以脂肪球的形式存在,乳脂肪球膜是包裹在乳脂肪球周围的三层生物薄膜,具有很高的营养价值。随着食品科学研究的深入和分离技术的发展,乳脂肪球膜中的活性成分及其功能作用正在逐渐被揭示。乳脂肪球膜是含有蛋白质、磷脂、鞘脂、神经节苷脂、胆碱、唾液酸和胆固醇的混合物,这些成分是具有重要功能的食品成分,应用于配方食品生产。本文综述了乳脂肪球膜中常见的蛋白质、脂质及其生物活性,综述了近年来乳脂肪球膜及其成分在改善肠道健康、改善大脑发育、改善肥胖及相关并发症、改善老年人虚弱、抗癌、抗氧化和缓解疲劳等方面的体内研究和临床研究进展,并讨论了其可能的作用机制,以期为乳脂肪球膜配料的研发及其在配方食品中的应用提供借鉴和参考。     

乳脂球膜中的营养成分在婴儿健康和发育中的作用

乳脂球(MFG)是哺乳动物腺分泌的,由三酰基甘油核心组成,周围是一个三重膜结构,即乳脂球膜(MFGM)。MFGM由复杂的蛋白混合物、脂质、维生素和矿物质等构成。据报道,MFGM可以促进大脑发育,保障人体免疫功能,促进肠道微生物生长等诸多积极影响。现如今,随着生产技术的不断创新,MFGM中的一些生物活性蛋白质和脂质可以通过纯化的方式富集,并添加到婴幼儿配方奶粉中,使其营养成分更加接近母乳,从而为许多无法直接以母乳喂养婴幼儿的母亲提供选择。本文综述乳脂肪球及乳脂肪球膜的主要成分、来源、功能及其对婴幼儿健康的影响研究,为缩小配方奶粉与婴幼儿营养需求的差异提供科学参考。     

不同脂肪来源婴儿配方乳粉与母乳脂质组成的差异分析

研究4 种不同脂肪来源的婴儿配方乳粉与母乳在总脂肪酸、sn-2位脂肪酸及甘油三酯上的脂质组成差异。结果表明,从样品中共检测出27 种脂肪酸及87 种甘油三酯,与母乳相比,4 种婴儿配方乳粉含有更多的饱和脂肪酸,较少的多不饱和脂肪酸,且母乳中超过70%的饱和脂肪酸酯化在甘油三酯的sn-2位,而4 种婴儿配方乳粉甘油三酯sn-2位更多的被不饱和脂肪酸占据,尤其是植物油基IF1和IF2,sn-2位不饱和脂肪酸高达80%。在甘油三酯组成方面,母乳中1-油酸-2-棕榈酸-3-亚油酸甘油三酯、1,3-二油酸-2-棕榈酸甘油三酯及一些中长链甘油三酯显著高于4 种婴儿配方乳粉（P＜0.05）,而婴儿配方乳粉含有更多的三油酸甘油三酯、1-油酸-2,3-二亚油酸甘油三酯及一些中链甘油三酯（P＜0.05）,并且脂肪来源的不同会显著影响婴儿配方乳粉的脂质组成,同为植物油基的IF1和IF2具有更相似的甘油三酯、脂肪酸组成及分布,并与添加了乳脂成分的IF3和IF4形成明显区分,且牛乳/植物油混合基婴儿配方乳粉在整体脂质组成上更加接近母乳。最后,基于多变量分析,发现共有16 种甘油三酯可用于区分人乳和婴儿配方奶粉。本研究结果有助于研发更接近人乳的婴儿配方乳粉。     

基于荧光漂白恢复技术检测乳脂肪球膜上生物分子的流动性北大核心CSCD

为了推动乳制品的精准评价,采用高分辨率激光共聚焦显微镜(CLSM)结合多荧光探针技术观察乳脂肪球的微观结构,并利用荧光漂白恢复技术(fluorescence recovery after photobleaching, FRAP)定量检测母乳、牛乳、羊乳中乳脂肪球膜上生物分子的流动性。结果表明:3种乳的微观结构基本一致,均出现了新月区,证明了新月区是局部磷脂富集区;乳脂肪球中甘油三酯和水溶性蛋白质的动态分子比例较高,极性脂质和磷脂酰胆碱的动态分子比例较为接近,鞘磷脂的动态分子比例最差;牛乳中甘油三酯的流动性慢于母乳和羊乳,母乳中极性脂的流动性最慢。FRAP可以直观地表征乳脂肪球膜上生物分子的流动性,可为乳状液中膜界面的生化特性研究提供新的方法。     

乳脂肪球膜的组成、营养及制备研究进展

乳中的脂肪以乳化的脂肪球形态分散于水相中,脂肪球被三层脂肪球膜包裹,近年来的研究表明脂肪球膜中的成分对婴幼儿的生长发育有至关重要的作用。本文介绍了乳脂肪球膜特别是其磷脂的组成及含量,添加入婴幼儿配方奶粉中乳脂肪球膜的营养作用,以及目前市售的富含脂肪球膜的产品及制备方式,为缩小配方奶与婴幼儿营养需求的差异提供科学依据。     

Efficient in vitro digestion of lipids and proteins in bovine milk fat globule membrane ingredient (MFGMi) and whey-casein infant formula with added MFGMi

The relative immaturity of the infant digestive system has the potential to affect the bioavailability of dietary lipids, proteins, and their digested products. We performed a lipidomic analysis of a commercial bovine milk fat globule membrane ingredient (MFGMi) and determined the profile of lipids and proteins in the bioaccessible fraction after in vitro digestion of both the ingredient and whey-casein-based infant formula without and with MFGMi. Test materials were digested using a static 2-phase in vitro model, with conditions simulating those in the infant gut. The extent of digestion and the bioaccessibility of various classes of neutral and polar lipids were monitored by measuring a wide targeted lipid profile using direct infusion–mass spectrometry. Digestion of abundant proteins in the ingredient and whey–casein infant formula containing the ingredient was determined by denaturing PAGE with imaging of Coomassie Brilliant Blue stained bands. Cholesterol esters, diacylglycerides, triacylglycerides, phosphatidylcholines, and phosphatidylethanolamines in MFGMi were hydrolyzed readily during in vitro digestion, which resulted in marked increases in the amounts of free fatty acids and lyso-phospholipids in the bioaccessible fraction. In contrast, sphingomyelins, ceramides, and gangliosides were largely resistant to simulated digestion. Proteins in MFGMi and the infant formulas also were hydrolyzed efficiently. The results suggest that neutral lipids, cholesterol esters, phospholipids, and proteins in MFGMi are digested efficiently during conditions that simulate the prandial lumen of the stomach and small intestine of infants. Also, supplementation of whey-casein-based infant formula with MFGMi did not appear to alter the profiles of lipids and proteins in the bioaccessible fraction after digestion.     

Analysis of major proteins and fat fractions associated with mare's milk fat globules

Although several studies have aimed to identify mare's milk proteins, only the major whey proteins and some caseins have yet been characterized. Incomplete sequencing of the equine genome and the difficulty of recovering highly hydrophobic proteins mean that little is known to date about the proteins associated with milk fat globules, which have been shown to play an important role in newborns' defense mechanisms. The fat fraction, in particular the distribution of unsaturated fatty acids, has been more extensively studied, but complex lipids are only partially elucidated. This study reports a 2-DE approach combined with a powerful method for de novo protein sequencing, and quali-quantitative data on complex lipid composition determined by high performance TLC (HPTLC) and GC. The presence in mare's milk of long-chain highly unsaturated fatty acids, and the evidence of close similarity between equine and human milk fat globule membrane proteins, support the use of mare's milk for human nutrition.     

Symposium review: The relevance of bovine milk phospholipids in human nutrition—Evidence of the effect on infant gut and brain development

This paper reflects the concepts reviewed during the presentation in the Joint MILK/Lactation Biology Symposium at the ADSA 2018 Annual Meeting. Our intention is to update the concepts and advances in the area of research regarding milk phospholipids or polar lipid fraction as part of a dairy ingredient used today in nutritional studies that focus on gut health as well as brain development of infants. Although processing advances have allowed the production of novel ingredients rich in milk fat globule membrane (MFGM) components, mostly monitored by phospholipid concentration and presence of membrane proteins, there is wide variability in their composition and structure. Furthermore, we aimed to include in the phospholipid fraction of milk nanovesicles designated as milk exosomes, which are secreted into milk by different secretion mechanisms than those of the fat globules but are also made up of a unique mixture of polar lipids. We consider imperative the study of polar lipid-derived structures from milk regarding composition and structure to gain insights into their biological effect in human health. Nevertheless, and tolerating the differences in composition and concentration of their components, studies supplementing the diet of infants with polar lipids (i.e., MFGM components) have shown significant advances in several areas of human health and well-being. Here we present a summary of the important components of MFGM and milk exosomes as well as an overview of the effects on gut health and brain and cognitive development when added to the diet of infants.     

Symposium review: Fat globules in milk and their structural modifications during gastrointestinal digestion

The fat globules in milk are unique oil droplets that are stabilized by a specific and structurally complex membrane, the milk fat globule membrane (MFGM). In the last decade, excellent progress has been made on studying the structure of the milk fat globules and the MFGM and how common processing treatments affect these structures to deliver dairy products with improved functional properties. Although the digestion of milk fat to deliver energy and lipid-soluble nutrients is essential for survival of the neonate, there is little understanding of the complex processes involved. The structural alterations to fat globules during gastrointestinal processing affect the way in which milk fat is digested, absorbed, and metabolized. The packaging of these globules within the MFGM or in other forms may affect the bioaccessibility of raw or processed milk fat globules; in turn, this may affect access of the gastrointestinal enzymes to the globules and, therefore, may influence the rate and extent of lipid digestion. This review focuses on recent advances in understanding milk fat globules during gastrointestinal digestion, including the effects of processing on their bioavailability and the kinetics of lipid digestion. Possible effects of the dairy matrix on lipid digestion and physiological responses are briefly described.     

Composition of milk fat from cows selected for milk fat globule size and offered either fresh pasture or a corn silage-based diet

The objective of this study was to examine the synthesis and composition of milk produced by dairy cows that secrete either small milk fat globules (SMFG) or large milk fat globules (LMFG), and to study their response to diets known to alter milk composition. Four groups of 3 multiparous dairy cows were assigned to 2 isoenergetic feeding treatments: a corn silage treatment supplemented with soybean meal, and fresh pasture supplemented with cereal concentrate. The 4 groups comprised 2 groups of 3 dairy cows that produced SMFG (3.44 μm) and 2 groups of 3 dairy cows that produced LMFG (4.53 μm). The SMFG dairy cows produced higher yields of milk, protein, and calcium. Nevertheless, their milk had lower fat and protein contents. Both SMFG and LMFG cows secreted similar amounts of milk fat; therefore, higher globule membrane contents in milk fat were observed in SMFG cows. Higher calcium mineralization of the casein micelles in SMFG cows suggests that it may be possible to improve cheese-making properties even if the lower protein content may lead to lower cheese yields. The SMFG cows secrete milk fat with a higher concentration of monounsaturated fatty acids and a lower concentration of short-chain fatty acids. They also have a higher C18:1/C18:0 ratio than LMFG cows. This suggests that SMFG cows have more significant fatty acid elongation and desaturation. The pasture treatment led to an increase in milk and protein yields because of increased energy intake. It also resulted in lower milk fat yield and fat and protein contents. The pasture treatment led to a decrease in milk fat globule size and, as expected, an increase in monounsaturated and polyunsaturated fatty acid contents. However, it induced a decrease in the protein content, and in calcium mineralization of casein micelles, which suggests that this type of milk would be less suitable for making cheese. This study also shows that there is no correlation between the cows, based on milk fat globule size and diet. These results open up possibilities for improving milk fat quality based on milk fat globule size, and composition. The mechanisms involved in milk fat globule secretion are still to be determined.     

Major proteins of the goat milk fat globule membrane

Fat is present in milk as droplets of triglycerides surrounded by a complex membrane derived from the mammary epithelial cell called milk fat globule membrane (MFGM). Although numerous studies have been published on human or bovine MFGM proteins, to date few studies exist on MFGM proteins from goat milk. The objective of this study was thus to investigate the protein composition of the goat MFGM. Milk fat globule membrane proteins from goat milk were separated by 6% and 10% sodium dodecyl sulfate-PAGE and were Coomassie or periodic acid-Schiff stained. Most of MFGM proteins [mucin-1, fatty acid synthase, xanthine oxidase, butyrophilin, lactadherin (MFG EGF-8, MFG-E8), and adipophilin] already described in cow milk were identified in goat milk using peptide mass fingerprinting. In addition, lectin staining provided a preliminary characterization of carbohydrate structures occurring on MFGM proteins from goat milk depending on α_S1-casein genotype and lactation stage. We provide here first evidence of the presence of O-glycans on fatty acid synthase and xanthine oxidase from goat milk. A prominent difference between the cow and the goat species was demonstrated for lactadherin. Indeed, whereas 2 polypeptide chains were easily identified by peptide mass fingerprinting matrix-assisted laser desorption/ionization-time of flight analysis within bovine MFGM proteins, lactadherin from goat milk consisted of a single polypeptide chain. Another striking observation was the presence of caseins associated with MFGM preparations from goat milk, whereas virtually no caseins were found in MFGM extracts from bovine milk. Taken together, these observations strongly support the existence of a singular secretion mode previously hypothesized in the goat.     

Factors affecting the concentration of sphingomyelin in bovine milk

Sphingomyelin is a phospholipid located in the outer leaflet of the plasma membrane of most cells and is a component of the milk fat globule membrane. Sphingomyelin and its digestion products participate in several antiproliferative pathways that may suppress oncogenesis. Although milk and dairy products are important sources of sphingomyelin in the human diet, little is known about factors that influence sphingomyelin concentrations in milk fat or whether concentrations can be modified via the nutrition of cows. Sphingomyelin concentrations were determined in milk from Holstein and Jersey cows matched for parity and stage of lactation. Sphingomyelin was more concentrated in milk fat from Holstein cows than in milk fat from Jersey cows (1,044 vs. 839 μg/g of fat). Concentrations in whole milk did not differ because of greater milk fat content for milk from Jerseys. Differences between breeds may be related to the greater fat globule size in milk from Jerseys. Sphingomyelin content in whole milk increased with increasing days in milk because of associated increases in milk fat content. Regardless of breed, primiparous cows had greater amounts of stearic acid and less palmitic acid in sphingomyelin than did older cows. The sphingomyelin concentration in milk fat of cows in a commercial Jersey herd was lower for cows in their fourth or greater parity. Sphingomyelin content in whole milk was greater for cows in late lactation because of greater milk fat content. Feed restriction of multiparous Holstein cows to 37% of ad libitum dry matter intake increased milk fat content but did not affect milk sphingomyelin content or milk fat globule size. Supplementation of the diet with 4% soybean oil did not affect milk composition, sphingomyelin content, or milk fat globule size. Milk was sampled seasonally from 7 herds throughout Illinois during a 2-yr period. Sphingomyelin concentration in milk fat was greatest during summer and least during winter, but whole milk concentrations did not vary across seasons. We conclude that 1) sphingomyelin content of milk fat is greater in milk from Holsteins than that from Jerseys, 2) sphingomyelin content in whole milk increases with stage of lactation, and 3) sphingomyelin content of milk fat is greater during summer. However, efforts to produce milk with a greater sphingomyelin content through altering management and nutrition are unlikely to be successful.