油脂干法分提及其应用

介绍了油脂干法分提的原理和意义，着重介绍分提设备以及干法分提在棕榈油、牛脂、无水乳脂、禽脂、鱼油中的应用。     

人乳脂肪球的研究进展

人乳是婴儿最理想的食物,人乳脂肪是人乳中的重要组成,不仅是婴儿生长发育所需能量的主要来源,也提供了各种脂溶性营养物质。人乳脂肪在乳清相中并非呈完全均匀地分散,而是以人乳脂肪球的形态稳定存在。人乳脂肪球是由一个三层的膜结构包裹住中心层状排列的甘油三酯组成,这种结构不仅维持了乳液本身的稳定性,还为婴儿的生长发育提供了特有的营养学功能。近年来,这种天然而特殊的物理形态引起了学者们的广泛关注。对国内外人乳脂肪球的相关文献进行综述,主要包括人乳脂肪球的形成、组成、营养学意义以及其在加工过程中的变化,并对今后研究的方向和重点进行了展望。     

不同粒径牛乳脂肪球的鞘脂浓度比较

采集泌乳期荷斯坦奶牛乳样,并采用重力法进行分层,对不同层牛乳的粒径参数进行测量,液相色谱串联质谱对大、小粒径脂肪球的鞘脂含量进行测定。结果表明,牛乳经重力分层后的粒径有显著变化,D_[3,2]在F1层为2.25μm,F4层为2.71μm,F7层为3.97μm（P<0.05）;D_[4,3]在F1层为2.37μm,F4层为3.09μm,F7层为4.16μm（P<0.05）,其他粒径参数Dv（10）、Dv（50）和Dv（90）也呈现从F1到F7层逐渐增大的趋势,比表面积（SSA）呈现逐渐减小的变化（P<0.05）。质谱分析F1和F7层牛乳中28种鞘磷脂（SM）、5种神经酰胺（Cer）、2种鞘氨醇（SPH）和12种糖鞘脂（HexCer）,与F1层相比,F7层有23种SM、4种Cer、1种HexCer和1种SPH含量显著增加（P<0.05）。这些数据表明乳脂肪球粒径的大小影响了鞘磷脂含量。     

缩短棕榈油干法分提结晶时间的探索与应用

对棕榈油干法分提工艺进行了改进,将棕榈油结晶过程由不分时间段的持续降温改为分若干个时间段的快速降温、恒温、慢速降温的阶段式结晶方式,并对该改进工艺和主要设备性能进行阐述。实践表明,该改进工艺可以缩短结晶时间,降低能耗,提高生产效率,而且有利于保持产品质量的稳定。     

1,3-二油酸-2-棕榈酸甘油三酯的干法分提富集工艺优化

为提高1,3-二油酸-2-棕榈酸甘油三酯(OPO)的含量,以化学酯交换联合酶法酸解反应制备的OPO为原料,采用单因素实验和正交实验考察干法分提条件(结晶温度、冷却速率、养晶时间)对OPO含量及提升率、sn-2位棕榈酸(PA)占总PA含量及提升率和分提液油得率的影响,确定干法分提的最优工艺条件。结果表明,干法分提的最优工艺条件为结晶温度6℃、冷却速率4℃/h、养晶时间3 h,在此条件下OPO含量为(38.84±0.39)%,OPO含量提升率为(46.07±1.47)%,sn-2位PA占总PA含量为(91.08±0.16)%,sn-2位PA占总PA含量提升率为(47.61±0.25)%,分提液油得率为(31.26±0.34)%。综上,通过干法分提可以获得OPO纯度更高的甘油三酯。     

棕榈油干法分提的工艺实践与研究

采用干法分提工艺对棕榈油进行分提,通过实践分析了工艺中结晶设备、原料组成、冷却状况、晶体异构对冷却结晶过程的影响,研究了压滤过程中的影响因素,给出了相关的技术参数,以期为实际生产提供指导和参考.     

牛乳脂肪球膜组分分离鉴定及其功能性研究进展

乳脂肪球膜（milk fat globule membrane,MFGM）是牛乳中脂肪球外表面包裹着的一层膜,在牛乳中的含量非常微小。但由于其具有良好的生理活性以及潜在的食品加工应用潜力,关于其展开的基础研究和应用基础研究受到广泛关注。本综述介绍MFGM的分离制备技术、结构、组分鉴定分析、生理活性及其应用特性的研究进展,以期为MFGM在食品工业尤其是在功能性食品中的应用提供一定的理论支持。     

棉籽油干法分提工艺的研究

以棉籽油为原料,利用干法分提对其进行改性。考察了结晶温度、冷却速率、养晶时间及搅拌速率对棉籽固脂碘值、0℃固体脂肪含量(SFC)及固脂得率的影响。确定的最佳分提工艺条件为:结晶温度5℃,冷却速率2℃/h,养晶时间10 h,搅拌速率15 r/min。所得固脂的碘值(I)为91 g/100 g,0℃SFC为31.6%,固脂得率为12.89%。     

人乳脂中甘油三酯分析方法及组成的研究进展

人乳脂对于婴儿的生长发育有举足轻重的作用。人乳脂是甘油三酯组成最复杂的脂类,详细分析人乳脂中甘油三酯的组成是油脂领域的一大难题。介绍了人乳脂中甘油三酯的分析方法,并比较了国内外人乳脂中甘油三酯的组成。总结了泌乳时期、母亲饮食等因素对人乳脂中甘油三酯组成的影响。对于了解人乳脂的生理功能和人乳替代脂的开发具有重要意义。     

天然发酵奶味饲料香味剂的研究

研究pH值、酶解温度和酶解时间对乳脂酶发酵奶油制备天然奶香饲料香味剂的影响.在单因素实验的基础上,采用响应面法对各影响因素进行优化并采用气相色谱-质谱联用仪(GC/MS)对优化组合进行分析得出产物致香成分及含量.结果表明:在发酵时间5.5h、pH6.5、酶解温度55℃、底物质量分数80％和酶添加量3.5％条件下,发酵所得天然奶香饲料香味剂致香成分19种,主要以短链脂肪酸及酯类为主,发酵物奶味浓郁、自然、香气柔和.     

Fractionation of milk fat by short-path distillation

Fractionation of milk fat by short-path distillation changes the chemical composition and physical properties of the resulting fractions. Increases in distillation temperature from 125 to 250 degrees C increased distillate yield from 0.3 to 42.7% (wt/wt). The distillate was enriched in short- and medium-chain fatty acids and low molecular weight acylglycerols, while the retentate was enriched in long-chain saturated and unsaturated fatty acids as well as high molecular weight acylglyerols. As distillation temperature increased, dropping points of the distillate increased. Relative to native milk fat, the solid fat content (SFC) vs. temperature melting profile of the distillate was depressed and that of the retentate was augmented, which correlated with the saturated long-chain fatty acid content in the fractions. Retentate crystallization parameters obtained by fitting the Avrami model to SFC-time data, did not change as a function of distillation temperature, but varied as a function of the degree of undercooling. Changes in microstructure observed by polarized light microscopy also appeared to be solely a function of the degree of undercooling, with no observable differences between retentates obtained at the different distillation temperatures. In addition, no changes in the retentate's free energy of nucleation (deltaGc) as a function of distillation temperature were found. The compressive storage modulus of the crystallized retentate increased as a function of increasing distillation temperature.     

Effects of canola oil dilution on anhydrous milk fat crystallization and fractionation behavior

Blends of anhydrous milk fat (AMF) and canola oil (CO) were cooled from 35 to 5°C at 0.1°C/min, held for 24 h, and centrifuged to separate the liquid and crystalline fractions. The blends’ crystallization behaviors and microstructures depended on the level of CO present. Onset and half times of crystallization reflected a slower crystallization mechanism at higher levels of CO dilution. These differences were accompanied by a change in microstructure from large spherulites to smaller particles. The biggest change occurred between the 1:4 and 1:5 blends. Canola oil dilution also influenced the polymorphism of milk fat. Whereas only the β′ polymorph was observed in the crystallized 1:2 blend, the β polymorph predominated in the 1:8 blend. Some solubilization of AMF solids into CO was observed. This increased gradually with increasing CO concentration. Compositional analysis revealed the exchange of AMF and CO species between the liquid and crystalline fractions. The crystalline fractions were slightly enriched in AMF triacylglycerols, particularly with the more dilute blends (1:7 and 1:8). Large amounts of oil were trapped in the crystalline fractions, particularly for the concentrated AMF:CO blends where the β′ crystals and spherulitic microstructures were observed. Although the solid fat content profiles of the fractionated blends were marginally higher than those of the starting blends, the samples were very soft and oily. This strategy of using CO to fractionate milk fat was limited by the poor separation of solids and liquid during centrifugation.     

脂肪替代品在乳制品中的研究与应用进展

介绍了脂肪替代品的国内外研究现状,分类、特点以及研究方法,并介绍了脂肪替代品在酸奶、冰淇淋、奶酪等乳制品中的应用。     

牛乳成分测量研究

研究了牛乳脂肪大分子和分子团对632．8 nm光波的散射特性；测定了散射光强和透射光强随脂肪浓度变化的关系；推导了表达脂肪含量的公式；计算了牛乳脂肪的重要光学参量。用透射比和散透比两种方法对上述内容分别进行研究对比，取得了一致结果。     

Transfer of dietary zinc and fat to milk--evaluation of milk fat quality, milk fat precursors, and mastitis indicators

The present study demonstrated that the zinc concentration in bovine milk and blood plasma is significantly affected by the intake of saturated fat supplements. Sixteen Holstein cows were used in a 4 × 4 Latin square design with 4 periods of 12 d, and 4 dietary treatments were conducted. A total mixed ration based on corn silage, grass-clover silages, and pelleted sugar beet pulp was used on all treatments. A high de novo milk fat diet was formulated by adding rapeseed meal and molasses in the total mixed ration [39 mg of Zn/kg of dry matter (DM)], and a low de novo diet by adding saturated fat, fat-rich rapeseed cake, and corn (34 mg of Zn/kg of DM). Dietary Zn levels were increased by addition of ZnO to 83 and 80 mg of Zn/kg of DM. Treatments did not affect daily DM intake, or yield of energy-corrected milk, milk fat, or milk protein. The high de novo diet significantly increased milk fat percentage and milk content of fatty acids with chain length from C6 to C16, and decreased content of C18 and C18:1. Treatments did not influence milk free fatty acids at 4°C at 0 or 28 h after milking. The average diameter of milk fat globules was significantly greater in milk from cows offered low de novo diets. Furthermore, the low de novo diet significantly increased the concentration of nonesterified fatty acids and d-β-hydroxybutyrate in blood plasma, the latter was also increased in milk. Treatments did not affect the enzyme activity of lactate dehydrogenase and N-acetyl-β-d-glucosaminidase in milk or the activity of isocitrate dehydrogenase and malate dehydrogenase in blood plasma. The low de novo diet significantly increased plasma Zn and milk Zn content, whereas dietary Zn level did not in itself influence these parameters. This indicates that the transfer of fat from diet to milk might facilitate transfer of Zn from diet to milk.     

Major advances associated with the biosynthesis of milk

The mammary gland has an incredible level of organization and a remarkable ability to convert circulating nutrients into milk components. This review highlights four areas of high interest in the biology of milk synthesis where advances over the last quarter-century have resulted in new understanding or revealed new opportunities. First, advances in our understanding of the mechanisms of milk secretion has led to a substantial increase in our knowledge of the intracellular origin of lipid droplets and the identity and potential function of milk fat globule membrane proteins in milk-lipid secretion. Second, recent breakthroughs have advanced our understanding of the nutritional regulation of milk fat and highlighted the interrelations between dietary components, digestive processes in the rumen, and the regulation of mammary synthesis of milk fat. Third, nutritional quality is becoming increasingly important in food choices because of consumer awareness of the links between diet and health. The traditional nutritional value of milk and dairy products is well established, but recent discoveries have identified a number of “bioactive” components in milk with potential to improve human health. Finally, the concept of genetic engineering and the use of animals as “bioreactors” and the “pharming” of proteins not normally found in milk have gained recognition, with the dairy industry ideally suited to take advantage of advances in these areas.     

The linear relationship between the proportion of fresh grass in the cow diet, milk fatty acid composition, and butter properties

Fresh grass in the cow diet improves the rheological and nutritional properties of butter. However, the relationship between the proportion of fresh grass in the diet and these properties is still unknown. The objective of the study was to determine the relationship between the proportion of fresh grass in the diet and the properties of milk and butter. Four groups of 2 cows were fed 4 isoenergetic diets characterized by increasing amounts of fresh grass (0, 30, 60, and 100% dry matter of forage) according to a Youden square design. Energy levels were similar among all diets. Thus, no effect of mobilization was observed and the results were only due to the proportion of fresh grass in the diet. Milk yield linearly increased with the proportion of fresh grass in the diet (+0.21 kg/d per 10% of grass). Fat yield remained unchanged. Thus, by effect of dilution, increasing the proportion of fresh grass in the diet induced a linear decrease in fat content. Milk fat globule size decreased by 0.29 μm when the proportion of grass reached 30% in the diet. Increasing the proportion of fresh grass in the diet induced a linear increase in unsaturated fatty acids percentages at the expense of saturated fatty acids. Relationships were +0.38, +0.12, +0.05 and −0.69 points/10% of fresh grass in the diet for C18:1 trans-11, C18:2 cis-9,trans-11, C18:3n-3, and C16:0, respectively. These modifications in fatty acid composition, and in particular in the spreadability index, C16:0/C18:1, were responsible for linear decreases in final melting temperature and solid fat content in butter fat, perceived in sensory analysis by a linear decrease in firmness in mouth. The nutritional value of butter was also linearly improved by the proportion of fresh grass in the diet by halving the atherogenicity index.     

基于人乳脂肪组成的酶法人乳脂肪替代物的构建

为了开发新型高相似性人乳脂肪替代物,依据中国人乳脂肪的脂肪酸组成和甘油三酯结构,以巴沙鱼油、樟树籽仁油、亚麻籽油、微生物油(富含ARA)及DHA藻油(质量比为153.81∶15.16∶62.33∶7.89∶10.81)为原料油脂,以固定化脂肪酶Lipozyme RM为催化剂,在60℃下酯交换反应8 h制备人乳脂肪替代物,测定其脂肪酸、sn-2位脂肪酸及甘油三酯组成及含量,分析其红外光谱图、熔融性质、结晶性质及流变学性能。结果表明,构建的人乳脂肪替代物中链脂肪酸含量为12%、亚油酸和亚麻酸总含量为19.53%且比例约为1∶1.5,ARA含量为1.17%,DHA含量为1.11%,其sn-2位富含棕榈酸(43.10%),结构甘油三酯含量高(58.75%),无反式脂肪酸生成,熔融温度低于人体温度且在20℃下仍能保持18.7%的固体脂肪含量,结晶形态细腻且流变性能优异。制备的人乳脂肪替代物具有应用于婴幼儿配方奶粉、婴幼儿米糊和婴幼儿饼干等各种婴幼儿食品的潜力。     

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。