牦牛乳风味物质及影响因素研究进展

牦牛乳是一种天然浓缩乳,其因牦牛特殊的生存环境而在脂肪、蛋白质、乳糖、干物质含量等方面具有独特性,因而牦牛乳的乳香风味与其它牛乳具有较大的差异。本文对牦牛乳中主要的风味物质进行了综述,概述了牦牛乳中挥发性风味物质的提取和检测方法,并对其主要的影响因素进行了简要的总结,此外,还对牦牛乳及其产品的发展前景进行了展望,以期为富含高营养的牦牛乳制品的开发利用提供理论参考。     

甘南牦牛乳及其制品加工技术研究进展

牦牛乳是一种天然浓缩乳,其脂肪、蛋白质、乳糖、干物质等含量均高于普通牛乳,且营养价值高,易消化吸收,被广泛应用于乳品加工中,是甘南地区的特色食品。对牦牛乳的营养成分、泌乳性能及其制品加工技术进行论述,表明牦牛乳营养成分含量的差异随地区海拔、产奶月份、泌乳天数而变化;牦牛乳泌乳性能受环境系统、胎次情况、挤乳次数的影响泌乳量存在差异;科学合理的加工技术可有效提高牦牛乳产品品质。     

牦牛乳物理化学特性的研究进展

牦牛乳被称为天然的浓缩乳,是西藏高原地区人们的主要食品.着重阐述了牦牛乳的物理特性、化学特性、泌乳性能等.与牛乳、山羊乳和水牛乳的物理化学特性对比分析,牦牛乳在物理特性上牦牛乳呈现比重高,冰点低的特点.在化学特性上牦牛乳呈现脂肪、蛋白质、乳糖等干物质均高于牛乳、山羊乳,而与水牛乳相似的特点.另外,牦牛乳中含有十五碳烯酸、二十碳五烯酸、二十二碳烯酸等功能性脂肪酸,而在牛乳中却没有.因此,牦牛乳较适合制作一些高端的乳制品.但是牦牛乳制品至今仍然为传统的几种产品如曲拉、酸油等,没有得到很好的开发.为更好地开发利用牦牛乳,应对其物理化学特性进行深入的研究.     

牦牛乳成分分析

与普通牛乳相比,牦牛乳中禽有更高含量的蛋白质、脂肪,是生产高级乳制品的优质原料;牦牛乳中含有各种人体所必需的氯矮酸,含有丰富的不饱和脂肪酸和功能性脂肪酸,含有丰富的维生素和矿物质,对人体健康非常有益。本篇综述针对于牦牛乳中的各种黍要的营养成分进行了具体的分析、归纳、总结,加深人们牦牛乳成分的认识,为后人对牦牛乳的研究奠定基础。     

利用β-乳球蛋白遗传变异体检测牦牛乳中的普通牛乳

建立简便、可靠的方法检测牦牛乳中添加的普通牛乳。在牦牛乳中加入5％-30％的普通牛乳，采用等电点沉淀法制备乳清，然后用聚丙烯酰胺凝胶电泳分离乳清蛋白。根据牦牛与普通牛β-乳球蛋白遗传变异体在电泳中的迁移率差异，可检测到牦牛乳中添加的5％的普通牛乳。该法也适用于牦牛奶粉的检测，对牦牛乳制品的质量监测有实际应用价值。     

源于不同原料乳曲拉的品质分析

为了比较分析牦牛乳、犏牛乳、黑白花牛乳和利用这3种牛乳所制曲拉的品质差异,以3种牛乳及其所制曲拉为研究对象,对3种牛乳的理化性质和3种曲拉在发酵过程中p H、滴定酸度、持水力、感官品质及质构特性进行了测定分析。结果表明:3种牛乳及其所制曲拉的品质之间存在一定差异。其中,牦牛乳的干物质含量为18.30%,蛋白质含量为5.80%、脂肪含量为6.15%,显著高于犏牛乳和黑白花牛乳(p0.05);犏牛乳的乳糖含量最高,其干物质、蛋白质和脂肪含量也较高;犏牛曲拉在发酵过程中的p H、滴定酸度、持水力、感官品质及质构特性与牦牛曲拉非常相近,表明其制作曲拉的品质与牦牛曲拉类似,说明犏牛乳在一定程度上可以替代牦牛乳作为曲拉的原料乳,用以解决牦牛乳资源短缺的难题。     

高体细胞牛乳的性质及对加工的影响

阐述了高体细胞牛乳化学成分及微生物的变化，论述了产生这些变化的原因以及这些变化对乳制品加工、贮藏和销售所带来的一系列不良影响。主要表现在高体细胞牛乳中脂肪氧化酶含量升高，引起游离脂肪酸含量上升，牛乳易产生酸败味；牛孔中蛋白水解酶以及血纤维蛋白溶酶含量增加，引起乳蛋白水解，造成干酪产量下降，凝固型酸乳凝乳不坚固，UHT灭菌孔保质期缩短等质量缺陷；牛乳中盐类比例失调，使牛孔热稳定性降低，凝固型酸奶的凝乳疏松且易碎裂，乳清易析出；乳中过氧化氢酶和过氧化物酶含量升高，使产品品质不稳定，风味欠佳；牛乳中有害微生物含量增加，降低产品的食用安全性；治疗乳房炎所用的抗生素残留阻碍乳酸菌的发酵过程。这些变化都可能对乳制品的生产造成巨大损失。     

牦牛乳的研究进展

牦牛乳是由生活在高海拔地区的牛种——牦牛所产生的一种天然乳,其乳中蛋白、脂肪、乳糖及干物质含量均高于其它牛种乳汁,且富含氨基酸、钙、铁、锌、维生素等营养物质。该文主要对牦牛乳的营养成分、功效以及其主要乳制品研究现状进行阐述,以期对牦牛乳及乳制品的开发和利用提供理论参考。     

牦牛乳Halloumi奶酪工艺优化及理化特性研究

以牦牛乳与荷斯坦牛乳为原料，通过牦牛乳与荷斯坦牛乳比例、氯化钙添加量、凝乳酶添加量、凝乳温度、热烫温度做单因素试验，以产率为评价指标进行四因素三水平正交试验，即牦牛乳与荷斯坦牛乳比例、氯化钙添加量、凝乳酶添加量、热烫温度，得到Halloumi奶酪最佳生产工艺为牦牛乳与荷斯坦牛乳比例4∶1、氯化钙添加量0.04 g/100 m L、凝乳酶添加量0.003 g/100 m L、热烫温度65℃。选取圆柱探头TA3/100，夹具TA-RT-KIT,测试速度为0.5 mm/s,返回速度为0.5 mm/s,形变量为50%的参数下测得单因素试验与正交试验产品的质构。制得的Halloumi奶酪水分含量26.04%，脂肪含量38.81%,pH 7.40，蛋白质含量30.16%。     

牦牛乳及其制品中苯甲酸来源分析及影响因素研究

建立牦牛乳及其制品中马尿酸、苯甲酸的高效液相色谱检测方法,测定牦牛乳头奶、混合奶及牦牛乳制品中马尿酸、苯甲酸含量,分析牦牛乳中马尿酸、苯甲酸的含量变化关系,并同时监测包括微生物、温度、时间等影响因素。结果表明:牦牛乳中天然存在一定量的马尿酸,未检出苯甲酸。牦牛乳制品中均检出马尿酸和苯甲酸。牦牛乳储存过程中,马尿酸在微生物作用下会生物降解为苯甲酸,该过程是牦牛乳中苯甲酸的主要来源,且微生物、温度及储存时间均是影响牦牛乳中马尿酸、苯甲酸含量变化的关键因素,其中微生物的影响更为主要。     

The Distribution of Fat in Dried Dairy Particles Determines Flavor Release and Flavor Stability

Dried dairy ingredients are utilized in various food and beverage applications for their nutritional, functional, and sensory properties. Dried dairy ingredients include milk powders of varying fat content and heat treatment and buttermilk powder, along with both milk and whey proteins of varying protein contents. The flavor of these ingredients is the most important characteristic that determines consumer acceptance of the ingredient applications. Lipid oxidation is the main mechanism for off‐flavor development in dried dairy ingredients. The effects of various unit operations on the flavor of dried dairy ingredients have been investigated. Recent research documented that increased surface free fat in spray dried WPC80 was associated with increased lipid oxidation and off‐flavors. Surface free fat in spray‐dried products is fat on the surface of the powder that is not emulsified. The most common emulsifiers present in dried dairy ingredients are proteins and phospholipids. Currently, only an association between surface free fat and lipid oxidation has been presented. The link between surface free fat in dried dairy ingredients and flavor and flavor stability has not been investigated. In this review, some hypotheses for the role of surface free fat on the flavor of dried dairy ingredients are presented along with proposed mechanisms.     

静态腌制过程中牛干巴理化特性

以牦牛背最长肌为原料,采用静态腌制法,研究不同腌制时间牛干巴内外部的水分、盐度、色泽、蛋白质含量变化特征,以及脂肪和蛋白氧化的变化.结果表明:随着腌制时间的延长,牛干巴内部和外部的水分含量逐步下降,而盐度先增加后下降;内部和外部的L*变化不显著(P＞0.05),但a*、b*在静态腌制的前3d降低,至第20天时升至最高值后缓慢下降,内部和外部差异显著(P＜0.05);随着水分的蒸发,蛋白质含量逐渐增加,且内部和外部无显著差异(P＞0.05);静态腌制过程中,牛干巴发生蛋白质和脂肪氧化,且蛋白质氧化和脂肪氧化之间存在相互作用,脂肪氧化程度先增后降,蛋白质氧化水平升至0.55nmol/mg后逐步下降.总之,牛干巴静态腌制过程中,肌肉成分发生均衡变化,30d的腌制有利于控制氧化程度.     

气相色谱法测定乳制品中共轭亚油酸的含量

共轭亚油酸（CLA）作为一种新型的功能性脂肪酸，其主要存在于瘤胃动物的乳和肉的脂肪中。CLA在乳制品中的含量受加工方式、贮藏等多种因素的影响。本文采用毛细管气相色谱法分析不同加工方法的各种乳制品中共轭亚油酸的含量，结果发现经发酵加工的乳制品中共轭亚油酸的含量明显高于未加工的原料乳，被测乳制品中以9c，11t结构的CLA含量为主，加工后的乳制品其反式CLA的含量都有所增加。     

特种乳加工技术研究进展

特种乳是指牛乳以外的其它家畜乳,具有独特的口感与营养价值,能满足不同民族及地区消费者的特殊饮乳需求,特种乳的加工技术也是乳品工业的重要组成部分。本文综述了牦牛乳、羊乳、马乳等特种乳及其乳制品的加工技术进展,为特种乳资源的深度开发利用提供参考,以期丰富乳制品品种,推动我国各品种乳的协同发展。     

Cholesterol and Antioxidant Vitamins in Fat Fraction of Whole and Skimmed Dairy Products

The skimming procedure is a common practice in dairy industry, and skimmed products contain less fat, less cholesterol and less fat-soluble vitamins than whole products. The aim of this research is to verify if something else happens during the skimming process to these compounds in milk and dairy products. Experimental milk and cream samples, ranging from 0.1 to 51.5 g fat/100 g, have been studied for beta carotene, alfa-tocopherol and cholesterol contents. The degree of antioxidant protection (DAP), useful to estimate the potential oxidative stability of fat in foods, has been calculated, combining these values. The same analytical protocol has been also applied to commercial products (fat content ranging from 0.1 to 85.0 g/100 g). As was expected, there is a good linear correlation between these compounds and fat content in experimental and in commercial samples; nevertheless, the composition of milk fat changes differently. During skimming process, in the residual fat matter, cholesterol concentration increases while antioxidant compound concentration decreases or remains unchanged. Moreover, in experimental and in commercial milk and dairy, the DAP values show that the residual cholesterol is more susceptible to oxidation in skimmed than in whole products. This aspect is particularly important from a safety point of view: actually, cholesterol oxide ingestion can be harmful and should be avoided even in a small amount.     

基于双波长紫外吸收的乳脂肪快速测定

为便于实施对乳品加工中乳品及管路残留乳脂肪含量的全面监控,建立一种基于双波长紫外吸收的乳脂肪快速定量方法。采用萃取-沉淀操作采集液态乳或加工管壁样本中的乳脂肪并直接测定204 nm和230 nm 2 个波长处的吸光度,再基于吸光度差ΔA204 nm－230 nm和乳脂肪标准曲线方程可确定样本中的乳脂肪含量。对于液态乳品样本,该方法的变异系数不大于3%,回收率在95.6%～102.9%之间,并可有效避免乳品热处理差异的干扰。此外,该方法也可成功用于不同加工条件下乳品加工管路中乳脂肪管壁残留量的测定。     

Factors affecting conjugated linoleic acid content in milk and meat

Conjugated linoleic acid (CLA) has been recently studied mainly because of its potential in protecting against cancer, atherogenesis, and diabetes. Conjugated linoleic acid (CLA) is a collective term for a series of conjugated dienoic positional and geometrical isomers of linoleic acid, which are found in relative abundance in milk and tissue fat of ruminants compared with other foods. The cis-9, trans-11 isomer is the principle dietary form of CLA found in ruminant products and is produced by partial ruminal biohydrogenation of linoleic acid or by endogenous synthesis in the tissues themselves. The CLA content in milk and meat is affected by several factors, such as animal's breed, age, diet, and management factors related to feed supplements affecting the diet. Conjugated linoleic acid in milk or meat has been shown to be a stable compound under normal cooking and storage conditions. Total CLA content in milk or dairy products ranges from 0.34 to 1.07% of total fat. Total CLA content in raw or processed beef ranges from 0.12 to 0.68% of total fat. It is currently estimated that the average adult consumes only one third to one half of the amount of CLA that has been shown to reduce cancer in animal studies. For this reason, increasing the CLA contents of milk and meat has the potential to raise the nutritive and therapeutic values of dairy products and meat.     

Nutritional Value and Technological Suitability of Milk from Various Animal Species Used for Dairy Production

Abstract: The analysis of nutritional value and selected traits of technological suitability of milk was performed on the basis of the available literature. This analysis concerned various animal species used for dairy purposes (cattle, buffalo, goats, sheep, camels, donkeys, and horses). It has been stated that a considerable diversity exists in the analyzed parameters and traits of milk, which results in various directions of milk utilization. Cow milk accounts for more than 80% of world milk production. It is the most universal raw material for processing, which is reflected in the broadest spectrum of manufactured products. Sheep and buffalo milk, regarding their high content of protein, including casein, and fat, make a very good raw material for processing, especially cheesemaking. Donkey and horse milk have the most comparable protein composition to human milk (low content of casein, lack of αs₁‐casein fraction and β‐lactoglobulin, and high content of lysozyme). Donkey milk is additionally characterized by a fatty acid profile distinctive from milk of other analyzed animal species. Camel milk also has valuable nutritional properties as it contains a high proportion of antibacterial substances and 30 times higher concentration of vitamin C in comparison to cow milk. The composition of goat milk allows using it as the raw material for dairy processing and also to some extent as a therapeutical product (low content or lack of αs₁‐casein).     

The Effective Factors on the Structure of Butter and Other Milk Fat‐Based Products

Butter and other milk fat‐based products are valuable products for the dairy industry due to their unique taste, their textural characteristics, and nutritional value. However, an increased consumer demand for low‐fat‐based products increases the need for an increased essential understanding of the effective factors governing the structure of milk fat‐based products. Today, 2 manufacturing techniques are available: the churning method and the emulsification method. The first is typically used for production of butter with a globular structure, which has become increasingly popular to obtain low‐fat‐based products, typically without presence of milk fat globules. The microstructure of milk fat‐based products is strongly related to their structural rheology, hence applications. Structural behavior is not determined by one single parameter, but by the interactions between many. This complexity is reviewed here. Parameters such as thermal treatment of cream prior to butter making, water content, and chemical composition influence not only crystal polymorphism, but also the number and sizes of fat crystals. The number of crystal–crystal interactions formed within the products is related to product hardness. During storage, however, postcrystallization increases the solid fat content and strengthens the fat crystal network. The fat crystal network is strengthened by the formation of more and stronger crystal–crystal interactions due to mechanically interlinking of fat crystals, which occurs during crystal growth. Postcrystallization is directly linked to chemical composition. The initially observed microstructural difference causing different rheological behavior will disappear during storage due to postcrystallization and formation of more crystal–crystal interactions.