高效液相色谱法同时测定人乳中视黄醇、α-生育酚和类胡萝卜素

目的应用高压液相色谱法同时测定人乳中视黄醇、α-生育酚、叶黄素和β-胡萝卜素。方法人乳样品经皂化后,石油醚乙醚提取,氮吹浓缩后,用C30柱分离,经紫外检测器和荧光检测器检测4种被测物。结果 4种脂溶性维生素在各自浓度范围内线性良好,相关系数均大于0.9990;三浓度水平加标回收率在70%~120%之间,相对标准偏差均小于20%。结论本文将校准后的标准品用液相色谱法进行纯度鉴定,提高了检测的准确度。通过方法学验证了本方法的准确性,灵敏性和稳定性,可同时测定人乳中视黄醇,α-生育酚,叶黄素和β-胡萝卜素的含量。通过对100个成熟乳样品的分析,初步建立了人乳中脂溶性维生素含量数据库。     

高效液相色谱法同时测定人乳中视黄醇、 α-生育酚和类胡萝卜素

目的 应用高压液相色谱法同时测定人乳中视黄醇、α-生育酚、叶黄素和β-胡萝卜素。方法 人乳样品经皂化后, 石油醚乙醚提取, 氮吹浓缩后, 用C30柱分离, 经紫外检测器和荧光检测器检测4种被测物。结果 4种脂溶性维生素在各自浓度范围内线性良好, 相关系数均大于0.9990;三浓度水平加标回收率在70%~120%之间, 相对标准偏差均小于20%。结论 本文将校准后的标准品用液相色谱法进行纯度鉴定,提高了检测的准确度。通过方法学验证了本方法的准确性, 灵敏性和稳定性,可同时测定人乳中视黄醇, α-生育酚, 叶黄素和β-胡萝卜素的含量。通过对100个成熟乳样品的分析, 初步建立了人乳中脂溶性维生素含量数据库。     

牛乳、羊乳和人乳中的蛋白质组成及消化特性研究

在分析牛乳、羊乳和人乳蛋白质组成的基础上,通过模拟胃肠消化环境,研究牛乳、羊乳和人乳中蛋白质的消化特性。结果表明:牛乳中的蛋白质主要由αs1-酪蛋白、β-酪蛋白和β-乳球蛋白组成,羊乳中的蛋白质主要由αs2-酪蛋白、β-酪蛋白和β-乳球蛋白组成,人乳中的蛋白质主要由β-酪蛋白和α-乳白蛋白组成。牛乳、羊乳和人乳中酪蛋白与乳清蛋白的比例分别为4.45±0.03,3.65±0.07,0.51±0.03。牛乳、羊乳和人乳中的蛋白质主要在肠液中消化,其中酪蛋白在胃液中消化120 min时的消化率分别为88.6%、89.7%、98.1%,在肠液中消化30 min时的消化率分别为97.6%、98.4%、98.9%,在胃肠液中消化30 min后,酪蛋白几乎完全消化。3种乳相比较,人乳中的蛋白质在胃肠中最易消化,而羊乳中的蛋白质比牛乳更易消化。     

α—乳白蛋白在婴儿营养中的重要性

理想的“母乳化”乳代用品应该考虑形成一种极似人乳的氨基酸结构,因为人乳蛋白质混合物含色氨酸和半胱氨酸非常丰富,蛋氨酸含量低,所以商业上现有蛋白质要获得此种结构很困难,甚至以乳清为主的配方也仅仅是与人乳接近,人乳有高浓度乳清蛋白质(占总蛋白质的70％)。其中乳糖合成酶复合体的一种组份α—乳白蛋白占乳清的41％,占总蛋白质的28％,牛乳蛋白质中只有3％是α—乳白蛋白,人乳与牛乳的α—乳白蛋白均有72％氨基酸系列相同,两蛋白质都含有(Wt/Wt)6％色氨酸和5％半胱氨酸,蛋氨酸只有0.9％,因此牛乳与人乳氨基酸组成的差别主要是由于α—乳白蛋白含量不同造成的,商业上可得到的牛α—乳白蛋白将会使婴儿配方结构有非常接近于人乳的氨基酸成分。α—乳白蛋白还将成为蛋白质摄入必须受到限定的病人膳食的重要组份。     

小角X-射线散射与结构预测法研究中国人乳β-酪蛋白的3级结构

通过小角X-射线散射与结构预测的方法研究人乳β-酪蛋白的3级结构,并分析其生理功能。通过使用DEAE Sepharose FAST Flow琼脂糖凝胶获得纯度大于90%的β-酪蛋白纯品,并对其溶液进行小角X-射线散射(0.2 mol磷酸盐缓冲溶液,10 mmol DTT,p H 6.7),将获得的人乳β-酪蛋白的结构信息与通过折叠识别及从头预测构建的预测模型进行比较,筛选出在试验条件下与试验结果最相符的人乳β-酪蛋白3级结构模型,该模型结构松散,含有较少的α-螺旋和β-折叠。同时结合模型对人乳β-酪蛋白磷酸化、糖基化及脂质化等蛋白质功能位点进行了分析,认为人乳β-酪蛋白含有12个可以与乳糖或葡萄糖结合的糖基化位点,7个脂质化位点,其磷酸化位点与已知的5个磷酸化位点相符。     

人乳与牛乳乳脂肪球膜蛋白质组的对比研究

人乳是婴幼儿生命初始阶段唯一能够摄入的食物,蛋白质是人乳中重要的营养成分,而牛乳作为代替人乳的常用原料已经被广泛的应用于婴幼儿食品中。本研究利用SDS-PAGE电泳和LC-MALDL-TOF蛋白组学方法将人乳与牛乳中乳脂肪球膜蛋白进行分离,能够发现人乳与牛乳脂肪球膜蛋白存在较大的差异。牛乳脂肪球膜中已鉴定出488种蛋白,人乳脂肪球膜中鉴定出的蛋白为1545种。牛乳脂肪球膜具有173种特异性蛋白,人乳脂肪球膜具有1230种特异性蛋白,在人乳与牛乳中存在315种同源蛋白。从蛋白质的GO(Gene Ontology)功能注释上来看,人乳脂肪球膜蛋白参与的生物过程有37%为代谢过程;具有的分子功能55%为结合作用;34%为参与细胞器构成。人乳脂肪球膜中有24种蛋白参与免疫相关的通路,主要为抗原加工和呈递。与牛乳相比,对人乳中乳脂肪球膜蛋白质在组成及功能上的研究,能够促进深入地了解人乳蛋白,并为以牛乳为原料的婴幼儿产品添加功能性蛋白提供参考。     

羊乳乳清蛋白组成和功能及其与人乳、牛乳的对比分析

本研究将羊乳、牛乳、人乳中乳清蛋白进行分离并结合液质联用技术鉴定,在羊乳、牛乳、人乳乳清蛋白中分别鉴定出156、278、454种蛋白质。与牛乳与人乳乳清蛋白对比显示,羊乳含有99种特异性表达蛋白质,与牛乳和人乳分别有31种和15种相同表达蛋白质。通过分析基因本体(gene ontology,GO)功能注释发现,羊乳乳清蛋白在生物过程中主要发挥生物调节作用;在分子功能上,主要体现在结合作用方面;在细胞组成上,参与的细胞组成主要为细胞器区和胞外区。羊乳乳清蛋白在以上三种功能上与人乳有较大差距,但与牛乳相近。通过分析京都基因与基因组百科全书系统(Kyoto Encyclopedia of Genes and Genomes,KEGG)代谢通路可知,羊乳主要参与补体和凝血级联反应以及吞噬作用,对人体免疫能力有积极影响。对羊乳与人乳、牛乳乳清蛋白组成及功能区别的研究,为羊乳的进一步研究和开发提供一定的理论参考。     

人乳中蛋白质的生理功能特性

论述了人乳中蛋白质的种类及其生理功能，以及人乳与牛乳在这些方面的差异，以期为婴儿配方食品的生产提供参考。     

利用二维电泳技术检测大麦种子纯度

利用蛋白质双向电泳技术和PDQuest分析软件对人工混合的不同纯度大麦的蛋白质电泳图谱进行分析,找到了不同品种大麦间的主要差异蛋白,并应用各差异点的3D高度数值与大麦纯度进行线性拟合,得到了不用差异蛋白质点相关的线性回归方程,并检验其准确性,实验取得了良好的效果,该方法可以较为准确地检测大麦种子的纯度。     

利用超高效液相色谱串联三重四级杆质谱定量检测人乳中的α-乳白蛋白

目的建立一种新型基于多肽标准品体系的人乳α-乳白蛋白的定量检测方法。方法从人乳α-乳白蛋白筛选出特异性多肽,并建立对应的检测方法;利用化学方法人工合成特异性多肽、同位素标记特异性多肽和内标。结果本方法所选择的多肽具有高度特异性,α-乳白蛋白的检测灵敏度为8.0 mg/100 g,精密度均小于5.22%,回收率均在97.21%~102.45%之间。结论本方法建立了利用特异性多肽检测人α-乳白蛋白的方法,具有较高的准确度、灵敏度和稳定性。通过对447份人乳样品进行检测,初步探索了人乳中α-乳白蛋白的含量范围,为人乳化配方奶粉的华人配方奠定理论基础。     

鲜乳及乳粉糊精掺假问题

目前,我国鲜牛（羊）乳及乳制品掺假是一个较为普遍的现象。鲜乳掺假会增加乳品加工企业的原料收购费及贮存、运输和加工成本,还严重威胁着产品质量,甚至决定着企业的生存和发展。俗话说“千里之堤,溃于蚁穴”,事实上,确有不少企业因无力控制乳原料掺假等等质量问题,在群雄逐鹿的乳品及冷饮市场竞争中不堪一击,不得不偃旗息鼓,被迫抱怨退出！而有的企业,则以低价倾销假冒伪劣乳制品的手段来打击竞争对手、占领市场,极大的破坏了乳品行业的利益,消弱了乳制品市场发展的后劲。然而,鲜乳及乳制品掺假不单是产品质量问题、企业声誉…     

Reduction of milk and milk product wastage

The paper examines the assessment of waste control based on effluent monitoring and the results of a BOD test for 'milk equivalent' measurement are interpreted and evaluated. The importance of reliable flow measurement is stressed and a table is given showing wastage from various dairy operations and methods of reducing losses recommended.     

生乳中豆浆、米汤掺假鉴别及其定量测定

为鉴别生乳掺假,采用非线性化学指纹图谱技术,建立基于"溴酸钠+硫酸锰+硫酸+丙酮"稳态体系的不同奶源地的纯生乳及掺入不同量豆浆、米汤的生乳的非线性化学指纹图谱,利用指纹图谱的直观特征信息能很好地将掺豆浆、米汤的生乳鉴别出来,并能对掺假物的种类进行判断。根据掺假生乳指纹图谱参数信息与掺假量的关系,可对生乳中掺入豆浆、米汤的相对含量进行评估。非线性化学指纹图谱技术为原料乳中豆浆、米汤的掺假鉴别及掺入物质的相对含量的评价提供了一种新的方法。     

乳中蛋白酶与UHT乳贮存中的胶凝现象

乳中的蛋白酶有2个主要的来源途径，乳中天然存在的蛋白酶和由某些微生物产生的蛋白酶，其中纤维蛋白溶酶和嗜冷菌产生的耐热性蛋白酶是存在于UHT乳中的主要蛋白酶，这些蛋白酶非常耐热，经UHT灭菌处理仍可存活。耐热性蛋白酶在UHT乳贮存中水解乳蛋白质从而导致了UHT乳的胶凝．简要介绍了纤维蛋白溶酶、嗜冷菌耐热性蛋白酶的性质、活性测定方法，论述了这些酶引起的UHT乳的胶凝性质、形成原因及影响因素，并提出了一些防止措施。     

山羊奶与牛奶和人奶营养成分的比较

对山羊奶、牛奶和人奶中蛋白质、脂肪、维生素、矿物质等主要营养成分进行了比较,分析了3种奶中主要营养成分的差别。通过比较发现,山羊奶在总体营养成分方面优于牛奶,更接近人奶。但山羊奶存在铁、叶酸和维生素B12含量较低以及羊奶膻味的问题,应在营养上对这方面加以重视。     

Nutrient content of milk and milk products: vitamins of the B complex and vitamin C in retail market milk and milk products

A survey was undertaken to update and extend information on the water-soluble vitamin content of milk and milk products on retail sale. The results are discussed in relation to previously published data. Apart from vitamin C the levels of vitamins in retail pasteurized cows' milk were very similar to those found in milk from the processing dairy. Levels of total vitamin C and folic acid in UHT full cream milk were negligible; vitamin B₆ and vitamin B₁₂ were respectively 73 and 56% of the levels in pasteurized milk. Except for nicotinic acid, pantothenic acid and biotin, the levels of vitamins in sterilized milk were lower than in pasteurized milk, particularly vitamin C, folic acid and vitamin B₁₂. When compared on an equivalent dilution basis, vitamin B₆, thiamine, folic acid and, especially, vitamin B₁₂ in evaporated milk were lower than in pasteurized cows' milk. In comparison, in full cream condensed milk only vitamin B₆ was particularly low; vitamin C was particularly well preserved. With the exception of vitamin B₁₂, vitamin levels in reconstituted spray dried milk were similar to those in pasteurized cows 'milk. Levels in filled' spray dried milk were on average 70% of those in ordinary dried milks. Apart from vitamin B₁₂ the levels of B vitamins in non health food yogurt were generally higher than in pasteurized milk, especially folic acid. The levels of vitamin B₁₂ and folic acid in goats' milk were only 22 and 11 % respectively of those in cows' milk, but the nicotinic acid level was four times higher. The level of vitamin C in raw sheep's milk was about five times that in pasteurized cows' milk; other levels, apart from folic acid which was similar, were between 1.3 and 5.2 times those in cows' milk.     

Subject: Transport and storage of milk and milk products

The factors affecting the condition of milk at the end of its stay in bulk storage are as follows: The temperature of the milk when put into storage; the bacteriological quality of the milk when put into storage; the state of cleanliness of the storage tank or silo and allied equipment at time of filling; the length of time the milk is held in storage, and each of these is dealt with individually. The current performance of incoming ex-farm milk temperature is reviewed and the necessity to store milk at temperatures below 4C where lengthy storage time is involved, is stressed. The general bacteriological condition of present-day incoming raw supplies is discussed and emphasis placed on the importance of exploiting the potential advantages of bulk collection to the full. The importance of good management of bulk stored supplies is underlined and tank cleaning and milk agitation discussed. The more pressing problems in dairy products directly associated with raw milk quality are discussed in some detail and the need for more informative and relevant testing methods considered. Reference is made to the proposed DTF Survey on Raw Milk Quality and a strong appeal made for this to be supported in full by the industry.     

Subject: Transport and storage of milk and milk products

Reference is made to the anticipated completion of churn conversion by 31st July, 1979. The main designs of bulk milk tanks currently in use on farms in England and Wales and the milk cooling systems associated with them are illustrated and discussed. Cleaning systems for both refrigerated and non-refrigerated tanks are described and their relative effectiveness indicated. Methods intended to reduce energy requirements and costs in connection with milk cooling are discussed. The relative importance of bulk milk storage equipment and other sources of contamination on the hygienic quality of refrigerated bulk milk is considered.     

Subject: Transport and storage of milk and milk products

The key factor in the transport and storage of short shelf-life products is temperature control throughout the whole distribution chain. A typical distribution chain is analysed and some of the problem areas discussed. The effect of temperature on cream, desserts, yoghurt and cottage cheese are considered to highlight possible problems of poor distribution.