UHT塑袋牛奶质量控制

本文对影响UHT塑袋牛奶质量的原料乳、包装膜、检验、设备和操作等进行了阐述,归纳了UHT奶常见质量问题及解决措施,提供了企业控制UHT奶质量的相关经验,可供乳品企业参考.     

复原乳检测标准发布 市场乱象能否终结

正复原乳是用女乃粉勾兑还原而成的牛奶,我国规定,低温巴氏奶绝不允许使用复原乳。但现实惰况是,出于降低成本的考虑,企业在生产过程中使用进口工业奶粉勾兑复原乳成为惯用手法。这不仅损害了我国奶农的利益,也侵犯了消费者知情权。从4月1日起,《巴氏杀菌乳和UHT灭菌乳中复原乳的鉴定》标准正式实施,复原孚的检测标准有了明确的规定。复原乳使用乱象复原乳又称还原奶,是指把新鲜牛奶经过高温杀菌干燥制成奶粉后,再兑入一定比例的水或者牛奶还原成液态奶     

热处理对乳中CLA含量的影响

目的:研究了不同热处理对乳中CLA含量的影响,同时探讨了UHT奶贮存过程中CLA含量的变化.方法:选用原料奶进行常规巴氏杀菌、煮沸和UHT热处理,分析样品的CLA含量,同时测定UHT奶贮存1、7、14、28d后CLA含量的变化.结果:原料奶中CLA含量最高,为5.306±0.097me/g脂肪酸,UHT奶中CLA含量最低,为4.772±0·180mg/g脂肪酸.下降10.06%.煮沸奶和UHT奶中CLA含量显著低于原料奶(P＜0.05),而常规杀菌奶与原料奶无显著差异(P＞0.05).在保质期内,UHT奶的CLA含量变化差异不显著(P＞0.05).结论:煮沸和UHT热处理会影响奶中CLA含量,UHT奶贮存过程中对CLA含量无显著影响.     

德国、美国、巴西奶农都有本难念的经

<正>近期,中国内地出现的"倒奶杀牛"现象引起了社会各界的高度关注,那么,世界三大奶制品生产国和出口国德国、美国和巴西奶制品发展情况如何?又是如何应对同类问题的呢?德国:做奶农基本无利可图德国超市里一盒1升装牛奶一般售价在1欧元左右,根据欧盟委员会农业预算的数据,目前德国每公斤牛奶(略轻于一升牛奶)的生产成     

不同热处理方式对牛奶乳清蛋白的影响

目的：比较不同热处理方式对牛奶中乳清活性蛋白的影响。方法：以奶场牛乳、巴氏杀菌乳、超高温瞬时灭菌(UHT)乳和蒸汽侵入式直接杀菌(INF)乳4种不同热处理方式的牛奶作为研究对象，观察4种牛奶活性蛋白含量及热处理后牛奶中美拉德反应产物含量等的变化情况；采用SEM、FTIR、荧光光谱分析仪和Malvern纳米粒度仪分析微观结构。结果：4种热处理牛奶中，奶场牛乳的乳清蛋白含量最高，INF杀菌乳与巴氏杀菌乳中乳清蛋白含量和美拉德反应产物含量相当；UHT灭菌乳的粒径及其乳清蛋白极性环境均显著增加；4种牛奶乳清蛋白二级结构中无规则卷曲逐渐增加，乳清蛋白结构从有序向无序转化。结论：蒸汽侵入式直接杀菌对乳清活性蛋白的损伤程度小于超高温瞬时灭菌，与巴氏杀菌相当，且此方法处理的牛乳保存期高于巴氏杀菌乳。     

常温奶就好比是水果罐头 专家建议尽量选择低温奶

正最近,牛奶又成为了媒体关注的焦点。在国家认监委对澳大利亚进口奶的品质进行质疑后,进口巴氏奶又被指"从国外进口至中国市场后,保质期被延长了"。常温奶、巴氏奶、复原奶、酸奶、乳饮料……面对超市里琳琅满目的奶制品,老百姓确实有点蒙圈。那么,这杯事关健康的牛奶,到底该怎么喝呢?进口的牛奶品质好还是本土的牛奶更新鲜?价格:进口奶比国产奶贵一倍多"德国进口的牛奶,9块9一升,比国产奶还要便宜!"     

不同类型热处理方式对牛乳品质的影响

目前市场上常见牛奶的杀菌方式有超高温瞬间灭菌(UHT)、巴氏杀菌等,这些牛奶的生产工艺不同,热处理强度不同,活性蛋白的变性率也各不相同。本实验通过比较不同方式热处理对牛奶中α-乳白蛋白、β-乳球蛋白和乳铁蛋白含量的影响,得出蒸汽浸入式直接杀菌(INF)对α-乳白蛋白、β-乳球蛋白和乳铁蛋白的热损伤程度低于UHT灭菌,与巴氏杀菌相当(P0.5),冷藏条件下,产品的保质期可达21 d,货架期高于巴氏杀菌牛奶。合适、恰当的热处理工艺,不仅可以杀死致病性微生物,同时又能最大限度地保留牛奶中的天然活性蛋白营养,保证牛奶的品质。     

ATP法测定奶中的细菌含量

为了评价ATP法在UHT奶中菌藩总数和商业无菌检测的实用性,本研究通过检测UHT乳中ATP本身的含量,以及微生物平板计数法和商业菌落总数Petfifilm俐测试片法对样品进行菌落总数和商业无菌检测,建立样品中ATP含量与菌落总数的对应关系。结果表明,不同品类UHT牛奶中ATP法结果与菌落总数Petrifilm^TM测试片法和国标平板计数法结果的相关性强,复现性好。由此可知,ATP法可以作为一种快速检测UHT奶中菌落总数和商业无菌的方法。     

不同热处理牛奶的动态体外消化研究

目的 研究4种不同热处理方式对牛奶消化的影响。方法 采用动态人胃肠消化系统模拟人体消化过程,分析奶场样品、巴氏杀菌乳、超高温瞬时灭菌（UHT）乳和蒸汽侵入式直接杀菌（INF）乳的pH变化、蛋白质消化率、胃排空速度以及胃肠消化后的肽段分布等。结果 奶场样品和巴氏杀菌乳在胃内的pH变化趋势基本一致,巴氏杀菌乳在胃内消化接近空腹状态的时间最短。巴氏杀菌乳中蛋白消化率最高,UHT灭菌乳的消化率明显低于其他3种样品。4种牛奶经体外单独胃消化后生成的肽段分子质量基本在5 000 u以下,而经体外连续胃肠消化后基本在1 000 u以下,更易于人体消化吸收。巴氏杀菌乳和INF灭菌乳的消化率和消化产物的肽段分子质量分析上各有优势,但总体趋势基本一致,无显著差异,且均优于UHT灭菌乳。结论 INF杀菌乳和巴氏杀菌乳的体外消化结果基本相当,优于UHT灭菌乳,为消费者提供了一种新的奶制品选择。     

区域乳企寻找温度与广度的平衡

区域乳企如今越来越看重低温奶市场的发展.2月24日,区域乳企阳光乳业首发上会,并计划加速布局低温奶市场.收购、推新品、加大研发投入……近半年内,阳光乳业、维记牛奶、燕塘乳业等区域乳企纷纷在低温奶领域有新动作.不过,如何在"温度"与"广度"上进行平衡,也是区域乳企需要思考的问题.     

巴氏奶——扛起未来奶业市场的大梁

近几年，奶业市场上吵的最火热的要数巴氏奶了，专家学者们也把目光转移到了巴氏奶上，并预言：巴氏奶成为世界主流饮用奶的步伐将加快，同时巴氏奶也是乳业可持续发展的方向。众多的专家学者对巴氏奶的未来很是看好，记者认为专家们此举主要是出于对巴氏奶营养功能的信赖。到底什么是巴氏奶？营养价值有多高？专家学者们怎样看待巴氏奶？巴氏奶为什么会成为乳业可持续发展的方向？在本文中，记者将一一回答这些问题，希望给读者朋友们一个更透明的巴氏奶……     

原料乳中血乳定性检测方法

研究了原料乳中血乳的检测方法,样品通过离心机离心后在离心力的作用下导致比重关系改变使的血乳下沉,通过目视判定是否含血乳.方法检出限为0.02mg/kg,且此方法操作简单,结果准确,适用于乳品企业进行原料乳中血乳的检测.     

Comparison of the immunogenicity of yak milk and cow milk

This is a comparison of potential allergenicity in a mouse model. Balb/C mice were sensitized by intraperitoneal injections (administered in three doses) of skimmed milk, casein, and whey protein from cow or yak milk. After 4 weeks, the mice were challenged and killed, sera were collected, and the spleens removed for analysis. An enzyme-linked immunosorbent assay was used to determine the specific antibodies (IgG and IgE) and cytokine. The number of mice with diarrhea was higher in the cow milk protein-sensitized group than in the yak milk protein-sensitized group. Serum (IgG, IgE) antibodies and histamine levels were also higher in cow milk protein-sensitized mice. Cytokine production by spleen-derived T cells showed high levels of interleukin-4 and interleukin-5 production and low levels of interferon-γ in cow milk protein and yak milk protein-sensitized mice. Lymphocyte proliferation ratio induced by yak milk protein was lower than cow milk protein. All results indicated that Maiwa yak milk protein may less allergenic than cow milk protein in mice.     

几种酵母菌添加剂对奶牛产奶量及乳成分的影响

将54头高产中国荷斯坦奶牛随机分为6组，1组基础对照组，5组（A，B，C，D，E）试验组，试验组在基础日粮的水平上添加15g不同型号的酵母菌制剂，预试期2周，正试期为6周。结果表明：不同型号的酵母菌对奶牛产奶量和奶成分有不同程度的影响，其中C和E组奶牛的产奶量分别比对照组有所增加，B和D组的产奶量与对照组相比增加显著（P〈0．05），A组则有所下降；不同型号的酵母菌制剂对牛乳成分也有不同程度的影响，试验组B，D，E组乳脂日产量比对照组有增加，并且差异显著（P〈0．05）；E组乳脂率增加，差异显著；蛋白质日产量除A组无显著性差异（P〉0．05），B，C，D，E组相比对照组都有所增加，其中C和E组相比对照组，差异显著（P〈0．05）；试验组的乳糖、非脂固形物产量与对照组没有显著差异（P〉0．05）；各试验组的所生产牛奶的比重、冰点、酸度与对照组无显著差异，但试验组的酸度除D组外均比对照组有所提高，乳中体细胞数均比对照组低，其中酵母菌C和D能显著减少乳中体细胞数（P〈0．05）。     

Densitometric determination of the fat content of milk and milk products

An automatable method for determining the fat content of milk and milk products was developed using a precise densitometer based on the principle of the resonant frequency U-tube oscillation. The sample is first decomposed with hydrochloric acid and the fat extracted with hexane. The density of the fat/hexane solution obtained varies with the fat content of the sample. Milk, cream and cheese samples were analysed. The mean values from the densitometric determination of the fat content did not differ from the mean values obtained by the corresponding gravimetric reference methods.     

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.     

Calibration of infrared milk analyzers: modified milk versus producer milk

Mid-infrared (MIR) milk analyzers are traditionally calibrated using sets of preserved raw individual producer milk samples. The goal of this study was to determine if the use of sets of preserved pasteurized modified milks improved calibration performance of MIR milk analyzers compared with calibration sets of producer milks. The preserved pasteurized modified milk sets exhibited more consistent day-to-day and set-to-set calibration slope and intercept values for all components compared with the preserved raw producer milk calibration sets. Pasteurized modified milk calibration samples achieved smaller confidence interval (CI) around the regression line (i.e., calibration uncertainty). Use of modified milk calibration sets with a larger component range, more even distribution of component concentrations within the ranges, and the lower correlation of fat and protein concentrations than producer milk calibration sets produced a smaller 95% CI for the regression line due to the elimination of moderate and high leverage samples. The CI for the producer calibration sets were about 2 to 12 times greater than the CI for the modified milk calibration sets, depending on the component. Modified milk calibration samples have the potential to produce MIR milk analyzer calibrations that will perform better in validation checks than producer milk-based calibrations by reducing the mean difference and standard deviation of the difference between instrument values and reference chemistry.     

An approach to the detection of synthetic milk in dairy milk: 4. Effect of the addition of synthetic milk on the flow behaviour of pure cow milk

The flow behaviour of cow milk, synthetic milk and their blends was evaluated with a Haake rheometer. Changes in flow behaviour are thought to be due to detergent, an important constituent of synthetic milk, which emulsifies the vegetable fat in the aqueous phase. The results are of value in detecting very low levels (1–10%) of synthetic milk in cow milk.