高效液相色谱法鉴别原料乳中碳水化合物掺伪

以Hypersil氨基柱为分离柱,乙腈-水(80∶20)为流动相,流速为1.0 m L/min,建立了用于同时鉴别原料乳中果糖、葡萄糖、蔗糖和乳糖掺伪的高效液相色谱法。结果表明,在0.5 mg/m L~20 mg/m L的范围内,线性关系良好,用于果糖、葡萄糖、蔗糖和乳糖掺伪鉴别的精密度分别为2.100%、1.500%、1.680%和2.975%,回收率分别为101.0%、100.0%、99.3%、99.3%,检出限分别0.21、0.25、0.22、0.20 mg/m L。此法准确可靠,可用于原料乳中此4种碳水化合物的掺伪检测。     

光谱技术在乳及乳制品研究中的应用进展

文章阐述了光谱技术在乳及乳制品掺假和掺伪检测、营养成分检测、抗生素检测、微生物污染检测,乳及乳制品种类的鉴定等方面的应用。综述了近红外光谱、拉曼光谱、高光谱成像技术在乳及乳制品品质检测和安全评定上的重要应用和研究进展,指出多种技术联合应用是未来研究的趋势。     

乳与乳制品中四种动物源性成分鉴定方法的研究

目的 针对小众乳与乳制品的掺假的现象,构建乳与乳制品中动物源性成分检测方法。方法 设计合成了牛、羊、驴、水牛的特异引物探针,优化乳与乳制品中核酸提取方法,对设计的荧光PCR方法进行了特异性、灵敏度、适用性进行验证。结果 该方法对于常见动物物种具有较强特异性和灵敏度,牛、羊、驴、水牛的检测灵敏度分别为0.001、0.01、0.01、0.01 ng。此外,该方法适用性较强,在各类乳与乳制品样品中均能检出标识动物源性成分和掺伪动物源性成分。结论 本研究构建的检测方法,特异性、灵敏度、检出限等指标均能满足日常实验需要,可为监管与检验提供有力的技术支撑。     

水牛乳和羊乳中掺伪牛乳高特异性酶联免疫检测方法

建立可检测水牛乳和羊乳中掺伪牛乳的双抗夹心酶联免疫检测方法。分别以牛Ig G和牛Ig G的Fc片段为抗原,制备抗牛Ig G的多克隆和高特异性单克隆抗体,并将以此蛋白作为包被抗体,构建双抗夹心ELISA方法。该方法标准曲线的IC50为4.3μg/m L,方法的灵敏度为0.1μg/m L。添加回收率在95%~105%之间,相对标准偏差小于12%。该方法无需复杂的前处理,检测时间为60 min,能准确检测水牛乳和羊乳中掺伪牛乳,避免了传统免疫方法在乳制品掺伪检测上的假阳性。     

原料乳——中国乳业发展瓶颈

<正>一直以来,牛奶和乳制品被公认为大自然赐予人类最理想的、最接近于母乳的完美天然食品。牛奶中至少有100多种营养成分,其中水、蛋白质、脂肪、碳水化合物、微量矿物质元素、维生素,免疫活性因子等都是人类赖以生存的营养素。因此,牛奶有“白色血液”、“完全食品”等美称。乳和乳制品已经成为人们非常喜爱的日常食品之一。随着人们生活水平的提高,食品安全、营养概念的增强,及乳制品消费量的激增,原料乳质量、供给量已成为中国乳业发展的瓶颈。原料乳安全质量问题堪忧原料乳的质量是影响乳制品质量的主要因素。奶源的重要性不言而喻,乳品企业如果没有充足的、高品质的原料奶做基础,生产将变成“无本之木,无源之水”。     

原料乳生产中空气源微生物的快速检测及控制方法

微生物的污染是影响乳制品安全的重要因素,主要以空气为媒介污染原料乳进而影响乳制品安全。本文概述了原料乳中微生物的来源、种类;空气中微生物的采集方法、检测方法以及如何控制原料乳中微生物。原料乳中可能污染的微生物有葡萄球菌、沙门氏菌、志贺氏菌、链球菌属、大肠杆菌等病原微生物和腐败菌、真菌。空气微生物的采样方法有自然沉降法和微生物采样器采样法,比较而知采样器采样法具有稳定、不受气候影响的优点;同时比较了固体和液体微生物采样器的优缺点。原料乳质量好坏直接影响到后续加工乳制品,乳中微生物指标成为制约原料乳卫生指标的关键因素,该指标一直倍受乳品厂家及消费者的关注。因此,保证原料乳的安全是保证乳品安全的前提。     

原料乳和乳制品中三聚氰胺快速检测方法的探讨

对国家标准《原料乳与乳制品中三聚氰胺检测方法》GB/T 22388—2008及《原料乳中三聚氰胺快速检测液相色谱法》GB/T 22400—2008进行了改进,优化了样品前处理和色谱条件,建立了适用于原料乳及各种乳制品中三聚氰胺的液相色谱检测法,提高了检测的灵敏度、准确度,并缩短了检测时间,提高了效率。     

原料乳中抗生素的控制与分析

原料乳的安全问题是国内乳品行业面临的共同难题,其中药物残留．特别是抗生素残留是原料乳中存在的安全问题之一。原料乳中抗生素残留物不仅影响乳制品加工（如严重干扰发酵乳制品的生产,影响干酪、黄油、发酵乳的起酵和后期风味的形成）,而且长期服用含低剂量抗生素残留的乳制品,会危害人体健康。因此,应采取一定的措施,防止含抗生素的原料乳进入后续加工过程。     

基于旋光法的原料乳中乳糖掺伪鉴别技术研究

旨在建立一种简便、高效的原料乳乳糖掺伪鉴别方法。以三氯乙酸为沉淀剂进行前处理,借助旋光仪,在589.30~589.44nm下,测定标准乳糖溶液的旋光度,绘制标准曲线,建立了一种基于标准曲线的原料乳乳糖掺伪定量鉴别法。所得回归方程的线性相关系数R2=0.9993,平均回收率达99.0%,相对标准偏差(RSD)为0.67%。与莱因-埃农氏法进行比对实验,结果无差异,但更快捷,成本更低。研究结果提示,本文所建方法实用、可靠。     

LAMP技术在检测原料乳及乳制品致病菌方面的应用

环介导等温扩增(LAMP,Loop-Mediated Isothermal Amplification)作为一种新的检测技术,具有操作简便、快速、特异性强等优点,目前已在原料乳及乳制品致病菌的检测中得到初步应用,本文综述了这一技术的原理、鉴别及检测的方法,及其在原料乳及乳制品检测方面的应用进展.     

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。     

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.     

模拟母乳及婴儿配方奶粉的研究

介绍了人乳中的主要功能因子及其对婴儿的生长发育所具有的生理意义。比较、分析了现阶段婴儿配方奶粉与人乳成分中存在的差别及不足，并针对婴儿的生长特点及现阶段生产技术，对婴儿配方奶粉的生产及发展进行了叙述。     

Decreased milk yield is associated with delayed milk ejection

To determine whether individual cow milking vacuum (within the short milk tube and the liner mouthpiece) could be substituted for milk flow technology to identify delayed (bimodal) milk ejection, and the possible relationship between bimodal milk flow and milk yield, we recorded milking data from 663 Holstein cows on a 3,600-cow Michigan dairy that milked 3 times per day. Overall, delayed milk ejection occurred in 45.6% of the milkings, and 98% of the cows with delayed milk ejection also had bimodal flow. Multivariable analysis revealed that milk yield during each individual cow milking was positively associated with increasing lactation number but negatively associated with increasing days in milk and delayed milk ejection. As the time between unit attachment and the estimated milk letdown (the lag period) increased, milk yield decreased; relative to a lag of <30 s, milk yield decreased by 1.8 and 3.1 kg for lags of 30–59 and ≥60 s, respectively. The final multivariate model had an adjusted coefficient of determination of 0.27. The negative association between delayed milk ejection and decreased milk yield in this study suggested that milking vacuum parameters from individual cows could serve as a useful tool to qualitatively estimate milk flow within a herd and that this information may be used to enhance herd productivity.     

免疫学检测羊乳中掺入牛乳成分

由于营养、价格和原料等原因，市场上在羊乳中掺入牛乳的现象常有发生。针对这种乳源性掺假陆续产生了多种检测方法，本文主要综述了以ELISA为主的免疫学快速检测方法。     

Effects of milk powders in milk chocolate

The physical characteristics of milk powders used in chocolate can have significant impact on the processing conditions needed to make that chocolate and the physical and organoleptic properties of the finished product. Four milk powders with different particle characteristics (size, shape, density) and "free" milk fat levels (easily extracted with organic solvent) were evaluated for their effect on the processing conditions and characteristics of chocolates in which they were used. Many aspects of chocolate manufacture and storage (tempering conditions, melt rheology, hardness, bloom stability) were dependent on the level of free milk fat in the milk powder. However, particle characteristics of the milk powder also influenced the physical and sensory properties of the final products.     

Effect of leaving milk trucks empty and idle for 6 h between raw milk loads

The US Pasteurized Milk Ordinance (PMO) allows milk tanker trucks to be used repeatedly for 24 h before mandatory clean-in-place cleaning, but no specifications are given for the length of time a tanker can be empty between loads. We defined a worst-case hauling scenario as a hauling vessel left empty and dirty (idle) for extended periods between loads, especially in warm weather. Initial studies were conducted using 5-gallon milk cans (pilot-scale) as a proof-of-concept and to demonstrate that extended idle time intervals could contribute to compromised raw milk quality. Based on pilot-scale results, a commercial hauling study was conducted through partnership with a Pacific Northwest dairy co-op to verify that extended idle times of 6 h between loads have minimal influence on the microbiological populations and enzyme activity in subsequent loads of milk. Milk cans were used to haul raw milk (load 1), emptied, incubated at 30°C for 3, 6, 10, and 20 h, and refilled with commercially pasteurized whole milk (load 2) to measure cross-contamination. For the commercial-scale study, a single tanker was filled with milk from a farm known to have poorer quality milk (farm A, load 1), emptied, and refilled immediately (0 h) or after a delay (6 h) with milk from a farm known to have superior quality milk (farm B, load 2). In both experiments, milk samples were obtained from each farm's bulk tank and from the milk can or tanker before unloading. Each sample was microbiologically assessed for standard plate count (SPC), lactic acid bacteria (LAB), and coliform counts. Selected isolates were assessed for lipolytic and proteolytic activity using spirit blue agar and skim milk agar, respectively. The pilot-scale experiment effectively demonstrated that extended periods of idle (>3 h) of soiled hauling vessels can significantly affect the microbiological quality of raw milk in subsequent loads; however, extended idle times of 6 h or less would not measurably compromise milk quality in subsequent loads in commercial tankers. Current tanker sanitation practices appear to be sufficient for maintaining raw milk SPC, LAB, and coliform levels, which are important measures of milk quality.     

奶啤的研制

以牛奶、麦芽和酒花为主要原料,通过二次生物发酵研制出具有奶香和啤酒风味的奶啤饮料。通过实验确定奶啤的最佳配方及生产工艺流程并对奶啤的稳定性进行探讨,从而研制出即有啤酒的低酒精度、泡沫丰富和适度的二氧化碳,又具有酸乳饮料的酸甜可口、营养全面的奶啤饮料。     

Invited review: Corrected milk: Reconsideration of common equations and milk energy estimates

Corrected milk equations were developed in attempts to bring milk weights to a standardized basis for comparison by expressing the weight and composition of milk as corrected to the energy content of milk of a specific composition. Expressed as milk weights familiar on farm and in commerce, this approach integrates energy contributions of the dissimilar components to make the mass units more comparable. Such values are applied in evaluating feed efficiency, lactation performance, and global milk production, as functional units for lifecycle assessments, and in translation of research results. Corrected milk equations are derived from equations relating milk gross energy to milk composition. First, a milk energy equation is used to calculate the energy value of the milk composition to correct to (e.g., 0.695 Mcal/kg for milk with 3.5% fat, 3.05% true protein, and 4.85% lactose). That energy value is divided into the energy equation to give the corrected milk equation. Confusion has arisen, as different equations purport to correct to the same milk composition; their differences are based on uses of different energy equations or divisors. Accuracy of corrected milk equations depends on the accuracy of the energy equations used to create them. Energy equations have evolved over time as different milk component analyses have become more available. Inclusion of multiple milk components more accurately predicts milk energy content than does fat content alone. Omission of components from an equation requires the assumption that their content in milk is constant or highly correlated with an included component. Neither of these assumptions is true. Milk energy equations evaluated on a small data set of measured milk values have demonstrated that equations that incorporate protein, fat, and lactose contents multiplied by the gross energy of each component more closely predict milk energy than equations containing fewer components or regression-derived equations. This provides a tentative recommendation for using energy equations that include the 3 main milk components and their gross energy multipliers for predicting milk energy and deriving corrected milk equations. Accuracy of energy equations is affected by the accuracy of gross energy values of individual components and variability of milk composition. Lactose has consistent reported gross energy values. In contrast, gross energy of milk fat and protein vary as their compositional profiles change. Future refinements could assess accuracy of milk fat and protein gross energy and whether that appreciably improves milk energy predictions. Fat gross energy has potential to be calculated using the milk fatty acid profile, although the influence on gross energy may be small. For research, direct reporting of milk energy values, rather than corrected milk, provides the most explicit, least manipulated form of the data. However, provision of corrected milk values in addition to information on components can serve to translate the energy information to a form familiar to and widely used in the field. When reporting corrected milk data, the corrected milk equation, citation for the energy equation used, and composition and energy contents of the corrected milk must be described to make clear what the values represent.     

毛细管电泳法对乳及乳制品中乳源蛋白的研究

采用毛细管电泳方法对原料乳、市售鲜奶、不同厂家的巴氏灭菌乳、不同厂家和产地超高温灭菌乳(UHT)、调味乳、乳酸饮料、复原乳、酸奶、奶粉中蛋白成分进行检测。选择聚乙烯醇涂层毛细管,采用柠檬酸缓冲体系,在紫外检测214nm、分离电压20kV条件下对乳及乳制品中的α一乳白蛋白(α-La)、β一乳球蛋白(β-Lg)、α-酪蛋白(α-CN)、β-酪蛋白(β-CN)和k-酪蛋白(k-CN)进行分离测定。结果表明:五种蛋白的含量在原料乳(巴氏灭菌乳、市售鲜奶)、UHT乳、酸奶、调味乳、乳酸饮料、复原乳中依次降低,而UHT乳含量随保质期的增加而减少,奶粉中蛋白质含量因其适应人群而有差异。乳及乳制品中蛋白质的含量与其存在形式、产地及加工工艺相关。