Sensory analysis and species-specific PCR detect bovine milk adulteration of frescal (fresh) goat cheese

The Brazilian market for dairy products made from goat milk is increasing despite the seasonality of production and naturally small milk production per animal, factors that result in high-priced products and encourage fraud. In Brazil, no official analytical method exists for detecting adulteration of goat dairy products with cow milk. The aim of this study was to design a strategy to investigate the adulteration of frescal (fresh) goat cheeses available in the Rio de Janeiro retail market, combining analysis of cheese composition and the perception of adulteration by consumers. Commercial goat cheeses were tested by using a duplex PCR assay previously designed to authenticate cheeses, by targeting the mitochondrial 12S ribosomal RNA genes of both species simultaneously. The PCR test was able to detect 0.5% (vol/vol) cow milk added during goat cheese formulation. The analysis of 20 locally produced goat cheeses (20 lots of 4 brands) showed that all were adulterated with cow milk, even though the labels did not indicate the addition of cow milk. To estimate the ability of consumers to perceive the fraudulent addition of cow milk, a triangle test was performed, in which cheeses formulated with several different proportions of goat and cow milk were offered to 102 regular consumers of cheese. Detection threshold analysis indicated that almost half of the consumers were able to perceive adulteration at 10% (vol/vol) cow milk. Effective actions must be implemented to regulate the market for goat dairy products in Brazil, considering the rights and choices of consumers with respect to their particular requirements for diet and health, preference, and cost.     

A gas chromatography-mass spectrometry-based metabolomic approach for the characterization of goat milk compared with cow milk

In this work, the polar metabolite pool of commercial caprine milk was studied by gas chromatography-mass spectrometry and multivariate statistical data analysis. Experimental data were compared with those of cow milk and the discriminant analysis correctly classified milk. By the same means, differences due to heat treatments (UHT or pasteurization) on milk samples were also investigated. Results of the 2 discriminant analyses were combined, with the aim of finding the discriminant metabolites unique for each class and shared by 2 classes. Valine and glycine were specific to goat milk, talose and malic acid to cow milk, and hydroxyglutaric acid to pasteurized samples. Glucose and fructose were shared by cow milk and UHT-treated samples, whereas ribose was shared by pasteurized and goat milk. Other discriminant variables were not attributed to specific metabolites. Furthermore, with the aim to reduce food fraud, the issue of adulteration of caprine milk by addition of cheaper bovine milk has been also addressed. To this goal, mixtures of goat and cow milk were prepared by adding the latter in a range from 0 to 100% (vol/vol) and studied by multivariate regression analysis. The error in the level of cow milk detectable was approximately 5%. These overall results demonstrated that, through the combined approach of gas chromatography-mass spectrometry and multivariate statistical data analysis, we were able to discriminate between milk typologies on the basis of their polar metabolite profiles and to propose a new analytical method to easily discover food fraud and to protect goat milk uniqueness. The use of appropriate visualization tools improved the interpretation of multivariate model results.     

Prediction of fatty acid profiles in cow,ewe, and goat milk by mid-infrared spectrometry

Mid-infrared (MIR) spectrometry was used to estimate the fatty acid (FA) composition in cow, ewe, and goat milk. The objectives were to compare different statistical approaches with wavelength selection to predict the milk FA composition from MIR spectra, and to develop equations for FA in cow, goat, and ewe milk. In total, a set of 349 cow milk samples, 200 ewe milk samples, and 332 goat milk samples were both analyzed by MIR and by gas chromatography, the reference method. A broad FA variability was ensured by using milk from different breeds and feeding systems. The methods studied were partial least squares regression (PLS), first-derivative pretreatment + PLS, genetic algorithm + PLS, wavelets + PLS, least absolute shrinkage and selection operator method (LASSO), and elastic net. The best results were obtained with PLS, genetic algorithm + PLS and first derivative + PLS. The residual standard deviation and the coefficient of determination in external validation were used to characterize the equations and to retain the best for each FA in each species. In all cases, the predictions were of better quality for FA found at medium to high concentrations (i.e., for saturated FA and some monounsaturated FA with a coefficient of determination in external validation >0.90). The conversion of the FA expressed in grams per 100 mL of milk to grams per 100 g of FA was possible with a small loss of accuracy for some FA.     

乳及乳制品中抗寄生虫药检测研究进展

抗寄生虫药是牛羊等产奶动物养殖过程中必不可少的投入品。这些药物经牛羊吸收代谢后, 容易残留在牛羊奶及其他动物组织中, 给消费者造成安全隐患。我国食品安全国家标准规定了牛羊奶中21种抗寄生虫药的最大残留限量值, 科研工作者们也建立了多种检测方法。本文对2018~2023年牛羊奶中抗寄生虫药的检测方法进行综述, 简要对比电化学传感器法、表面增强拉曼光谱法、胶体金免疫试纸条法、液相色谱-质谱法、液相色谱-高分辨质谱法的优缺点, 并对抗寄生虫药检测方法的发展方向进行了讨论和展望, 为乳及乳制品中抗寄生虫药的定性筛查和定量检测提供技术参考。     

蛋白质组学技术在不同物种乳掺假检测中的应用

乳品是人类重要的营养源，然而乳品掺假现象时常发生，近年来尤以向乳品中掺假动、植物蛋白，向特色畜乳中掺假牛乳等方式为主，这不仅损害了消费者的利益，甚至会危害消费者的健康。该研究总结了目前常见的掺假行为及相关检测方法，并介绍了蛋白质组学技术——一种通过确立特定生物标记物来区别不同物种乳的技术。作者查询了国内外近十年来牛乳和特色乳掺假方面的研究报道，关键词设置为“蛋白质组学”、“乳品”、“真实性”、“生物标记物”等，按照奶畜乳类别将所得文献进行分类。分别对奶牛乳、羊乳、驼乳、水牛乳、牦牛乳、驴乳的掺假物、潜在标记物和检出限等方面进行了总结和分析，以期为乳品真实性鉴定和保障乳品质量安全提供有效的工作思路。     

Differentiation of perirenal and omental fat quality of suckling lambs according to the rearing system from Fourier transforms mid-infrared spectra using partial least squares and artificial neural networks analysis

Fourier transform mid-infrared (FT-IR) spectroscopy was evaluated as a tool to discriminate between carcasses of suckling lambs according to the rearing system. Fat samples (39 perirenal and 67 omental) were collected from carcasses of lambs from up to three sheep dairy farms, reared on either ewes milk (EM) or milk replacer (MR). Fatty acid composition of the samples from each fat deposit was first analyzed and, when discriminant-partial least squares regression (PLS) was applied, a perfect discrimination between rearing systems could be established. Additionally, FT-IR spectra of fat samples were obtained and discriminant-PLS and artificial neural network (ANN) based analysis were applied to data sets, the latter using principal component analysis (PCA) or support vector machines (SVM) as processing procedure. Perirenal fat samples were perfectly discriminated from their FT-IR spectra. However, analysis of omental fat showed misclassification rates of 9–13%, with the ANN approach showing a higher discrimination power.     

Past, present, and future perspectives of small ruminant dairy research

The objectives of this paper are to review small ruminant dairy research in relation to the dimensions of the dairy goat and dairy sheep industries in the United States and the world. At least 10 countries depend on goats and sheep for between 30 to 76% of total milk supply. Leading among developed countries is Greece producing 178 kg milk per person per year with 61% from sheep and goats. Most developing countries need research, extension service, and public support to improve apparent productivity of goats and sheep. Domestic supply from all milk sources is <100 kg/person per year, and annual apparent yields average <100 kg of milk/goat, <50 kg of milk/sheep, which makes supplies of animal protein and calcium from domestic sources very low. Statistical data on goat and sheep production for United States are not available. The small population of DHIA tested US dairy goats averaged in recent years >700 kg of milk/goat per year, and some dairy sheep breeds may produce as much as 650 kg/yr. The need for more milk availability appears to be reflected in the dramatic increases of dairy goat populations during the last 20 yr: 52% for the world, 56% for developing, 17% for developed countries, while sheep populations decreased by 3% for the world, by 6% in developed, but increased 14% in developing countries. Research has been sparse on the unique qualities of goat and sheep milk compared with cow milk. Much development work by various agencies has been devoted to reducing mortality and improving feed supplies in harmony with the environment; this work is mostly published in proceedings of scientific meetings, often not in English. Results have shown in many cases that dairy goats and dairy sheep can be very profitable, even in developing countries with difficult climate and topographical conditions.     

A simultaneous triplex TaqMan real-time PCR approach for authentication of caprine and bovine meat,milk and cheese

Goat foodstuffs are considered as healthy foods with high nutritional value. This study demonstrated the development and validation of a triplex real-time PCR on the basis of species-specific and species-conservative TaqMan probes for the simultaneous identification of caprine and bovine DNA in meats, milk and cheeses with a prerequisite designed endogenous control. In this research, caprine and bovine meat, milk and cheese were specifically identified via developed primers and probes, and the limits of detection of this methodology were 0.005 and 0.01 ng DNA of milk and cheese from goat, and 0.01 and 0.05 ng DNA of milk and cheese from cow. Taken together, this approach was elaborated to address dairy adulteration issues to eliminate the fraud of economically motivated goat milk and cheese adulteration by adding cow milk.     

基于牛乳非蛋白生物标志物定量检测山羊乳中掺加的牛乳

为克服酶联免疫吸附法无法检测羊乳中掺加的经过热处理的牛乳的局限，本研究首先通过气相色谱-质谱法发现牛乳区别于山羊乳的关键非蛋白生物标志物为N-乙酰氨基葡萄糖，然后基于该标志物开发基于高效液相色谱手段定量检测山羊乳中掺加的牛乳的方法。样品在70?℃经1-苯基-3-甲基-5-吡唑啉酮衍生60?min后，在高效液相色谱仪上使用反相C18色谱柱对目标物进行分离，在245?nm紫外波长下对其进行检测，根据N-乙酰氨基葡萄糖含量推算山羊乳中掺加的牛乳量。该方法的牛乳掺加量检出限和定量限分别为0.3%和1.0%，在1%～100%的牛乳掺加范围内线性良好，相关系数为0.999?4，该方法的加标回收率为100.4%～105.1%，在10、50?mg/L和100?mg/L加标质量浓度下，日内和日间精密度分别为1.8%和2.0%、1.7%和3.7%、2.6%和2.7%。该方法具有较高的灵敏度、准确度和精密度，可用于山羊乳中掺加牛乳的定量分析。     

Use of sandwich IgG ELISA for the detection and quantification of adulteration of milk and soft cheese

The aim of this work was to develop an assay capable of detecting adulteration of soft goat, sheep and buffalo milk cheese with bovine milk from cheaper sources. A previously developed indirect competitive ELISA had a lower sensitivity when applied to cheese, compared with milk. A sandwich ELISA was developed utilising the same monoclonal antibody in combination with a polyclonal goat anti-bovine IgG antibody. Once optimised, the ELISA was found to be highly specific. Detection limits in milk were 0.001% cows’ milk adulteration of sheep or buffalo milk, and 0.01% cows’ milk adulteration of goat milk. Detection limits in soft cheese were 0.001% in goat cheese and 0.01% in sheep or buffalo cheese. The assay was highly reproducible with both intra- and inter-assay coefficient of variation <10%. The ELISA performance makes it suitable for development as a kit for use in routine surveillance of milk and soft cheese.     

Application of immunological methods for the detection of species adulteration in dairy products

A number of enzyme‐linked immunosorbent assays (ELISAs) have been developed for the detection of milk adulteration in dairy products. Target antigens have been caseins, lactoglobulins, immunoglobulins and other whey proteins. Polyclonal and monoclonal antibodies have been used in a variety of formats including direct, indirect, competitive and sandwich ELISAs. ELISAs have been successfully applied to the detection of cows' milk adulteration of sheep, goat and buffalo milk. Goat milk adulteration of sheep milk has also been detected. A number of ELISAs have also been applied to cheese. It is recommended that ELISA should be used in combination with PCR to ensure compliance with current legislation.     

A 100-Year Review: Advances in goat milk research

In the century of research chronicled between 1917 and 2017, dairy goats have gone from simply serving as surrogates to cows to serving as transgenic carriers of human enzymes. Goat milk has been an important part of human nutrition for millennia, in part because of the greater similarity of goat milk to human milk, softer curd formation, higher proportion of small milk fat globules, and different allergenic properties compared with cow milk; however, key nutritional deficiencies limit its suitability for infants. Great attention has been given not only to protein differences between goat and cow milk, but also to fat and enzyme differences, and their effect on the physical and sensory properties of goat milk and milk products. Physiological differences between the species necessitate different techniques for analysis of somatic cell counts, which are naturally higher in goat milk. The high value of goat milk throughout the world has generated a need for a variety of techniques to detect adulteration of goat milk products with cow milk. Advances in all of these areas have been largely documented in the Journal of Dairy Science (JDS), and this review summarizes such advances.     

绵羊奶组成和营养特性

绵羊奶是我国乳制品工业的"新增量",养殖规模和产奶量快速上升,然而,我国目前的绵羊奶产业水平还处于初级阶段,规模化加工制品几乎为零.绵羊奶营养价值高,总固形物在各种乳源中含量最高,除了具有较高含量的蛋白质、脂肪、矿物质和维生素以外,绵羊奶的活性功能因子丰富,乳铁蛋白、活性肽、乳脂肪球膜及低聚糖的组成、含量和生物活性与牛...     

牛羊乳混掺检测鉴别技术研究进展

近年来,羊乳以其较好的营养特性渐成流行趋势,由于季节波动的影响,其价格远高于牛乳。在经济利益的驱动下,羊乳中掺入牛乳的现象时有发生,且呈现日趋严重的趋势,制约了羊奶产业的良性发展,迫切需要建立快速准确的牛羊乳混掺定性定量检测技术体系。本文对牛羊乳的差异及据此建立的、业已报道的相关检测技术进行了比较分析。常用检测技术主要包括色谱技术(气相色谱、气相色谱-质谱联用、高效液相色谱-质谱联用、高效液相色谱)、电泳技术(聚丙烯酰胺凝胶电泳、等电点聚焦电泳、毛细管电泳)、酶联免疫技术、聚合酶链式反应技术等,介绍了各种检测技术的原理及特点,并分析其可行性,为探索新的高效检测方法提供了思路,为牛羊乳混掺检测分析提供文献参考。     

Use of MALDI-TOF MS technology to evaluate adulteration of small ruminant milk with raw bovine milk

Detection of adulteration of small ruminant milk is very important for health and commercial reasons. New analytical and cost-effective methods need to be developed to detect new adulteration practices. In this work, we aimed to explore the ability of the MALDI-TOF mass spectrometry to detect bovine milk in caprine and ovine milk using samples from 18 dairy farms. Different levels of adulteration (0.5, 1, 5, 10, 20, 40, 60, and 80%) were analyzed during the lactation period of goat and sheep (in May, from 60 to 90 d in milk, and in August, from 150 to 180 d in milk). Two different ranges of peptide-protein spectra (500–4,000 Da; 4–20 kDa) were used to establish a calibration model for predicting the concentration of adulterant using partial least squares and generalized linear model with lasso regularization. The low molecular weight part of the spectra together with the generalized linear model with lasso regularization regression model appeared to have greater potential for our aim of detection of adulteration of small ruminants' milk. The subsequent prediction model was able to predict the concentration of bovine milk in caprine milk with a root mean square error of 11.4 and 17.0% in ovine milk. The results offer compelling evidence that MALDI-TOF can detect the adulteration of small ruminants' milk. However, the method is severely limited by (1) the complexity of the milk proteome resulting from the adulteration technique, (2) the potential degradation of thermolabile proteins, and (3) the genetic variability of tested samples. Additionally, the root mean square error of prediction based only on one individual sample adulteration series can drop down to 6.34% for quantification of adulterated caprine milk and 6.28% for adulterated ovine milk for the full set of concentrations or down to 2.33 and 4.00%, respectively, if we restrict only to low concentrations of adulteration (0, 0.5, 1, 5, 10%).     

Identification and differentiation of goat and sheep milk based on diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) using cluster analysis

A new methodology for identification and differentiation of goat and sheep milk was developed based on FT-IR spectroscopy using hierarchical and discriminant analysis. Forty-nine goat and 38 sheep defatted and freeze-dried Greek milk samples were analyzed. FT-IR spectra were obtained in the diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) mode. The spectral region 1840–950 cm⁻¹ was used to ‘fingerprint’ milk types. Main peak used for differentiation of goat/sheep milk is located at 1745 cm⁻¹, which is correlated to the degree of sugars carboxyl methyl esterification. Hierarchical and discriminant analyses were based on the absorptions of the above spectral region. These analyses showed that the samples of goat milk can be differentiated from the samples of sheep’s.     

Occurrence of aflatoxin M1 in raw and market milk commercialized in Greece

From December 1999 to May 2000, 114 samples of pasteurized, ultrahigh temperature-treated (UHT) and concentrated milk were collected in supermarkets, whereas 52 raw milk samples from cow, sheep and goat were obtained from different milk producers all over Greece. Sample collection was repeated from December 2000 to May 2001 and concerned 54 samples of pasteurized milk, 23 samples of bulk-tank raw milk and 55 raw milk samples from cow, sheep and goat. The total number of samples analysed for aflatoxin M₁ (AFM₁) contamination by immunoaffinity column extraction and liquid chromatography was 297. In the first sampling, the incidence rates of AFM 1 contamination in pasteurized, UHT, concentrated and cow, sheep and goat raw milk were 85.4, 82.3, 93.3, 73.3, 66.7 and 40%, respectively, with only one cow raw milk and two concentrated milk samples exceeding the EU limit of 50 ng l^-1. In the second sampling, the incidence rates of AFM 1 contamination in pasteurized, bulk-tank and cow, sheep and goat raw milk were 79.6, 78.3, 64.3, 73.3 and 66.7%, respectively, with only one cow and one sheep raw milk samples exceeding the limit of 50 ng l^-1. The results suggest that the current regulatory status in Greece is effective.     

Milk adulteration: Detection of bovine milk in bulk goat milk produced by smallholders in northeastern Brazil by a duplex PCR assay

The aim of this study was to investigate the adulteration of goat milk produced by smallholders in semiarid northeastern Brazil with bovine milk as an adulterant. The study was requested by the association of smallholder producers in the region to investigate and to inhibit adulteration practices as a need to ensure the quality and safety of goat milk. A duplex PCR assay has been developed and standardized. Further validation was performed in 160 fresh bulk goat milk samples. The detection limit of the duplex PCR was 0.5% bovine milk in goat milk and the results indicated that 41.2% of the goat milk presented to market was positive for bovine milk. Making the test available to the association of producers, together with extension activities, have been applied to reduce adulteration in goat milk sold to small-scale dairy plants and to ensure the species origin for goat milk in the state of Paraíba.     

近红外光谱法用于掺假羊奶的快速无损鉴别

利用近红外光谱技术结合多种化学计量学方法,研究了快速鉴别掺假羊奶的方法。将淀粉溶液,含尿素的淀粉溶液,含尿素和奶油的淀粉溶液按不同比例掺入纯羊奶中,进行近红外光谱采集。分别采用偏最小二乘差别分析(PLS-DA),fisher线性判别和多层感知器(MLP)神经网络法建立校正模型并进行检验验证。结果表明,MLP神经网络的鉴别效果最好,其校正模型的正判率达到99.4%,验证集的正判率达到100%。说明采用近红外光谱技术结合适当的化学计量学方法可以实现羊奶掺假检测的快速无损鉴别。     

Acid and rennet gelation properties of sheep,goat, and cow milks: Effects of processing and seasonal variation

Gelation is an important functional property of milk that enables the manufacture of various dairy products. This study investigated the acid (with glucono-δ-lactone) and rennet gelation properties of differently processed sheep, goat, and cow milks using small-amplitude oscillatory rheological tests. The impacts of ruminant species, milk processing (homogenization and heat treatments), seasonality, and their interactions were studied. Acid gelation properties were improved (higher gelation pH, shorter gelation time, and higher storage modulus (G′) by intense heat treatment (95°C for 5 min) to comparable extents for sheep and cow milks, both better than those for goat milk. Goat milk produced weak acid gels with low G′ (<100 Pa) despite improvements induced by heat treatments. Seasonality had a marked impact on the acid gelation properties of sheep milk. The acid gels of late-season sheep milk had a lower gelation pH, no maximum in tan δ following gel formation, and 70% lower G′ values than those from other seasons. We propose the potential key role of a critical acid gelation pH that induces structural rearrangements in determining the viscoelastic properties of the final gels. For rennet-induced gelation, compared with cow milk, the processing treatments of the goat and sheep milks had much smaller impacts on their gelation properties. Intense heat treatment (95°C for 5 min) prolonged the rennet gelation time of homogenized cow milk by 8.6 min (74% increase) and reduced the G′ of the rennet gels by 81 Pa (85% decrease). For sheep and goat milks, the same treatment altered the rennet gelation time by only less than 3 min and the G′ of the rennet gels by less than 14 Pa. This difference may have been caused by the different physicochemical properties of the milks, such as differences in their colloidal stability, proportion of serum-phase caseins, and ionic calcium concentration. The seasonal variations in the gelation properties (both acid and rennet induced) of goat milk could be explained by the minor variation in its protein and fat contents. This study provides new perspectives and understandings of milk gelation by demonstrating the interactive effects among ruminant species, processing, and seasonality.