不同生鲜水牛乳滴定酸度的分析

按GB 4789.18—2010《乳与乳制品检验》标准对云南省主要奶水牛养殖小区、合作社同一季节26户养殖户的228个水牛生乳及相同来源不同月份的655个水牛生乳的酸度进行滴定,同时进行酒精检测和掺碱试验,并对日粮组成、饲喂模式及胎次和泌乳天数进行普查。同一季节不同来源的228个水牛生乳滴定酸度在10~13°T的占83.8%;相同来源不同月份的655个水牛生乳样品的滴定酸度在10~13°T的占86.4%;总的883个生鲜水牛乳滴定酸度为10~13°T的占85.7%,大于14°T占10.6%,小于10°T仅占3.6%。     

A survey of foodborne pathogens in bulk tank milk and raw milk consumption among farm families in pennsylvania

A 2-part study was conducted to determine the risk of exposure to human pathogens from raw milk. The first part of the study focused on determining raw milk consumption habits of dairy producers. A total of 248 dairy producers from 16 counties in Pennsylvania were surveyed. Overall, 105 (42.3%) of the 248 dairy producers consumed raw milk and 170 (68.5%) of the 248 dairy producers were aware of foodborne pathogens in raw milk. Dairy producers who were not aware of foodborne pathogens in raw milk were 2-fold more likely to consume raw milk compared with dairy producers who were aware of foodborne pathogens. The majority of dairy producers who consumed raw milk indicated that taste (72%) and convenience (60%) were the primary factors for consuming raw milk. Dairy producers who resided on the dairy farm were nearly 3-fold more likely to consume raw milk compared with those who lived elsewhere. In the second part of the study, bulk tank milk from the 248 participating dairy herds was examined for foodborne pathogens. Campylobacter jejuni (2%), Shiga toxin-producing Escherichia coli (2.4%), Listeria monocytogenes (2.8%), Salmonella (6%), and Yersinia enterocolitica (1.2%) were detected in the milk samples. Salmonella isolates were identified as S. enterica serotype Typhimurium (n = 10) and S. enterica serotype Newport (n = 5). Of the 248 bulk tank milk samples, 32 (13%) contained ≥1 species of bacterial pathogens. The findings of the study could assist in developing farm community-based educational programs on the risks of consuming raw milk.     

高效液相色谱-三重四级杆质谱联用法检测荷斯坦和水牛原料乳中磺胺类药物残留

目的分析目前我国南方地区荷斯坦原料乳和水牛原料乳中磺胺类药物的残留情况。方法采集浙江和广西地区荷斯坦牛牧场和水牛牧场的120份原料乳,采用高效液相色谱-三重四级杆质谱联用法检测其中的磺胺类药物残留。结果方法的检出限和回收率分别为0.05~0.10μg/L和73.2%~108.3%。水牛乳中磺胺类药物的残留量低于6.67μg/L,荷斯坦牛乳中磺胺类药物的残留量低于7.88μg/L。结论高效液相色谱-三重四级杆质谱联用法检测牛乳中磺胺类药物残留的结果准确可靠,我国南方地区的荷斯坦原料乳和水牛原料乳总体上处于安全范围。     

Molecular surveillance of Toxoplasma gondii in raw milk and Artisan cheese of sheep,goat, cow and water buffalo origin

This study is aimed at investigating the molecular prevalence of Toxoplasma gondii in raw milk and cheese of different animal species (sheep, goat, cow and water buffalo) in Kayseri Province, Türkiye, to provide a preliminary assessment for contamination risk. A total of 200 milk and cheese samples were analysed by real-time PCR. Toxoplasma gondii DNA was detected in two (8%) ewes and one (4%) goat raw milk sample, while none of the cheese samples were positive. These results indicated that the presence of T. gondii DNA in raw milk samples sold in Kayseri Province might be a risk factor for public health.     

Effect of temperature on raw whole milk density and its potential impact on milk payment in the dairy industry

The objective of this study was to determine the effect of temperature on whole milk density measured at four different temperatures: 5, 10, 15, and 20 °C. A total of ninety-three individual milk samples were collected from morning milking of thirty-two Holstein Friesian dairy cows, of national average genetic merit, once every two weeks over a period of 4 weeks and were assessed by Fourier transform infrared spectroscopy for milk composition analysis. Density of the milk was evaluated using two different analytical methods: a portable density meter DMA35 and a standard desktop model DMA4500M (Anton Paar GmbH, UK). Milk density was analysed with a linear mixed model with the fixed effects of sampling period, temperature and analysis method; triple interaction of sampling period x analysis method x temperature; and the random effect of cow to account for repeated measures. The effect of temperature on milk density (ρ) was also evaluated including temperature (t) as covariate with linear and quadratic effects within each analytic method. The regression equation describing the curvature and density–temperature relationship for the DMA35 instrument was ρ = 1.0338−0.00017T−0.0000122T² (R² = 0.64), while it was ρ = 1.0334 + 0.000057T−0.00001T² (R² = 0.61) for DMA4500 instrument. The mean density determined with DMA4500 at 5 °C was 1.0334 g cm⁻³, with corresponding figures of 1.0330, 1.0320 and 1.0305 g cm⁻³ at 10, 15 and 20 °C, respectively. The milk density values obtained in this study at specific temperatures will help to address any bias in weight–volume calculations and thus may also improve the financial and operational control for the dairy processors in Ireland and internationally.     

Prevalence,antimicrobial resistance,and molecular characterization of Campylobacter spp. in bulk tank milk and milk filters from US dairies

Campylobacter spp. are frequently isolated from dairy cows as commensal organisms. Sporadic Campylobacter infections in humans in the United States are generally attributed to poultry, but outbreaks are also commonly associated with dairy products, particularly unpasteurized or raw milk. Bulk tank milk samples and milk filters from US dairy operations were collected during the National Animal Health Monitoring System Dairy 2014 study and analyzed using real-time PCR and traditional culture techniques for the presence of thermophilic Campylobacter species. The weighted prevalence of operations from which we detected Campylobacter spp. in either bulk tank milk or milk filters was 24.9%. We detected Campylobacter spp. in a higher percentage of operations with 100–499 cows (42.8%) and 500 or more cows (47.5%) than in operations with 30–99 cows (6.5%). Campylobacter spp. were also more frequently detected in operations in the west than the east (45.9 and 22.6%, respectively). We isolated Campylobacter spp. from approximately half of PCR-positive samples, representing 12.5% (weighted prevalence) of operations. The majority (91.8%) of isolates were C. jejuni, but C. lari and C. coli were also isolated. We detected resistance to tetracycline in 68.4% of C. jejuni isolates, and resistance to ciprofloxacin and nalidixic acid in 13.2% of C. jejuni isolates. Based on pulsed-field gel electrophoresis, we found that dairy-associated C. jejuni were genotypically diverse, although clonal strains were isolated from different geographic regions. These results suggest that bulk tank milk can be contaminated with pathogenic Campylobacter spp., and that the consumption of unpasteurized or raw milk presents a potential human health risk.     

An analysis of the relationship between bulk tank milk quality and wash water quality on dairy farms in Ontario, Canada

The objective of this study was to identify regions at high risk for bacterial water or milk contamination, as well as risk factors associated with high bacteria counts in raw milk in Ontario, Canada. Between 2003 and 2004, the Dairy Farmers of Ontario (DFO) tested water samples from 5,421 farms in Ontario for the presence of Escherichia coli and coliforms. The water samples were collected as “point-of-use” samples, meaning that each sample was taken from a tap or water hose in the milk house as soon as the water was turned on. Routine, monthly raw milk bacterial counts were determined by DFO using BactoScan (Foss, Hillerød, Denmark). BactoScan data were retrieved from DFO for all of the farms with water test results. The prevalence of samples with E. coli and coliforms in water and elevated bacteria counts in raw milk was 13.6, 53.8, and 2.8%, respectively. The spatial analysis, using a scan statistic, revealed 1 coliform and 3 E. coli clusters of contaminated water, but no clusters of elevated milk bacteria counts in raw milk in southern Ontario. The coliform water contamination cluster was the largest, with a radius of approximately 200 km. Regression analysis indicated that risk factors associated with the occurrence of high levels of bacteria in raw milk were elevated average monthly somatic cell count, increased total milk production, cooler seasons of the year, and the presence of E. coli in wash water.     

Microbiological quality of raw milk used for small-scale artisan cheese production in Vermont: Effect of farm characteristics and practices

This study 1) evaluated the overall milk quality and prevalence of 4 target pathogens (Listeria monocytogenes, Staphylococcus aureus, Salmonella spp., and Escherichia coli O157:H7) in raw milk used for small-scale artisan cheesemaking and 2) examined specific farm characteristics and practices and their effect on bacterial and somatic cell counts (SCC). Raw milk samples were collected weekly from 21 artisan cheese operations (6 organic) in the state of Vermont that manufactured raw-milk cheese from cow (12), goat (5), or sheep (4) milk during the summer of 2008. Individual samples were examined for standard plate counts (SPC), coliform counts (CC), and SCC. Samples were also screened for target pathogens both quantitatively and qualitatively by direct plating and PCR. Overall, 86% of samples had SPC <10,000 cfu/mL, with 42% <1,000 cfu/mL. Additionally, 68% of samples tested were within pasteurized milk standards for coliform bacteria under the United States’ Grade A Pasteurized Milk Ordinance at <10 cfu/mL. Log₁₀ SPC and CC did not differ significantly among species. Similarly, method of sample delivery (shipped or picked up), farm type (organic or conventional), and duration of milking (year-round or seasonal) did not have significant effects on farm aggregated mean log₁₀ SPC, CC, or SCC. Strong positive correlations were observed between herd size and mean log₁₀ SPC and between log₁₀ SPC and CC as well as SCC when data from all animal species were combined. Although SCC for cow milk were significantly lower than those for goat and sheep milk, 98, 71, and 92% of cow, sheep, and goat milk samples, respectively, were within the compliance limits of the United States’ Grade A Pasteurized Milk Ordinance for SCC. Fourteen of the 21 farms (67%) were positive for Staph. aureus, detected in 38% of samples at an average level of 20 cfu/mL. Neither L. monocytogenes, E. coli O157:H7, or Salmonella spp. were detected or recovered from any of the 101 samples tested. Our results indicate that the majority of raw milk produced for small-scale artisan cheesemaking was of high microbiological quality with no detectable target pathogens despite the repeat sampling of farms. These data will help to inform risk assessments that evaluate the microbiological safety of artisan and farmstead cheeses, particularly those manufactured from raw milk.     

高效液相色谱法分析原料乳和奶粉中三聚氰胺

建立了二极管阵列检测器-高效液相色谱测定原料乳及奶粉中三聚氰胺的方法。奶粉样品经三氯乙酸超声提取,乙酸铅沉淀蛋白,三氯甲烷除去脂肪和非极性杂质,PROELUTPXCSPE阳离子交换固相萃取小柱进一步除去样品基质干扰,氨化甲醇洗脱。实验对色谱分离条件进行了优化,三聚氰胺的质量浓度在1.0～100.0μg/mL范围内与色谱峰面积呈良好的线性关系,回归方程为y=89.763x-113.72,相关系数为R2=0.9988。加标回收率为90.5%～105.0%,相对标准偏差(RSD)小于4.0%。该方法简单、快速,结果准确可靠。     

原料乳与乳制品中碳水化合物质量控制研究进展

原料乳与乳制品中碳水化合物具有极高的营养价值,对人体健康具有重要作用,但其掺伪现象较普遍,严重影响了原料乳与乳制品的品质。文章综述了原料乳与乳制品中碳水化合物及其掺伪物质检测技术研究进展,旨在为做好原料乳与乳制品中碳水化合物质量控制提供科学依据。      

碳酸水保藏生牛乳及其去除效果的研究

以添加不同量碳酸水的生牛乳（4℃）为研究对象,检测其冷藏期的理化指标及菌落总数,并进行碳酸水去除实验,探索一种延长生牛乳冷藏保存期的方法。结果表明:添加碳酸水可延缓生乳的酸败,且溶解的CO₂浓度越高,抑菌作用越显著;在碳酸水去除实验中,CO₂浓度为41.47 mmol/L的生乳在55℃、-0.085^-0.095 MPa条件下旋蒸15 min后,其水分含量、CO₂含量及热稳定性可恢复到对照组水平。碳酸水不会对生牛乳的理化性质造成影响且易去除,因此,可以采用添加碳酸水的方法延长生牛乳的冷藏保存期。      

HPLC测定原料乳与乳制品中三聚氰胺质量分数的不确定度评定

建立高效液相色谱法测定测定原料乳与乳制品中三聚氰胺质量分数的不确定度评定方法,采用GB/T22388-2008高效液相色谱法测定测定原料乳与乳制品中三聚氰胺质量分数。建立数学模型,根据《测量不确定度评定与表示》(JJF1059—1999)中有关规定评估其不确定度。结果表明,按数学模型计算奶粉中三聚氰胺质量分数为2.70mg/kg,扩展不确定度为0.064mg/kg,结果表达为(2.70±0.064)mg/kg。该方法建立的数学模型合理、可靠。     

西藏乳及发酵乳制品中乳酸菌与酵母菌分布

西藏当地牦牛乳及发酵乳制品中的微生物分布备受科研人员的关注,而且重点多集中在其中的乳酸菌和酵母菌。本文对西藏当地乳及乳制品中乳酸菌与酵母菌的分布做了详细的介绍,包括原料乳、曲拉和藏灵菇乳中的乳酸菌和酵母菌的研究现状,并对今后的发展趋势做了分析。      

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.     

Composition and properties of bovine milk: A study from dairy farms in northern Sweden; Part I. Effect of dairy farming system

This study was part of a larger project that aimed to understand the causes for increasing variation in cheese ripening in a cheese-producing region in northern Sweden. The influence of different on-farm factors on raw milk composition and properties was investigated and is described in this paper, whereas the monthly variation in the milk quality traits during 1 yr is described in our companion paper. The dairy farming systems on a total of 42 dairy farms were characterized through a questionnaire and farm visits. Milk from farm tanks was sampled monthly over 1 yr and analyzed for quality attributes important for cheese making. On applying principal component analyses to evaluate the variation in on-farm factors, different types of farms were distinguished. Farms with loose housing and automatic milking system (AMS) or milking parlor had a higher number of lactating cows, and predominantly Swedish Holstein (SH) breed. Farms associated with tiestalls had a lower number of lactating cows and breeds other than SH. Applying principal component analyses to study the variation in composition and properties of tank milk samples from farms revealed a tendency for the formation of 2 clusters: milk from farms with AMS or a milking parlor, and milk from farms with tiestall milking. The interaction between the milking system, housing system, and breed probably contributed to this grouping. Other factors that were used in the characterization of the farming systems only showed a minor influence on raw milk quality. Despite the interaction, milk from tiestall farms with various cow breeds had higher concentrations (g/100 g of milk) of fat (4.74) and protein (3.63), and lower lactose concentrations (4.67) than milk from farms with predominantly SH cows and AMS (4.32, 3.47, and 4.74 g/100 g of milk, respectively) or a milking parlor (4.47, 3.54, and 4.79 g/100 g of milk, respectively). Higher somatic cell count (195 × 10³/mL) and lower free fatty acid concentration (0.75 mmol/100 g of fat) were observed in milk from farms with AMS than in milk from tiestall systems (150 × 10³/mL and 0.83 mmol/100 g of fat, respectively). Type of farm influenced milk gel strength, with milk from farms with predominantly SH cows showing the lowest gel strength (65.0 Pa), but not a longer rennet coagulation time. Effects of dairy farming system (e.g., dominant breed, milking system, housing, and herd size) on milk quality attributes indicate a need for further studies to evaluate the in-depth effects of farm-related factors on milk quality attributes.     

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。     

Aflatoxin M1 in raw,UHT milk and dairy products in Sicily (Italy)

A survey on 73 milk samples from different animal breeds and 24 dairy products samples from Sicily, Italy, was carried out for the presence of aflatoxin M₁ (AFM1) by LC-fluorescence detection after immunoaffinity cleanup. AFM1 was detected in 48% and 42% of the milk and dairy samples at concentration ranges between <5.0–16.0 and <5.0–18.0 ng L^?1, respectively. Within the raw milk samples, 92% had an AFM1 content below 5.0 ng L^?1, in 7% of the cases it was in the range 5.0–10.0 ng L^?1 and 1% was contaminated between 10.0 and 20.0 ng L^?1. For the dairy products, ultra-high-temperature treated (UHT) milk, milk cream and cheese, the incidence was 42%, of which 83% contained less than 5.0 ng L^?1 and 17% contained 10.0–20.0 ng L^?1 AFM1. The levels of contamination found justify continuous monitoring for public health and to reduce consumer exposure.     

应用16S rDNA全序列测序技术鉴定生鲜乳中的细菌种类

采用玻璃珠法提取生鲜乳中分离的34株细菌基因组DNA,用细菌通用引物(27f/1492r)PCR扩增16S r DNA片段并测序,与Gen Bank数据库同源序列比对,系统发育树聚类分析,并结合形态学和生理学特征确定了34株菌的种属地位。结果表明,共鉴定出16个种属。3个生鲜乳样中细菌种类及其分布特点不同。其中1号样有7种细菌,以Acinetobacter sp.(不动杆菌属)为主,2号样有6种细菌,以Klebsiella sp.(克雷贝氏杆菌属)为主,3号样有6种细菌,分布较为分散。从致病性来看,分离菌株主要为条件致病菌或腐败菌,无烈性致病菌。      

The occurrence of Staphylococcus aureus on a farm with small-scale production of raw milk cheese

In recent years, the small-scale production of raw milk products has increased in Norway, and there is some concern that such foods may pose a risk of staphylococcal food poisoning to consumers. The aim of the study was to evaluate potential sources of contamination of raw milk cheese with Staphylococcus aureus on a bovine dairy farm with small-scale production. Samples for bacteriological analyses (n = 144) were collected from the animals, the environment, processing equipments, from humans, and from cheeses at various stages of production. Staphylococcus aureus was isolated from 10 of 11 cows, the farmer, equipment, the environment, and the cheese. Seventy-five Staph. aureus isolates were genotyped by pulsed-field gel electrophoresis, tested for enterotoxin (SE) production by reversed passive latex agglutination, for SE genes by multiplex polymerase chain reaction, and for penicillin resistance by the cloverleaf method. Five different pulsotypes were identified and SE gene fragments were identified in 11 isolates, but no isolates produced SE or were penicillin resistant. Staphylococcus aureus was found throughout the farm, and appeared to be spread with the milk to the environment, equipment, and to products. One pulsotype dominated and was identified from most sample sites on the farm. Raw milk products are vulnerable to contamination with Staph. aureus. Strategies to reduce the occurrence of Staph. aureus in bulk milk are of particular importance on farms where milk is used for raw milk products.