Department of Nutrition and Food Sciences, University of Vermont, Burlington 05405, USA.
J Dairy Sci. 2010 Jan;93(1):134-47. doi: 10.3168/jds.2009-2426.
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. Log(10) 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 log(10) SPC, CC, or SCC. Strong positive correlations were observed between herd size and mean log(10) SPC and between log(10) 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.
本研究 1）评估了小规模手工奶酪制作中使用的原料奶的整体牛奶质量和 4 种目标病原体（单核细胞增生李斯特菌、金黄色葡萄球菌、沙门氏菌和大肠杆菌 O157：H7）的流行情况，2）检查了特定的农场特征和实践及其对细菌和体细胞计数（SCC）的影响。2008 年夏季，从佛蒙特州的 21 家手工奶酪厂（6 家为有机农场）每周采集一次原料奶样本，这些奶酪厂使用牛奶（12 家使用牛奶，5 家使用山羊奶，4 家使用绵羊奶）生产原料奶奶酪。对单个样本进行标准平板计数（SPC）、大肠菌群计数（CC）和 SCC 检测。还通过直接平板和 PCR 定量和定性筛选目标病原体。总体而言，86%的样本 SPC<10,000 cfu/mL，其中 42%<1,000 cfu/mL。此外，根据美国 A 级巴氏杀菌奶条例，68%的样本中大肠菌群细菌<10 cfu/mL，符合巴氏杀菌奶标准。种间 SPC 和 CC 的对数(10)差异不显著。同样，样本交付方式（邮寄或自取）、农场类型（有机或常规）和挤奶时间（全年或季节性）对农场聚集平均对数(10)SPC、CC 或 SCC 均无显著影响。当合并所有动物物种的数据时，观察到 herd size 与平均对数(10)SPC 之间以及 SPC 与 CC 和 SCC 之间存在强烈的正相关关系。尽管牛奶奶制品的 SCC 明显低于山羊奶和绵羊奶，但分别有 98%、71%和 92%的牛奶奶制品、山羊奶奶制品和绵羊奶奶制品的 SCC 样本均符合美国 A 级巴氏杀菌奶条例规定的 SCC 合规限值。21 家农场中有 14 家（67%）检测到金黄色葡萄球菌阳性，在 38%的样本中平均水平为 20 cfu/mL。在 101 个测试样本中，未检测到单核细胞增生李斯特菌、大肠杆菌 O157：H7 或沙门氏菌。我们的结果表明，尽管重复采样农场，但大多数用于小规模手工奶酪制作的原料奶的微生物质量很高，没有检测到目标病原体。这些数据将有助于为评估手工和农场奶酪的微生物安全性提供信息，特别是那些使用原料奶生产的奶酪。
