Shi X, Qian C, Murphy S I, Wiedmann M, Martin N H
Milk Quality Improvement Program, Department of Food Science, Cornell University, Ithaca, NY 14853.
JDS Commun. 2022 Nov 18;4(1):1-4. doi: 10.3168/jdsc.2022-0252. eCollection 2023 Jan.
Anaerobic butyric acid-producing sporeforming bacteria (BAB) are important microbial contaminants in raw milk that may lead to premature spoilage of certain cheeses during aging. A study was conducted to determine the baseline levels of these spores in raw milk from 7 conventional Northeast United States dairy farms over a 1-yr period. The overall mean BAB concentration was 1.79 log most probable number per liter with spore levels differing significantly by farm. A post-hoc farm management practices survey was conducted to determine if there was an association between farm practices on BAB levels in raw milk from these farms. Survey questions included variables related to bedding, milking preparation procedures, teat and udder cleanliness scoring, holding area cleaning procedures, and udder clipping or flaming frequency. Each variable was fitted with a linear mixed-effects model, which revealed no significant association between farm-level factors and the initial BAB concentrations in raw milk; this finding was likely due to the small sample size in this study. To demonstrate the usefulness of our data beyond the initial baseline levels of BAB spores in raw milk, we used this data set to calculate minimum number of individual samples that would be needed to be collected in future studies, which was determined to be 96 to 126 samples, to evaluate the association between farm-level factors and BAB spore concentrations in raw milk. Overall, this study provides dairy industry stakeholders with baseline data on BAB spore levels in raw milk, along with a demonstration on how these data could be used in future studies to calculate sample sizes needed to assess the effect of farm management practices on BAB levels in raw milk.
产丁酸厌氧芽孢形成菌（BAB）是生牛奶中的重要微生物污染物，可能导致某些奶酪在陈化过程中过早变质。本研究旨在确定美国东北部7个传统奶牛场在1年时间内生牛奶中这些芽孢的基线水平。BAB的总体平均浓度为每升1.79个对数最可能数，不同农场的芽孢水平差异显著。随后进行了农场管理实践调查，以确定这些农场的管理实践与生牛奶中BAB水平之间是否存在关联。调查问题包括与垫料、挤奶准备程序、乳头和乳房清洁评分、储存区清洁程序以及乳房修剪或火焰消毒频率相关的变量。每个变量都拟合了线性混合效应模型，结果显示农场层面的因素与生牛奶中初始BAB浓度之间没有显著关联；这一发现可能是由于本研究的样本量较小。为了证明我们的数据在生牛奶中BAB芽孢初始基线水平之外的有用性，我们使用该数据集计算了未来研究中需要收集的最少个体样本数量，确定为96至126个样本，以评估农场层面的因素与生牛奶中BAB芽孢浓度之间的关联。总体而言，本研究为乳制品行业利益相关者提供了生牛奶中BAB芽孢水平的基线数据，并展示了如何在未来研究中使用这些数据来计算评估农场管理实践对生牛奶中BAB水平影响所需的样本量。
