Miller R A, Kent D J, Boor K J, Martin N H, Wiedmann M
Milk Quality Improvement Program, Department of Food Science, Cornell University, Ithaca, NY 14853.
Milk Quality Improvement Program, Department of Food Science, Cornell University, Ithaca, NY 14853.
J Dairy Sci. 2015 Jul;98(7):4338-51. doi: 10.3168/jds.2015-9406. Epub 2015 May 7.
Bacterial endospores (also referred to as spores) present in raw milk are capable of surviving pasteurization and other adverse conditions encountered during dairy powder production. Therefore, requiring low spore levels in raw ingredients (e.g., raw milk) may be necessary for producing dairy powders with low spore counts. To identify potential associations between management practices and spore levels in raw milk, we sampled bulk tank raw milk from 33 farms throughout New York State every other month for 1yr. Following spore pasteurization (80°C for 12min), samples were incubated at 3 different temperatures to enumerate psychrotolerant (6°C for 10 d), mesophilic (32°C for 48h), and thermophilic (55°C for 48h) spores. An additional enrichment procedure was used to detect spores present at low levels (<10 spores/mL). Overall, psychrotolerant, mesophilic, and thermophilic spores were detected (at levels ≥10 spores/mL) in 1, 74, and 58% of bulk tank raw milk samples, respectively. Although thermophilic spore levels could not be quantified (due to bacterial swarming), mesophilic spore levels ranged from below detection (<10 spores/mL) to 680 spores/mL. Data collected through surveys were used to identify management practices associated with either mesophilic or thermophilic spore levels. We found that different management practices are associated with mesophilic and thermophilic spore levels. Low mesophilic spore levels in bulk tank raw milk samples were associated with (1) large herd size, (2) use of sawdust or sand bedding, and (3) not fore stripping during the premilking routine. Management practices that were associated with lower odds of having a thermophilic spore level ≥10 spores/mL are (1) large herd size, (2) spray-based application of the postmilking disinfectant, (3) dry massaging the udder during the premilking routine, and (4) the use of straw bedding. Collectively, these results suggest that different management practices may influence mesophilic and thermophilic spore levels in raw milk.
原料乳中存在的细菌芽孢（也称为孢子）能够在巴氏杀菌以及奶粉生产过程中遇到的其他不利条件下存活。因此，要生产孢子数低的奶粉，可能需要原料（如原料乳）中的孢子水平较低。为了确定管理措施与原料乳中孢子水平之间的潜在关联，我们在1年的时间里每隔1个月从纽约州的33个农场采集一次储奶罐中的原料乳样本。经过芽孢巴氏杀菌（80°C处理12分钟）后，将样本在3个不同温度下培养，以计数耐冷性（6°C培养10天）、嗜温性（32°C培养48小时）和嗜热性（55°C培养48小时）孢子。另外采用一种富集程序来检测低水平存在的孢子（<10个孢子/毫升）。总体而言，分别在1%、74%和58%的储奶罐原料乳样本中检测到了耐冷性、嗜温性和嗜热性孢子（水平≥10个孢子/毫升）。尽管嗜热孢子水平无法定量（由于细菌群体扩散），但嗜温孢子水平范围从低于检测限（<10个孢子/毫升）到680个孢子/毫升。通过调查收集的数据用于确定与嗜温性或嗜热性孢子水平相关的管理措施。我们发现不同的管理措施与嗜温性和嗜热性孢子水平相关。储奶罐原料乳样本中嗜温孢子水平低与以下因素有关：（1）牛群规模大，（2）使用锯末或沙子作垫料，（3）挤奶前常规操作中不进行预挤奶。与嗜热孢子水平≥10个孢子/毫升几率较低相关的管理措施有：（1）牛群规模大，（2）挤奶后消毒剂采用喷雾式施用，（3）挤奶前常规操作中对乳房进行干式按摩，（4）使用秸秆作垫料。总体而言，这些结果表明不同的管理措施可能会影响原料乳中嗜温性和嗜热性孢子水平。
