Evanowski Rachel L, Murphy Sarah I, Wiedmann Martin, Martin Nicole H
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. 2023 Mar;106(3):1687-1694. doi: 10.3168/jds.2022-22372. Epub 2023 Jan 27.
Bacterial spores, which are found in raw milk, can survive harsh processing conditions encountered in dairy manufacturing, including pasteurization and drying. Low-spore raw milk is desirable for dairy industry stakeholders, especially those who want to extend the shelf life of their product, expand their distribution channels, or reduce product spoilage. A recent previous study showed that an on-farm intervention that included washing towels with chlorine bleach and drying them completely, as well as training milking parlor employees to focus on teat end cleaning, significantly reduced spore levels in bulk tank raw milk. As a follow up to that previous study, here we calculate the costs associated with that previously described intervention as ranging from $9.49 to $13.35 per cow per year, depending on farm size. A Monte Carlo model was used to predict the shelf life of high temperature, short time fluid milk processed from raw milk before and after this low-cost intervention was applied, based on experimental data collected in a previous study. The model predicted that 18.24% of half-gallon containers of fluid milk processed from raw milk receiving no spore intervention would exceed the pasteurized milk ordinance limit of 20,000 cfu/mL by 17 d after pasteurization, while only 16.99% of containers processed from raw milk receiving the spore intervention would reach this level 17 d after pasteurization (a reduction of 1.25 percentage points and a 6.85% reduction). Finally, a survey of consumer milk use was conducted to determine how many consumers regularly consume fluid milk near or past the date printed on the package (i.e., code date), which revealed that over 50% of fluid milk consumers surveyed continue to consume fluid milk after this date, indicating that a considerable proportion of consumers are exposed to fluid milk that is likely to have high levels spore-forming bacterial growth and possibly associated quality defects (e.g., flavor or odor defects). This further highlights the importance of reducing spore levels in raw milk to extend pasteurized fluid milk shelf life and thereby reducing the risk of adverse consumer experiences. Processors who are interested in extending fluid milk shelf life by controlling the levels of spores in the raw milk supply should consider incentivizing low-spore raw milk through premium payments to producers.
生牛奶中发现的细菌孢子能够在乳制品生产过程中遇到的严苛加工条件下存活，包括巴氏杀菌和干燥。对于乳制品行业的利益相关者来说，低孢子含量的生牛奶是理想之选，尤其是那些希望延长产品保质期、扩大销售渠道或减少产品变质的人。此前一项研究表明，一项农场干预措施，包括用氯漂白剂清洗毛巾并彻底干燥，以及培训挤奶厅员工专注于乳头末端清洁，可显著降低储奶罐中生牛奶的孢子水平。作为该先前研究的后续，我们在此计算与上述干预措施相关的成本，根据农场规模，每头奶牛每年的成本在9.49美元至13.35美元之间。基于先前研究收集的实验数据，使用蒙特卡洛模型预测了在应用这种低成本干预措施前后，由生牛奶加工而成的高温短时液态奶的保质期。该模型预测，未经孢子干预的生牛奶加工而成的半加仑装液态奶容器中，有18.24%在巴氏杀菌后17天会超过巴氏杀菌乳条例规定的20,000 cfu/mL的限量，而接受孢子干预的生牛奶加工而成的容器中，只有16.99%在巴氏杀菌后17天会达到这个水平（降低了1.25个百分点，降幅为6.85%）。最后，开展了一项消费者牛奶消费情况调查，以确定有多少消费者经常在包装上印的日期（即保质期）临近或过后饮用液态奶，结果显示，超过50%接受调查的液态奶消费者在这个日期之后仍继续饮用液态奶，这表明相当一部分消费者接触到的液态奶可能含有大量形成孢子的细菌生长以及可能相关的质量缺陷（如风味或气味缺陷）。这进一步凸显了降低生牛奶中孢子水平以延长巴氏杀菌液态奶保质期、从而降低消费者不良体验风险的重要性。有兴趣通过控制原料奶供应中的孢子水平来延长液态奶保质期的加工商，应考虑通过向生产商支付溢价来激励生产低孢子含量的生牛奶。
