Does whole milk spoil faster than skim milk?

BY?ALISON COOPER

全脂牛奶是否比脫脂牛奶更易腐壞

全文1675字? 預(yù)計(jì)閱讀時(shí)間 4分鐘

We've all had moments of uncertainty (and, let's face it, paranoia/?p?r?'n???/) about the state of the food sitting in our refrigerators. You might be able to eyeball some of the suspicious items, check for expiration dates on others, and with some — milk, usually — you'll probably take a?quick whiff?and hope for the best. But if you've ever looked at a shelf-life chart to figure out how long your milk might last, you might have noticed that on skim milk is said to last a day or two longer than whole milk. Why is that?

我們每個(gè)人都有對(duì)冰箱里的食物疑慮的時(shí)刻（面對(duì)現(xiàn)實(shí)吧知给，就是妄想癥）险耀。你或許會(huì)打量某些可疑物品，查看他們的保質(zhì)期段化，對(duì)于某些牛奶茵休，你會(huì)迅速地聞聞薪棒，寄希望是最佳狀態(tài)。但如果看過貨架期表來查看保質(zhì)期榕莺，你可能會(huì)注意到脫脂牛奶的保質(zhì)期比全脂牛奶長(zhǎng)一兩天俐芯。為什么呢？

Before we get started, we should state that there is by no means universal agreement on this issue. Some dairy scientists say skim lasts longer because certain fat-loving microbes can't develop as quickly in nonfat milk. Others say that whole milk lasts longer because free fatty acids might actually be natural?preservatives. Still others say that maybe there isn't a difference in spoilage rate at all — it's just that we notice flavor changes more in skim milk [sources:?Murphy,?Roberts].

在我們開始之前钉鸯，需要聲明在這個(gè)問題上絕沒有普遍共識(shí)吧史。一些乳品科學(xué)家說，脫脂牛奶保質(zhì)期更長(zhǎng)是因?yàn)?strong>親脂微生物無法在脫脂牛奶中快速繁殖唠雕。另外的人說贸营，全脂保質(zhì)期更長(zhǎng)吨述，因?yàn)橛坞x脂肪酸極可能是天然防腐劑。還有些人說钞脂，腐敗率是不存在差異的——只是我們留意到口味在脫脂牛奶中變化更大罷了揣云。

There's been only one major controlled study on the spoilage rates of whole and skim milk, and it was somewhat inconclusive. Skim milk was found to spoil slightly faster, but the researchers weren't exactly sure why.?Psychrotrophic, or cold-resistant, bacteria are what cause spoilage in the fridge, and they multiplied at the same rate in both types of milk.

關(guān)于全脂牛奶和脫脂牛奶的變質(zhì)率只有一項(xiàng)主要的對(duì)照研究，某種程度這項(xiàng)研究是無結(jié)果的冰啃。研究發(fā)現(xiàn)灵再，全脂牛奶的腐敗速度略快，但研究人員不能確定原因亿笤。嗜冷菌、耐寒菌催生了冰箱里的腐化栋猖，他們?cè)趦煞N牛奶中繁殖速度是一樣的净薛。

When the milk spoiled, both whole and skim contained similar strains of bacteria. There was a pronounced difference in how whole and skim milk reacted when they were injected with the same spoilage/'sp??l?d?/?microorganisms, but they affected the milk's taste and smell more than they did the spoilage rate. (Whole milk, for the record, tended to turn sour, and skim milk was on the bitter side [source:?Deeth and Khusniati].)

牛奶腐敗時(shí)，脫脂和全脂牛奶有著相似的菌株蒲拉。注入相同腐敗微生物后肃拜，全脂和脫脂牛奶有明顯不同的反應(yīng)，但比起腐敗率的變化雌团，他們更多地影響牛奶的風(fēng)味燃领。（記錄發(fā)現(xiàn)，全脂牛奶傾向變酸锦援，脫脂牛奶傾向變辛酸）

So for the purposes of your average milk consumer, there's really no hard-and-fast rule about which kind will spoil faster. If whole milk does last longer than skim, the difference is so slight that any given gallon of skim milk could outlast any given gallon of whole milk.

所以對(duì)牛奶普通消費(fèi)者而言猛蔽，并沒有關(guān)于哪種腐壞更快的嚴(yán)格規(guī)則。若全脂牛奶確實(shí)比脫脂牛奶保質(zhì)期長(zhǎng)灵寺，差別是如此之小曼库，以至于任何一加侖的脫脂牛奶可能比全脂牛奶更耐喝。

The spoilage rate depends on so many variables — manufacturer, production methods, milk formulation, plant sanitation, storage temperatures, pH and moisture content, to name a few — that a small change in just one of them could give any particular container of milk a slightly longer shelf life than another.

變質(zhì)率關(guān)乎許多變量——制造廠略板、生產(chǎn)方式毁枯、配方、衛(wèi)生叮称、貯存溫度种玛、酸堿度、濕度瓤檐，其中任意一個(gè)的細(xì)微變化都可以使一罐牛奶比另一罐保存更長(zhǎng)赂韵。

A couple of other factors make things even more ambiguous. For one, it's pretty much impossible to pinpoint the exact moment of spoilage. Depending on your sense of smell and taste (and your tolerance for changes in milk flavor), you might turn up your nose at a gallon of milk that someone else might readily swig.

另外一些因素使問題變得更加含糊。比如說距帅，幾乎不可能查明從哪一刻開始腐敗右锨。考慮到你的嗅覺和味覺（和你對(duì)于牛奶風(fēng)味的耐受力）碌秸，你可能對(duì)別人很輕易喝下的一加侖牛奶嗤之以鼻绍移。

And there's no federal regulation of milk expiration dates in the United States — only 20 states have standards, and they vary widely. One state might mandate a?"sell by" date of a certain number of days after?pasteurizatio?/p?st?ra?'ze???n/?, and milk jugs in another state will be printed with a "use by" date [source:?Cormier].

在美國(guó)悄窃，是沒有關(guān)于牛奶保質(zhì)期的聯(lián)邦法律規(guī)定的——只有20個(gè)州有標(biāo)準(zhǔn)，他們相差甚遠(yuǎn)蹂窖。一個(gè)州可能強(qiáng)制要求殺菌后牛奶的“最遲銷售”日期轧抗，而另一個(gè)州的牛奶壺會(huì)印上“之前使用”日期。

The upshot: Don't base your milk purchases on which type might last longer. If you're concerned about shelf life, you'd be better off following a few simple steps to slow down milk spoilage, whether you're a whole or skim drinker.

總之瞬测，不要根據(jù)哪種類型的牛奶期限更長(zhǎng)來購(gòu)買横媚。無論是全脂還是脫脂牛奶，若你擔(dān)心他們的保質(zhì)期月趟，最好遵守些簡(jiǎn)單的步驟來延緩腐敗灯蝴。

?First, make sure your refrigerator is the correct temperature: It should be set at 40 degrees Fahrenheit/'f?r?n'ha?t/(4.4 degrees Celsius/'selsi?s/）[source:?FDA].?Store your milk on an interior shelf instead of on the door, which fluctuates more in temperature. And put your milk back in the fridge as soon as possible — leaving it out on the counter for even a few minutes exposes it to light and heat, giving bacteria a chance to spring into action.

首先確保你的冰箱處于合適溫度：調(diào)到40華氏度（4.4攝氏度）。在內(nèi)置架上而不是門邊貯存牛奶孝宗。并且盡快將牛奶放入冰箱——哪怕放在外面幾分鐘穷躁，當(dāng)暴露在光線和熱量下，細(xì)菌也會(huì)趁虛而入因妇。

Sources

·?Cormier, Roger. "When Is the Actual Expiration Date on Your Milk?" Mental Floss. Sept. 2, 2014. (April 1, 2015) http://mentalfloss.com/article/58358/when-actual-expiration-date-your-milk

·?Deeth, Hilton, T Khusniati et al. "Spoilage patterns of skim and whole milks." Journal of Dairy Research. May 2002. (March 27, 2015) http://www.ncbi.nlm.nih.gov/pubmed/12222801

·?Food and Drug Administration. "Refrigerator Thermometers: Cold Facts about Food Safety." March 10, 2015. (April 1, 2015) http://www.fda.gov/Food/ResourcesForYou/Consumers/ucm253954.htm

·?Ledenbach, Loralyn H and Robert T Marshall. "Microbiological Spoilage of Dairy Products." Compendium of the Microbiological Spoilage of Foods and Beverages. 2010. (April 1, 2015) http://link.springer.com/chapter/10.1007%2F978-1-4419-0826-1_2

·?Murphy, Steven C. "Shelf-Life of Fluid Milk Products: Microbial Spoilage." Cornell University. June 30, 2009. (April 1, 2015) https://foodsafety.foodscience.cornell.edu/sites/foodsafety.foodscience.cornell.edu/files/shared/documents/CU-DFScience-Notes-Bacteria-Milk-Shelf-Life-Evaluaton-06-09.pdf

·?Roberts, Bob. "Sour Milk." Penn State College of Agricultural Sciences. (April 1, 2015) http://extension.psu.edu/food/preservation/faq/sour-milk