What Happens to Milk?

Milk, as it turns out, is a colloid: just a bunch of fat and protein particles hanging out together in a liquid. It's about 85 to 90 percent water, and in their pure form, milk's proteins do not like each other. They repel each other and evenly spread out throughout the liquid.

事實證明，牛奶是一種膠體：只是一堆脂肪和蛋白質(zhì)顆粒懸浮在液體中。大約 85% 到 90% 是水，而且在純凈形式下，牛奶中的蛋白質(zhì)互不相容。它們相互排斥并均勻地分布在整個液體中。

When you leave milk out in temperatures over 40 degrees Fahrenheit, however, it invites the growth of bacteria. Most milk nowadays is pasteurized, but that doesn't completely eliminate bacteria, which can also re-contaminate milk once it's opened.

然而，將牛奶放在40華氏度（大約為4攝氏度左右）以上的溫度時，就會滋生細(xì)菌?，F(xiàn)在大多數(shù)牛奶都經(jīng)過巴氏消毒，但這并不能完全消除細(xì)菌，一旦打開，細(xì)菌也會重新污染牛奶。

The bacteria start eating up the milk's lactic acid, thereby decreasing the milk's PH. Decreasing the PH not only makes the milk taste sour, but it forces the milk's protein particles to coagulate together into curds. Welcome to the world of spoiled milk.

細(xì)菌開始吃掉牛奶的乳酸，從而降低牛奶的PH。降低PH值不僅會使牛奶變酸，還會迫使牛奶的蛋白質(zhì)顆粒凝結(jié)成凝乳。歡迎來到變質(zhì)牛奶的世界。

Opened milk will spoil within five to seven days, whether you leave it out on the counter or not. Even if you leave it unopened, fresh milk will spoil between five to 10 days. Ultra-pasteurized milk lasts between 30 to 90 days unopened but still spoils eventually.

無論您是否將其放在冰柜里，已開封牛奶都會在5-7天內(nèi)變質(zhì)。即使未開封，鮮奶也會在5-10天內(nèi)變質(zhì)。超巴氏殺菌牛奶未開封可保存 30 至 90 天，但最終仍會變質(zhì)。

The long and short of it is that if you leave your milk out, you're hurrying up an inevitable process. And rotten milk won't always smell off to people.

總而言之，如果你忘記喝完牛奶，就會加速一個不可避免的過程。而腐爛變質(zhì)的牛奶味并不能及時讓人聞到。

Any perishables left out at temperatures of more than 40 degrees Fahrenheit for over two hours. If you've left your milk sit out for more than one hour at temperatures at or over 90 degrees Fahrenheit, it's not safe to drink.

任何易腐爛的物品在華氏40度以上的溫度下放置超過2個小時就會開始變質(zhì)。如果牛奶在華氏90度（約為32攝氏度）或以上的溫度下放置超過1小時，則飲用這些牛奶是不安全的。

2026年3月7日于東原璞閱