How Long Can Milk Sit Out Before it Is No Good?


"Does this taste bad to you?" Those are the words many people utter as they test the limits of milk's usability. Milk is best preserved in a cool environment, under 45 degrees Fahrenheit. But in many households, milk is taken out of the refrigerator and left to sit out at the breakfast or dinner table. Unbeknownst to the family drinking it, the milk may be going bad as it sits out in the open. There are limits to the amount of time milk can sit out before spoiling.

Time and Temperature Limits

  • The time limits for leaving any food out of its optimum environment is two hours. Milk is no different. The optimum temperature for milk is below 40 degrees. After two hours the milk has warmed to the point where it has become hospitable for bacteria. Actually, milk should never be allowed to reach a temperature over 45 degrees. Above that temperature, bacteria can begin to colonize in the milk. This means that the milk could go bad before the two-hour mark if the room is warm. So, after everyone gets their fill at the table, put the milk back in the refrigerator.

Signs of Bad Milk

  • Milk can be bad before it begins to smell or taste bad. Warm milk is bad and should be thrown away no matter what it tastes or smells like. It has already surpassed the temperature for accommodating bacteria. Of course, you should toss any milk that smells sour or tastes tangy or bitter. Milk that has begun to curdle or separate should also be thrown away.

The Organic Exception

  • Organic milk can be left out longer than traditionally pasteurized milk. The reason is not because the milk is organic, but the way the milk is processed for transport. Organic milk is processed by ultrahigh temperature treatment. The milk is heated to 280 degrees Fahrenheit for up to four seconds to kill all the bacteria in the milk. Pasteurized milk is not heated to such a high temperature, but is heated longer. The process does not kill all the bacteria. When pasteurized milk is left out, the bacteria begin to colonize quickly from within when the milk reaches the right temperature. Organic milk has no bacteria in it, so colonization takes longer to occur. You must still throw it out after it sits out for two hours.

A Word on Expiration

  • Expiration dates are stamped on milk to record how long it has been since the day it was pasteurized. The milk can be stored properly until this day and remain fresh. Pasteurized milk can usually last two weeks from pasteurization. Organic milk treated with the ultra high temperature treatment can last six months from the treatment date.

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