As a food safety expert, I can tell you that the shelf life of unrefrigerated milk can vary greatly depending on several factors, including the initial temperature of the milk, the ambient temperature of the environment, and whether the milk has been pasteurized or not.

Pasteurized milk, when left out at room temperature, can spoil rather quickly. Generally, it's recommended not to leave pasteurized milk out for more than two hours at room temperature, or one hour if the room temperature is above 90°F (32°C). After this time, bacteria can multiply rapidly, leading to spoilage.

Raw milk, which has not been pasteurized, can be even more dangerous because it can contain harmful pathogens that are not destroyed by pasteurization. It should always be refrigerated and never consumed unrefrigerated.

It's important to note that the smell and taste of milk can be good indicators of spoilage. If the milk has an off smell, appears lumpy, or tastes sour, it should be discarded immediately.

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According to the US Food and Drug Administration, refrigerated foods, including milk, should never be out of the fridge at room temperature for longer than two hours.read more >>