How long does it take for milk to spoil unrefrigerated?
A half gallon of milk (in the paper carton, not plastic) got left in the car for 1.5 hours in about 80 degree (~27 °C) weather (evening so no direct sunlight). Is it still probably safe to eat if one has a strong stomach or pretty risky? Any particular signs to watch for to indicate it is no longer safe? Carton bulging? Off smell? Etc? How quickly will milk spoil (unopened) in warm summer weather like that?
I don't think anything will be wrong with that milk.
- If it's fresh milk, which I doubt, you should consume it in less than three days.
- If it's pasteurized milk, which is much more likely, it'll be unaffected.
Signs of spoilage are a sour smell and sour taste. You should make a habit of always smelling your milk (food) before drinking (eating) it. If it doesn't smell like you'd expect, taste it. If it doesn't taste like you'd expect, ditch it.
Milk is cultivated with lactobacillus, a bacteria that's beneficial for us. So, even though milk may taste sour, it doesn't mean that it's undrinkable. In Holland, there's sour-milk (karnemelk), that some people consume (I don't like it, myself).
Under the right circumstances, milk will turn into yogurt, thanks to the lactobacillus...
At any rate, if in doubt, throw it out.
I agree with your advice. In my experience even if there might be a slight something-more-than-nothing smell on milk which has passed the expiry date (with some significant time), there might be absolutely no taste difference.