Does Fat-Free Or Whole Milk Curdle (Go Sour) Faster?


2 Answers

Florent Lefortier Profile
I’m not sure whether you want to know how fast milk curdles when it’s heated, or how fast milk spoils or “goes bad,” so I’ll try to answer both!

What Spoils Faster – Whole Milk Or Fat-Free Milk?
There’s a lot of debate about this online, and no definitive answers – probably because there are quite a few variables, so it’s difficult to test.

Some people argue that whole milk lasts longer, but that might just be that it takes longer to taste bad because of the high fat content. Fat-free milk doesn’t have anywhere near as much taste, so you’re more likely to notice if it’s on the turn.

What Influences The Speed At Which Milk Curdles?
  • When the cow was milked. Just because both cartons of milk have the same sell-by date, it doesn’t mean that they were milked on the same day. Not all milk companies calculate sell-by dates in the same way.
  • Pasteurization. Ultra-pasteurized milk will last in the fridge for a lot longer than standard milk.
  • Changes in temperature. If you leave the milk out of the fridge for too long, and then put it back in, the sudden change in temperature can cause it spoil more quickly.
  • Contamination. If you’re cooking and accidentally drop some flour into the milk carton, the introduction of new bacteria could cause the milk to spoil more quickly.
What Curdles Faster – Whole Milk Or Fat-Free Milk?
There’s no final answer for this one, either, but the majority seem to think that fat-free milk curdles faster. If you think about it logically, it probably does, as thick cream (which contains a lot of fat) can be heated to quite a high temperature before it will curdle.

The speed that milk curdles doesn’t actually depend on the fat content, though – it depends on the protein. The following things affect the speed that milk curdles:

  • Method of curdling
  • Temperature
  • Amount of acid in whatever you’re mixing the milk with
Hope that helps!
Anonymous Profile
Anonymous answered
Well, me and my friend are doing it as a science fair project, and it turns out fat free milk spoils first. Try taking the milk and seeing how long it takes to sour.

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