Ever wondered why milk goes sour, I mean we have all had those moments when you are really looking forward to a fresh glass of milk then we make our way to the fridge and pour a nice glass of milk to realize after a deep sip that the milk has in fact gone sour, you not alone.
Milk has bacteria( lactobacillus) which produces lactic acid that creates the sour taste, due to the acidity in the milk the protein curdle and the liquid goes its part. In certain temperatures the effect of the sour taste is high likewise it is also high if the presence of water is found then it too would be more likely to go sour. One of the proteins called " casein" is probably the reason the milk curdles its the reason why milk is white.