❓ why
Why does milk go sour?
foodscience
Quick Answer
Bacteria in milk ferment its sugar, lactose, into lactic acid, which makes it taste sour and curdle.
The Full Story
Even pasteurised milk contains some bacteria that survive heating or enter later. Lactic acid bacteria feed on lactose and produce lactic acid, lowering the milk's pH from about 6.7. As acidity rises, casein proteins clump together, forming curds. Refrigeration at 4 °C or below slows bacterial growth dramatically.
Key Facts
1.Standard pasteurisation heats milk to 72 °C for 15 seconds.
2.Louis Pasteur developed the heating technique in the 1860s, originally for wine.
3.Yoghurt and cheese are made by controlled souring of milk.
YouTube Angle
Suggested video title for this topic:
"What Happens When Milk Goes Sour"