Why does milk curdle after being boiled with ginger? I had heard that raw or simply pasteurized milk does curdle if ginger is put in it before it reaches its boiling point.
Alright, so yesterday I boiled the pasteurized milk at 23:00. Room temperature was around 17 degrees Celsius.
In the morning I put in the ginger and then started boiling it, but the milk curdled! (I had put the plain tea leaves and sugar also along with the ginger).
When the milk had been boiled in the previous night, why did it then curdle with ginger in the morning?
I boiled the remaining milk separately and it was fine.
If you want to prevent the milk from curdling when adding ginger, you have to boil the ginger or at least add it to boiling milk.

Ginger protease (the curdling agent in fresh ginger) is rapidly destroyed at temperatures above 70°C. It does not matter if the milk has been boiled in advance if you add ginger to cold or room-tempered milk, it will still curdle.