Why does black tea become milky when it is cold?

|Why does black tea become milky when it is cold?|

Due to the emulsification of the thearubigins, theaflavins and polyphenols in black tea due to the rapid decrease in temperature; this effect is only easier to occur in black tea produced in summer and autumn (the reason is that there is sufficient sunshine in summer and autumn, which allows a lots of polyphenols to be generated in black tea).
In addition, the emulsification is not easy to occur when the tea is brewed too weak.