Clouding in tea is a result of the colloidal precipitate that is formed. This is called ‘tea cream’. Tea creaming takes place when black tea is cooled below 400 C. A weak complexion is formed between caffeine and polyphenols (theaflavins and thearubigins). The tendency to cream down varies from tea to tea. In black tea without milk complexation and subsequent precipitation that occurs is negligible due to just 4% of caffeine.
In tea with milk a similar association takes place between the milk protein casein and various polyphenols. Due to the availability of casein in milk tea the complexion is greater resulting in larger precipitation.