Tea cream formation

Caffeine reacts with catechins and catechin-based molecules in tea extracts to form tea cream. It gives discoloration and precipitation of complexed substances, affecting the visual appeal, flavor, and color, besides reducing the shelf-stability of the beverage.

As freshly prepare tea cools, the color of the drink darkens and a red/brown color develops. This change is particularly noticeable in more concentrated extracts of black tea, where a color change from dark brown to milky-red occurs.

The cloudiness has been term “tea cream” because it resembles tea to which cream has been added. It is the haze or precipitate that is formed when as strong infusion of tea is allowed to cool down; the relationship between cream formation and quality was first demonstrated by Bradfield an Penny in 1944. Polyphenols, caffeine, protein, carbohydrates, polysaccharides, free amino acids, flavones, catechins and minerals were found to participate in the formation of green tea cream. Caffeine, catechins, theaflavins, and thearubigins are known to be major constituents of tea cream.

This material is typically removed in order to obtain a product that is soluble in cold water.
Tea cream formation 

Instant tea: Cream processing

On cooling, a tea solution becomes opaque and lightens in color. This is due to the formation of tea cream, a colloidal substance which contains the same components as the original extract.

Tea cream is a coacervate formed of a complex between caffeine, catechins, and the oxidized catechins of black tea.

The conditions under which cream forms determined the chemical composition of the complex and its physical properties.

Cream processing can be accomplished by maintaining the temperature above 65 °C or by removal of the cream, for example by cooling followed by precipitation or centrifugation. Cream treatment is especially necessary for cold water-soluble instants, which are commonly used for beverages like ice tea.

Tea cream causes particular problems in production of instant tea for the US market, which is required to be of clear, bright appearance when reconstituted with cold water.
Instant tea: Cream processing