Chocolate Guinness Cake With Tea

Our answer

Using tea instead of Guinness in Nigella's Chocolate Guinness Cake (from Feast and on the Nigella website) is an interesting idea, but we are concerned that the cake would not rise as well. Bicarbonate of soda (baking soda) is the raising agent in the cake and this needs an acid to react with. Guinness is slightly acid which helps the reaction. Tea is also very slightly acidic but not as much as Guinness and may not be quite enough to give a robust reaction with the bicarbonate of soda, even when combined with the sour cream.

Guinness also contains carbon dioxide and this will also slightly help the cake to rise as it bakes. Tea will not have the same aereation quality so could lead to a less well risen and denser cake.