Bicarbonate of Soda

bicarbonate of soda (Sodium bicarbonate, NaHCO₃) has been used in cookery for so long that, despite its chemical label, it has largely escaped the growing opposition to ‘chemical’ additives. It is an alkali which reacts with acid by effervescing—producing carbon dioxide. It is therefore a leavening agent in baking, if used in conjunction with, say, tartaric acid (see cream of tartar) or lemon juice. See baking powder and leaven.

The alkaline properties of bicarbonate of soda can also be used to soften the skins of beans and other pulses. And a pinch added to the cooking water makes cabbage and other green vegetables greener, by its effect on the pigment chlorophyll. However, it also induces limpness (by breaking down hemicelluloses) and the loss of vitamins B1 and C; and the practice, which dates back to classical Rome and used to be recommended in Britain and N. America, has largely died out. McGee (1984) provides a detailed explanation and cites a forthright injunction from Tabitha Tickletooth (1860):

Never, under any circumstances, unless you wish entirely to destroy all flavour, and reduce your peas to pulp, boil them with soda. This favourite atrocity of the English kitchen cannot be too strongly condemned.