Colour and Cooking: Chlorophyll

Appears in

Oxford Companion to Food

Oxford Companion to Food

By Alan Davidson

Published 2014

  • About
People like green vegetables to stay green when cooked, not to turn olive. Chlorophyll is not soluble in water, so the green which is to be preserved will not leach out into the cooking water, which is one blessing. However, there are lots of other things which can affect it. Chlorophyll is a complex substance. It is quickly affected by an alkali or an acid, and by the application of heat.

The effect of an alkali, whether already present in the cooking water or added in the form of bicarbonate of soda, is to prevent the replacement of the central magnesium atom in chlorophyll with hydrogen. The vegetable then acquires an unnaturally bright green colour. Some might find this attractive, but the penalties to be paid are formidable. Not only is there a heavy loss of vitamin C, but the cell walls of the vegetable are disrupted and it becomes mushy, even slimy. So it is best to avoid alkaline water and not to add bicarbonate of soda.