Lemons and other citrus fruits are well known for their colourful pitted skins and tart, refreshing taste. Lemons contain citric acid and have a high vitamin C content. The peel of a lemon consists of two layers: the outer zest and a white inner layer, the pith. Surprisingly, it’s this zest and pith which contain significant levels of valuable antioxidants, more in fact, than lemon juice itself. The zest also contains essential oils – the most common of which is called limonene.