Naturally it’s found in citrus fruits and is used as a preservative and flavouring under the e-number E330, it’s also used as a cleaning agent. The polarising microscope reveals a beautifully colourful substance varying in form from soft feathers to glacial mountains.
It’s only a weak organic acid but recently citric acid has been used in stem cell research to convert adult cells into embryonic-like stem cells in a simple process involving a 25-minute citric acid bath. This could in future be used to regenerate all sorts of bodily tissue. More importantly, it’s a vital substance in home-brewing.