Citric acid is found naturally in citrus fruits, especially lemons and limes. It’s what gives them their tart, sour taste. A manufactured form of citric acid is commonly used as an additive in food, cleaning agents, and nutritional supplements.

https://en.wikipedia.org/wiki/Citric_acid#:~:text=Citric%20acid%20is%20an%20organic,metabolism%20of%20all%20aerobic%20organisms.