There's a reason lemons have been used to clean kitchens for centuries. It turns out the science has always been there. Nature's cleaning kit. Simple ingredients, real science, zero synthetics. What Is Citric Acid and Why Does It Clean? Every lemon contains roughly 5 to 8 percent citric acid by dry weight. That single compound is what makes lemon useful as a cleaning agent, and understanding how it works tells you exactly when to reach for it. Citric acid kills bacteria by cr