What causes coffee to stain?

The compounds in coffee that cause staining are tannins, which are polyphenols that occur naturally in many plants, including coffee beans, tea leaves, and red wine grapes. Tannins have a high molecular weight and a complex structure, which makes them resistant to breakdown. When tannins come into contact with proteins, such as those in teeth or other organic surfaces, they can bind to them and cause discoloration.

The amount of staining that occurs depends on a number of factors, including the type of coffee, the brewing method, and the length of time that the coffee is in contact with the teeth. Coffee that is brewed with a high concentration of coffee grounds, or that is left to sit for a long time, will produce more staining than coffee that is brewed with a lower concentration of coffee grounds or that is drunk quickly.

In addition to tannins, coffee also contains other compounds that can contribute to staining, including caffeine, chlorogenic acids, and melanoidins. Caffeine is a stimulant that can cause the blood vessels in the teeth to dilate, which can make the teeth appear darker. Chlorogenic acids are a type of antioxidant that can also cause the teeth to become discoloured. Melanoidins are a group of nitrogen-containing compounds that are produced when coffee is roasted. Melanoidins can also contribute to staining.

Coffee stains can be removed with a variety of methods, including brushing the teeth with a whitening toothpaste, using a mouthwash that contains peroxide, or by drinking a glass of milk after consuming coffee. However, it is important to note that some of these methods may only be effective in removing surface stains, and that deeper stains may require professional treatment.