In the fruit area of large supermarkets, we often see lemons with orange-yellow color and fragrant smell. The lemon itself is a fruit with extremely high nutritional and medicinal value. Lemons contain abundant citric acid, and are known as the "citric acid warehouse". The main nutritional components in lemons, in addition to carbohydrates, also include calcium, phosphorus, iron, vitamin B1, vitamin B2, vitamin C, and niacin, etc.