Lemon contains an ingredient called citric acid. If the PH test paper is used to test the acidity and alkalinity of citric acid, the pH value is about 2. The acid content of citric acid is relatively high. Because the taste of citric acid is sour, and the main component of lemon is citric acid, lemon is naturally sour. Although lemon is very sour, it contains a lot of vitamin C, which has whitening effect, and the citric acid contained in it specifically inhibits the effect of calcium salt.

Lemon contains an ingredient called citric acid. If the PH test paper is used to test the acidity and alkalinity of citric acid, the pH value is about 2. The acid content of citric acid is relatively high. Because the taste of citric acid is sour, and the main component of lemon is citric acid, lemon is naturally sour. Although lemon is very sour, it contains a lot of vitamin C, which has whitening effect, and the citric acid contained in it specifically inhibits the effect of calcium salt.