1, dry lemon slices, the reason for the bitterness is the lemon seeds, remove it will not be bitter.

2, fresh lemon slices, boiling water will become bitter, not more than 50 degrees out of the bubble will not be bitter, the bitterness will increase with the increase in temperature.

Expanded:

Lemon is rich in vitamin C, sugar, calcium, phosphorus, iron, vitamin B1, vitamin B2, niacin, quinic acid, citric acid, malic acid, hesperidin, naringenin, coumarin, high amount of potassium and low amount of sodium, etc., which is very beneficial to the human body. Vitamin C can maintain the production of various tissues and intercellular matrix in the human body and maintain their normal physiological functions. The matrices, bonding and gliogenesis in the human body need vitamin C to protect them. When vitamin C is lacking, the interstitium between cells - the gelatinous substance - follows. As a result, cell tissues become brittle and lose the ability to resist external forces, and the human body is prone to scurvy, which has more uses, such as the prevention of colds, stimulate hematopoiesis and anti-cancer effects.

References:

Lemon