Because edible lye is added to it. The main chemical composition of edible lye is sodium carbonate and a small amount of sodium bicarbonate. When these substances are heated, the following reaction occurs is CO32 minus plus 2H plus equals CO2 plus H2O, CO32- plus H plus equals HCO3 minus, and this reaction releases pungent gases. At the same time, sodium carbonate and sodium bicarbonate have a flavor of their own, and as the carbon dioxide wafts out, it also produces a pungent odor.