Jewish supermarkets and food stores are obligated to remove the Chametz products during the Passover Holidays.
Chametz (leavening) is made from one of five types of grains combined with water and left to stand for more than eighteen minutes. The consumption, keeping, and owning of chametz is forbidden during Passover. Yeast and fermentation are not themselves forbidden as seen for example by wine, which is required, rather than merely permitted. According to Halakha, the ownership of such chametz is also proscribed.