Chametz

Chametz (also chometz, ḥametz, ḥameṣ, ḥameç and other spellings transliterated from Hebrew: חָמֵץ / חמץ; IPA: [χaˈmets]) are foods with leavening agents that are forbidden to Jews on the holiday of Passover.

Chametz is a product that is both made from one of the five species of grain and has been combined with water and left to stand raw for longer than eighteen minutes (according to most opinions) and becomes leavened.

Traditional Jewish homes spend the days leading up to Passover cleaning and removing all traces of chametz from the house.

Chametz is a product that is both made from one of five species of grain and has been combined with water and left to stand raw for longer than eighteen minutes (according to most opinions) and becomes leavened.

This is the basis of all historic fermentation processes in human culture that were utilized for the production of beer, wine, bread and silage, amongst others.

Chametz from the five species is the result of a natural microbial enzymatic activity that is caused by exposing grain starch—which has not been sterilized, i.e. by baking—to water.

A typical side effect of this biological leavening is the growth of the naturally adhering yeasts in the mixture, which produce gaseous carbon dioxide from glycolysis, which causes the fermented dough to rise and become increasingly acidic.

That suggests that gluten is a necessary component of chametz, as it holds the dough together while rising, allowing the formation of a fluffy bread loaf.

Whether a chemical leavener such as baking soda may be used with flour in making egg matzoh is disputed among contemporary Sephardic authorities.

Mixtures consisting of less than 50% chametz that are not usually consumed by people (such as medicine or pet food—even if perfectly edible) may be owned and used on Passover but may not be eaten.

[16] According to halakha (Jewish law), if chametz is found during Shabbat or Yom Tov, it must be covered over until Chol HaMoed, when it can be burned.

Ashkenazi custom is generally to avoid such products, in case some water was mixed into the liquid, which could cause the mixture to become chametz.