Chametz is forbidden during Passover. But what is chametz, exactly?
The Hebrew word chametz is often translated as “leaven.” But the English word “leaven” doesn't quite capture the true meaning. Popular Passover desserts, such as sponge cakes and meringue cookies, are technically leavened. They contained whipped egg whites that trap air and give them a light, spongy texture that mimics the airy texture of a baking-powder-raised cake.
In the Torah, chametz refers specifically to the five grains of ancient Egypt: wheat, oats, rye, barley, and spelt.
Chametz is related to the Hebrew word chamutz, which means “sour.” Sometimes chametz is translated as “fermented,” because fermented foods often taste sour.
Many fermented foods such as sour cream, sauerkraut and yogurt are permitted during Passover. But chametz -- including bread and beer -- is prohibited. Is it simply because chametz refers to fermented grains? If that is the case, what is it about fermented grains that makes them off-limits at Passover? Why are foods made with fermented milk and grapes not only permitted, but (in the case of wine) central to the Passover Seder?
The common explanation is derived from the Biblical account. In their haste to leave Egypt, the Israelites had no time to let the bread rise.
But a closer reading of the text adds confusion.
The night before they left, the Israelites were commanded to slaughter and roast a whole lamb, consume it, and burn any leftovers. Surely, while the lamb was roasting, they could have baked a few loaves of bread, right?
In the ancient world, it wasn’t that easy. There was no such thing as Fleishmann's yeast in a little red-and-yellow package that would allow them to bake bread from scratch in just a few hours. This kind of purified, fast-acting yeast is a 20th-century product.
Until recently, all bakers used a wild-yeast starter culture. They mixed wheat or rye flour with water to make a thick batter. Over two or three days, the yeast on the grain's surface (and in the air) would feed off the wet mixture and multiply enough to become an effective leavening agent. Bacteria, which were also present in the mixture, would cause fermentation and impart a sourdough flavor. The starter would then be mixed with more flour and water to make a dough, allowed to rise, and baked into bread.
Even when bakers used leftover starter from a previous batch, or harvested yeast from a vat of beer, it would still take considerable time for the yeast to multiply and develop sufficient strength to leaven dough. So, the Torah claim is right. Israelites fleeing Pharaoh truly had no time to let the dough rise.
But the lack of time cannot be the only factor when talking about the significance of chametz. After all, fermenting grapes and milk is also time-consuming. Why, then, are wine and cheese not forbidden at Passover?
The answer is that for the ancients, bread was a luxury. Wine and cheese were necessities. Or to put it more precisely, wine and cheese were important food-preservation strategies.
Before modern technology, people had no choice but to ferment grapes into wine if they wanted to preserve them for future consumption. The same was true for surplus milk: It was fermented into yogurt or cheese, allowing it to be stored and consumed several days—or even several months—after it came out of the cow.
The production of wine and cheese has always depended on the rhythms of nature. Wine is made at the time of harvest, cheese at the time of milking.
Not so with bread and beer. They can be made anytime. The grains that go into them are already dry, so they do not need to be fermented in order to be preserved. Yeast is not essential, either. (But the yeast on grape skins is essential to wine-making, just as the bacteria that settles into milk is essential to yogurt- and cheese-making.)
Bread and beer were trademark foods of ancient Egypt. They were a luxury then, and they are a luxury now.
God instructed the Israelites to give up yeast-raised bread because He wanted to teach them that freedom is more important than luxury. He wanted them to prove to themselves that they could survive— and even flourish—without the trappings of the civilization they had just fled.
Three thousand years later, we Jews give up chametz at Passover to remind ourselves of the same lesson. If we Jews take seriously the exhortation to be a “light unto the nations,” we do not need bread. But we certainly need freedom. That is one of the great insights of the Torah.