For the past week we have been living without chametz. No bread, no pita and no fluffy cakes. In their stead we have been living on matzo and its by-products: matzo brei, matzo cookies, and everybody’s favourite, the “matzo-and” breakfast, including matzo-and-butter, matzo-and-jam, and matzo-and-chocolate-spread. Seven days of digestive nirvana.
Here’s a question that most people believe they can answer: What is the definition of chametz? The most common answer is “Chametz is flour that has come into contact with water for more than eighteen minutes”. Yes, that’s halachically true, but what is the scientific definition of chametz? Is there some kind of chemical change that transpires eighteen minutes after flour touches water? Again, most people think they can answer this question: After eighteen minutes the dough begins to rise. Chametz is dough that has leavened, where “to leaven” is defined by the Oxford Dictionary as “Cause (dough or bread) to ferment and rise by adding leaven, as in ‘leavened breads are forbidden during Passover’”.
Well, that’s what I used to think until I recently took a deep dive into the chemistry of bread-making. Wheat flour has three major components: Starches, four different kinds enzymes, the most important being beta-amylase, and two different kinds of proteins, gliadin and glutenin. Another ingredient necessary for making bread is yeast, a single-cell micro-organism, related to the mushroom. Here is a simple tutorial on how bread is made:
- Enzymes break down the starches, which are essentially large chains of glucose units joined by glycosidic bonds, into simple sugars.
- The yeast feed on the sugars, converting them into carbon dioxide and alcohol.
- Meanwhile, the gliadin and glutenin join to form gluten, a stringy protein that gives the dough its flex, especially after it has been kneaded. Gluten forms a sort of skin on the outside of the dough.
- Gluten traps the carbon dioxide inside the dough, giving it the fluffy texture that we associate with leavened bread.
That’s it in a nutshell. The only question we have to answer is “Which of the above steps causes dough to become chametz?” This question is relevant at each of the above steps:
- Yeast cannot feed on complex carbohydrates. Without enzymes such as amylase the starches cannot be broken down into yeast fuel. It could be posited (it actually has been posited) that if these enzymes, particularly beta-amylase, were somehow removed from the flour, it could never become chametz.
- Without yeast, carbon dioxide will not be produced, and the bread will not rise. My wife makes challah every Shabbat and she has found that sometimes even with yeast the dough does not rise. While there is always a small amount of wild yeast in the air, it is insufficient to cause leavening for all but the most seasoned bread makers. When Am Yisrael were in Egypt, their leavening agent was “Se’or”, or “sourdough starter”. Indeed, the Torah juxtaposes the words se’or and chametz [Shemot 12:15]: “On the [day before Pesach] you shall clear away all se’or from your houses, for whoever eats chametz from the first day until the seventh day, that soul shall be cut off from Israel”
- Without gluten, the carbon dioxide will not become trapped inside the dough and the dough will not rise. Rice has a much lower concentration of gluten than wheat, and so rice dough does not rise. Oats have more gluten than rice, but less than wheat. While rice is not considered chametz, oats are one of the five grains that can become chametz.
So which factor makes something chametz? Enzymes? Yeast? Gluten? Perhaps it is some combination of the three? Or maybe it’s something else altogether? This past Shabbat I read seven (7) halachic papers (ma’amarim) and convincing cases were made for each and every one of these factors as well as other factors I have not mentioned. Moreover, each paper showed why every other factor is irrelevant to the definition of chametz. Of course each of these opinions have serious halachic ramifications. And so we seem to find ourselves in a classic “Ten Jews – Eleven Opinions” situation.
Let’s return to our starting point: flour mixed with water becomes chametz after eighteen minutes. This rule seems arbitrary: without yeast or some other leavening agent the flour will not rise. On the other hand, assuming a small amount of yeast has been harvested from the air, the extent of the leavening will be temperature-dependant: the higher the temperature of the water, the faster the leavening will be. Halacha is cognizant of this dependency as it enforces the use of “mayim she’lanu” – water that has been left to cool to room temperature – in the making of matzo. What if we use refrigerated water? Can the eighteen-minute limit be lengthened to, say, thirty minutes? The answer is “no”, and this answer leads to an irrefutable conclusion: The definition of chametz, while capable of being described via chemical processes, is not an assertion of fact. Rather, it is a statement of legal convention: Whether or not the dough has risen, it is considered chametz precisely eighteen minutes after it touches water and it may not be eaten the entire holiday of Pesach. Rav Ohad Fixler, after spending ten pages identifying beta-amylase as the source of chametz, essentially retracts his assertion and concludes his treatise with the following words: “Bread was one of the inventions of Egypt… In the Book of Bereishit we read about the separation existing in Egypt between the Egyptians and the Jews in eating bread. Leavened bread is a class symbol that distinguishes between Israel and Egypt… The ability to leaven is at the foundation of Pesach as the source of the difference between the people of Israel and Egypt and the ability to preserve the natural and unique nature of the Jewish people in materials (i.e. food) that are capable of being like [the prohibited] actions of the Egyptians.” In other words, chametz is not a physical prohibition, it is a metaphysical prohibition.
I’d like to propose a slightly different direction. Rav J.B. Soloveichik, writing in Festival of Freedom, discusses the first mitzvah given to Am Yisrael as a nation [Shemot 12:2] “This month is the head of the months, it is for you the first month of the year”. The mitzvah of “Kiddush HaChodesh”, sanctification of the new month, was specifically chosen as the first mitzvah: “The slave lacks time experience. While everything exists in time, only a human being is capable of experiencing time. G-d endowed man with time awareness, the ability to sense and feel time and the existential stream of selfhood… to live time rather than to live in time. [Slaves] float with the tide of time because there is no alternative to it… A slave who is capable of appreciating each day, of grasping its meaning and worth, of weaving every thread of time into a glorious fabric… is eligible for Torah. He has achieved freedom”. In a similar vein, the first prohibition that Am Yisrael are given as a nation is the prohibition of chametz. The prohibition of chametz is clear proof that time matters. While the dough might look and taste exactly the same after eighteen minutes as it does after thirty minutes, the dough is prohibited after eighteen minutes. If you eat that dough on Pesach, you will be cut off from the rest of the nation. Because for better for worse, time matters.
And from my experience, eighteen minutes is just enough time to make some matzo.
Shabbat Shalom and Chag Sameach veKasher,
Ari Sacher, Moreshet, 5777
Please daven for a Refu’a Shelema for Moshe Dov ben Malka and Yechiel ben Shprintza.
 There are other components, just in far lesser concentrations, and so they have been omitted.
 Sourdough starter usually requires about a week to “brew” and then it is kept in the fridge. Having to throw out sourdough starter is a real big deal. It means that unless a person has access to dry yeast, bread cannot be made for days after Pesach is over. Thanks to R. Menashe Kempler for this factoid.
 The Chabad.org translation that I usually use translates both se’or and chametz as “leaven”.
 Listen to Rav Shabtai Rappaport’s innovation (in Hebrew) at http://www.etzion.org.il/he/הגדרת חמץ. Rav Rappaport asserts that it is the slightly sour taste of the bread that makes it chametz, and not the leavening.
 We quoted similar words from “Festival of Freedom” in our shiur of Pesach 5773.