A More Flexible Future Orthodoxy

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A More Flexible Future Orthodoxy: The Case of Chametz

by R. Gidon Rothstein

One of the bedeviling questions for Orthodox Jews is how and when our religion can change. We know that some of the changes in culture, society, and the flow of history must wash over us, while we cling faithfully to our Rock, refusing to be swept away.

For many, that is one of Judaism’s strong points. It is precisely the sense of a Creator, Torah, and halachah that does not bend to whims or fads that they see as one of the best proofs that we follow a faith of truth, not an idolatry of whatever becomes fashionable.

I meet too many Jews who assume halachah as we have it now is halachah as it always will be

Other Orthodox Jews, equally faithful, agree with the value of that where it applies, but struggle to differentiate acceptable change from unacceptable, work hard to stay within the bounds of the religion our ancestors passed down to us, yet also want to be as open to legitimate novelty as possible. Some in this camp, who work to balance fidelity with openness, can find themselves chafing, wishing there was room for this or that adaptation to new circumstances.

One aspect of the issue that seems to me too little noted is that some of the current inflexibility of Jewish law is not what Hashem wanted. Rather, it is a consequence of our continuing exile, particularly our lack of the semicha, the original rabbinic ordination,that could allow us to staff and seat a Sanhedrin empowered to enact significant religious change. When Eliyahu comes (or the semicha is renewed in some other way), a Sanhedrin’s powers to see the Torah with new eyes can be formidable, in ways we seem to forget.

Part of the value I see in offering a sense of how the system itself expected to be able to reconsider issues and to confront new situations more effectively is that it reminds us both of the room for change that halachah allows and of the need for systemically legitimate pathways to that change. It is my hope that, with Pesach gone for almost another year, the question of the definition of chametz offers a politically quiet enough opportunity to look at the possibilities for change, given a renewed Sanhedrin, without setting off any pre-existing sensitivities.

Defining Chametz

When I ask what chametz is, I don’t mean its theological ramifications, or why Hashem prohibited it on Pesach, or what lessons we should learn. I mean only and simply, what is it?

The instinctive and understandable reaction is that we all know. As laid out clearly in Pesachim 35a, five grains—wheat, barley, oats, rye, and spelt—can be used for matzah on Pesach because they become leavened, chametz, when mixed with water.

What if that isn’t true? What if, for an easy example, other foods also leaven when left in water?

That glides over the role of yeast. The process by which leavening occurs points to several ways a Sanhedrin might rethink the list of foods that can become Torah-level chametz. Rabbi Dovid Cohen of the CRC (disclosure: he is my cousin) summarizes it this way:

Although a grain which soaks in water for 18 minutes is chametz, in order to make good bread one needs yeast. Yeast is the living microorganism which converts some of the flour into the carbon dioxide which fluffs up the batter and causes it to “rise.” The air we breathe contains yeast. Therefore if one makes a batter of flour and water it will eventually rise even if no yeast is added, because yeast from the atmosphere will find its way into the batter. But most bakers do not have the patience to wait all day for their bread to rise, so they add their own yeast… only yeast that comes from one of the five grains is a problem on Pesach … yeast [that] does not contain any ingredients from the five primary grains (as it often does not)…is not chametz even though it has the same characteristics as seor (emphasis added).

R. Zushe Blech at Kashrut.com writes similarly:

Matzah is…bread made from one of the five grains…that has not been allowed to ferment…The world “leaven” actually means “risen,” and Chometz refers to bread that has been leavened

Leavening is the process by which gasses are created and trapped in dough so that it rises… Chemical leavens, such as baking soda (sodium bicarbonate), work by reacting with acids present in the dough to produce carbon dioxide…typically used in crackers and cakes. Yeast…is a biological leaven. The yeast cells eat sugar in the dough and secrete an enzyme called zymase…the zymase converts the rest of the sugar into carbon dioxide (and a small amount of alcohol) – a process called fermentation – which in turn causes the bread to rise.

Both presentations accurately tell us the halachic view of what can become chametz, how it becomes chametz, and what is considered seor. Rarely do we stop to ask, is that necessarily true, or is it only currently true?

Becoming Chametz

The Gemara contrasts these five grains, which leaven, to orez and dochan (commonly translated as rice and millet) which do not. Rambam notes, both in his Mishnah commentary to Challah 1:1 and Laws of Chametz and Matzah 5:1, that orez and dochan do puff up into something dough-like, but the Gemara categorized it as sirchon, rotting (the translator of Rambam’s Mishnah commentary used ipush, going rancid), not leavening.

More insight into what the Gemara meant by leavening comes from its brief discussion of when dough has sufficiently leavened to obligate karet. Based on a discussion in Pesachim 48b, Shulchan Aruch Orach Chayyim 459:2 rules that when the dough begins to show cracks, it is proof it has become chametz.

It seems that chametz is that food which, mixed with water and even without a deliberately added leavening agent, ferments into a dough that whitens and develops cracks as it is pulled together. As far as the Gemara and therefore halachah knows, only the five grains have that quality.

What if that isn’t true? What if, for an easy example, other foods also leaven when left in water? Remember that R. Cohen had said that we add yeast to make dough leaven more quickly—what is the standard for how much leavening has to happen how fast to qualify?

Who Taught Us How To Define Chametz?

I raise these questions because I don’t know of anywhere that the Gemara defends or derives its definition of chametz; it seems to assume it. That might be because Moshe Rabbenu conveyed exactly this definition to Yehoshua and on to later generations. Just as that tradition defined the Four Species to wave on Sukkot, it may equally have included this definition of leavening. If so, it is a part of the Oral Law handed down at Sinai and completely unchangeable.

But it seems equally plausible that the Torah used a word whose meaning was well-understood in its time, since those were the only options for leavening. If Chazal assumed (not decreed; it is hard and complex to overturn decrees) this definition of chametz, it would open the door to a Sanhedrin deciding that other processes might qualify as leavening as well.

Is it impossible for a Sanhedrin to decide that Chazal defined chametz as it existed in their time, but did not exhaust the possibilities for what is chametz?

I first thought of this when I encountered the view of R. Yoel Bin-Nun that the proper observance of the custom of avoiding kitniyot on Pesach would actually extend to all food that looks like chametz. Kitniyot isn’t my topic, but R. Bin-Nun reminds us that we today have more foods that look and taste like chametz than in the time of the Gemara, many of them foods that were unknown to the Gemara (such as potatoes and corn).

A Sanhedrin might decide that this doesn’t matter, that the Torah only cares about our eating leaven which was around during the Exodus. That itself would seem to have radical implications. It would change chametz from being about the inherent flaw in leavening to a more historical memory of a certain event, since much food that was, in many ways, as leavened as chametz would be allowed for consumption on Pesach.

But are we sure a Sanhedrin wouldn’t agree with R. Bin-Nun, and say that yes, foods that look like chametz look that way because they draw enough yeast from the air so that they, too, become halachic chametz? Is it impossible for a Sanhedrin to decide that Chazal defined chametz as it existed in their time, but did not exhaust the possibilities for what is chametz, that in our expanded world we have found other ways to arrive at the result the Torah prohibited?

I think this latter view gains support from looking at how the Gemara arrived at its list of the five grains. Yerushalmi Challah 1:1 (quoted in Rash mi-Shantzs commentary to Challah) says the Sages checked the world around them and found (badku u-matzu) that these were the only five grains that leaven as opposed to rotting. That sounds like an unabashedly practical claim, not an halachic one. If, in the fifteen hundred years since then, we have found previously unknown foods that undergo a similar enough process, how would a Sanhedrin react?

The Five GrainsTradition of the Oral Law?

Rash mi-Shantz to Challah quotes another view in the Yerushalmi, R. Shmuel b. Nachman, who shama kulhon from Yeshayahu 28:25. The phrase I left in Aramaic roughly translates as “heard them all,” which can be read in one of two ways, with differing ramifications for our question.

The possibility I find less likely is that R. Shmuel b. Nachman was reporting a tradition of how to read the verse such that it reveals the complete list of foods that can be chametz, matzah, or obligated in challah. Since R. Shmuel b. Nachman’s view isn’t widely accepted, that would seem to pose a problem for Rambam, who held–both in his introduction to his Mishnah commentary and in the beginning of Hilchot Mamrim–that a reading of a verse handed down as tradition never became a matter of dispute (Rambam’s position is itself difficult; I don’t adduce it as proof, only to show why I suspect that’s not the way he read R. Shmuel b. Nachman).

The Five GrainsA Human Derivation of a Verse?

A more likely way to read it, I think, is that there was a loose tradition that these five grains were the crucial ones, perhaps starting with the practical considerations we’ve already seen. R. Shmuel b. Nachman found that the verse in Yeshayahu could be read to indicate those five.

Once he read it that way, we might argue that our best reading of Scripture tells us these are the crucial five.

That brings us to another too-little known ability of the Sanhedrin. In Mamrim 2:1, Rambam notes that a court can also interpret a verse, using all the hermeneutical tools at its disposal. In such situations, a later court has the right to adopt a different reading. Their new reading can contradict the halachic conclusion of the previous court’s, even without their claiming to be greater thinkers or scholars. That’s not true for traditions a court transmits, nor for decrees a court makes, some of which can never change and some of which require a court greater in wisdom and number.

But derivations, the result of the best efforts of human reasoning and judgment, are open to each court’s determinations. If so, a duly authorized Sanhedrin could easily decide that it preferred a different reading of Yeshayahu 28:25. That would clear the way to also re-open the question of what can become chametz, matzah, or obligated in challah.


R. Cohen’s summary of the leavening process above pointed out the odd fact that we today assume that halachic seor can only come from the five grains, despite our knowing of other equally powerful sources of yeast and leavening—biological and chemical ones. As R. Cohen said, all seor is yeast, but not all yeast is seor.

Is that necessarily so, or is that because the Gemara only knew of grain-based seor?Once we are less certain of the five grains as the be-all and end-all of chametz (unless a Sanhedrin decides that no, it’s only these five), we can easily wonder why other leavening agents, particularly the biological ones, would not also qualify as seor. With all the ensuing ramifications.

The Sanhedrins Long To-Do List

As I said at the start, I don’t raise this issue for any immediately practical reasons or because of my fascination with chametz. I do it as a reminder that there’s a bigger halachic world out there than we realize. Much of what we have today is that way because for one and a half millennia we haven’t had a Sanhedrin performing one of its essential functions, bringing new eyes to the world of Torah as the world around us changes.

I meet too many Jews who assume halachah as we have it now is halachah as it always will be. Some hate that, and decide to change halachah in inappropriate ways; others revel in it and say that what is now is what always should be.

Each are partially correct. Some halachot are unchangeable, regardless of the difficulty in upholding them. Other halachot need the availability of a Sanhedrin to change, and are now relics hanging on until we have the full restoration of the halachic system to its ideal self.

Chametz and other questions—and there are many, once we start looking–will have to wait for a Sanhedrin. But refreshing our awareness of the vistas the Sanhedrin could decide to open up, realizing the backlog of 1500 years of halachic issues that have not been able to be handled fully in the way that Hashem wanted, is part of revivifying our longing for its return.

Like on Seder night, where each step of the redemption deserves its own dayyenu, part of what I want to show here is that the return of the Sanhedrin would deserve its own dayyenu, for reasons that already resonate with many of us here and now.

About Gidon Rothstein


  1. An interesting article but I think Rabbi Rothstein oversteps in shifting the focus of Chametz from grain to yeast. The fact is that those same natural flee-floating yeasts that cause moistened grain to start fermenting are also responsible for spoilage of all moist sugar-containing foods — which really includes all vegetation and even meat to some extent. It’s not just that his Seder wine was yeast-fermented grape juice, but the grapes had already started fermenting from natural yeasts even before they were juiced, and the banana on his counter during Pesach was also undergoing natural fermentation (especially if it went uneaten and started browning).

    Because of this it just doesn’t make sense to define Chametz as being purely yeast-based; the definition has to be qualified — and it makes the most sense to limit it to (bread) grain since Chametz is clearly juxtaposed to bread. The (Five) Grain definition is therefore related to bread and not to Chametz per se.

    So we know that the definition of Chametz can’t just be ‘Grain’, because Matza is obviously made from Grain. It also can’t just be Yeast-Based Fermentation, because (a) it’s too common and (b) it’s actively required for halachically mandated wine (and at least present to some extent even in grape juice). Grain + Yeast-Based Fermentation is obviously a workable definition.

    So if to expand the Yeast+ definition beyond Grain requires a hard stop short of everything edible — how do we come up with that stop line?

    Kitniyot expands the set but sets a stop line at some combination of plant products that look like grain and/or are likely to get contaminated with grain. Harav Bin-Nun would prefer that the definition focus on foods that behave like Yeast+Grain. Either way some relationship to Grain needs to be part of the expanded definition.

    • I also thought the example was a poor choice. My own favorite is e-paper reading devices. And what could be more “shabasdik” than sitting and learning or reading? They have no back-lighting. their print is temporary, so it is at least arguable that if electricity itself doesn’t inherently involve melakhah, they should be permitted.

      Beer is to wine as bread is to baked rice paste, and yet wine and rice-bread are not chameitz. For that matter, qitniyos doesn’t really expand the definition of fermentation, because dry beans are also prohibited. And while eating matzah is a mitzvah, eating that rice-bread is violating the minhagim of qitniyos.

      Last, I don’t know if there is such a thing as non-yeast-based fermentation, but I doubt it would be permissible once invented. Halakhah doesn’t seem to care about microscopic entities. So, whether there is or isn’t air-born yeast involved wouldn’t be a defining factor.

      • I had a discussion about e-readers with a Sr. Rabbi at the Eretz Chemda Institute which led to a discussion of whether they have ‘futurists’ that look at the likely development of future technologies and try and pre-determine halachic problems and answers (they do).

        It was his personal opinion that within decades hi-tech will be so intrusive in our lives (think skin-embedded electronics and moving sidewalks) that mainstream Orthodox Judaism will be forced to revisit the original Electricity on Shabbat debate.

        • I had this same conversation last night with our assistant rabbi who is setting up the tikkun leil shavuot schedule when I told him my topic would be Brain Computer Interfaces. When you realize that the central nervous system runs on electricity and that we can now operate a prosthesis the same way one does a natural hand, it makes you think.

  2. An interesting additional question is what would the system look like without a Sanhedrin but without the eit laasot of writing down the oral law?
    As I put together a shiur on brain computer interfaces it more strongly reminds me how much we would benefit (for many reasons) from a functioning Sanhedrin.

    There is some comfort in the “as long as we follow the process, that’s what HKB”H wants” approach.

  3. I applaud, without qualification the general thrust of the article. Realising that Jewish law as it is done today, may be the best we can do, but it is absolutely not how Jewish law is supposed to be, is very important.

    To add a point, strictly speaking, as far as I can tell, according the Shulchan Aruch one can actually bake a nice fluffy cake on Pesach, as long as he’s careful not to let the batter sit for 18 minutes (actually more like 45, but that is a side issue, see Yerushalmi). This has always seemed a but odd to me and I’m inclined to think a future Sanhedrin would ban the use of baking powder.

    Nevertheless, I must point out the following:

    1) Rye and Oats are, without any doubt whatsoever, not among the five species. There is simply no excuse for continuing this misinformation.

    2) All five species are varieties of Wheat and Barley. It is logical to assume that species of wheat and barley unknown to Hazal are also forbidden. Indeed, this is how we already treat Spelt, which is also perhaps not one of the five species. Since we also treat Rye the same way, it seems we have extended the concept even further. (Oats are different matter, since it is, in fact, impossible to make a dough out of them that will leaven).

    3) A lump of dough (a kernel of wheat is quite different matter) that has been left to sit for 18 minutes (actually 48) is assur, however it is not necessarily actually “hametz”. Rather, this is the limit Hazal set for dough that shows no actual signs of leavening beyond which it must be gotten rid of – because we don’t know. To claim otherwise, as people routinely do, strikes most people outside the club as simply outlandish and fanciful, and rightly so.

    4) A kernel of wheat left to sit in water for 18 minutes is certainly not hametz.

    I would agree with the suggestion that, in general, Shabbat halacha is a better area to explore these ideas.

  4. Joel, I’m actually quite interested in that topic – would you be able to email me your sources and conclusions?

    • Sure, when I’m done. Please email me offline. I’m focusing on Shabbat issues but it clearly has many other implications as well. Among my tentative conclusions are:

      *electricity and halacha will be reexamined along the lines of R. Shlomo Zalman Auerbach on hearing aides for a more nuanced conclusion,

      *BCI without a “maaseh” will still be attributed to the thinker in order to avoid “ownerless” acts (at least drabannan),

      *the further we get away from Talmudic times the flimsier the sources for talmudic/halachic analysis of technological change become,and

      *Al Jolson was right – Wait a minute, wait a minute, you ain’t heard nothin’ yet

  5. Gabriel M raises an important point. Oats, and other gluten free gains, cannot be chametz. Indeed, oats was not a known grain for human consumption in ancient times. If it was cultivated at all in the middle east, it was purely for animal feed and not made into a dough. Gluten is necessary to form the web-like structure that defines any bread. While chazal did not know anything about yeast (yeast was not discovered until the 19th century), they clearly knew what we call sourdough starter (se’or) and what grains rise or not. Oats might be kitniyot, but it is not and cannot be one of the five grains that is chametz (the mistake, I believe, traces to Rashi who mistranslated the name for one of the five, not realizing that oats were not cultivated in the time of the Bible or Talmud). This has important ramifications for those who rely on oat matzah to fulfill a mitzvah. One can call it a kula, but it is probably not a fulfillment of the mitzvah at all. I would think a person who cannot eat gluten would be patur from the mitzvah, but eating oats would be problematic.

    Another point: Modern day commercial processed flour will not rise in 18 minutes (or probably even 30 or 60 minutes or more) since the yeasts in the flour are killed in the bleaching process and there are fewer airborne yeasts in urban areas than in rural ones. But go buy a freshly milled, unprocessed organic flour and make bread in the suburbs or rural areas and see how quickly it rises when water is added. Granted, that does not lend itself to clearly defined rule-making, but it should help us understand why we don’t usually witness fast rising dough today.

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