I don’t know much about chemistry or alcohol, so please bear with me for a moment.

At what point does wheat- or barley-derived ethanol become Chametz? Is it naturally Chametz, or does it require a catalyst to ferment?

  • Ethanol is a byproduct of fermentation (yeast eats sugars and then excretes ethanol and CO2). If there's ethanol, then it already is fermenting.
    – Double AA
    Apr 4, 2018 at 15:23
  • @DoubleAA Like I said, I know very little on the topic. If you want to post that as an answer, go right ahead.
    – DonielF
    Apr 5, 2018 at 0:45
  • I understand the chemistry of a fermentation reaction but I don't understand at what point a wheat kernal sitting in a bowl of water (or wort in general) is considered halakhically leavened, which seems to be your question. But שכר המדי is right there in the Mishna, so go figure
    – Double AA
    Apr 5, 2018 at 6:44

1 Answer 1


A quick internet search indicates that typically, at least at the industrial level, the grain is milled and mixed with water as part of the initial processing which later leads to fermentation. Once the grain touches the water, the 18-minute clock starts ticking, leading to Chametz even if there is no actual measurable fermentation or visible rising. Fermenting requires yeast (or a chemical means of transforming the starch/sugar into alcohol. But Chametz doesn't require that - it just requires grain + water + time.

  • 1
    Is this really true? The time estimate is just a way of quantifying when leavening may have occurred. It's not a magic number. For instance if you left it in cold water, it never becomes Chametz, even if 18 minutes pass (OC 457:2) and similarly in extra warm environments even less than 18 minutes is problematic (459:1). It's not about time but about leavening. 18 minutes is the Gemara's estimate for a "deaf dough": dough that isn't exhibiting classic signs of rising (cracked surface, etc.) and you don't have another dough to compare it to.
    – Double AA
    Apr 5, 2018 at 6:33
  • I know there are variations from the classic "18 minutes" - in addition to temperature (I did know that made a difference, though I didn't know "in cold water it never becomes Chametz"), I know if the dough is being continuously worked it makes a difference. But that being said, I find it hard to believe that "grain mixed with water for processing" in a normal commercial process would NOT become halachic Chometz within a reasonable (perhaps temperature adjusted) amount of time. It is certainly clear that nothing extra (yeast or a chemical catalyst) is needed to become Chometz. Apr 5, 2018 at 14:43
  • That's not clear at all. We may Lechumra avoid anything after 18 minutes but that's not the original law. Again 18 minutes is a estimate for normal dough. Dough made in a perfectly sterile environment would never rise and never be Chametz. Theoretically.
    – Double AA
    Mar 26, 2019 at 23:03
  • when leading up to fermentation the grain is cracked and mixed thoroughly into water which is bad soledus bo for a long time to extract the sugars from the grain. This liquid is then drained and the grains are then rinsed again. This liquid produced from this process is more certainly chometz as the hot water will have caused a change. This unfermented liquid is called the wort. After fermentation is complete for the purpose of distilled alcohol this fermented liquid is called the mash.
    – Dude
    Apr 7, 2022 at 21:17
  • 1
    Even before the wort is made most of the grain being used to make the wort is malted grain. It's true that sometimes unsalted grain is used but the majority of the grain bill will be malted grain. This grain itself is chometz. The process for making malted grain is after the grain is harvested it is wet and set in a room at a controlled temperature for a few days so it will sprout. After the grain sprouts it is then heated at varying temperatures and for varying lengths of time. This cooking of the grain brings out specific desired flavors and colors.
    – Dude
    Apr 7, 2022 at 21:19

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