[Avodah] Yeast isn't chameitz

[Micha Berger]

On Tue, Apr 28, 2009 at 09:43:19PM -0400, T613K at aol.com wrote to Areivim:
: Yeast itself is not chometz, although, when  combined with flour and water 
: (and other ingredients), it causes dough to become  chometz...

I think more to the point of issur veheter, the issur "kol machmetzes lo
socheilu" is understood to refer only to fermented and leavened foods that
can cause something to become chameitz (R' Yehudah and stam bereiasa,
but no issur kareis) or were thereby made chameitz (R' Eliezer). See
Pesachim 43b.

In any case, even though yeast would qualify as a leavening agent, it's
not included in the pasuq.

I recall R' Menachem Zupnik saying in a Shabbos haGadol derashah that
chameitz that is not ra'ui la'achilah, only la'achilas kelev, is assur
as machmetzes, not chameitz. Thus preserving the kelal in kol haTorah
qulah in defining ochel as something a person could eat. Machmetzes
needn't be ocheil nefesh, and therefore broadens the scope.

But that's a 15 yr old memory. Might be garbled.

Tir'u baTov!
-Micha

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