Question:
There are only 5 grains that can become chametz, so there must be a common denominator between them, it would seem that gluten is the common link between four of the grains, however oats don't have gluten, so either the oats of today are not the actual oats mentioned in the gemara and halacha, or there must be some other common denominator between all five grains besides gluten that makes only these five become chametz.
Is it known what exactly this is?
Answer:
Hello,
In consultation with a professional in this field, the poskim rule that the oats we have today are siboles shual, one of the five grains. There was a Professor Felix who wanted to suggest something similar to what you are saying; however, the poskim rejected his idea. True, oats don’t contain gluten, but it isn’t the gluten that makes the “chimutz"; rather, it is the type of starch in these grains that becomes chametz. Chazal also say that rice and other legumes don’t become chametz; rather, it is called sorchon. Why Chazal said this, I don’t know.
Best wishes
