The Shulhan Aruch (Siman 467) discusses a case in which a kernel of wheat was discovered in a pot of rice or other dish cooked on Pesah. The status of the rice depends on whether the wheat kernel appears to have already become Hames. Therefore, if it is completely closed, showing no sign of swelling or cracking, Maran is lenient. The wheat should be removed and burnt, whereas the rice and the pot are permitted for use. Ashkenazim are strict in this case.
However, if the wheat kernel is cracked, it is Hames. Even though the taste of wheat emitted into the cooked rice is miniscule in comparison to the amount of rice, Hames on Pesah is forbidden even "B’MasheHu"-in a minute amount. Therefore, the rice, pot and spoon used to stir are all considered Hames.
Hacham Ovadia discusses an interesting case, in which, after being discovered, the kernel of wheat was subsequently lost before it could be determined whether the wheat was closed or cracked. In such a case, Hacham Ovadia is lenient based on a "Safek Safeka"-a double doubt.
If the wheat was found on the last day of Pesah, Hacham Ovadia rules that one should wait until after Pesah to ask the Rabbi whether the rice is forbidden as Hames that passed through Pesah. At that time, Hames does not cause the rest of the mixture to become prohibited in such a miniscule amount.
