From: Rabbi Moshe Sofer
To: Rabbi Yitzchak Nosson
Rabbi Yitzchak Nosson poses questions about leavened wheat mixed with good wheat, nullifying garlic's sharpness in flour before Pesach, and drawing water in vessels that held fruit juice. The Chasam Sofer rules that leavened wheat imparts discernible chametz taste making nullification ratios moot.
Source: Shu"t Chasam Sofer OC §129