Why Must Cheese be Certified Kosher for Passover?

Shulchan Aruch (Orach Chaim 442:5) writes that cheese that was made with wheat vinegar must be destroyed before Pesach. Mishnah Berurah explains that this is true, even if the vinegar is less than one part in sixty and does not give any taste to the cheese. Since the vinegar helps form the cheese (maamid), the regular halachos of bitul (nullification) do not apply. The same holds true for the bacterial cultures that are used to form the cheese. If the cultures were grown on glucose derived from chametz, the cheese may not be eaten on Pesach. Kosher l’Pesach cheese is made from kosher l’Pesach cultures.

The Gerald & Karin Feldhamer OU Kosher Halacha Yomis is dedicated to the memory of Rav Yisroel Belsky, zt”l, who served as halachic consultant for OU Kosher for more than 28 years; many of the responses in Halacha Yomis are based on the rulings of Rabbi Belsky. Subscribe to the Halacha Yomis daily email here.