Q. May I add milk to my coffee that was heated in a fleishigs microwave oven? What if the microwave had been cleaned out, and had not been used in the past 24 hours (aino ben yomo)?
A. In a previous Halacha Yomis, we have seen that if food is heated uncovered in a fleishig microwave oven, even if the microwave is clean, the food will still absorb a secondary fleishig taste (nat bar nat) from the walls of the microwave. Although this food is not fleishig, and eating it will not necessitate waiting 6 hours before eating dairy, nevertheless the minhag of Ashkenazim is that we do not eat this food together with dairy. Therefore, one may not add milk to coffee if it was heated in a fleishig microwave that had been used to heat meat in the past 24 hours. But one may drink milk immediately afterwards.
However, if the microwave had not been used with meat in the past 24 hours, the fleishig taste in the walls of the microwave becomes stale and will be nullified. In such a case, if one has no other means of obtaining hot water, Chochmas Adam (48:2) writes that one may heat coffee in such a utensil, even with the intent to add milk. However, if one has another option for obtaining hot water, Chochmas Adam writes that this may not be done. Although some Poskim are even more lenient and allow heating the water with the intent to add milk, even in a case where one has another option, Rav Belsky, zt”l held that one should follow the ruling of Chochmas Adam. However, if one cooked water with the intent that it remain pareve, and later they change their mind, they may serve it with dairy, since the stale fleishig taste has already unintentionally been nullified.
This column comes from OU Kosher’s Halacha Yomis dedicated in memory of Rav Chaim Yisroel ben Reb Dov HaLevy Belsky, zt”l, Senior OU Kosher Halachic Consultant (1987-2016). Subscribers can also ask their own questions on Kashrus issues and send them to email@example.com. These questions and their answers may be selected to become one of the Q and A’s on OU Kosher Halacha Yomis.