Question: [Wednesday, 13th Kisleiv, 5782]
I originally baked a potato Kugel in a fleishig oven, and would like to know if I am allowed to reheat it in a Pareve oven, and what is the law if I ready did so, does my oven remain Pareve.
If your meat oven was clean of any meat residue at the time that you baked the potato Kugel, or if you preheated the oven in a way that any residue would be burned, and the Kugel was not baked simultaneously with uncovered meat or chicken, then it may even initially be reheated in a Pareve oven. If, however, there was unburnt meat residue in the oven at the time that the Kugel was baking, and certainly if it baked at the same time as actual uncovered chicken or meat, then you may not reheat it in a pareve oven, and if you do so then you pareve oven should be koshered. In general, if you preheated your meat oven for 15 minutes or more prior to putting the Kugel inside, then we can consider that any residue has been burned and it is considered as if the oven is clean regarding the above law to allow him to reheat in a pareve.
Explanation: The issue with reheating a Pareve food that was cooked in Fleishig Keilim within a pareve vessel, is in regard to whether we consider the pareve food to have absorbed actual meat taste which can then be transferred to the Pareve vessel. Now, in the case of an oven the only possible way for meat taste to be transferred to a Pareve food is through the vapor. If there is meat cooking in the oven at the same time as the Pareve food, or if there is unburnt meat residue in the oven at the same time, then the vapor of the meat is absorbed by the Pareve food and makes it be considered as if it was cooked with meat. Now, just as one may not heat up a potato from a chicken soup inside of a pareve pot, so too one may not heat up this potato Kugel in a pareve oven. If, however, the meat oven was clean of any residue at the time that the Kugel baked inside of it, then it remains Pareve and may be reheated in a pareve oven. This applies even if the meat oven was Ben Yomo of baking meat at the time that one baked the potato Kugel, as although in such a case we consider the potato Kugel to have absorbed the meat taste that was absorbed in the walls of the oven, this taste is very diluted and is Halachically defined as Nat Bar Nat Dihetera, of which we rule that it may even initially be eaten with dairy utensils, and hence may be reheated in even a dairy oven, not to mention a pareve oven [although according to Ashkenazim may not be eaten with actual dairy]. This is aside from the fact that some opinions hold that dry items do not release any vapor, and according to them seemingly the potato Kugel remains completely Pareve if there is no meat residue in the oven even if it is Ben Yomo.
Sources: See regarding the status of Pareve food that was baked in a meat or dairy: Michaber Y.D. 97:3; Rama 108:1; See regarding the issue of vapor in today’s ovens: Rama 108:1; Igros Moshe Y.D. 1:40; Maharsham 3:208; Minchas Yitzchak 5:20; Chelkas Yaakov 2:136; Kinyan Torah 1:24; Badei Hashulchan 92:166; Darkei Halacha p. 242 Pischeiy Halacha p. 27; 157; Minchas Yitzchak 5:20; Hakashrus 1:39-40; See regarding the issue of vapor by dry foods-Lenient: Toras Chatas 35:6 [See Minchas Yaakov ibid]; Masas Moshe 4:30; P”M O.C. Hanhagos Horaos Issur Viheter Seder Sheiyni 37, brought in Pischeiy Teshuvah 92:6 that only liquids release vapor; Beis Meir 461; Poskim in Darkei Teshuvah 92:164; Igros Moshe 1:40; See regarding the issue of vapor by dry foods-Stringent: Tur 451:15 regarding Charara “And it releases vapor”; Bach 451:13; M”A 451:30; Yad Yehuda 92 Aruch 53; Masas Binyamin 42:58; Chacham Tzvi 20; P”M 451 A.A. 30; Rivash 295; Tzemach Tzedek O.C. 43; Shoel Umeishiv Chamisha 4; Beis Shlomo Y.D. 1:162 and 164; Maharsham; Daas Sofer; Levushei Mordechai; Poskim in Darkei Teshuvah 92:164; Rav Elyashiv in Beis Yitzchak; See Peri Haretz Y.D. 2:14; See that preheating oven gets rid of residue: Minchas Yitzchak 5:20; Hakashrus 1:40; See regarding the allowance of Nat Bar Nat Dihetera to eat in opposite utensils: Michaber and Rama 95:1; Semak 213; Semag 140-141; Taz 95:5; Lechem Hapanim 95:8; Biur Hagra 95:8; Chulin 111b regarding fish