“Question: If I cook parev food in a clean meaty pot, does the food become meaty? And do I need to wait six hours after eating the food before eating dairy?
Discussion: The classification of a parev food cooked in a clean meaty pot is “nat bar nat d’hetero” (abbreviation for nosein ta’am bar nosein ta’am; i.e. the meat originally cooked in the pot imparts meat bliyos into the pot and these bliyos are defined nat rishon or nat. When a parev food is subsequently cooked in this pot these nat rishon bliyos are imparted into the parev food item rendering the parev food nat bar nat.)
Nat bar nat bliyos are not as potent as the food item from which they were imparted, and therefore regarding a permissible food item they have a more lenient status than the original food item; whereas nat bar nat bliyos imparted by a forbidden food item are not subject to any leniencies because the original issur status remains on them, and this is not “weakened” by transfer of bliyos.
The Shulchan Aruch (Yoreh De’ah Siman 95 se’ifim 1-2) rules that a nat bar nat food may be eaten together with food of the other “type”. I.e. if potatoes were cooked in a clean meaty pot, they may be eaten together with dairy foods. The Remo (ibid) posits that the minhag is to be stringent and not to eat the nat bar nat food item together with food of the other “type”. Even according to the Remo, this is only l’chatchilo. If the nat bar nat food has already been mixed with food of the other “type” the Remo (ibid) permits it to be eaten, since this is considered b’dieved (ex post facto). (The Maharshal quoted in the Shach s.k. 4 posits that if the parev food was roasted [without liquid, as opposed to cooked in liquid] in the meaty pot, it is forbidden to be eaten with dairy, even ex post facto.)
The aforementioned applies to a ben yomo pot (i.e. that has been used within the last 24 hours to cook meat). However, if the pot was eino ben yomo (i.e. it has not been used within the last 24 hours to cook meat), the Remo (ibid) maintains that the custom is to be lenient and allow the nat bar nat food to be eaten with food of the other “type”. (The exception to this is if the parev food is a dovor chorif – i.e. very sharp or spicy and thus has the ability to rejuvenate eino ben yomo bliyos. For example, if onions are fried in an eino ben yomo meaty pot, one may not cook or eat the onions together with dairy foods.)
Regarding whether one needs to wait six hours after eating a parev food that was cooked in a meaty pot, the Shach (Yoreh De’ah Siman 89 s.k. 19) infers from the Remo (Yoreh De’ah Siman 89 se’if 3) that even in a situation where it is indeed forbidden to eat the parev food together with dairy, one does not need to wait six hours before eating dairy.
Conclusion: Parev food cooked in a clean meaty pot is classified nat bar nat d’hetero. The Shulchan Aruch (Yoreh De’ah Siman 95 se’ifim 1-2) rules that a nat bar nat food may be eaten together with food of the other “type”; the Remo (ibid) maintains that the minhag is to refrain from eating nat bar nat together with food of the other “type”. This applies specifically to a ben yomo pot; regarding eino ben yomo the Remo is lenient (with the exception of dovor chorif).
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