Cooking Milk and Meat in One Oven by Rabbi Chaim Jachter


Reprinted with permission from the Journal of Halacha and Contemporary Society Fall 1996


An issue faced in every Jewish home is establishing a protocol for cooking milk and meat in one oven.  There exist many opinions among rabbinic authorities regarding this issue, ranging from extremely lenient ones to those that are quite strict.  This essay will explore the positions of the Gemara and the Rishonim regarding this question and will outline four different protocols for use of an oven for milk and meat from four major Halachic authorities.  We will begin by reviewing the Talmudic discussion of the Halachic status of Reicha – aroma emitted by foods.


Reicha – Aroma Emitted by Food

The Gemara (Pesachim 76b) records a debate between Rav and Levi whether Reicha Milta or Reicha Lav Milta – is the aroma emitted from food Halachically significant or not?  The case discussed in the Gemara is Kosher meat cooked in the same oven with, but without touching, non-Kosher meat.  According to Rav, the aroma emitted by the non-Kosher meat renders the Kosher meat not Kosher because Reicha is Halachically significant.  Levi, however, rules that the meat remains Kosher because Reicha is not Halachically significant.  These rulings apply also to milk cooked simultaneously with meat in the same oven.

Rishonim disagree regarding which opinion is accepted as the Halachic norm.  Rashi (s.v. Amar Lecha) asserts that the Halacha follows the opinion of Levi.  Tosafot (s.v. Osra) cites the opinion of Rabbeinu Tam who rules in accordance with Rav.  Rif (Chullin 32a) and Rambam (Hilchot Maachalot Assurot 15:33) also rule that Levi’s is the Halachically accepted opinion.  However, they assert that even Levi does not permit one to deliberately (Lechatchila) cook Kosher meat in the same oven as non-Kosher meat.  Levi only permits post facto (B'dieved) the Kosher meat that has been cooked in the same oven with non-Kosher meat. 1

The Shulchan Aruch (Yoreh Deah 108:1) rules in accordance with Levi that Reicha is not Halachically significant.  However, the Mechaber adopts the limitations of the Rif and Rambam that one may not deliberately cook Kosher and non-Kosher meat simultaneously in one oven.

The Rama then adds a series of stringent rulings on this issue, which incline the Halacha towards Rav while essentially ruling like Levi that Reicha is not Halachically significant.  First, the Rama notes the custom to avoid cooking Kosher/non-Kosher or milk/meat together in one oven even if the oven is large.2

The Rama subsequently presents a variety of situations where there are opinions that even Levi would agree that Reicha is Halachically significant.  These include where Chametz is cooked simultaneously with food intended for Passover use, if either food is sharp, such as onions or hot peppers (Davar Charif)3, or if the oven is not ventilated.4  Also, something Pareve cooked with either milk or meat in one oven should not be eaten (Lechatchila) with the opposite type of food (for example, a kugel cooked simultaneously with chicken in the same oven, should not be deliberately eaten together with milk.  See Aruch Hashulchan 108:14-15 who explains that B’dieved it would be permitted if one has difficulty finding something else to eat).  The Shach (no. 9) adds that if one places food in the oven with the intention that its aroma be transmitted to the other foods, then all agree that in this case the Reicha is Halachically significant.

The overall theme of this chapter in the Shulchan Aruch is best expressed by the heading printed in the text of the Shulchan Aruch: “One should not cook Kosher and non-Kosher in one oven.”  The Rama notes that all these rules apply equally to milk and meat.  Therefore, it is not surprising that the Aruch Hashulchan (Yoreh Deah 108:9) rules that one may not initially cook even lean Kosher meat with lean non-Kosher meat.5 Similarly, Pri Megadim (Siftei Daat 108:18 (1)) rules that it is best to avoid cooking Kosher and non-Kosher bread simultaneously in one oven.  Moreover, because of the concern of spills, one should not cook meat and milk simultaneously one above the other, even if both foods are covered (Rama 92:8 and 97:1).  Only if the covered foods are placed side by side are they permitted to be cooked simultaneously (Pri Megadim, Siftei Daat 108:10).  If, B’dieved, one cooked milk and meat simultaneously in an oven, a competent Halachic authority should be consulted.6 It should be noted that the Shulchan Aruch speaks mostly of cooking7 milk and meat simultaneously and not consecutively.  Rama (108:1), however, applies these rules to cooking milk and meat consecutively beneath a flat pan (i.e. a confined area) if both the milk and meat emitted steam (Zeiah).  8


Zeiah – Steam That Emerges From Food

The Rama’s introduction of the problem of cooking milk and meat consecutively in the same oven brings us to the issue of Zeiah – steam emitted from food.  The Shulchan Aruch (92:8) cites the Teshuvot HaRosh (20:26) that “if one placed a pan of milk beneath a pot of meat, the steam emerges [from the milk] and is absorbed into the pot [of meat] and renders it forbidden” (because of the mixture of milk and meat).  The Rosh cites the source for Zeiah being Halachically significant as being the Mishna in Masechet Machshirim (2:2), which states that the steam that rises from a bathhouse that is ritually unclean (Tamei) is itself ritually unclean.9 We see from this Mishna that the steam that rises from something retains the status of the item from which it emerged.  Thus, steam that rises from milk is considered by Halacha to be milk.

An important question needs to be raised at this point.  When the Talmud discusses Kosher meat being cooked simultaneously with non-Kosher meat, there is no mention of concern for Zeiah.10 Moreover, we seem to be stricter with Zeiah, which the Shulchan Aruch rules can render food non-Kosher, than with Reicha, which we say is Kosher B’dieved.  We will cite six approaches to answer this problem.  These answers are not of mere academic concern.  They serve as the basis for the variety of protocols suggested by great Halachic authorities regarding cooking milk and meat consecutively in the same oven.


Mishkenot Yaakov

Because of these questions, the Mishkenot Yaakov (Yoreh Deah 34) rejects the assertion of the Rosh and Shulchan Aruch that Zeiah is Halachically significant.11 He believes that one may cook milk and meat consecutively if the oven is clean.  This Mishkenot Yaakov appears, however, to be the lone authority to take this approach.  Virtually all other authorities accept that Zeiah is Halachically significant.


Aruch Hashulchan

The Aruch Hashulchan (92:55) writes that Zeiah is a relevant concern only in a small, enclosed area and not in an open area.  He continues that the aforementioned case in the Shulchan Aruch provides an example of an enclosed area “such as a very small oven in which a pot is placed and upon it is placed a second pot – the Zeiah rises and fills the area because it does not have a place to escape.”  The scope of Reicha, however, is not limited to such a situation.  In addressing the issue of Reicha, the Talmud does not mention the issue of Zeiah because it is not speaking about a situation of cooking both foods in a small, enclosed area.  The Aruch Hashulchan concludes, “but when [cooking in an] open area which has air such as in our ovens [meaning that the food is not placed in a tightly enclosed oven as in the time of the Talmud] the Zeiah rises in the air and does not render non-Kosher the pot that is close to it.”

Rabbi Feivel Cohen (Badei Hashulchan 92:180), on the other hand, points out that Rama 92:8 seems to contradict this assertion of the Aruch Hashulchan.  The Rama writes of the possibility of Zeiah when meat is hung above pots of cooking milk.  Accordingly, the Rama is concerned with Zeiah even if the cooking area is not confined and closed.12


Pri Megadim

The Pitchei Teshuva (92:6) cites a suggestion made by the Pri Megadim (in his Hanhagot Horaat Issur V'Heter 2:37), that perhaps the rule of Zeiah applies only to steam that emerges from liquids but not from solid food.  This would explain why the Talmud, when discussing Reicha, does not mention the concern of Zeiah – because it speaks of roasting meat, whose Zeiah according to this approach is not Halachically significant.  The Acharonim debate whether this suggestion of the Pri Megadim is correct.13


Rav Moshe Feinstein

Rav Moshe Feinstein (Igrot Moshe Yoreh Deah 40) suggests a variation of Pri Megadim’s approach.  He suggests a consideration of leniency even if the Zeiah emerging from solid foods is considered Halachically significant.  He infers from the language of Rama (108:1) that one does not have to assume that Zeiah emerges from solid foods as one must when dealing with liquid foods.  Only when we see that solid food emits steam do we have to be concerned with Zeiah.  According to Rav Moshe’s approach, one may say that the Talmud is speaking of a situation where the meat did not emit steam, and therefore the Talmud makes no mention of Zeiah.


Chavat Daat

Chavat Daat (Biurim 92:26) and other authorities (see Badei Hashulchan 92:166) rule that Zeiah’s Halachic impact is limited to saying that it rises from food and is absorbed into a pot above the food.  However, Halacha does not ascribe to Zeiah the ability to extract (Maflit) food absorbed in an oven roof above it and subsequently to serve as a conduit for this extracted food to enter the food below it.  According to this approach, milk and meat pots cooking side by side constitute only a problem of Reicha and not of Zeiah, since there is no opportunity for the Zeiah to enter the other food.

Hence, one can account for the Talmud’s omission of the concern for Zeiah because it is not speaking of Kosher food placed above cooking non-Kosher food.  Nevertheless, many authorities, most notably the Dagul Mirevava (92:8, also see aforementioned Badei Hashulchan), disagree with this assertion.  They would say that cooking milk and meat consecutively in the same oven constitutes a serious problem because the Zeiah from the second cooking extracts the Zeiah absorbed from the first cooking.


The Rosh

The Rosh, whose responsum is the point of departure for the Halachic discussion of Zeiah, raises the possibility in that responsum that a hot pot prevents the absorption of Zeiah.  Accordingly, a hot oven roof cannot absorb Zeiah.  Aruch Hashulchan (92:55) adopts this approach as normative Halacha.  This easily accounts for the Talmud’s omission of the concept of Zeiah because Zeiah is relevant in relatively few circumstances – when the pot above the cooking food is cold or when food not enclosed in a pot is placed above cooking food.  However, Rav Moshe (Igrot Moshe Yoreh Deah 40) is representative of the Halachic consensus that rejects this approach.  Indeed the Shulchan Aruch seems clearly to rule that a hot pot absorbs Zeiah.  (He did not limit his ruling, that absorption occurs, to a case where the pot was cold).  14

The common denominator of the six approaches outlined is that they somehow limit the applicability of the concern for Zeiah.  The Halachic authorities must do so because they must account for the fact that the Talmudic discussion in Pesachim 76 mentions only Reicha but not Zeiah.  Whether an authority has an expansive or restrictive view of the applicability of Zeiah will have an impact upon how that authority rules concerning consecutive use of milk and meat and in one oven.  We will outline the Halachic protocols of four major authorities regarding this question.


Four Halachic Protocols:

Aruch Hashulchan

According to the approach of Aruch Hashulchan, one would be permitted to cook milk and meat consecutively in the same oven, provided the oven is clean.  The cleanliness of the oven eliminates the problem of Reicha, and the fact that we do not cook in small confined areas removes the problem of Zeiah.16  Rabbi Hershel Schachter routinely tells inquirers that they may adopt this approach.  Rabbi Schachter reasons that the problem of Zeiah applies only to Hevel – thick steam – an assertion supported by Biur Hagra (92:39).  Rav Schachter counsels, however, that one wait for the oven to cool down from dairy use before the meat use and vice versa (see Pesachim 26b).


Rav Aharon Lichtenstein

Although Rav Lichtenstein permits one to eat in a home where the opinion of the Aruch Hashulchan is followed, he recommends that one adopt a stricter standard.  He suggests that one either wait twenty-four hours between cooking milk and meat in the same oven17 (it is reported that Rav Moshe Feinstein permitted this as well18) or Kasher the oven between cooking milk and meat in the same oven within twenty-four hours.  One Kashers the oven for this purpose by cleaning it and letting it run for an hour at its maximum temperature.19 The laws regarding a microwave, however, may be different.


Rav Moshe Feinstein

Rav Moshe (Igrot Moshe Yoreh Deah 40) indicates that one may cook milk and meat consecutively in one oven if either the milk or meat pots are covered.  This is based on the Rama (92:8), who states Zeiah does not constitute a problem if a pot is covered.21 In addition, Rav Moshe (as mentioned previously) rules that one has to be concerned that solid food emits Zeiah only if one is aware that it has done so.  Rav Moshe does not mention the option of waiting twenty-four hours between cooking milk and meat; this is an oral report quoted in his name.


Rav Feivel Cohen

Rav Cohen (aforementioned citation in the Badei Hashulchan) as well as the Chelkat Yaakov (2:136) and Minchat Yitzchak (5:20) strongly urge that one acquire two separate ovens for milk and meat.  They believe that the use of milk and meat in one oven is so fraught with Halachic problems that a great effort should be expended to avoid these problems.  In addition, Rabbi Cohen rules that one should have separate grates for milk and meat for both the oven and stove top.  Rav Moshe (aforementioned responsum), on the other hand, wholeheartedly endorses the generally accepted practice to use one set of grates both for milk and meat.22  Rav Moshe notes that on Pesach, the common practice is to be strict and to change grates from Chametz use to Pesach use.  This reflects an extra stringency, which is consistent with the very strict nature of the Halachot of Pesach.



We have seen that there are many differing approaches to the question of cooking milk and meat consecutively in one oven.  These opinions reflect the many different approaches to the scope of the applicability of the concern for Zeiah.  One should seek guidance from a Halachic advisor as to which of these protocols to adopt in practice.


1. See, however, the Ran (Chullin 32a in the pages of the Rif) s.v. Veha Detani.

2. This custom is quite strict in light of the fact that Tosafot (Pesachim 76b s.v. Osra Rava), who rules in accordance with Rav, asserts that Rav would agree that aroma emitted from one food does not affect another food if the oven is large enough to allow any Reicha to dissipate.

3. See Gilyon Maharsha (thereupon, s.v. V'kol Shekein).  For a description of what is considered a Davar Charif, see Rama 95:2 (at the end) and Aruch Hashulchan 96:13-14.

4. Rav Binyomin Forst (The Laws of Kashrus, p.143) writes that this does not apply to conventional ovens, since they are ventilated.  However, he asserts that microwave ovens might not be sufficiently ventilated to say that their Reicha is not Halachically significant.  There is no Halachic standard to objectively define the required amount of ventilation.  A Halachic expert must make a determination.

5. The Talmud considered the fat in the meat to be the source of the aroma emitted.  See Taz 108:1 and Shach 108:1, who disagree with the Aruch Hashulchan.

6. Certain judgments may have to be made that require a decision from a Halachic authority.  An example is if a significant financial loss is involved (Hefsed Meruba).

7. It should be noted that even though the Talmud mentions roasting meat as generating Reicha, Rama (108:2) writes that one should be strict regarding cooking meat and milk simultaneously unless either the oven is open slightly (to permit the aroma to leave the oven), or, in a B’dieved situation, in case of significant economic loss.

8. See Aruch Hashulchan 108:17.

9. The Vilna Gaon (Biur HaGra 92:39) cites a different source.  He cites Chullin 108b, which states that covering a pot is equivalent to stirring a pot.  The Vilna Gaon explains that the Hevel (thick steam) of the pot transfers the taste of the food throughout the pot.  According to this source, it would appear that this rule is limited to a thick steam and not just any steam rising from food.

10. See Yabia Omer 5: Yoreh Deah 7; Minchat Yitzchak 5:20; and Rav Noach Oellbaum, Mesora 4:23-34 for discussion whether Zeiah is of biblical or rabbinic origin.

11. He points out that Rashi (Chullin 108b s.v. Ne’eir) states that the concern when one covers a pot (see note 9) is that the water on the bottom of the pot will now spread throughout the pot.  The Mishkenot Yaakov writes that Rashi seems to be concerned exclusively with the spread of the water but not with the spread of the steam emerging from the food.

12. Rav Akiva Eager (92:8 s.v. Shehayad Soledet) seems to adopt a middle approach concerning this question.  He writes that if there is a question if the Zeiah is Yad Soledet Bo (hot to the touch – the Halachic definition of when something is hot and can be absorbed into a vessel; see Rabbi Forst, The Laws of Kashrus, pp. 403-404), then one may rule leniently if the foods are not enclosed in a small confined area.  This is apparently because ספק דרבנן לקולא, one may rule leniently in case of doubt when dealing with a question rooted in a law of rabbinic origin.  If, however, the foods were cooking in a small confined area, then even in a case of doubt if the Zeiah was Yad Soledet Bo one must rule strictly, as there is a question of infraction of a biblical law (ספיקא דאורייתא לחומרא).  Apparently, Rabbi Akiva Eiger believes that the question of Zeiah is of biblical origin (see note 10) when foods are cooking in an enclosed area and of rabbinic origin when the foods are cooking in a more spacious cooking area.

13. See Aruch Hashulchan (92:54), who rejects this distinction.  Also see Rav Moshe’s nuanced approach to this issue in the responsum cited in the text.  For a summary of the opinions regarding this question, see Yabia Omer 5: Yoreh Deah 7:4-5.  Chelkat Yaakov (2:136) rules strictly on this matter, because empirical evidence indicates that Zeiah emerges from solid foods.

14. The Maharsham (3:208) suggests another point of leniency concerning Zeiah.  He suggests that any “food” (Beliot) extracted by Zeiah from the roof of the oven would be nullified by the food in the pot, which presumably contains sixty times more food than what is extracted.  He adds that the rule “אין מבטלין איסור לכתחילה,” that one is forbidden to intentionally nullify forbidden food, is not a relevant concern because there are many reasons to rule leniently and limit the applicability of Zeiah.  Therefore, at worst the Zeiah creates merely a Safek Issur, something prohibited because of doubt.  He cites the Shach (92:8), that the prohibition to nullify forbidden foods does not apply to foods forbidden merely because of doubt.  See, however, Darchei Teshuva 99:37, who cites authorities who disagree with this assertion of the Shach.

15. This would appear to apply even to a small microwave oven.  Aruch Hashulchan limits the applicability of Zeiah to a situation in which the two foods are cooked simultaneously in a small confined area.

16. This approach reflects the accepted practice of Eastern European Jewry as recorded in the aforementioned Teshuvot Maharsham and in Rabbi Shlomo Kluger’s Teshuvot Tuv Taam Vedaat (3:1:176).  It is hardly surprising that the Aruch Hashulchan's ruling is in harmony with the practice of Eastern European Jewry of his time.  A hallmark of the Aruch Hashulchan is his recording, and most often defending, the Halachic practices of Eastern European Jewry.

17. This reduces the question from a biblical issue to a rabbinic issue.  Halacha considers food absorbed in a utensil to become inedible after twenty-four hours (נותן טעם לפגם) and hence permitted.  It is forbidden to cook milk in a meat pot that has not been used for more than twenty-four hours only on a rabbinic level (the Rabbis forbade it lest one confuse a utensil used within twenty-four hours and one that was not; see Avoda Zara 76a).  Since an oven for meat (for example) not used in twenty-four hours does not pose a problem on a biblical level and there are so many limitations on the applicability of Zeiah, Rav Lichtenstein (and Rav Moshe) believes that in this situation one may rule leniently.

18. Oral communication from Rabbi Efraim Greenblatt, a leading disciple of Rav Moshe who is the author of the voluminous Rivevot Ephraim.  Rav Greenblatt reports that he heard this ruling in the name of Rav Moshe.

19. Rav Lichtenstein follows the ruling of his father-in-law, Rabbi Joseph B. Soloveitchik that an oven may be Kashered by running it at its highest temperature for at least an hour.  Rav Lichtenstein’s ruling is cited by his student Rabbi Shmuel David (Alon Shevut 130:9-23).

Rav Moshe does not offer this suggestion because he believes that this is not sufficient to Kasher an oven.  He requires that the oven be heated to at least 700OF in order to be Kashered (see Igrot Moshe 1:59 and Rav Shimon Elder’s Halachos of Pesach, pp.179-181).  Rav Feivel Cohen (Badei Hashulchan 92:80; Biurim s.v. Lechatchila) objects to this approach because most of our conventional ovens are coated with porcelain, which is considered by most authorities to be earthenware, which cannot be Kashered.

Chelkat Yaakov (2:136) objects to Kashering an oven from meat to milk (except on an occasional basis), based on the Ashkenazic custom (see Magen Avraham 509:11) not to Kasher from milk to meat and vice versa.  One could reply that since the basis for this custom is the concern for confusion, that one may forget to Kasher the utensil and use the wrong utensil in preparing food, this is not such a pressing issue when concerning ovens where there exist many lenient considerations as we have discussed.  It is very reasonable to state that regarding a situation like Kashering an oven between milk and meat, the custom was never intended to apply.  Even if one forgets to Kasher, one still has the opinions of the Aruch Hashulchan and others to rely upon.  The source for saying that we are not concerned lest someone forget in a situation where the food will be Kosher B’dieved even if he did forget is the Rosh (Chullin 1:5), and Taz (Yoreh Deah 2:4).

20. For a discussion of Kashering a microwave oven, see Rabbi Shimon Eider, Halachos of Pesach, p.182, and Professor Zev Lev (Techumin 8:21-36).  It should be noted that this problem can easily be solved in a microwave oven by covering both the milk and meat foods.

21. Those who rule strictly and require one to use two separate ovens for milk and meat point out that the Rama concludes that one should be strict Lechatchila.  Rav Moshe responds (Igrot Moshe Yoreh Deah 3:10) that this point refers only to cooking covered milk and meat foods, one above the other, simultaneously.  If cooked consecutively, argues Rav Moshe, the concern for spills is irrelevant and is thus permitted Lechatchila.

22. Rav Moshe relies on the fact that pots, not food, are placed on the grates, and the Halacha states that two utensils do not absorb from one another (Rama 92:8).  Rav Cohen objects to this because an exception to this rule is when there is liquid present between the utensils, which can serve as a medium to transfer taste (Beliot) absorbed in the utensils.  His concern is for spills that cause liquid to sometimes be present between the pot and the grate.  However, Rav Cohen defends Rav Feinstein’s position by citing the ruling of Chavat Daat (Biurim 92:20) that a small amount of liquid cannot cause a transfer of taste from one utensil to another.  The amount of liquid that would lodge between a pot and the oven or stove grate is presumably considered by Rav Moshe to be only a small amount that is incapable of transmitting taste.

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