YESHIVAT HAR ETZION
ISRAEL KOSCHITZKY VIRTUAL BEIT MIDRASH (VBM)
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Hilkhot Kashrut

Shiur #22: Transfer of Taste Through Smell and Steam:
Ovens and Microwaves (I)

By Rav David Brofsky

Introduction:

In previous shiurim, we discussed the environment in which taste can be transferred from one substance or utensil to another. We noted that in order to facilitate a transfer of taste, the proper medium and environment are required. Usually, that entails a liquid, and the heat of a keli rishon or similar. 

This week, I would like to begin our study of ovens. 

Ovens are unique in that there is no direct contact between the prohibited substance and the permitted substance. Any transfer of taste occurs through the air. Therefore, we must ask, can taste be transferred in an oven, either between two foods cooking simultaneously, or between the oven and the food?

We will divide our discussion into three parts. First, we will ask whether the "smell" of food (reicha) bears any halakhic significance. Secondly, we will consider the impact of steam (zei'ah) on our question. Finally, we will present the different approaches to the use of ovens and microwaves in the contemporary kitchen.

Reicha:

The gemara (Pesachim 76b) cites a debate regarding kosher meat which was roasted with non-kosher meat. Rav opines that the kosher meat is prohibited. Levi, on the other hand, maintains that since "reicha lav milta" (smell is insignificant) the kosher meat is unaffected and is permitted. In other words, Rav and Levi argue whether the reicha of a prohibited substance prohibits a permitted substance. 

What are they arguing about? 

Rav apparently believes that just as taste may be transferred through direct physical contact, it may also be transferred, under certain circumstances, through reicha. 

I would like to suggest two possible understandings of Levi's opinion.

1. On the one hand, Levi may completely disagree with Rav, believing that taste simply cannot be transferred without physical contact. Apparently, even if one were able to sense the taste of the prohibited substance, if it is attributable to "reicha" alone, it is not halakhically considered "taste." 

2. On the other hand, Levi may agree with Rav that taste can be transferred even through the air, but think that generally the taste is too dilute to be halakhically significant, similar (though not identical) to the principle of "nat bar nat" (see shiur #16). However, under the proper conditions, according to this understanding of Levi's opinion, taste may indeed be transferred even through reicha.

Let us suggest a few practical differences between these approaches.

1. Some Rishonim (see Hagahot Maimaniyot Hilkhot Ma'akhalot Asurot 15) suggest that Levi would agree that reicha is significant if the foods are cooked in a very small oven, and that he only permitted the kosher meat if the two substances were cooked together in a large ventilated (gadol u-piv patuach) oven. Others disagree. 

Seemingly, if Levi denies that taste can be transferred without physical contact, then the oven's size should be of no consequence. However, if Levi agrees that there is a transfer of taste, but it is usually not potent enough to be halakhically problematic, exposure to reicha in a small, unventilated oven may be more problematic. 

2. The Bavli implies that it is never permitted intentionally to cook kosher and non-kosher food together in the same oven. Only if they were mistakenly cooked together does Levi maintain the kosher food is permitted. The Yerushalmi disagrees, and permits cooking kosher and non-kosher meats together, le-khat'chila, in the same oven.

One might suggest that if the debate between Rav and Levi concerns the level of potency of the reicha, certainly one would not be permitted to cook them together, le-khat'chila, in the same oven. This would be similar (although not identical) to "ein mevatlin issur le-khat'chila," i.e., intentional nullification of prohibited substances, which is forbidden. 

However, if Levi actually believes that taste cannot be transferred through the air, then aside from "mar'it ayin" or other technical reasons, there should be no obstacle to cooking them together, le-khat'chila, in the same oven. 

3. Furthermore, the Rishonim discuss the status of bread or fish cooked in an oven with kosher meat. The Gemara relates that Rav Kahana prohibited eating milk with bread that was baked in the same oven as meat, and that Rava would not allow the consumption of milk with fish which were roasted in the same oven with meat. 

The Rishonim debate whether these opinions are only in accordance with Rav, who holds "reicha milta," or whether even Levi, who generally permits kosher meat roasted with non-kosher meat, would agree that in this case, the bread or fish still should not be consumed with milk.

Those who adopt the latter approach, and assume that even Levi would discourage eating this meat or fish with milk, offer a number of explanations.

The Ran (Chullin 32b), for example, suggests that since one who eats the bread can "sense the taste" of meat, one should not eat it with milk, as it appears as if he is eating meat with milk. Alternatively, he suggests that this may merely be a stringency relating to basar be-chalav.

The Rif (Chullin 32b) offers two explanations. Firstly, he notes that if we permit the consumption of milk with bread that was baked with meat, one may come to assume that even roasting kosher and non-kosher meats together is permitted. By prohibiting the bread with milk, Chazal are making a statement that while permitted be-diavad, le-khat'chila this should not be done. 

All of the above answers imply that there is no FUNDAMENTAL obstacle to eating this bread with milk; rather, it is inappropriate because of the messages it may convey.

The Rif, however, in his second answer, alludes to another approach. He suggests that just as a "davar she-yesh lo matirin," i.e., a mixture which contains a substance which is only temporarily prohibited, such as muktzeh, chadash, or even chametz (according to some), cannot be nullified in a mixture - "even at a ratio of one to a thousand" - and one must wait until the issur is permitted, similarly, since one may eat the bread in a totally permitted fashion (i.e., alone) then one should not eat it with milk. 

He explains that "one to a thousand" is like reicha, and just as a "davar she-yesh lo matirin" is not permitted, similarly, this bread must not be eaten with milk. While one might ask how this is different from a case in which milk accidentally falls into water, in which case one may cook meat in the water if the ratio was less than one to sixty (see Rema YD 99:6), the equation of a mixture of "davar she-yesh lo matirin" and this bread implies that the bread actually contains a small percentage of meat, which is ordinarily "batel," though not in this case. 

If so, we have once again demonstrated that even Levi may agree that reicha is a form of taste, which generally may be overlooked but is, at times, significant. 

I would like to bring to our attention another explanation of Rav Kahana and Rava's stringency. 

The Rambam (Hilkhot Ma'akhalot Asurot 15:33) writes, 

One should not roast kosher meat with non-kosher meat in the same oven, even though they do not touch each other. If, however, one roasted them together, (the kosher meat) is permitted... because rei'ach cannot prohibit, only the taste of a substance can prohibit.

In this halakha, the Rambam implies that rei'ach is not considered ta'am.

However, elsewhere (9:23) the Rambam writes,

Bread which was baked with roasted meat, and fish which were roasted with meat, may NOT be eaten with milk. However, fish which were cooked in a pot used previously for meat MAY be eaten with milk.

In other words, the Rambam, in this halakha, contrasts "nat bat nat" and reicha. Unlike "nat bar nat," which does NOT affect the fish, reicha is sufficient to prohibit drinking milk with these fish. Why does the Rambam choose to contrast these two halakhot?

One might suggest that while reicha is NOT sufficiently potent to prohibit kosher meat roasted with non-kosher meat, "as only the TASTE of a substance can prohibit," it IS potent enough to prohibit the consumption of milk with fish or bread roasted with meat. This, of course, is in contrast to "nat bar nat, which has no potency and therefore has no halakhic ramifications" (according to the Rambam). 

In other words, the Rambam presents three levels of ta'am: taste transferred through contact, taste transferred through the air, and secondary taste. "Nat bar nat" is halakhically insignificant; reicha is significant but not enough to prohibit a substance; and ta'am may actually prohibit another substance.

Reicha – Halakhic Conclusion:

The Rishonim debate whether the halakha is in accordance with Rav or Levi. While Rabbeinu Tam (Tosafot Pesachim 76b s.v. Asra) accepts Rav's opinion, the majority of Rishonim rule that reicha is "lav milta," and as such cannot prohibit another substance.

The Shulchan Arukh (YD 108:1) also rules in accordance with Levi and writes that while one should not intentionally roast kosher and non-kosher meats together, after the fact, the kosher meat is still permitted. 

Regarding ovens, as reicha applies only to simultaneous baking or roasting, there should be no halakhic obstacle to cooking meat in a clean, dairy oven, or even in a clean non-kosher oven! However, as we shall see, there is another concern - zei'a (steam). 

Next week we will address the impact of steam of the kashrut of ovens, and discuss different approaches to the proper usage of ovens and microwaves.