Transfer of Taste - Netinat Ta'am

  • Rav David Brofsky

Keli Rishon, Sheini and Iruy (1)


Regarding Last Week's Shiur:


Last week, we addressed a common question. What if one finds a dairy spoon in the "fleishig" dishwasher?


I noted that while one could invoke the Rema who posits that a dairy spoon found in the "fleishig" cutlery drawer is permitted, one should be stringent in this case, being that the dairy and meat silverware were definitely washed together.


For one who wishes to be stringent in this case, one can kasher the spoon by simply waiting 24 hours and immersing it into a pot of boiling water, and then rinsing it in cold water.


However, I would like to emphasize that this recommendation should be viewed as a "chumra," and therefore if one is unable to kasher the utensil, one may certainly rely upon the many reasons to be lenient which I enumerated in the shiur.


Furthermore, I should note that some allow the use of a single dishwasher for both dairy and meat dishes, consecutively, as long as in addition to thoroughly cleaning the filter, one either waits twenty four hours, and/or runs a clean cycle in between, thereby kashering the dishwasher (kebol'o kakh polto).


One should consult a halakhic authority regarding this matter.




In previous shiurim, we discussed various aspects of ta'am. We analyzed the unique qualities of a mixture of similar (min be-mino) and dissimilar (min be-she'eino mino) substances, the role of prohibited ta'am in a mixture, and its impact upon permitted foods. Furthermore, we discussed issues relating to the quality of ta'am, such as "nat bar nat" and "noten ta'am lifgam."


This week, we must address the ways in which ta'am may be transferred from one substance to another. Ultimately, our discussion will help us to tackle many common kitchen accidents, as well as to address the proper use of sinks in a kosher kitchen.


Which Environment is Conducive to Netinat Ta'am?


When addressing the environment in which ta'am may be transferred from one substance to another, we must distinguish between a number of important issues.


1. Medium:


What is the medium through which the ta'am may travel?


Dry foods:

Generally speaking, ta'am may only travel through an appropriate medium. If the two substances that come in contact are dry, for example, the ta'am's ability to spread throughout the mixture may be limited.


Here, the halakha distinguishes between fatty foods, which are viewed as a sufficient medium, and non-fatty (lean) foods. When at least one of the foods is fatty, the issur may spread throughout the entire permitted substance - as if they were cooked together - and the heter is permitted only if it contains sixty times the issur. Furthermore, the area of contact between the issur and heter should be removed (kedei netila). If, however, both pieces are lean, the ta'am of issur cannot travel throughout the permitted substance, and one must merely remove the area of contact, "kedei netila."


While we shall return to these cases, let us assume for now that both substances, or at least the bottom piece, are at a temperature of at least "yad soledet bo" and are located in a keli rishon. We shall address variations of this case later in the shiur.


When two hot, dry utensils come in contact with each other, no transfer of taste is possible (see Rema YD 92:8). This is the source for the common custom of "double wrapping" food when placed in a non-kosher oven. Even if we suspect that non-kosher ta'am may reach the cooking tray, the taste is absorbed in the outer layer and cannot penetrate from the outer to the inner wrap, similar to two utensils that touch each other.


Wet Foods:

The most common medium, however, is liquid. If a prohibited substance comes in contact with a permitted substance through the medium of a liquid (i.e., in the same pot), we assume that the ta'am spread throughout the entire mixture. Therefore, the permitted substance may only be salvaged if it contains sixty times the amount of the prohibited substance. In that case, as we described in previous shiurim, the heter may be eaten.


2. Heat:


The Gemara enumerates a number of ways to facilitate the transfer of taste. The most prominent, and certainly the most common, is heat. At what temperature do food or utensils absorb the taste of another?


The Gemara never explicitly discusses this question. The Shulkhan Aruch (YD 105:2), assuming that one may equate the environment in which food cooks (on Shabbat) to the environment in which taste can be transferred, posits that the temperature is "yad soledet bo," literally, the heat at which one would reflexively withdraw one's hand. The Gemara (Shabbat 40b) asserts that at this temperature one violates the prohibition of bishul (cooking) on Shabbat.


The precise definition of "yad soledet bo" continues to be the subject of debate between halakhic authorities. Rav Moshe Feinstein (Igrot Moshe OC 4:74) claims food under 110 degrees Fahrenheit (43 degrees centigrade) should not be considered "yad soledet bo." Rav Shlomo Zalman Auerbach (Minchat Shelomo 1:91:8) suggested a temperature of 113 degrees fahrenheit (45 degrees centigrade). 


Interestingly, the authorities debate whether one may literally test the heat of a substance to see if one's hand recoils. The Derisha (OC 318:5) implies that one should not rely upon this test. The Issur Ve-Heter (34:20), however, writes that "yad solodet bo" is when an average person's hand recoils. The Kaf Ha-Chaim (OC 318:143) suggests that the temperature at which one would refrain from eating food because of its heat is to be considered yad soledet bo.


In addition, not every source of heat can induce a full transfer of taste. The Rishonim debate whether ta'am may be transferred only in a keli rishon, or also in a keli sheni. They also discuss the ability of pouring (iruy) to affect the transfer of taste. I would like to dedicate the next portion of our shiur to this question.


3. Place of Contact Between Issur and Heter:


As mentioned above, taste may only travel from a prohibited substance to a permitted substance if there is a proper medium (liquid, for example) and if the proper environment (i.e., heat) exists. The Rishonim note that not only must the temperature must be at least yad soledet bo, but the source of the heat is also of great importance.


Clearly, taste may be transferred when the substances are in a keli rishon. However, the Gemara does not define a keli rishon in the context of our discussion - hilkhot ta'arovot. Furthermore, the Gemara does not address whether taste can be transferred in a keli sheni, or even through iruy (pouring). Rather, the discussion of different sources of heat appears primarily in the context of bishul (cooking) on Shabbat.


Therefore, we must first determine which sources of heat may cause bishul on Shabbat, and then question whether the laws of bishul apply to the transfer of taste (belia).


The laws of bishul on Shabbat are vast and deserve comprehensive treatment. However, we shall attempt to summarize at least one aspect of bishul on Shabbat – the source of heat.


The Mishna (Shabbat 42a) states: "One should not place spices into a pot which has been removed from the fire." In other words, not only may one not place uncooked food in a utensil on the fire, but even into a utensil taken off the fire. Both are considered to be a keli rishon. Incidentally, the Yerushalmi, in a number of places, implies that once a utensil has been removed from the fire, it is only considered a keli rishon mi-derabanan.  There is no evidence of this in the Talmud Bavli, and therefore many claim that the Bavli and Yerushalmi disagree on this issue. 


Furthermore, the Gemara (Shabbat 42b) states that "keli sheni eino mevashel." In other words, bishul cannot be accomplished in a pot into which the contents of a keli rishon were poured. For example, it seems that one may place raw food into a bowl of hot soup, on Shabbat, as the bowl is only a keli sheni. Why? 


Seemingly, this should be dependent upon different understandings of the prohibition of bishul on Shabbat. What role does the source of heat play in bishul? Am I primarily concerned with the physical change which occurs when food is exposed to heat? Or, do I define bishul as an ACT of causing a physical change with occurs within proximity of a certain source of heat (i.e. a keli rishon). When food is placed near alternate source of heat (i.e. a keli sheni), this does not constitute an ACT of bishul.


Some Rishonim cite the Yerushalmi, which claims that since even a keli rishon that is no longer on the fire is only prohibited mi-derabanan, apparently, a keli sheni is too far removed from a true keli rishon and is therefore permitted. This Yerushalmi implies that "bishul" on Shabbat is a function of the proximity of the food to a source of heat, and not just of the physical change in the food. This, of course, may explain why "bishul be-chama," cooking with the heat of the sun, is permitted on Shabbat. The assumption being that bishul mi-deoraita by definition, means cooking with direct contact with fire.


Tosafot (Shabbat 42b), on the other hand, seem to imply that since a keli sheni's heat is not constant, as the walls do not retain the heat of the food, its ability to cook is diminished. Apparently, food will not be sufficiently changed by the heat of a keli sheni. As for "bishul be-chama," while theoretically the sun IS also a problematic source of heat, since it is not "derekh bishul" (see Rashi), it is not prohibited.


(Incidentally, the poskim discuss whether one may cook in a microwave oven on Shabbat. According to Rav Moshe Feinstein, microwave cooking has become "derekh bishul" and is therefore prohibited. Others, however, claim that since there is no direct source of heat, cooking in a microwave may be permitted, or at least permitted mi-de'oraita. While this may not be of great practical importance, the discussion may be relevant regarding the proper method of reheating food up on Shabbat in a hospital, and other similar cases.)


Practically speaking, the Gemara lists of number of cases in which a keli sheni may cook, and therefore some Rishonim write that one should be stringent regarding foods which are considered "kalei bishul" – i.e., foods which cook quickly. We are generally hesitant to put almost any uncooked food into a keli sheni. This question, however, is complicated and is outside of the scope of this shiur. For further research, see OC 318:5.


Regarding hilkhot kashrut, the Rishonim debate whether we should equate bishul on Shabbat to belia (aborption) of prohibited substances. For now, I would like to restrict our discussion to a keli sheni which contains hot liquids. The status of solids transferred to a keli sheni, i.e., davar gush, and iruy, will be discussed next week.


Most Rishonim are inclined to equate them, and therefore conclude that taste cannot be transferred in a keli sheni. According to this view, if one were to immerse a ben yomo meat spoon into a cup of hot coffee (with milk), or, if one were to insert a dairy spoon into a hot bowl of chicken soup, neither the cup or bowl, nor their contents, nor the spoon, are affected, as the entire incident took place in a keli sheni.


Others insist that a keli sheni does cause the taste to penetrate "kedei kelipa" - into the outer surface - of the food. Therefore, if a fruit were to fall into a hot bowl (keli sheni) or non-kosher soup, one may remove the peel and eat it. However, if a dairy spoon was inserted into a hot bowl of soup, the spoon would certainly need to be kashered, and the soup might be prohibited, depending on whether there were sixty parts of soup against the spoon.


Still others (Maharshal Chullin 7:71) insist on equating bishul and belia, and therefore a hot keli sheni may facilitate a complete transfer of taste throughout the entire substance. The Maharshal, however, admits that a substance cannot both "maflit u-mavlia," emit and absorb taste, in a keli sheni. Therefore, while the above-mentioned meat spoon may prohibit the coffee, the coffee cannot subsequently transfer its taste to the cup, and therefore while the spoon and the coffee are prohibited, the cup is permitted!


The Shulchan Arukh (105:2) cites the opinion of the majority of Rishonim, which limits belia to a keli rishon. He then cites the opinion of the Rashba, and comments that while "initially (le-khat'chila) one should be careful regarding a keli sheni, be-diavad the substance is permitted without kelipa, as long as it is rinsed." In other words, one should not allow kosher food to come in contact with non-kosher food in a keli sheni, but if they accidentally came in contact, the food and the pot are permitted.


The Acharonim question whether the custom is in accordance with the lenient ruling of the Shulchan Arukh. Many are stringent (see Taz 105:4), except when there may be financial loss. Furthermore, some note that while at times we may be lenient regarding the food, which cannot be repaired, and is therefore considered "be-di'avad," the utensil, which may (usually) be repaired, should be kashered. A halakhic authority should be consulted in cases regarding a keli sheni.


Next week, we shall continue our discussion of the proper environment for netinat ta'am, as we address the question of the status of solid foods transferred from a keli rishon to a keli sheni (davar gush), and pouring (iruy), as well the proper use of kitchen sinks.