Avodah Zarah, chapter five, mishnah two. This mishnah is extremely important for the principles of kashrus in general. Its context is yayin nesech - that is the forbidden substance - becoming mixed into other things, and from here it opens a wide door into the laws of mixtures. But the substantive principles discussed in it, and which actually operate within it, are two, and we will begin with them.
The first principle - "taam k'ikar" (taste is like substance):
When the taste of a forbidden item is present inside a permitted item, we relate to that taste as though the forbidden item were physically there. Therefore a mixture of permitted material, even with only a small amount of forbidden material, is forbidden - because of the presence of the taste. This stands in contrast to cases of dry with dry, two items whose tastes do not mix into one another, where we apply nullification by majority: a simple majority of permitted against a minority of forbidden is enough, and the mixture is permitted. But where there is transfer of taste, as long as the taste of the forbidden item is present, the mixture is forbidden.
A qualification is in order: transfer of taste occurs in one of the following ways:
When there is an actual presence of the forbidden substance in the mixture, such as wine that became mixed in.
When the contact took place at a heat of yad soledes bo - even if all of the forbidden substance was removed, the taste has passed over.
When the forbidden substance sat together with the permitted item for twenty-four hours - here too we say that the taste passes over.
The second principle - "nosen taam lifgam" (imparting a taste that spoils):
If there is a transfer of taste, but that transfer damages the taste of the permitted host, the transfer of the bad taste does not forbid it - and this assuming there is a majority of permitted material there. In a case where the forbidden wine mixes in a way that ruins the taste, after the fact the mixture may be eaten. This principle underlies many of the leniencies stated regarding mishaps that occur in the kitchen.
The words of the mishnah:
"Yayin nesech shenafal al gabei anavim - yediachem v'hein mutaros" - forbidden wine that spilled onto grapes. Whole grapes, with the stem in place and the opening sealed, are impervious to liquid: their skin is smooth, it does not absorb and it does not hold liquids. Therefore rinsing is enough to remove the entire forbidden mixture, and we have no basis to assume that any taste remained. Certainly there is no actual residue of the forbidden substance, and no taste passed into the grapes either, since the skin of a grape does not absorb taste under normal circumstances.
However, if the grapes and the wine remained mixed together for more than twenty-four hours, we say that a bit of taste was indeed absorbed. So too if the wine was hot, it had the power to transfer taste. And likewise the Yerushalmi noted that the case must specifically be one where the stem is intact, for if the stem is missing at the top of the grape, an opening is created there through which the wine penetrates inside. But when all these conditions are met - cold wine, less than twenty-four hours, and an intact stem - a rinse in cold water alone suffices, and the grapes are permitted.
"V'shenisbak'u - asuros" - if those grapes were split, meaning there is a crack in the skin through which the wine penetrated into the grape itself, they are forbidden, since rinsing will not help. We must be concerned that a presence of wine remained inside and that its taste is discernible, and as long as the wine can be tasted in the grapes, the mixture is forbidden.
How do we determine whether the taste is present?
The Gemara's approach is that if the taste is present, the item is forbidden. Therefore one must find a trained palate - a cook, or anyone whose sense of taste is finely tuned - and let him assess the situation: is the taste of wine discernible here or not? The Gemara refers to such a person as a 'kapila armai', a gentile cook, and he is asked to give his opinion innocently, without knowing that his assessment carries halachic consequences. For several reasons Ashkenazi practice rejected this option entirely: it is simply not practical to locate a 'kapila armai' who will answer for the sake of Heaven, and beyond that, he may well lie, since our kashrus is no concern of his.
Because of this there is a fallback plan, which among Ashkenazim became the primary plan: if there is sixty times the volume of permitted food against the volume of the forbidden substance, or more, we assume that the taste is no longer discernible and the mixture is permitted. Among Sephardim, by contrast, one may still rely on a 'kapila armai' - if a gentile cook happens to be available, and if one can extract his opinion without hinting to him about the halachic implications.
A further point: one must distinguish between a substance mixed with its own kind and a substance mixed with a different kind. When two items whose tastes differ become mixed - and our Mishnah assumes that the taste of a grape is not the taste of wine - we have two distinct tastes blending together, and it is possible to ask whether the taste is discernible. A separate question is the law of kosher wine that became mixed with non-kosher wine, and that is discussed in a Mishnah further on, at the end of the chapter, where we will deal with it. Here the assumption is that with a split grape there is no way to estimate how much wine penetrated inside, and the taste of the wine will be felt - and therefore all the split grapes are forbidden.
"U'vate'einim u'vatemarim, im yesh bahen b'nosen ta'am - asuros" - and with figs and with dates, if they impart taste, they are forbidden.
This clause does not appear in all versions of the text, but according to the version before us it refers to forbidden wine that spilled onto fresh figs (as opposed to dried figs) or onto dates. Figs are unique in that their skin is soft and porous, so taste seeps through it into the fruit itself - unlike grapes. Once the wine has spilled onto the figs, there is reason to be concerned that its taste will find its way into the fig itself. The skin of a date, on the other hand, does repel water and does not absorb much, but dates have many cracks and crevices, and there is no guarantee that after rinsing no residue of wine remains lodged in those crevices.
Because of this complication with fresh figs and with dates, if residue of wine remains in them in a quantity whose taste is discernible - "if they impart taste" - they are forbidden. And once again, making that determination will require that same 'kapila armai'. Rinsing alone is not sufficient here, since we know that residue remained.
"Ma'aseh b'Baisus ben Zonin" - there was an incident involving Baisus ben Zonin.
An incident cited in a Mishnah is always meant to reinforce the principle stated just before it, not to contradict it. The Gemara explains that words are missing here, words that introduce the principle of nosen ta'am lifgam, taste that spoils. For with fresh figs and dates we assume that pouring wine on them improves their taste or moistens them - and that is precisely the problem. Here, however, we are dealing with dried figs, grogaros, whose taste is ruined once wine is added to them, and so this is a case of nosen ta'am lifgam: the taste, even if it is present, is a bad taste - and hence the leniency.
And so the Mishnah says: "Ma'aseh b'Baisus ben Zonin shehevi grogaros bisfinah, v'nishtabrah chavis shel yayin nesech v'nafal al gabeihen, v'sha'al l'chacham v'hitiran" - he was transporting dried figs on a ship, a barrel of wine belonging to one of the gentile passengers broke, and the wine spilled onto the dried figs. Not knowing how to proceed, he asked the sage who was available to him, and the sage permitted the dried figs. And why were they permitted? Because the wine imparted a spoiling taste to them, as the Mishnah goes on to explain.
"Zeh haklal" - this is the rule.
"Kol shebahana'aso b'nosen ta'am" - wherever the contribution of taste is to a person's benefit, improving or enhancing the taste or the texture of the food, if the taste is present and can be identified, the mixture is forbidden.
"Kol she'ein bahana'aso b'nosen ta'am" - wherever there is a contribution of taste but it is to the detriment of the food, the mixture is permitted after the fact, though certainly not in the first instance.
"K'gon chomets shenafal al gabei grisin" - the Mishnah offers an example: grisin are ground legumes, and when they are hot, vinegar spilled onto them harms their taste and detracts from it. Therefore, if forbidden vinegar splashed onto hot grisin, after the fact they are permitted.
The Gemara goes on to ask what the ruling is with cold gerisin (crushed beans), and whether we must distinguish between a mixture that begins by detracting from the taste and ends by improving it, and one that begins by improving the taste and ends by detracting from it. These questions were left unresolved, and therefore we rule strictly. The bottom line: a mixture of a forbidden substance with a permitted one is forbidden, and only when it can be established that the contribution to the taste is certainly detrimental is it permitted after the fact.
Without opening an entire Pandora's box, it is worth noting that this is the origin of a discussion that comes up constantly in kitchen kashrus: is the vessel ben yomo, that is, was it used within the last twenty four hours? The idea is that after twenty four hours, the tastes absorbed in the walls of the pot are no longer tasty but detrimental - and who wants those stale tastes? From here we see that one can be lenient when the transferred taste is more than twenty four hours old, under ordinary circumstances and subject to a hundred and one qualifications - topics that lie beyond our Mishnah.