If a non-kosher food falls into a pot of kosher food and we are not sure whether it was nosain ta’am, the Gemara (Chulin 98a) says that we can get a non-Jewish k’feila (chef) to taste the food. If the non-Jew can assure us that the non-kosher taste is not detectable, then the food is acceptable. Though this halacha is brought by the Mechaber (Y.D. 98:1), the Rema says that we should not rely on a k’feila, and the pot of food must be considered non-kosher.
Are there any situations where we can rely on te’ima in order to permit a food?
The reason for the chumrah of the Rema is not clear.1 Rav Belsky said that the Rema was only machmir when the non-Jew is being asked to detect slight nuances of taste. In such cases, he cannot be relied upon because there is not a sufficient mirsas. Even if the Jew tastes it afterwards and can detect the forbidden taste, the non-Jew can save face by claiming that he missed it. In situations where a non-Jew is being asked to determine whether a strong flavor is either present or completely absent, and there is no way for him to save face if he is caught lying, then the chumrah of the Rema would not apply.
The Shulchan Aruch 96:1 says that if an onion was cut with a fleishig knife we can rely on te’imas Yisrael to classify this onion as pareve. The Shach 96:5 says that we can only rely on te’imas Yisrael for a bidieved situation. For instance, if part of this onion fell into a pot of milk, a Yisroel can taste the remaining piece of onion. If the onion does not have any meat flavor, the milk would be permitted. But one cannot rely on a te’imas Yisrael to intentionally add the onion to the milk.
Therefore, we cannot use recycled steam from dairy to cook a pareve kettle. Even if the mashgiach can attest that the condensate return has no dairy flavor, we should not rely on this to label a product pareve lichatchila. However, this would be effective in bidieved situations.
If one needs to determine if his meat was salted, he may lick the meat, even though this would not be permitted had we known it was not salted (Taz 98:2). The Pri Migadim explains that putting non-kosher in one’s mouth and spitting it out is only an issur dirabbanan. If we are in doubt as to whether the food is kosher or not, we permit doing this because we say safek dirabbanan likulah2.
This is the basis for our te’imas Yisrael on boiler water to determine if it is pagum. If we are uncertain what the level of pegima is in the water, the water is safek issur. If the water in fact is pagum then it should be immediately detectable. Therefore, it is permissible for a Yisrael to check to make sure that the boiler water is pagum, and will not transfer non-kosher ta’am, by putting it in his mouth and spitting it out. (Warning: Boiler water might have harmful chemicals in it.)
The Pri Migadim (M.Z. 98:1) explains that although we can rely on te’ima to ascertain that a taste is present (salty, pagum), we cannot rely on putting a food in our mouth to determine if a non-kosher taste is not present. The only way to guarantee that a taste is not present is by swallowing the food. This is obviously not permitted in cases of safek issur.
One should not rely on a non-Jew to taste the boiler water. Boiler water is only considered pagum if it is nifsal mei’achilas adam. It is not sufficient if the water is slightly pagum or has an off taste. This is obviously up to interpretation and a non-Jew might exaggerate the level of pegimah. Moreover, it takes a certain level of training to be able to determine what level of pegimah we consider to be nifsal mei’achilas adam. Additionally, it goes without saying that if the Yisroel does not have access to check on the water then there is no mirsas at all.
Summary: Though in general we do not rely on a k’feila to determine if a food is kosher, there are a few situations where we can.
1. We can rely on te’imas k’feila in situations where there is sufficient mirsas.
2. We can rely on te’imas Yisrael of heter in bidieved situations.
3. We can put food in our mouths and spit it out if the issur is only a safek. This only helps us where we are trying to detect the presence of a taste (salty, pagum) but cannot be relied upon to say for certain that a non-kosher taste is not present.
1 See Rebbi Akiva Eiger (98:1)
2 Rabbi Belsky holds that this leniency only applies to tastes that can be detected by the tongue, and not to tastes that can only be detected by swishing the food around inside one’s mouth.