Gemara

37a - Mishnah: If Leah borrowed from Rachel spices, water or salt to make a dough, the dough may be taken only in the Techum common to both of them;

R. Yehudah says, if she borrowed water we are not concerned for Rachel's Techum, for water is insignificant.

38a - Question: Why isn't the water and salt Batel to the dough?

Answer #1 (R. Aba): Rachel's property cannot be Batel in Leah's.

Objection (R. Oshaya): Min b'Eino Mino is Batel. And even Min b'Mino is Batel according to Chachamim of R. Yehudah!

Answer #2 (Abaye): Chachamim decree that water and salt are not Batel lest the women make a joint dough (and they will think that each may take it to her Techum).

Answer #3 (Rava): Spices are added to give taste, so they are not Batel. (The same applies to water, for it is essential to the dough.)

Answer #4 (Rav Ashi): It is a Davar she'Yesh Lo Matirim. Such things are not Batel even in 1000.

Chulin 6a (Rafram): Since Se'or and spices are added for their taste, they are not Batel.

Avodah Zarah 69a - Question: If a mouse fell into vinegar what is the law?

Answer (Ravina): (Even though mice have a strong taste), we are not more stringent than when Terumah falls into Chulin, if the (volume of) the vinegar is 100 times (that of) the mouse, it is permitted.

Rejection (Rav Tachlifa bar Giza): Perhaps the mouse is considered like spices of Terumah. Since they are added for taste, they are not Batel, even if the Chulin is more than 100 times their volume!

Orlah (2:4): Any Isur that ferments or spices Chulin:

If the Isur is Terumah, it makes the Chulin Dimu'a (like Terumah mixed with Chulin).

If the Isur is Orlah or Kil'ai ha'Kerem, it forbids the Chulin.

(2:6): This refers to Min b'Mino. If it is Min b'Eino Mino we are sometimes lenient and sometimes stringent:

If Se'or of wheat fell into a dough of wheat, and it is enough to ferment it, it forbids, whether or not the dough is 100 times its size. If the dough is not 100 times its size, it forbids whether or not it is enough to ferment it.

(2:7): Min b'Eino Mino we are sometimes lenient and sometimes stringent. If grits were cooked with lentils, and it is enough to give taste, it forbids, whether or not the Heter is 100 times the Isur. If it does not give taste it does not forbid whether or not the Heter is 100 times its size.

Rishonim

Rambam (Hilchos Ma'achalos Asuros 16:1,2): If an Isur ferments or spices Heter, or if the Isur is important, it is not Batel. If Se'or or spices of Terumah fell into a dough or Tavshil of Chulin, and it is enough to ferment or spice it, it is Meduma. If the Se'or or spices were Kil'ai ha'Kerem or Orlah, the dough or Tavshil is Asur b'Hana'ah.

Tosfos (Avodah Zarah 69a DH k'Tavlin): The Gemara suggested that the mouse is like spices, and they give taste even to more than 100 times their volume. There is no suggestion that they forbid even without giving taste.

Poskim

Rema (YD 98:8): All Isurim that apply nowadays are Batel in 60 parts of Heter, except for Chametz b'Pesach and Yayin Nesech. This is if the Isur does not give taste. If it gives taste and it is intrinsically forbidden (as opposed to Heter that absorbed Isur), it is not Batel even in 1000 as long as it is tasted. Therefore, salt and spices which are added for taste are not Batel in 60.

Beis Yosef (Reish Siman 112): Something added for taste is not Batel, like it says in Chulin (6a), even regarding an Isur mid'Rabanan.

Question (Taz 11): If forbidden fat falls on a food, why is it Batel in 60? It is added for taste! This is not difficult when permitted meat fat falls into milk, for then the fat is not intrinsically forbidden. It is forbidden only because of the mixture. But when the fat itself is Isur, this should be like a Nolad egg, which forbids even more than 60. (Even though the egg gives color and taste, taste itself is enough to forbid.) Even though the Rema forbids only when the Isur can be tasted, since we are concerned that it can be tasted even when there is 60, we may not taste it so we must always be stringent!

Answer (Taz 11): Indeed, when there is 60 it usually cannot be tasted, so we may sample the mixture. However, if we can taste the Isur, it is forbidden. Regarding the egg, since we see that it gives color, we are concerned that it also gives taste.

Answer #2 (Isur v'Heter, cited in Taz 11): We are concerned (even with 60) only for a sharp Isur. The Rema discusses salt and spices. Fat gives taste, but it is not sharp.

Shach (28): Usually, Isurim that are not added for taste are Batel in 60. However, if one tastes the Isur, obviously it is forbidden. The stringency of salt and spices is that we assume that they give taste even in 1000, for they are added for taste. Therefore, if we would clearly know that it does not give taste, e.g. if a grain of salt or spices fell into a large pot, it is permitted. This is like Tosfos (Avodah Zarah 66a Sof DH Tavlin).

Shach (29): Mid'Rabanan, it is forbidden even in 1000.Or Zaru'a permits even nowadays to rely on a Nochri Mesi'ach l'Fu Tumo (unaware of the consequences) to tell us whether or not it can be tasted.

Shach (30): If salt and spices fell into something with the same taste, they are Batel in 60.

Gra (35): The Rema holds like Tosfos (Chulin 108b DH Amai). Some say that the stringency of something added for taste is even if it is not intrinsically forbidden.

Kaf ha'Chayim (80): If Asur salt was added but it was not enough to add taste, and together with Heter salt it gives taste, this is Zeh v'Zeh Gorem; it is permitted.

Shulchan Aruch (105:14): If salt absorbed blood, e.g. from salting meat, and it was put in a pot, if the food in the pot is at least 60 times as much as the salt it is permitted. Likewise, if meat that was salted but not rinsed was put in, if there is 60 times as much food as salt it is permitted.

Shach (46): We cannot say that it suffices to have 60 times as much food as blood, for we do not know how much blood is in the salt.

Beis Yosef (Sof ha'Siman): Surely the salt is less than a 60th of the food. Otherwise, it would be too salty to eat!

Rema: The salt is Batel even though it gives taste, because it is not intrinsically forbidden. It is forbidden only because of the blood inside. The Ne'esar (salt, which is forbidden because of the blood) cannot forbid more than the Oser (the blood).

Aruch ha'Shulchan (72): One may not dip food in such salt. However, in pressed circumstances one may put such salt into food. This is not considered Mevatel Isur l'Chatchilah.

Mishnah Berurah (OC 442:27): If Chametz was used to be Ma'amid or flavor cheese it is not Batel, since it is for taste. However, this is only mid'Rabanan (according to most Poskim). Therefore, b'Di'eved if one forgot to do Bi'ur, if it is a major loss he may throw the value of the Chametz to the sea and benefit from the cheese.