Over the last few days, we have been learning one of the most central sugyot on the topics of טעם כעיקר and ביטול. The first of these principles states that the taste of non-kosher foods is considered like the food itself. This means that if a piece of pork falls into a cooking stew and is then removed, the stew will be forbidden if it has the taste of pork in it. This is why we need kosher dishes, and different dishes for meat and milk.
The second principle states that there are times when non-kosher foods, even if fully present, can be considered to be nullified and no longer forbidden. This can normally happen (Biblically) when there is a majority – רוב - of kosher foods (in dry mixtures, more in number; in liquid mixtures, the majority of the volume). However, when there is taste – the forbidden food tastes different than the kosher food, and it is a liquid-type mixture where the taste disperses throughout – then it is Biblically forbidden because of טעם כעיקר. Rabinically we require 60 (a stand-in for taste) in cases which are similar to the Biblical one of טעם כעיקר. The only case we do not require it for, and can use the principle of רוב even Rabbinically, is when it is a dry mixture of same-tasting items. In this case, there is no possibility of taste or of dispersing taste throughout a mixture, and thus רוב suffices (See Hullin 99b-100a, and Tosafot 100a, s.v. Biryah).
The chart below summarizes these principles.