If forbidden and permitted foods are mixed together thoroughly the mixture is permitted if no one forbidden component is more than 1/60 of the total (98:1,6,9; see 99:1-2,4). In defining a component, things that have the same name are regarded as the same whether or not they taste the same; see 98:2. For some types of forbidden foods amounts different from 1/60 are required; for other types any amount makes a mixture forbidden (see 98:7-8). If an intrinsically forbidden component can be detected by its taste or by its effect on the mixture (e.g., 87:11;102:1), or if a forbidden component can be recognized but cannot be removed (104:1,3), the mixture is forbidden even if the component is less than 1/60 (98:8;105:14).
It is forbidden to mix forbidden food with permitted food to produce a permitted mixture; if this was done, the person who did it or for whom it was done is forbidden to derive benefit from the result (94:5-6;101:6). It is forbidden to use a utensil that has absorbed forbidden food if the utensil is sometimes used for less than 60 times as much permitted food (99:7;122:5).
If a mixture contains less than 1/60 of a forbidden component, and more of that component is added so that the total reaches 1/60, the mixture becomes forbidden; but if a mixture contains less than 1/60 of meat (or milk) it does not become forbidden even if milk (or meat) is added to it afterwards (99:6).
If an entire (dead) creature or (named) body part that has always been forbidden is mixed with any amount of permitted food the mixture is forbidden, but if the forbidden component can be recognized and removed the remaining mixture is permitted if the forbidden component was less than 1/60 of it (100:1-3). Similarly, if a portion of food that is intrinsically forbidden and is large enough to serve to guests in its present condition is mixed with any amount of permitted food, the mixture is forbidden as long as the portion may have remained intact (69:14;81:2; 92:3;101:1-7;105:9;106:1).
If food that is only temporarily forbidden or that can be made permitted without much effort is mixed with any amount of permitted food of the same type, the mixture is forbidden until the forbidden component becomes permitted; but if it is mixed with permitted food of a different type, or is not intrinsically forbidden, or became forbidden only after it was mixed, or can be recognized and removed, the mixture is permitted if the forbidden component is less than 1/60 of the total (102:1-4).
Shulchan Aruch, Copyright (c) 1999 Project Genesis, Inc.