Two weeks ago, we explored the topic of efshar li'sochto, and saw that when a meat and milk are cooked together, they may remain forbidden even after they are separated. This depends on whether we understand the prohibition of meat and milk to be based on the fact that they were cooked together, which does not change even after they are separated, or based on the fact that there is a mixture of tastes, which would be negated once they are separated.
Now, these above reasons are relevant to basar bi'chalav, and this is the only application of this concept in the Gemara. Interestingly, however, some Rishonim, as well as the Shulkhan Arukh, extend this prinicple to other prohibitions. According to Shulkhan Arukh (YD 106:1, in contrast to 32:9) that if - for example, a potato absorbed pork taste, and then it was placed in a pot of stew and continued to cook so that now there is no pork taste left in the potato or the soup, nevertheless, the potato remains forbidden (although the soup is permissible). What is the reason that the potato remains forbidden, if there is no longer any forbidden taste? It is the principle of efshar li'sochto assur.
This principle, now, no longer is unique to basar bi'chalav, but applies to all forbidden mixtures and is understood to mean that once a food becomes forbidden it cannot become permissible again. Why should this be so? It has to do with the idea of status of objects and what I call the "stickiness factor." There might be a certain criterion for an object to attain a status. However, once that status obtains, it will not automatically be lost even if the criterion are no longer satisfied. A good analogy might be that of employment. A person will not be hired until they meet certain criteria. However, once this person is an employee, he or she will not automatically be fired as soon as they fall short of those criteria.
It is similar with halakhic statuses. Take, for example, the status of being a "food." Does something have to be edible to a human to be a food, or is it enough that it is edible to a dog? The answer is - it matters when. According to some Rishonim, for food to be able to become tamei, impure, as food, it needs to have originally be fit for human consumption. Once it is defined as food, however, it will remain defined as food even if it becomes inedible for humans. Only when it becomes completely inedible - even to a dog- and loses even the tiniest shred of "foodness," will it stop being food and not be able to become tamei. (See Rambam and Ra'avad, Tumat Okhlin, 2:15).
The same is true here. To become forbidden, an object has to have absorbed enough from the forbidden food that there is some trace of its taste. However, once forbidden, it will remain forbidden even after the forbidden food is no longer tastable. This is the principle of efshar li'sochto applied to other forbidden foods. It recognizes that some halakhic realities are not "states" which change when the reality changes, but "statuses" which continue to adhere - the stickiness factor! - even when circumstances change.
No, will the status ever go away? Do we have a circumstance by this food mixture that parallels that of "not being edible even by a dog"? It seems that we do. When - to take our example - the potato not only has so little pork in it that the pork cannot be tasted, but it has absolutely no pork in it anymore, when there is not even a shred of the original offensive food, then the forbidden status disappears. This is no longer a case of efshar li'sochto, but one of efshar li'hafrido - the two items are completely separated. In this case, the Shulkhan Arukh rules that the originally permissible item returns to its original state of permissibility (YD 105:7).
We have, in the last two discussions, seen the concept of efshar li'sochto and efshar li'hafrido applied to basar bi'chalav and to other forbidden mixtures. We will continue this discussion next week in a parallel manner, looking at the principle of chatikha atzma na'asit neveilah - the piece of meat itself becomes a carcass (forbidden food) - as it applies both to basar BiChalav and other forbidden mixtures.