Processing Foods to Remove Impurity
3-2-2001 | IslamWeb
Question:
Does vinegar or salt used in processing forbidden items such as pork or wine change their impurity so that they are acceptable? Is processed cheese from unslaughtered animals legal?
Answer:
All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad 
is His slave and Messenger.
Alcohol, pork and all other impurities, if their nature and reality are changed completely to another thing, and if no trace of them is found, then most of the scholars believe that their ruling becomes the ruling of the thing to which they have been changed.
To add more light on this issue we say the following: scholars differ about whether the impure things become converted and changed completely into pure new things. The Shaafi’i and Hanbali Schools of jurisprudence are of the view that the ruling concerning these things does not change and they remain impure. But these two schools give one exception to this ruling: alcohol. They say that if alcohol is transformed into vinegar, it becomes pure because alcohol is impure only if it causes drunkenness; otherwise, it is pure. But other impure things are impure in themselves (their nature), so their impurity does not change. The evidence for this is the Hadeeth, which forbids eating the meat or drinking the milk of the animal that eats impurities.
The Hanafi and Maaliki Schools of jurisprudence are of the view (according to their most common opinion), that the impure things that convert into pure ones become pure, as it is impossible to clean these impurities from the things themselves. They say that when the Sharee’ah describes something as impure, it means the thing in its initial form and state. If the same thing gets transformed to a different thing, its ruling is the ruling of the new thing not the old one.
The reality of anything changes if any of the components of that thing changes, let alone if all its components are changed. For example, if the corpse of a dog or a pig decomposes and dissolves in a salina, the salt to which it changes is no longer the flesh and bones which are forbidden. This is the opinion of Ibn Taymiyyah and his student Ibn Al-Qayyim 
. So, we believe that anything that melts down and changes completely from its initial state or form into a completely different thing, this last thing is lawful, as this is the opinion of the majority of the scholars.
As for pure things to which an impure component (from a dead animal or a pork ….) is added, they become impure too.
The ruling is that any liquid or fluid, which gets in touch with an impure thing, becomes impure too except the pure water. Abu Hurayrah 
narrated that the Prophet was asked about a mouse which fell in some ghee (cooking butter), and he said: “If the ghee is stagnant take the mouse and what is around it and throw them, but if the ghee is liquid do not approach it [i.e., discard everything]." [Ahmad, Abu Daawood and An-Nasaa-i]
For more benefit on food into which impurity has fallen, please refer to Fataawa 321622, 357877, and 406789.
Allah knows best.