As-Salamu Alaykum wa Rahmatullahi wa Barakatuh.
In The Name of Allah, Most Gracious, Most Merciful.
All Praise and Thanks are due to Allah, and peace and blessings be upon His Messenger.
In response to this question, the European Council for Fatwa and Research (ECFR) issued the following Fatwa:
The Council ruled that if alcohol naturally becomes vinegar, then it is considered halal and pure (tahir), based on the consensus of scholars. However, scholars have differing opinions regarding vinegar that is produced through deliberate processing and treatment, such as the addition of salt, bread, or specific chemicals. Some argue that it remains pure and can be used, as it has undergone a complete transformation from its original state of being alcohol. Others contend that it does not become pure and should not be used, as we are commanded to abstain from alcohol.
Having considered both opinions, the European Council for Fatwa and Research (ECFR) concluded that the first opinion, which states that vinegar deliberately made from alcohol is pure and may be used, is correct. This is because acetification, the process of turning alcohol into vinegar, removes the element that makes alcohol primarily haram: intoxication. Therefore, it becomes permissible, especially considering the numerous benefits that can be derived from vinegar, such as medicinal and culinary uses.
It is important to note that any ruling is entirely bound by reason and wisdom. In the case of vinegar, we recognize that the element of intoxication has been completely eliminated. This is affirmed by the Hadith of the Prophet Muhammad (PBUH):
“نِعْمَ الأُدُمُ الخَلَّ”
“What a good seasoning is vinegar,” without specifying the kind or type of vinegar. We also note that the Prophet (PBUH) did not instruct us to inquire about the origin of the vinegar or make any specific inquiries in that regard. As for statements that prohibit acetification, they serve to emphasize the firm stance of Islam regarding alcohol itself, ensuring that no one becomes complacent in this matter.
Allah Almighty knows best.