Naturally-occuring malic - https://www.buzznet.com/?s=Naturally-occuring%20malic acid is usually extracted - https://search.usa.gov/search?affiliate=usagov&query=extracted from apples. It is more common to find synthetic malic acid supplier - https://ingreland.com/products/malic-acid-supplier/ acid being added to foods which is synthesised from butane gas.

Therefore, malic acid has had no contact with wheat through either process and can safely be said to be gluten free.