Question: Is it permissible to prepare “pickles” by placing cucumbers in salt-water or vinegar on Shabbat?
Answer: The Gemara in Masechet Chullin (97b) tells us: “A pickled item is considered cooked,” meaning that any item which has been steeped for a certain amount of time in salt-water or vinegar is considered to have been cooked. Thus, if something forbidden for consumption has been pickled with other foods which are permissible for consumption, the entire mixture is now forbidden for consumption as if they had been cooked together, for the pickling process transfers flavor from one food to the other and the entire mixture is now full of forbidden flavor.
It seems that the same should apply to Shabbat that just as it is forbidden to cook on Shabbat, it should likewise be forbidden to pickle on Shabbat as well.
“Pickling is like Cooking” Regarding Shabbat
Nevertheless, the Rambam (Chapter 22 of Hilchot Shabbat, Halacha 10) and other great Poskim agree that the idea that “pickling is like cooking” applies only to the laws of Kashrut, for instance, if cheese and meat were pickled together, they are both prohibited for consumption as if they were cooked together. However, regarding Shabbat, pickling is not like cooking, for the Torah only prohibits cooking with fire and the like, and pickling is not included one of these forbidden methods. (Maran zt”l deals with this issue at length in his Chazon Ovadia-Shabbat, Part 4, page 448.)
However, all opinions agree that one may not prepare pickles on Shabbat, for even according to the opinions that this does not constitute a Torah prohibition, there is nevertheless a rabbinic prohibition to do so, for just as we say “pickling is like cooking” regarding the laws of kosher, the same applies to Shabbat as well.
It is therefore completely forbidden to pickle cucumbers, eggplants, olives, green tomatoes, and the like on Shabbat, for “pickling is like cooking.”