Speaking of which... pickled foods! Pickled cucumbers (also very popular in Poland), sour cabbage (a.k.a. sauerkraut), but also other vegetables (beetroots, carrots, onions, olives... so much stuff can be pickled

This could mean an introduction of a pickling barrel that you'd have to fill with brine and put vegetables in (similar to how leather production works now) - maybe add modifiers by adding some dill and/or other spices (why don't we have garlic yet either?).
This might necessitate introduction of salt as an item (other than "salt crystals") - possibly by boiling out salt water (although brine could be created directly from salt water... or even just simply use salt water directly).