Does a zinc metal coating react with coffee in a coffee grinder? I'm restoring an old coffee grinder and I want to give the grinder mechanism a nice zinc / silver coating.

But I read it is not safe for zinc to be in contact with acidic foods.

When I look at the pH, coffee's is 4.6 &ndash; 4.3 which is quite acidic:
https://angelscup.com/blog/taste/coffee-acidity-flavor-ph-acid-reflux-and-low-acid-coffee/

Not sure if the zinc and coffee are likely to react in such a scenario. Should I maybe choose a silver plating?

Before cleaning with citric acid. 



After cleaning with citric acid, Al foil and baking soda
If you plate the pieces with zinc or silver, the main source of zinc/silver in the ground coffee will be from abrasion between the parts and the coffee beans and not from chemical attack.

A few milligrams of zinc or silver (or iron for that matter) won't to do any harm to your health, specially if diluted in many coffee cups along several months or years.

In fact, Zinc was used therapeutically in dosages upwards of hundreds of milligrams per day for months, or more, with no permanent health issues.

Silver, on the other hand, has much lower acceptable exposure limits and while not particularly toxic, I'd not put it in parts of the device that are guaranteed to put metallic silver into the ground beans.