TLDW: Their mandarin orange wine was a bit too bitter. Testing, unscientifically, if they can tell a difference. They can. They think it lowers the bitterness.
Interesting. I’m mainly a beer brewer (only my first cider recently) so I’ve not had a brew that’s “too bitter”, as with beer you WANT them to be bitter, usually. I’ve heard to add a pinch of salt to a pot of coffee.
What about post fermentation? I'd assume that's where salt is added to a salted gose, for example.
Then again, lots of brewing books will discuss how to analyze and alter the mineral component of your tap water to match whatever European city you are mimicking.