I have learned more from threads like this... great topic.
First a story. One cold rainy night, while wandering the streets of Dublin a few years ago (airline pilot on a layover) I happened into a pub and ordered a Beamish Stout, a bowl of bean soup, a healthy chunk of brown bread & a few tablespoons of the richest Irish butter I'd ever eaten. The combo was the perfect antidote for such a depressing day and place. I'd visited Kilmainham Gaol that afternoon. A Victorian era prison, the monument commemorates all of the patriots of the Irish revolution against English Imperialism. Unlike the American revolution however, the English hanged all of the Irish patriots and would be founding fathers... The magical dancing of the highly nitro'd Stout as it settled, got me thinking...The conclusion? That I'd have another beer.
Ever since then I've marveled at mouth feel. Over the course of the last year I've experimented with flake ads. Two of my beers in particular lend to my limited understanding. Here's what I've experienced:
A) My go to house IPA, that I almost always have in the pipeline. Normally, split a 10 gallon batch with half destined for the keggerator. That pairs well with my spicy culinary habits, or as a sedative to suffer through evening TV. The other 5 gallon half gets bottled and often given away as motivational gifts.
The 10 gallon malt bill: 22lbs 2 row, 1 pound crystal 15, 1 pound Munich and
seasonally I add 1 pound of flaked wheat.
Until I tried adding the wheat, I didn't understand how wheat was the throttle for huge head retention compared to the "Reinheitsgrebot" (no adjuncts) version. The thicker creamier version is a different animal than the exact same beer without the wheat. Wheat changes everything, from how much carbonation the beer can hold, to how the hops seem to be showcased. I like both styles, but the version with the wheat seams more well suited to fall and winter, while the thinner, crisper non-wheaten version of the exact same recipe, is better IMHO in the warmer spring and summer months.
B) A dry Irish stout all grain kit beer
https://www.morebeer.com/products/irish-stout-grain-beer-kit-advanced.html that came with flaked barley.
Young yet, I just tasted my first bottle last night. HELLO BARLEY. I really brewed this batch for a buddy who travels to Ireland all the time and grouses that he can't buy good beer in the states. The other stouts I've made were thickened up with silly adjuncts like baker's chocolate and powdered peanut butter or oatmeal, but this recipe actually got there (my target mouth feel) by the flaked barley that it came with. 20 lbs. British Pale 2 lb. Black Roasted 4 lbs. Flaked Barley.
I can't imagine adding flaked barley to an APA or lighter beer without seriously changing the targeted flavor. In addition to thicker creamier results, barley makes this beer taste different.