Why is beer tasty?

Actually, many people consider Guinness to be an acquired taste; that is, few people like it the first time they try it. The special flavor qualities that make it unique often turn people off the first few times they have it until they develop a liking to it. There are a few things that contribute to Guinness's unique flavor, not the least of which is sour beer -- yikes! It's hard to believe, but about three percent of every new batch of Guinness is sour Guinness -- beer that has been boiled down to about half of its initial volume and then "vinegarized." Also, if you've ever had the pleasure of drinking Guinness Extra Stout on draught, then you've experienced that incredible rich, creamy head that never seems to dissipate. They get that by using special Guinness taps that inject nitrogen gas into the beer, which, together with the the carbon dioxide carbonation, create the most unique head known to man. A common misconception about Guinness is that it's a heavy beer. It's not, really. There are far fewer calories in a pint of Guinness than many other genuinely heavy beers.