The use of hops in beer did not become ubiquitous until nearly 1800 AD (1). For most of its lengthy history, beer was herbed to impart balance and contained no hops. Everyone who has tried gruit ale(2) knows by its absence the particular flavor lupulin imparts in a beer. Beer without gruit (herbs) or hops is a cloying malt bomb and overall a rather unpleasant drink.
Hops are used to provide not only bitterness, offsetting the malt sweetness in beer, but also aroma and other distinct flavors—such as spicy, herbal, or citrus (3). Hop bitterness levels within beer are measured by a system called International Bittering Units or IBUs (4). Without getting too technical (read: boring), the IBU scale measures the dissolved alpha acid (bittering agent within the lupulin) content of a beer. The quantity and quality of alpha acid in hop cones varies among hop vine varieties and is of great interest to those who make beer. To beer drinkers, the variety of hops used in brewing imparts different flavors to the finished beer. For example, Cascade or Centennial hops can impart a grapefruit flavor (5).
Hops have moved to the forefront of brewing in recent times, becoming a big star in the craft beer revolution. Hop terms like “hop head”—a person who likes dominant hop flavors in his beer—are more common in every day beer lingo. West coast American breweries such as Rogue Ales in Oregon and Stone Brewing Company in California specialize in hop-dominant beers. American India Pale Ales (IPAs), Double IPAs, and American Strong Ales have stronger hop profiles and many breweries continue to push the IBU limits in their beers.
Hoppy beers may not be popular with everyone but the harder to find hopless beers have definitely fallen out of favor. Although not apparent to the casual sipper, hops are an extremely important flavor component of nearly all styles of beer.