Mike Snider

USA TODAY

Beer lovers are far from souring on craft beer, but many brewers are turning to sour beers and other new twists to keep the growing beer category fresh.

In addition to beers that may cause lips to pucker, there's an inpouring of hoppy but lower-alcohol session brews and luxuriant, wildly inventive beers borne out of collaborations between brewers.

Such experimentation is "pushing the envelope of what beer can be and finding new flavors," says Greg Engert, beer director of Bluejacket brewery and restaurant in Washington, D.C.

As overall U.S. beer consumption has declined slightly in recent years, craft beer is on the rise. Consumers spent an estimated $14.3 billion on craft beer in 2013, according to the Brewers Association, up 20% from the $11.9 billion spent in 2012.

"The craft brewing industry has evolved from a raggedy bunch of home brewers and dreamers to a bona fide 10% segment of the $100 billion American beer industry," writes Brooklyn Brewery co-founder and president Steve Hindy in his recent book, The Craft Beer Revolution: How a Band of Microbrewers is Transforming the World's Favorite Drink (Palgrave Macmillan, $25).

Actually, it's even more than that, as last year craft beer's share of the total U.S. beer market grew to more than 14%, the association says. Today there are more than 2,800 craft breweries in the U.S., surpassing even pre-Prohibition days.

"You are seeing a big boom in not just production facilities that are doing shipping of beer offsite, but also in the on-premise sales of brewpubs," says Engert, who oversees a lineup of 25 on-site brewed beers at Bluejacket, which opened late last year near Nationals Park.

At breweries and brewpubs, brewers are trying new styles to satisfy their creative urges — and quench ever-adventurous customer palates. "Over the last 150 to 200 years, beers got kind of mainlined into a very clean and consistent product," Engert says. "A lot of craft brewers today are interested in making crisp and clean full-favored lagers, hop-driven IPAs (India Pale Ales) and pale ales, but also want to showcase that wild side of beer."

A perfect example is the growing sour beer movement. Building off classic Belgian and German styles, U.S. brewers are using wild yeast and bacteria to create beers that range from slightly tart to downright puckering.

Belgian-born brewer Peter Bouckaert began making sour beers 17 years ago at New Belgium Brewing Co. in Fort Collins, Colo., including a red ale called La Folie, which takes two years to age, resulting in a sourness that the brewer equates to that of a Granny Smith apple. A recent release, Transatlantique Kriek, is a blend of a sour cherry lambic ale with a Champagne-like consistency.

Russian River Brewing Co. is another brewery that led the charge for barrel-aged sour beers and was among the first to let beers spontaneously ferment in open-air vats, allowing the growth of bacteria, airborne yeast and Brettanomyces, a yeast that can bring out fruity and funky flavors. Bluejacket has one, too.

The Santa Rosa, Calif.-brewpub, however, remains a testament that super-hoppy beers have not been set aside. Russian River has become a beer geek destination for its hopmonsters, including the double IPA Pliny the Elder and the hard-to-find, draft-only Triple IPA Pliny the Younger. IPA sales account for about 70% of production at the brewery, while sours make up 10%.

"It's cool to see such a big interest in the consumer side in sour beers as well as from the brewers," says Natalie Cilurzo, company co-owner with husband and brewmaster Vinnie. "But it's still all about IPA."

Craft beer industry leader Samuel Adams (Boston Beer Co.) has also embraced sour and funky beers, too, with a tart, spicy beer called Tetravis, created with a base ale called Kosmic Mother Funk (available year-round, first released in September 2013).

Women, in particular, seem to gravitate to sour beers, says Kim Jordan, who co-founded New Belgium in 1991. "Where more of the mainstream beers in the U.S. have been seen as a man's drink, I think craft brewers are more approachable for women," she says. "Some particular styles, sour being among them ... are really appealing to (women) because they are sophisticated and flavorful and not crazy (alcohol) bombs."

The brewery also recently released a beer that reflects another trend: lower-alcohol beers, or session beers, so named because you can have more than one or two in a drinking session. Some industry experts say session beers top out at 4.5% alcohol, but Snapshot is a 5% wheat beer just now hitting stores, with a slight tartness — a possible gateway beer to new sour explorations.

Similarly, Widmer Brothers Brewing recently released its Citra Blonde Summer Brew, now in its third year of availability, which has a healthy hoppiness despite its 4.3% alcohol level. Also available this spring is Goose Island Endless IPA, a new 5% alcohol limited release with a grassy, earthy aroma and bitterness from Amarillo hops.

Brewers are also finding inspiration through collaboration. Bluejacket and New Belgium, along with Brooklyn Brewery, teamed up for three beers, featured during their seminar on collaboration ales at the SAVOR craft beer and food event this weekend in Washington, D.C. The beers will subsequently be available on tap at Bluejacket, as well as in Colorado and New York.

One, a malty ale that got its name from a favorite Flemish poem of Bouckaert's called Twee Horsen. All three use a strain of Brettanomyces, known for its funky flavor — as well as the additions of oak spirals and endive as an ingredient. "With craft beer you can mix different flavors in small levels and it surprises you what they will do to the ultimate overall characteristic of the beer," Jordan says.

Another, the sour and funky Rheinard de Vos (the red fox), was inspired by a wine that Engert, Bouckaert and Brooklyn Brewing brewmaster Garrett Oliver shared during a brewing brainstorming weekend in New York. "None of our breweries would have come up with these beers had we not gotten together for this fateful weekend in New York City," Engert says.

It's an opportune time for new beer exploration as the industry celebrates American Craft Beer Week May 12-18 with activities planned nationwide. And many pioneering breweries, including Boston Beer Co., Bridgeport Brewing, Pyramid Breweries and Widmer Brothers Brewing, both in Portland, Ore., celebrate 30th anniversaries this year.

"A lot of those packaging brewers made it through the more difficult times of the late '90s and really boomed," says Paul Gatza director of the Brewers Association, which puts on SAVOR and the Great American Beer Festival. "Every year now we're going to hear about anniversaries going forward."