SAVOR attendees left with a sample of Terra Incognita, a collaborative beer that underwent a second fermentation in the bottle. (Tim Carman/The Washington Post)

The most memorable beers were, tart, acidic and refreshing, or complex, earthy and mouth-puckering. Let’s start with Terra Incognita, the collaboration that Sierra Nevada Brewing Co. and Boulevard Brewing Co. whipped up expressly for this year’s beer-and-food festival, held June 8 and 9 at the National Building Museum.

Sierra Nevada cooked up the wort, then shipped the unfermented beer to Boulevard in Kansas City, reversing the path of the 19th-century pioneers who followed the California Trail to the American West.

At Boulevard, the wort was fermented and siphoned into 21 barrels, some of which held wine or bourbon, some freshly fashioned out of new oak. After two months, all were sampled, and the contents of 12 were deemed suitable for the blend. As a final flourish, the brewers added a dash of the wild yeast Brettanomyces to spark a new fermentation in the bottle.

The result is a chestnut-colored beer, with some of the chocolatey notes of a brown ale, the funky horse-blanket flavor of a Belgian lambic and a piercing sour finish. Attendees were handed a bottle as a parting souvenir. The beer will continue to evolve for months, maybe years in the bottle, “but when you open a bottle, point it away from you,” warned Boulevard brewer Steven Pauwels. “It keeps carbonating!”

(How can you obtain Terra Incognita? If you missed SAVOR, you’re probably out of luck. But Boulevard has officially entered the local market, and its limited-release Saison-Brett is well worth seeking out.)

Elsewhere on the floor, Bell’s Brewery in Galesburg, Mich., was offering its own take on nonstandard fermentation. The Wild One is a blend of ales that spent 6 to 9 months in wine barrels, spontaneously fermented by the microscopic bugs living in the wood. Tannin and a dash of vanilla smooth out the acidity. Normally, you’d have to travel to Bell’s Eccentric Cafe and General Store to sample the Wild One on draft or buy a 750-mililiter bottle.

You didn’t need to score a SAVOR ticket to sample rare beers, however. Out-of-town brewers were eager to strut their best stuff at area bars. A few hours before the Friday session of SAVOR, ChurchKey was pouring Blushing Monk from Founders Brewing Co. in Grand Rapids, Mich. This strong (more than 13 percent alcohol by volume) Belgian-style ale is an ode to raspberry, with a massive tart, fruity flavor obscuring the alcohol content. The beer will never be more than a sporadic release, says Founders president and CEO Mike Stevens, due to the expense (it requires $2,000 worth of pureed raspberries per 30-barrel batch) and the royal mess each batch makes.

At the opposite end of the alcohol scale, Flying Dog Brewery in Frederick was offering its version of a Berliner weisse — a tart, effervescent ale that undergoes a lactic fermentation — at a symposium last week. The ale, quite refreshing at only 4.4 percent alcohol, was flavored with sour cherry, arguably an improvement on the raspberry syrup that Germans like to dose this style with.

Later this summer, Sierra Nevada will release another sour, funky ale called Brux in conjunction with Russian River Brewing Co. in Santa Rosa, Calif. But sour beers are a drop in the brew kettle in terms of craft beer volume, and Sierra Nevada president Ken Grossman, at a SAVOR salon, cast doubt on how common these more exotic styles will ever become. Barrel-aging “throws a wild card into your operation,” he commented. What emerges from the barrel can be a finely nuanced brew, or it can be vinegar.

“Having an all-wooden brewery would be pretty disastrous,” Grossman said. “If you have a little 10-barrel brewery, maybe you can base your brewing on barrel-aging. But with a larger brewery, you need something more consistent.”

Asked if sour is becoming the new bitter, with wild ales replacing India pale ales in the hearts of beer geeks, Ken’s son Brian answered succinctly, “Hell, no!” Most of the beer-drinking population, he noted, still equates sour with spoilage.

But who would have predicted a generation ago that highly hopped IPAs would become the most popular craft beer style?