Boston ? It is banned in 13 states and sure doesn’t come in a six-pack.

The Boston Beer Co., maker of Samuel Adams beer, has released an updated version of its biennial beer Utopias — now the highest alcohol content beer on the market. At 27 percent alcohol by volume and $150 a bottle, the limited release of the brandy-colored Utopias comes as more brewers take advantage of improvements in science to boost potency and enhance taste.

Since the 1990s, craft brewers have produced a number of “extreme beers” that challenge old notions of beer and the decades-old laws that have governed them. By law, these specialty drinks still are classified as beer when they are based on fermented grain.

Paul Gatza, director of the national Brewers Association in Boulder, Colo., said new yeast research allowed brewers to experiment with the emerging science that pushed the traditional cap of 14 percent alcohol by volume for beer.

“As a result, these new beers, like Utopias, balance sweetness, higher alcohol content and more ingredients,” Gatza said.

Utopias has reached its unique strength through a 15-year aging process in barrels at the Boston Beer Co.’s brewery. It’s aged and finished in wooden containers like Scotch whisky barrels and sherry casks. Its yeast strains are used in making malts and champagne.

A quick sip unveils a cognac-like hit combined with vanilla, honey and maple flavors.

The long production cycle is what limits its availability. This holiday season, for example, Boston Beer Co. is only releasing 10,000 bottles with a suggested retail price of $150.

The 13 states that prohibit its sale because of the high alcohol content are Alabama, Arkansas, Georgia, Idaho, Mississippi, Montana, New Hampshire, North Carolina, Ohio, South Carolina, Tennessee, Vermont and Washington.