After an unsuccessful attempt last year, Jester King Brewery has announced its newest fruited sour, this time refermented with Texas blueberries.

Named Colour Five, the new barrel-aged sour beer uses a blend of 89 percent Das Überkind, a saison, and 11 percent RU55, a farmhouse red ale, as the base beer. The Austin-based brewery then refermented the blended beers in a stainless steel tank. This allowed Jester King to “keep a constant blanket of carbon dioxide over the beer, in order to stave off oxygen, which can lead to the growth of acetobacter,” which is the bacteria that produces acetic acid leading to extreme sourness in a beer. In addition, the brewery froze the blueberries prior to refermentaion, cutting down on the acetobacter that on was present on the skin of the fruit. Finally, carbonic maceration was also used to burst open the skins of the berries, instead of crushing them.

Jester King Colour Five 1

Last year’s attempt at producing a sour, barrel-aged beer with blueberries was unsuccessful and the entire batch was dumped down the drain after it was found to be to acetic for the brewery’s standards.

“On the whole, we’re quite willing to sit back and allow fermentation with native yeasts and bacteria to take our beer in all sorts of interesting directions,” explained the brewery about the failed attempt in a blog post.

“But one part of our process that we do control very carefully is temperature. We keep our barrel room right around sixty degrees Fahrenheit year-round in order to keep acetobacter (the bacteria that produces acetic acid) at bay. At extremely low levels, acetobacter can add some pleasant complexity and depth of flavor, but if allowed to grow, it can easily take over. Unfortunately, our first attempt at blueberry refermentation became overly acetic and was dumped. Jester King is a very experimental brewery, and part of what this means is that some of our experiments fail.”

Jester King Colour Five 3

The label art was produced by Josh Cockrell.

“The art is inspired by sacred geometry, both from the protective pentagrams of the Pythagoreans and in alchemy,” said Cockrell. “These shapes are reflected in the natural geometric patterns found on a blueberry. Both pentagons and a five point star appear within this geometry when looking closely at a blueberry head on. The ὑγιεία pentagram and 5 classical planets plus the sun and moon are represented in the final artwork. Colour Five is an extension of this theme of fives in that blue itself is the 5th color in the visible spectrum.”

Colour Five will be available on draft and in 500-ml bottles ($16) at the brewery starting on Oct. 31 with a limit of one bottle per person per day. Approximately 2,000 bottles were produced, and other than future special events, it will remain a brewery exclusive.