wild yeast infections

I've lived in Hawaii for about a year now, and during that time I've brewed about a dozen beers. Of those dozen beers, at least three started out lovely, and then developed problems after a few months in bottles. The most persistent problem I've had has been extreme overcarbonation, leading to gushing when the bottles are opened, or even reaching levels that cause the bottles to explode. I brewed a few dozen batches of beer back in San Francisco before moving here, and never had this problem there, so I started thinking it must have something to do with the climate in Hawaii.

My thoughts about the cause of this over-carbonation have developed over time. The first beer to over carbonate was my Lilikoi Amber, and the first theory I came up with was the addition of lilikoi juice in secondary fermentation shocked the yeast into temporary inactivity, and then, when the beer had gone into bottles, the yeast recovered from its shock and started fermenting the new lilikoi sugars. For a while I was convinced this was the answer. But then a bottle of a different beer--without lilikoi--exploded.

The next theory I came up with was that the priming sugar I was using--regular old table sugar--was resulting in more vigorous bottle-conditioning than the refined dextrose sugar you buy at the brew shop. And so I switched back to dextrose for a batch... and had the same problem develop.

Another thought was that the warm fermentation temperatures were responsible. A lot of the beers I brew use English style yeasts that prefer fermentation temperatures in the mid 60s. The coldest I've been able to keep my fermenters here has been closer to 72 degrees. And so I decided to try a Belgian yeast known for enjoying fermentation temperatures in the mid 70s. The beer turned out great, but the few bottles I have left are turning into gushers too.

So the over-carbonation problem doesn't result exclusively from using lilikoi juice, or table sugar, or from having yeast-strains that react badly to Hawaii's warm climate. All of those things might be contributing, but the crux of the biscuit is probably something else.

My new theory is one of the first ones presented to me, by my friend Danny (of Deeper Roots brewing). It's also the main theory that shows up in the "trouble-shooting sections" at the back of basic homebrewing books, and it's the theory offered by most of the beer judges who sampled my gusher entry to this year's Longshot Competition. Being that it's the first theory often presented, of course I ignored it until now.

What's the theory: wild yeast.

I brew outside, in the open air, at the back of Palolo Valley. Palolo Valley is a lush place, with lots of rainfall and lots of dense, jungle-like vegetation. The air is thick with life, probably literally.

For many of the beers I've brewed here, I finished the process by hand-ladling the cooled wort from the kettle to the fermenter, and I did this out in the open air. On several occasions I had a breeze kick up during this part of the process. Usually the breezes here are a welcome relief, but when you're out in the open with five gallons of highly fermentable liquid, the feel of the wind blowing over you--and the thought of all the invisible yeast spores it carries--is pretty disheartening.

So, in hopes of addressing this problem, I'm trying to limit my wort's exposure to the breeze. With the last batch I brewed I erected a wind-block (as shown in the picture above), kept the kettle lid on during cooling, and transferred the cooled wort to the fermenter while indoors. Chances are I won't know if it worked until three months after putting the beer in bottles--in the experience I've had here so far, all the beers seemed fine at first, and then started gushing after a few months capped--but if I still have overcarbonation problems, I might try using Campden tablets.

Does anybody else have any other suggestions? Feel free to leave them in the comments section.