Once the wort leaves the koelschip and is loaded into these puncheons, they are left un-bunged until after the first round of primary fermentation has subsided, a process which usually takes around 2 weeks. It is typical for the wort to experience a lag time of 2 to 4 days before initial fermentation begins, but in some cases this lag time has lasted upwards of 1 to 2 months. I also found it very interesting to learn that certain barrels would undergo multiple rounds of high krausen. After the initial high krausen subsides and the barrels are bunged, this time marks the first pulling of nails to taste the beer. At this early stage, the beer will taste extremely bitter and astringent with quite a high degree of grainy / corny flavor. When sampling after 1 to 2 months in oak, the beer begins to taste cleaner (less bitter and astringent) while still remaining quite rough around the edges. It is at this point that the tasters begin screening the samples for off-flavors.

When asked about the degree of variability seen among barrels within the program, Jeff indicated that there was quite a lot of variation seen in regards to the off-flavors that could occur. However, the beers that did not develop significant off-flavors fell into a more narrow spectrum. Within the first year of aging, the beers that did not develop off-flavors tended to all show similar levels of bitterness and maltiness with subtle variations of fermentation characteristics that tended to be lemony, hay-like, and mildly barnyard in nature.

The most common off-flavors to be found within the program, all of which would lead to that barrel being dumped, were butyric acid, acetic acid, isovaleric acid, wet dog, or a muddy / swampy flavor. Jeff indicated that in their standard farmhouse program, which uses their house mixed culture for fermentation, about 1 in 10 barrels will end up being dumped. On the other hand, within their Spon program, about 1 in 4 to 5 barrels will end up developing off-flavors which require them to be dumped. Barrels that are dumped are typically reused to house future Spon batches, but only after they undergo a thorough rinsing and steam cleaning to reduce any microbial load in the barrels which could interfere with future spontaneous inoculations. Despite the higher degree of loss seen within the program, Jeff spoke to the fact that most off-flavors that would require dumping showed up within the first year of aging, a lucky fact that saves the brewery from having to age beers for up to 3 years only to find out late in that beer’s life cycle that it would be unusable.

When it came time to blend this year’s Spon Méthode Gueuze batches, the beers that were included in the blend were selected based on both their flavor profiles as well as a general adherence to the volume to age ratios used by traditional gueuze blenders. This resulted in approximately 10% of the blend being 3 year old beer, 30% being 2 year old beer, and 60% being 1 year old beer. This blending scheme creates a final product with an average age of 18 months at the time of bottling, which of course means that the average age of Spon Méthode Gueuze is 24 months or more by the time it becomes available for consumption.

I was interested to learn what flavor changes commonly occurred during the six month aging time between bottling and release. Jeff’s answer to this question indicated that the number one change that they noticed was an increase in the overall acidity of the blend. This rise in acidity after bottling occurs in both their Spon blends and the blends coming out of their mixed culture program as well. In both cases, they plan for this increase in acidity by creating a more mellow blend to start with. The other major change that they notice after bottling is an increased presentation of Brettanomyces aromatics. Many of the horsey, hay, and farmyard aromatics are already detectable at bottling time in the Spon components that are more than 12 to 18 months in age, but these characteristics seem to become more present after bottle conditioning as well. Like increases in acidity, this trend towards greater aromatics after bottling is present in their mixed culture program as well. Many of the beers blended from their mixed culture program aren’t as old as the components being used in the Spon blends. As such, their mixed culture beers usually don’t portray strong Brett aromatics at the time of blending, but will begin to show these traits after 6 to 8 weeks in the bottle.