Style: “Chocolate Stout”
Color: Black
ABV: 10.6%
Price Point: $22 for 750 mL
Technical Notes:
From the bottle, “Brooklyn Black Ops does not exist. However, if it did exist, it would be a robust stout concocted by the Brooklyn brewing team under cover of secrecy and hidden from everyone else at the brewery.  Supposedly Black Ops was aged for four months in bourbon barrels, bottled flat, and re-fermented with Champagne yeast, creating big chocolate and coffee flavors with a rich underpinning of vanilla-like oak notes.  They say there are only 1,000 cases.  We have no idea what they’re talking about.”

Hedonic Notes:

The beer pours an inky black with a coffee colored head.  Bubbles in the foam are small and persistent even as the beer warms.

A malty caramel smell with faint bourbon notes make up the aroma.  As the beer warms a very distant solvent flavor can be detected.  Vanilla notes come out as the beer reaches near room temperature along with slight coffee scents.

Sweet, thick, roasted malt flavors form the start of the taste and are followed by a vanilla and oak notes, with a faint red fruit flavor in the middle.  Cocoa and toffee form the transition to the finish along with some more sweet malty notes and hints of coffee following.  The vanilla, in particular, comes out nicely as the beer warms.  As in the aroma, an ethanol solvent character comes out slightly as it warms.

From the start, the {{mouthfeel}} has a noticeable viscosity and feels very heavy and mouth-coating.  The alcohol character comes out a bit as the beer warms, but does not feel like a 10.6% beer.

Both the flavor and aroma have great balance.  Though complex, the flavors complement each other and strike a balance between the smoky and sweet notes that is simply remarkable.  The beer is, despite its robust and formidable character, surprisingly palatable.  That said, it is certainly not a lawnmower beer, but would be great with smoked salmon and plenty of time to drink it.  Serving as a dessert beer would also work very well.  Even when warm, the beer does not taste as alcohol-solvent like as one might expect for the content, I suspect that aging will improve this characteristic.  Overall, Brooklyn’s Black Ops is a great beer that is definitely worth the investment.

Rating:  4.5 out of 5 corks .  This is an excellent stout that has a wonderful amount of balance.  Try aging this for a few months and see how it develops.

Foam is a critical component in a beer’s appearance, texture and even aroma.  Foam color tells one about the malts used and bubble size lends hints about the level of carbonation and the protein content.  Bubble size and persistence influence how beer feels when drunk.  Because of the very high surface area, foam is able to act as a great interface for mass transfer, accounting for a great deal of the aroma one smells in beer.

Bubble size and persistence are two very important features of the foam that lend insight to the beer’s composition.  The size of bubbles is an indicator of the pressure inside the bubbles and the overall carbonation of the beer.  Bubble stability or persistence indicates a large number of properties responsible for maintaining the beer-air interface.

A collection of bubbles in beer foam. Notice that some of the smaller bubbles appear to be growing into larger ones. Thanks to Placbo on Flickr.

Smaller bubbles require more internal pressure to maintain curvature.  The force on a bubble’s interior surface due to pressure difference is described as the area integral of the normal vector to the bubble’s surface (this simplifies to

, where ΔP is the pressure difference between the inside and outside of the bubble and r is the bubble radius), while the force of surface tension is described as

, where γ is the fluid’s surface tension.  Balancing the two equations so that the force is zero (indicating a stable bubble) yields the solution

This equation says that the pressure of a bubble is inversely proportional to the radius and directly proportional to the surface tension.  In other words, at constant internal pressure, smaller bubbles indicate higher surface tension.  We thus see that beers which tend to have smaller bubbles (like stouts and porters) tend to be a bit more viscous and have higher sugar and protein content.  Conversely, light lagers tend to have larger bubbles due to lower content of interface-stabilizing compounds.

As demonstrated by A. Leike, beer foam decay obeys an exponential decay.  In a paper for which he won an Ig Nobel prize in 2002, Leike shows empirically that the foam height obeys the equation

where h₀ is the initial height and τ is a decay constant dependent on the particular beer.  One may thus compare foam stability of beer on a quantitative basis given measurements over time if observations are conducted carefully.

The exact parameters that determine the value of τ are quite detailed and varied.  Sugar and protein content play important roles, but so do polyphenol concentrations, presence of lipids or sterols and even alcohol content.  Foam stability in general is a topic of great interest currently and beer is just one of many areas of application for such research.

                          

Style: Wild American Ale with Blueberries
Color: A translucent red stream leaps from the bottle, recalling a Lambic almost instantly. Pinkish foam forms with large bubbles and dissipates quickly.
ABV: 5.0%
Price Point: $17 (Note: this beer was very limited production. I am told that it is sold out. -Ed.)
Technical Notes: Fermented with Brettanomyces and finished with champagne yeast. Blended from several sour beer barrels.

Hedonic Notes:
Bubbles rise up the length of the glass and seem to spring forth out of the glass as the beer sits. A sour smell dominates the aroma, calling up images of {Brettanomyces} and {Acetobacter}. Hints of blueberry and champagne appear in the background. Slight red fruit scents are present throughout and mask blueberry notes.

The first sip is very sour initially and fades into sweetness. Faint blueberry notes are masked yielding to Brett horse-blanket. Blueberry mingles with and is virtually indistinguishable from red fruit in a sweet finish. The precise balance of Brett sour and fruity sweet make for an almost sour fruit candy taste. Indeed, the funky flavor of Brett does not overpower any single characteristic of the beer, merely reminding the drinker of its presence. Champagne notes form an ever-present backbone, conjuring images of a sparkling fruit wine. Very high levels of carbonation combined with a specific sweetness make for a champagne mouthfeel.

The beer is light overall, but the effervescence makes it easy to overlook the nuances of its body. The technique using Brettanomyces, and a variety of barrel aged samples is characteristic of Lambics. Indeed, the flavor reminds me a great deal of Lindeman’s brews, a delightful balance of sweet and sour. As an aside, the Wild American Ale category is largely underdeveloped and it is nice to see a brewery pursuing an often overlooked category. The beer, as most of the Excelsior! brews, is very well balanced. Surprisingly, the beer offers a distinct Brettanomyces flavor without being off-putting. It is magnificently palatable overall, and like the aforementioned Lindeman’s beers, may form a delightful introduction to beer and wild beer for the uninitiated.

Rating: 4.5 out of 5 corks .

Science!
Prior to the advent of defined yeast strains and careful genetic management, brewers of wine and beer often used blending techniques to produce consistent and reliable final products. The techniques of blending select not only yeast strains for desirable qualities, but involve the mixing of young and old beers or wines with very different characteristics and compounds in solution, exposing old microbes to new materials.

Microbes may exist in solution or on the surface of the fruit (many wild yeasts reside on the skins of fruit), but rely on molecular diffusion for sugars and nutrients to reach the cells. Compounds must diffuse through the fruit’s cellulosic matrix to reach the yeast cells. In the case of Lambics, fermentation may demand up to three years to completely mature.

Depending on the time of year and immediate conditions at the time of brewing or preparing grapes (especially the amount of time since the last rain), different wild microbes may infect the wort or must. Add in the very long maturation time and these fermentations require either very precise control of the fermentation process or a number of different permutations of a particular fermentation, each with different flaws and strengths.

Mixing these different permutations has the potential to produce a consistent and desirable product. The often unpredictable nature of fermentations necessitates such approaches in large-scale endeavors. Mixing old beer with young beer (a three year and one year fermentation is often used when making Gueuze) reinvigorates fermentation. Certain oxidative yeasts (Brettanomyces, most notably) take a very long time to ferment completely, often in excess of 8 months before the yeast fully start autolyzing and/or falling out of solution.

For comparison, Saccharomyces are bred to be rapid fermenting yeasts and typically finish their work in two weeks before they start dropping out of solution and begin fining the product. Some other participants in the fermentation process (e.g. Pediococcus taking up to 4 months) also are slow fermenting, necessitating long maturation times. Most bacteria in wild fermentations, however, tend to work very rapidly and play little role in aging. Indeed, it is very often that the dominance of the bacteria reproducing very quickly that makes controlling the process difficult and introduces undesirable flavors. Blending different vintages is almost always necessary in making wild ales that are consistent and perhaps merely even palatable.

Further Reading: Sparrow, Jeff. WildBrews: Beer Beyond the Influence of Brewer’s Yeast. Brewer’s Publications: Boulder, CO. 2005.