Sunday, November 29, 2009

Another Extreme Beer

News broke this week of another entry into the race to create the strongest and most extreme beer on the commercial market. Scottish brewer BrewDog, currently the largest independent brewery in Scotland, recently announced the release of a 32% ABV imperial stout aged in whisky casks quizzically named Tactical Nuclear Penguin.

Aside from bragging rights used in marketing, high-gravity extreme beers are quite an accomplishment and a testament to the skill of a brewer. Alcohol is a toxic substance (hence the root word for intoxication), especially to microorganisms. Even though their entire existence is spent converting sugar to alcohol and carbon dioxide, most yeast strains cannot survive as their environment approaches 10% to 12% alcohol by volume.

So how are such high-gravity beers made? The first step is in the choice of yeast used, and some brewers have developed their own robust yeast strains in their house laboratories. Even so, these specialized species cannot achieve the record-setting levels of 25% ABV or above without a lot of prodding from the brewer.

Such a batch begins with making a very large starter, which is a type of mini-brew used just to increase the cell count of the yeast before introducing it to the wort. Homebrewers will commonly make a starter out of nothing but sugar, yeast and water, allowing it to grow for hours or days before brewing. The greater number of yeast cells that can begin fermentation immediately when introduced forgoes a lot of other problems as well.

The second consideration is to use highly fermentable grains, that is, grains with abundant starch content that can be fully converted and fully attenuated by the yeast. Likewise, fermentation is given another starting boost by highly oxygenating the wort once the yeast has been pitched, generally by agitation or even bubbling pure oxygen through the liquid.

Fermentation will naturally proceed quite vigorously at first and will begin to slow after a certain point, eventually coming to a halt once the consumable sugar content has been depleted. For that reason, brewers of high-gravity beers will continuously make small additions of sugar to feed the yeast and keep it alive and active, sometimes for weeks or months.

Eventually, any ale or lager yeast will reach its limit of survivability as the alcohol levels continue to rise. Thus, brewers will sometimes switch to other strains of yeast in later stages to finish off the fermentation to the target levels. Champagne yeast is a favorite alternative, as it is highly tolerant to alcohol and neutral in flavor.

However, BrewDog used none of these methods in brewing their record-setting beer, instead relying on a bit of a brewing cheat. Although water freezes at 0°C, ethanol does not freeze until −114°C. By freezing the wort after fermentation, the water content will freeze into a solid block of ice that can be easily removed, leaving behind the unfrozen alcohol in a much stronger beverage.

This method of freezing and removing the water is used in producing the German beer style eisbock, strong beers of about 16% ABV so named after this process. BrewDog did not actually brew a 32% beer but instead made a 10% imperial stout that was held at −20°C for three weeks. The result may be the same in the final product but the achievement is far less impressive than actually coaxing and manipulating yeast to perform far beyond their limits.

Sunday, November 8, 2009

Is Beer Vegan?

The question was recently raised about whether or not craft beer (or beer in general) can be considered vegan. As people become more conscious about what they eat and where their food comes from, and especially as organic claims and certification more often than not blur the lines of truth and nutrition, this can be a genuine concern to those on restricted diets.

First of all, all beer is clearly a vegetarian foodstuff. Vegetarianism is the abstaining from eating the flesh of all animals, and no meat products are ever used in any brewing process of any kind. (Medieval recipes exist for variations on a rather unappealing brewed beverage known as cock ale, but that is a topic for another day.)

However, modern veganism is much more restrictive than a traditional vegetarian diet. As defined by the American Vegan Society, “[t]he vegan diet excludes flesh, fish, fowl, dairy products (animal milk, butter, cheese, yogurt, etc.), eggs, honey, animal gelatin, and all other foods of animal origin.” This means avoiding not only animal flesh but all animal byproducts and derivatives.

From simply an ingredient standpoint, most beer can be considered wholly vegan. Even the most adventurous craft beers include nothing but malted grains, hops, water, fruit or spice additions, and yeast. (Any beer containing honey obviously cannot be considered vegan.) Yeast itself is classified as a fungus, so although it is an independent microorganism it should offer no objection as mushrooms and tofu are acceptable to the vegan diet.

The point at which some beers may garner the disapproval of vegans lies in the various methods used for clarification of the beverage. Many craft brewers prefer to leave their beers unfiltered as it can enhance body and flavor, so these should offer no objection whatsoever. But an additional clarification step at the end of the brewing process can be problematic, depending on the method used.

One popular method of clarifying beer is the addition of finings near the end of the brewing process. Finings are materials that function as flocculation points for yeast in suspension to collect and eventually sink to the bottom under their own weight, where they can be easily removed in bulk. Even though very little of the fining material remains in the finished product, this practice is enough to render the beer non-vegan if animal byproducts are used.

Specifically, at one time brewers used a material known as isinglass as a fining material. Isinglass is a collagen product obtained from the swim bladders of sturgeon, and it has a few other cooking applications in confectionery and dessert-making. However, many modern brewers are abandoning the use of isinglass in industrial brewing—not over vegan objections but simply due to the expense, as the material has become quite costly.

Another fining material very popular with homebrewers is known as Irish moss. Irish moss is a red algae containing carrageenan that looks much like any other herb when dried, and is of course wholly vegan. Other fining substances such as gelatin from fats, casein from cheesemaking or albumen from chicken eggs are so rarely used any more they are virtually nonexistent within the modern commercial brewing industry.

Most clarification processes used today do not involve added finings at all but instead rely upon physical filtration methods. The beer flows through either a very fine-grade industrial microporous screen or, more commonly, diatomaceous earth. Diatomaceous earth is a chalk-like mineral product formed from the fossilized remains of diatoms, or phytoplankton with a calcareous skeleton. It is cheap, easy to replace and recycle, and is the preferred method of filtration for many craft brewers today.

Of course, nothing beats first-hand information. Virtually all American craft beer on the market today is wholly compliant with the vegan philosophy, but if you are still concerned talk to the brewer directly. Most would be happy to explain their process to you and rather flattered that you showed such a detailed interest in their profession.