Yeast Geneology

(Image: S cerevisiae under DIC microscopy, via Wikimedia Commons user Masur)

At the Smithsonian food blog, Food & Think, there is an interesting bit about the origin of lager yeast.

As you may know, most beer we drink is brewed with a species of yeast called Saccharomyces cerevisiae. Depending on the type of beer, a different strain of this yeast is used. For ales, brewers use a strain of ale yeast, which ferments more or less at normal room temperatures (15-20C) and is known as top-fermenting yeast. For a lager, one would use a lager yeast, which is a bottom fermenting yeast that functions at cooler temperatures (around 5C). Additionally, lager yeast is able to digest raffinose, a sugar present in wort (unfermented beer) that ale yeast cannot ferment. This means that lager yeast can contribute to a higher sugar-to-alcohol conversion and results in a less sweet beer.

Previously, scientists had compared the genomes of lager and ale yeast and found that lager yeast resulted from a cross between S. cerevisiae and another type of yeast. Recently, this type of yeast, which was previously undescribed, has been identified, as described in a recent paper in PNAS. Interestingly, this yeast is native to South America, suggesting that modern lagers (even European ones) owe many qualities to a species of New World yeast. Previous to the European exploration of the Americas, lagers in Europe may have been brewed with unhybridized S. cerevisiae, resulting in a different beverage than what we identify as lager beer today.

It seems that globalization hasn't been such bad news for beer, after all.

Archaeology of Beer

 The Smithsonian Magazine website, there is a really interesting article about brewers trying to re-create fermented beverages as they might have been made thousands of years ago. (One familiar example of this is the Dogfish Head Brewery's Midas Touch, pictured above, a beer based on an Iron Age recipe including Muscat grapes, saffron, and honey.) Many brewers have enlisted the help of Patrick McGovern, an archaeologist from the University of Pennsylvania specializing in ancient libations. Go check out the article, and maybe it will inspire you to brew your own version of an ancient brew!

(Image:  Dogfish Head Midas Touch, a Creative Commons Attribution (2.0) image from add1sun's photostream)

The Science of Cooking with Beer

Via BoingBoing, there is an interesting article about why beer batter makes fried food delicious at Scientific American. In short, beer contains three things that make it a great batter ingredient: foaming agents, carbonation (a.k.a. dissolved carbon dioxide), and alcohol. Carbon dioxide is more soluble in water at cold temperatures, so when beer batter is heated it releases bubbles of carbon dioxide that are trapped by the foaming agents (in most beers this is carbohydrates and proteins from the barley malt), making a light crispy crust. The pockets of air in the crust insulate the delicate food inside, allowing it to gently steam and keeping it moist. The alcohol in beer batter boils at a lower temperature than water, meaning that, when cooked, this batter releases moisture faster than batter made with just water, allowing it to cook faster. Only after all of the water and alcohol have evaporated will the Maillard reaction* take place, making starches and proteins in the batter golden brown and delicious.

*Note: The article says that the Maillard reaction takes place above 130 degrees Fahrenheit, but this is incorrect. It actually takes place above 130 degrees Celsius, which is about 265 degrees Fahrenheit.

Another good reason to cook with beer, and not necessarily just in beer batter, is that beer adds great flavor to dishes. Beer contains its own flavors - smoky, sweet, bitter, or acidic, or a combination of these, depending on the variety. Beer also contains alcohol, which helps amp up other flavors in a dish. Alcohol is able to dissolve many flavors that are not very soluble in water, like essential oils and other organic compounds. These compounds are key flavor components of foods like black pepper, chili peppers and tomatoes, among many, many others. This means that adding any alcohol-containing liquid to a dish can dissolve these flavor compounds, making them more available to your taste buds and increasing their flavor.

In case all of this had put you in the mood to cook with some beer, I've included a recipe below for Black Bean and Sweet Potato Chili, which I whipped up for the Superbowl last Sunday. It's delicious, cheap, and healthy, and the dark beer included in the recipe adds a little smoky flavor as well as some alcohol to dissolve the spicy and tomato flavors in the chili.

Happy St. Paddy's Day!

In honor of St. Patrick and the Irish (just for today, that's everyone on earth), I present you with Ten amazing facts about Guinness, everyone's favorite Irish beer. Well, my favorite Irish beer, anyway. Sláinte!