Bottling A Better Beer With New Yeast Strains

Of all the fermented foods and drinks, none appears to be as ubiquitous as beer. This frothy beverage has been enjoyed for millennia and has become part of American lifestyle. When it comes to spending some time with buds, enjoying a high life, or refreshing the spirit, this choice continues to be a favorite.

The history of beer is somewhat cloudy in that its origins are relatively unknown. What is known is its formulation, which is relatively simple. All one needs is a source of starch, usually grains, water and of course yeast. The latter is the key to any good beer as it ferments the starch not only into alcohol but also a number of different chemicals giving both aroma and flavor. Many of these byproducts also carry some health benefits including several polyphenolics and antioxidants.

Traditionally, beer has been made using one particular type of yeast, Saccharomyces cerevisiae, yet other species are also known to be involved in the brewing process. One beer type, lager, uses S. pastorianus, which itself is a hybrid of cerevisiae and another species, S. eubayanus. When placed into the brewing mixture, known as the wort, what comes out is a traditional straw-yellow concoction with a pleasant flavor and moderate alcohol concentration.

By changing the source of nutrients and also the addition of a number of other ingredients, such as hops, this basic formulation can lead to a myriad of different options. For this reason, lager is the most popular beer style with hundreds of different brands, each containing specific organoleptic properties. Modifying the wort is one way to do it yet thanks to a recent study, there may be another in which the alteration is based on the fermenter itself.

Last month, a Finnish group reported on their efforts to improve beer by altering the nature of the yeast. They attempted to determine if developing hybrids much like S. pastorianus could eventually lead to better taste and aroma. What they found revealed how we may be able to naturally develop a greater diversity in the future and also how possibly to save time and money for the brewers themselves.

The team decided to focus on the two species, S. cerevisiae and S. eubayanus. Instead of using complex molecular biological techniques, they chose instead to do things the old fashioned way by forcing the two to interact. The process takes advantage of auxotrophy, in which an organism cannot produce a molecule necessary for survival. Without external addition of the nutrient, the cell dies. In this case, the team used a strain of S. eubayanus unable to make the amino acid lysine and a strain of S. cerevisiae unable to produce a component of RNA, uracil.

When it was time to make the hybrids, the group simply took both strains and put them into a basic medium without supplementation of either lysine or uracil. Then, they waited for 3 to 7 days. Sure enough, colonies began to appear, meaning they had hybrids capable of making both molecules. Using a combination of genetic identification techniques, the establishment of these new strains containing pieces of both parental yeasts was confirmed.

Once the hybrids were developed, the real fun could begin. Using traditional brewing methods, the new strains were given the opportunity to prove themselves in the wort. The results were fascinating. First, the hybrids were stable at both warm and cool temperatures such that they could survive in environments the parents could not stand. They also reduced the time for fermentation not by hours but days. Finally, and perhaps more interestingly, they produced more alcohol than their parents. By the end of the fermentation process, the concentration was between one and two percent higher.

But faster fermentation and higher alcohol can only go so far. The next hurdle dealt with the taste and aroma. Although tasting might have been a good means to find out, the researchers decided to use more accurate methodologies to determine the chemical composition of their new beers. Specifically, they used Gas Chromatography and Flame Ionization Detection (GC-FID) for the flavor compounds.

They focused on several different flavor-based chemicals. Some were pleasant such as 3-methylbutyl acetate, which has a banana/pear aroma and ethyl esters, which offer fruity sensations. Others were less than enjoyable such as the methyl alcohols which offer a solvent-like emanation and taste. When the analyses were complete, the hybrids once again proved their worthiness. The levels of fruitiness were as high if not higher than the parents while the levels of the methyl alcohols were lower. The beers were not only better in chemistry but would also make for excellent quaffs.

There was one more benefit to these yeasts although this had less to do with the chemistry and more to do with public perception. Because the formation of these new strains was done through an entirely natural process, it would be considered non-genetically-modified. This meant these strains could be used in regular manufacture without any concern from regulatory or other oversight.

The success of the experiments opens a new door to a wider diversity of beers in the future. Though the new varieties made in the lab may not find their way onto shelves anytime soon, they represent the beginning of a potential industrial renaissance. By focusing on natural hybrids to improve beer flavor, alcohol content and even fermentation time, the overall brewing culture has the opportunity to improve. As for drinkers, the chance to enjoy even more flavorful options may soon be a reality.