If this is a naive question please forgive, but what is unique about the different strains of yeast that would allow them to create/impart different flavors? Is it something with the biological make-up of a particular strain or some other native charachteristic to yeast metabolism? As a follow-up can the yeast organism be sufficiently isolated to "breed" for particular flavor profiles?

-Steve B

RESPONSE:

This is a very complex subject that genetices and other researchers are only beginning to understand and believe me, I really have only a rudimentary understanding of what is going on inside the yeast cell. It is in the genetic make up of each strain. Each strain does almost the same thing as another strain (of the same specie). However over the eons of time each strain has had to express certain enzyme systems over others in order to cope with its particular environment: nutrient source, climate etc. With millenniums of time, these slight changes in the enzyme systems have become permanente fixtures in its genetic make up. These slight changes give you the rich variations in flavor by-products from strain to strain; the different abilities to handle the sugars especially maltotriose in the wort; the ability to function better at cool or warm environments; etc and etc. Many thousands of strains are in nature waiting to be discovered. It is up to interested parties (brewers, winemakers, bakers, researcher etc.) to go out looking for them. Pardon my clumsy way of explaining the various strains.

These various strains can be identified only by DNA fingerprinting. The different genus, species and strains can and are isolated and can and are being breed or mated. With out much success. First, there are so many different strains in nature with all the wonderful characteristics that we are looking for that screening nature seems simpler than breeding. Breeding or mating can be done but it is not always simple. Some yeast are made to sporulate. The spores of different strains or species with favorable fermentation characteristics are mated. The off spring sometimes carry the best of both strains but often time they also carry undesirable weakness of one of the strains; slow fermentation rates, H2S production etc. Often times they change after several generations.

The problems are the same with the fusion technique. The cell walls of two different genus are dissolved and the cytoplasm, nucleus and DNA of each are mingled. The resulting off spring can carry the best of each parent but more often carry bad luggage from one of the parents. They often do not remain stable after several to many generations.

Genetic engineering is the most promising approach to producing a designer yeast that will produce the ideal beer, but at this time our society will not accept this approach. Breeding is OK. GMO is not. Thanks for your good question. It was not easy to answer. Please ask more if my answer still leaves you puzzled or whets you appetite for more information.

Dr. Clayton Cone