An Advanced Entry in Brewing Research

Rory McGowen

A couple of years ago I began some research that will more than likely be ongoing throughout most of my brewing career. The hope is that this research will eventually become the documentation for a larger research paper. The early results of this project were incorporated into one of the brewing classes that I teach - "Brew 204 - Understanding Your Yeast." I have incorporated some of the class notes from that class into this document as this is merely a continuation of the research for the overall project. In addition, much of this documentation is original research, and my conclusions are opinions and conjecture based on that research.

This research documentation almost requires the tasting of the results of the experimentation to fully understand the impact of its preliminary conclusions. So in addition to this research documentation, there should be a significant number of bottles arranged on the table as well. Each of these bottles is numbered and labeled and has a corresponding number on the maps (included) where the yeast is accepted as originating from. Please feel free to taste the various bottles as you progress through this documentation. The "beverages" within the bottles are fermented sugar water. No flavoring has been added. The only "flavors" that you should taste are those imparted by the yeast. And while they may not necessarily taste good, each will taste and smell somewhat different. Sugar water was used as the base in the experiment so that there would be little impact from the flavor of the solution to interfere with the desired result, demonstrating the differences in flavors of the yeasts.

Variances in recipes and styles of beverages from region to region was, in part, due to variances in Dominant Yeast Strains (DYS) suitable for creating those beverages. This is at least what I hope to prove overall. This documentation deals more with classifying and categorizing yeast strains and their region of origin. I also pose more questions for myself within the text of this documentation that will hopefully be addressed at a later time.

In modern brewing, I teach people to use a yeast that is tailored to a person's individual needs. In that decision, one should weigh in factors such as style of beverage, activity levels and fermentation speed, alcohol tolerance, ambient temperatures, degree of flocculation, attenuation, pH levels, and top fermenting v. bottom fermenting. In answering these questions, a modern brewer can exactly meet the needs of their projects.

However, medieval brewers could not do this. It wasn't until 1878 when Wilhelm Kuhne coined the word enzyme to describe the catalyst that he thought had to be in the yeast, being the first to correctly identify that yeast were directly responsible for fermentation. But Medieval brewers often contributed divine intervention to the process of fermentation. It wasn't until after 1100 CE that the lees (sediment) was "accepted" of containing a necessary component in fermentation. After this time, brewers would often keep the lees of particularly good batches of alcohol in clay pots to start other batches.

Spontaneous fermentation, the act of allowing a must to openly ferment, was made possible in many areas of the Old World because for hundreds of years, brewers had been returning their leftovers and their lees to the environment, until finally DYS prevailed in an area. Modernly, European countries can still practice spontaneous fermentation thanks to their ancestors. In America, we are still generations from any single area having a DYS which will produce consistent results.

As a side note, there are thousands of millions of types of yeast. Of those, only 250 will produce fermentation. And of those, only 24 will produce drinkable alcohol. Your odds of getting the right yeast in spontaneous fermentation are 24 in 250 or 10.4:1 in an area that does not have a DYS. Also in spontaneous fermentation you do not control which yeast inoculates your must; giving you completely random results.

However, while the modern American brewer might envy the European brewer for this ability, we must then take into consideration that the medieval brewer had to use whatever the DYS in their area was for all of their brewing. Meaning that they could not tailor their yeast to the needs of their brew. They had to tailor their brew to the needs of their yeast.

This could account for and explain why certain areas became known for specialty brews. Often these brews were named for the region or area they came from: Champagne, Burguny, Montpellier, Epernay, et cetera. It could explain why dark beers did really well in Germany, and Ales did well in England.

Again, extrapolating the regional differences in DYS, this could also account for variances in recipes from region to region. Medieval brewers may have been adding or substituting ingredients in an attempt to make up for the differences in DYS. As you will taste in the samples provided, each yeast adds a distinct flavor, aroma, and character to the sugar water solution. Perhaps it was these differences that Medieval brewers were trying to compensate for in their recipes.

Imagine if you will a brewer in the Champagne region of France trying to make a moderately alcoholic wine with plenty of residual sugar for sweetness. But the DYS in Champagne is what we now call Champagne Yeast, and would have been trying to turn the brewers efforts into a high alcohol dry wine. The brewer would have had to add enough sugars to compensate for the high alcohol (16-18%) and still leave some residual sweetness. While a brewer in England trying to make mead with a DYS more suited for ales, would have been hard pressed to get above about 12-14% alcohol; resulting in a recipe with a lot less required sugars. Supporting ingredients may have been added or removed to compensate for DYS flavors.

Some in the Current Middle Ages teach to match your yeast to your application. For instance, if you are wanting to make a Sweet Mead, with a moderate alcohol percentage (12%) you wouldn't want to use a champagne yeast that is going to ferment out to 16-18%, you might want to use a Pasteur Red or RC212 with a starting SG of 1.125. But it you are trying to make a dry mead with a high alcohol content you might use the champagne yeast with a starting SG of 1.125. See how the same SG is used for two totally different meads just by changing the yeast? By knowing what yeast you are using, you can tailor your beverage to the correct style and type you are wanting.

Perhaps the Medieval Brewers actually knew this without really knowing why it worked, and were doing the exact reverse of what we teach today. Instead of matching the yeast to the brew, they were trying to match the brew to the yeast. That would go a long way to explaining variances in recipes from region to region. It would also support my earlier statement as to explaining why certain regions simply chose to specialize in the type of brew that best fit their region.

Taking this into consideration, it is possible for the Current Middle Ages brewer to be more accurate in their competition brewing. As you will see by the maps provided, there are certain yeasts that are "identified" or "associated" with certain areas or regions. If a Current Middle Ages brewer wanted to enter competition, and wanted to closer approximate their region's or country's DYS, thereby upping their Authenticity score, they could base their choice of yeast on what was more than likely the DYS in their area. If however, that same Current Middle Ages brewer is trying to make a good drinking brew, I would highly recommend selecting a yeast appropriate to the task.

Now to the experiment, and the tasting. The experiment starts with 2 1/2 gallons of water. Heated on the stove to boiling. Stirring constantly to avoid scorching (thereby altering the flavor), enough sugar was added to raise the Specific Gravity to 1.130. The solution was removed from heat and transferred to a sanitized bottling bucket and ice added to reduce the temperature of the solution. This also brought the SG down to 1.105, or a Potential Alcohol of 14%. I figured that was a good medium for all the yeast varieties.

22oz beer bottles were washed, sanitized, and left upside down in advance of the experiment. One at a time, each bottle was then turned over, had the lip wiped with Grain Alcohol, and a packet of yeast added to it. In the case of the liquid yeasts, the package was not pre-started, but instead opened and had its yeast packet removed and added to a bottle just like the dry yeast. Each bottle was then filled with the sugar solution to just above half full, fitted with an airlock, and had the empty yeast packet taped to the bottle for identification. The bottles were then placed in a dark, temperature controlled room with a constant temperature of 74F. Several bottles suffered blowback, or the foam produced by the yeast escaping out the airlock. In such cases, a fresh airlock was prepared and the previous one replaced.

One month later, the bottles were opened. The contents carefully removed to leave as much lees behind as possible. SG reading were taken, and then each was bottled into the 12oz bottles that are on the table in front of you, and labeled with corresponding numbers placed on the map to denote the region the yeast represents.

The purpose of the experiment is not only to demonstrate the differences that the yeasts produce, but also to measure the PA each yeast provides, classify the influence it had on the solution, get an idea of why and how Medieval Brewers may have altered their recipes to account for the variations of yeast from region to region.

Each yeast does taste somewhat different, and the aromas are diverse. I have recorded these results and added them to the continued research for the overall project.

One result that I didn't expect was that many of the beer yeasts fermented out to higher alcohol percentages than I anticipated. Also, a couple of the yeasts appeared to be unfinished. I may add these yeasts back into the next phase of the research for continued study.

At this time, I am still within what I would call the middle of the experiment. Classifying and cataloging the yeasts and all their characteristics. This will eventually lead to evaluation of period recipes and classifying them by location and DYS within that region, and evaluating how the recipes may vary from region to region and evaluating similarities and differences in recipes of like beverages. This will then either support or negate the hypotheses that I have put forth in this part of the overall experiment.

It may also lead to a possible change within the Current Middle Ages of people choosing yeast based on where there personas may have been practicing their crafts, which may lead to more accurate representations of the beverages being reproduced.

While I will still continue to choose yeast appropriate to the beverage that I am making when I am making beverages just intended to be drinking beverages, if my hypotheses are eventually supported by my continued research, then beverages made for competitions will be made with a yeast variety that more closely matches the region that my persona would have been creating the beverage. Hopefully, if my hypotheses are upheld by my continued research, then this might become a new standard in reproducing beverages for competition, in general.

http://www.realbeer.com/spencer/Experiments/big-yeast.html

http://www.skotrat.com/brewrats/yeast.cfm

Leistad, R. (1996). Yeast Culturing for the Homebrewer. MI: G.W. Kent, Inc.

Kunath, B. (1998). Fearless Brewing. New Jersey: Chartwell Books.

Papazian, Charles. The New Complete Joy of Home Brewing. Avon Books, 1991.

Lutzen, Karl F., Stevens, Mark. Brew Ware : How to Find, Adapt, & Build Homebrewing Equipment. Storey Books, 1996.

Fix, George J. Principles of Brewing Science, Second Edition. Brewers Publications, 2000.

Yet Another Newbie Guide to Brewing. 21 Feb. 2001. Medieval Brewer's Home Page http://www.forgottensea.org/medievalbrewers/yang.html

Intermediate Guide to Brewing. 28 Feb. 2001. Medieval Brewer's Home Page http://www.forgottensea.org/medievalbrewers/igb.html

Brewing 204 - Understanding Your Yeast. 21 Feb. 2001. Medieval Brewer's Home Page http://www.forgottensea.org/medievalbrewers/brew204.html