Thursday, October 09, 2014

Yeast Trials

How do different varieties of yeast affect the flavor of a fermented beverage?

For some time now, Brian has been wanting to work out the answer to this challenging question. He's had a long running debate with his father about the impact of yeast and its contributions to the end product. Carl has made all of his mead with a single strain of yeast and the mutations it has spawned over the last fifteen years and Brian has been interested to know if perhaps other yeasts in combination with certain varietal honeys might yield an even better outcome. So, to explore in more detail which flavors come directly from the yeast and which flavors might result from other factors, he has developed a yeast trial to gather information that can only be gleaned by tasting lots of different samples. 

Below are the yeasts that Brian selected for his trials. They include ale, lager, saison, hefeweizen, white wine and red wine, and yeasts specifically marketed as mead yeasts, in both dry and liquid form. The twenty three yeasts include a range of alcohol tolerances and flavor profiles and he decided to try each of them with four different varietal honeys and one cider to compare flavor profiles.

All of the yeasts have different pitching instructions and we carefully followed the instructions provided by the yeast suppliers. Some required rehydration at 40C (104F) and with a scientist in the house we were fortunate to have access to some pretty useful equipment like the machine below. Carl used this shaking incubator to evaluate permeability of fluids through candidate elastomers tested in the development of artificial hearts. Conveniently, it also came in handy for keeping the yeasts happy at a constant 40C.

Disposable pipettes were used to add reproducible amounts of yeast to each bottle and will later be used to take samples for testing with a refractometer without contamination from other yeasts.

Here are some of the leftover rehydrated yeasts.

We color coded the honey/cider variety with balloons and then labeled each bottle with the starting amount of sugar and the kind of yeast used in it.

Some yeasts started to work almost immediately; most started within twelve hours and one took more than a day. Below you can see the balloon start to inflate in one of the early starters. Brian pricked a hole in each balloon once they started to ferment so that they would release the CO2 but still prevent contamination from foreign substances.

Even though Brian started preparing the materials for the trial early in the day, it took us most of the night to prepare all of the bottles and mix in the honey and yeasts. In the morning the boys were very interested in the colored balloons coming alive on the kitchen table.

Below, all have started fermenting.

Once the fermentation process has ended and the balloons deflate we'll work out a systematic way to taste and evaluate the samples.  Won't that be fun!

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