The Great Riesling Yeast Experiment (Part II)

The saga continues with the racking of my experimental Riesling fermented with two different yeast strains. Read this if you missed part one.

Up to this point the two batches of Riesling have been fermenting separately.  One in a primary fermentation bucket and the other in a six gallon carboy. Little could be observed of the two wines.

However, I recently got a chance to see, smell, and taste the two Riesling batches when I racked them into their respective carboys. Here’s what I found.

Opening the Primary Fermenters

After seven days in their primary fermentation containers it was time to check chemistry and rack off of the lees.

I opened up the lid to the plastic fermenter with the R-HST Riesling in it and was greeted by an interesting aroma. Not only was it a different aroma than the W15 Riesling, it smelled odd. I’m not entirely sure what it was but it had a tinge of sulfur to it. My wife really disliked the aromas wafting her way as she helped me prepare to rack.

The W15 had been bold and fruity up to this point and didn’t disappoint when I removed the airlock. This wine smelled very fruity. I was expecting the same when I taste tested it.

Testing the Wines

With the lids removed I drew a sample of each wine to test its chemistry. The first thing I checked was the specific gravity. The R-HST weighed in at 1.008. This means there is still a bit more sugar yet to be fermented.

The W15 Riesling was at an even 1.000. So in the same period of time the W15 yeast had burned through a bit more sugar than the RHST.

This was particularly surprising because both wines came from the same kit and were inoculated at the same time (within about one minute of each other). I expected some differences in behavior between the two but this was a much larger difference then what I was anticipating.

The W15 did seem to ferment more vigorously. The airlock looked like it was boiling at its peak. The difference in airlock activity was a solid indication that the W15 yeast was fermenting more quickly.

Not only was the specific gravity different, the titratable acidity (TA) different as well. The pH, however, remained the same between the two.

Sampling the Wines

Any time I take a sample for testing I also taste it. This is why I love making wine. But before I tasted it I took a good look at the two wines.

They both had similar yellow colors and were quite cloudy. The W15 Riesling was more cloudy than the RHST Riesling.

I tasted the W15 Riesling first and what a surprise! Despite the bold grape smell it had strong grapefruit flavors. My wife picked out lemon and lime. Both of us agreed that it had an intense citrus flavor. Not much grape flavor at all.

Then I moved on to the R-HST. This wine was noticeably sweeter, as evidenced by the higher specific gravity. I could taste a faint hint of pear as well as white or unripe peach. Despite the odd aroma this wine tasted far better than the other. I’m really excited to see how this one develops.

The marked difference between the two wines is quite surprising at this stage of the wine making process. My research indicated that differences in wine due to different yeast strains took six months or more to manifest. However, here I am with one week old wines that have vastly different aroma and flavor profiles.

Racking the Wines

Each Riesling was racked from their primary fermenter to three gallon carboys for secondary fermentation. Upon completing the racking process I was afforded my first side by side visual comparison of the wines. The samples I took looked nearly identical because they were so small, however, seeing three gallons of each in a glass carboy revealed a startling difference.

The W15 Riesling was very cloudy and had a pale milky yellow color. On the other hand the R-HST Riesling was a deeper yellow or almost orange color and nearly transparent.

From here the wines will continue to ferment separately. They will be treated exactly the same up to the bottling stage, at which time I’ll blend the two together in varying proportions as I mentioned here.

Lessons Learned

1. The effects of yeast on a wine can be immediately obvious. Perhaps this is a result of my choice of yeast. I purposefully chose two strains that were very different from one another for this experiment.

2. Different yeast strains ferment at different rates. Upon seeing, smelling, and tasting the difference between the two this doesn’t come as a huge shock but it was also a point I’d never come across in my research.

3. Chemical changes in the wine are not consistent from one yeast to another even when starting with the same raw materials. My two Riesling batches had different pH and TA even after only a week of fermentation.

4. You shouldn’t rely on the volume markings on the side of the primary fermenter. I found out when I racked that the 3 gallon mark on my primary fermenter is not actually three gallons.

Have you found this experiment interesting thus far? If so, please let me know in the comments!

Read Part III now!