The Great Riesling Yeast Experiment bottled and ready to consume.The Great Riesling Yeast Experiment has drawn to a close. The two different Rieslings produced during the experiment have now been finished, blended, and bottled. If you missed the first two parts here is Part I and Part II. Otherwise here’s a brief summary of the experiment.

Starting with a single six gallon World Vineyard Riesling Kit from Winexpert I split it into two three gallon batches. Each batch was then fermented with a different strain of yeast.

The purpose of the experiment was two fold:

1. determine if different yeast strains could produce different flavor and aroma profiles.

2. see if I could create a more complex wine by blending wines made from the same grapes that had been fermented with different yeast strains.

Parts I and II cover making the wine. In this part I’ll share how the wine was finished, blended, and bottled.


Degassing turned into quite a project. I ended up degassing on two separate occasions because of how long it was taking.

Up until the first degassing the wine had been stored at around 66 degrees (F). When wine is stored below 72-75 degrees (F) the degassing process can take much longer because the cooler temperatures help carbon dioxide stay suspended in the liquid. This was evidenced by the 20+ minutes of degassing during this first round that didn’t get all of the carbon dioxide out.

After my first attempt I moved both wines where I could store them in the low 70’s. They sat for one week before I started round two of the degassing process.

The increased storage temperature made all the difference in the world! I was able to fully degas both wines in about 30 minutes.

Clarifying The Wines

The problem with degassing in two stages was that the second degassing stirred up everything that had cleared up to that point. I added the isinglass clarifier at the time of the first degassing per the kit instructions. However, when I degassed the second time the wines were just as cloudy as they were prior to the first degassing.

The RHST Riesling cleared completely within a week of the second degassing without any additional clarifier. This wine was never really that cloudy to begin with.

The W15 Riesling was another story. This wine had always been really cloudy. The isinglass didn’t do much to begin with but the second degassing undid any progress it had made to date.

To clear the W15 I had to add a bentonite slurry. It took two more weeks but it did finally clear. Just in time for my parents to give me a hand  blending and bottling.

All in all both Rieslings sat for four weeks during degassing and clearing. This was much longer than I would have liked, however, it was necessary to keep from bottling sediment and floating isinglass. No off flavors were picked up from sitting on the lees though. That was a relief.

Blending and Bottling

The last step was to get these two wines blended together and into the bottles. Keeping in mind the purpose of the experiment I decided on the following blending scheme:

  • 100% W15 Riesling
  • 75% W15 / 25% RHST
  • 50% W15 / 50% RHST
  • 25% W15 / 75% RHST
  • 100% RHST Riesling

Not all of the wine could be blended or bottled this way due to complications that arose during the bottling process. Namely the autosiphon stirred up the lees and the last gallon or so got cloudy all over again. However, most of the wine produced was blended and bottled according to this scheme.

To blend these different percentages accurately I used two one gallon glass jugs in which the two wines were blended four bottles at a time.

This jug was used to blend four bottles of wine at a time. The lines represent the 50% and 100% fill lines.

The 50/50 blending jug. (Filled with extra W15 Riesling)

I filled the jug pictured here with two wine bottles worth of water (1500ml) and marked a line on the glass with a permanent marker. I then added another two bottles of water and marked that line. This is where I blended the 50/50 Riesling. (The jug currently is housing some additional W15 left over after blending)

For the other blends I filled the second jug with three wine bottles worth of water (2250ml) and marked a line. Then I added a fourth bottle of water and marked that.

All the water was poured out and all the jugs, bottles, and equipment were meticulously sanitized.

The first four bottles my parents and I blended were the 50/50 blend. We racked one wine to the 50% line and then the other wine up to the 100% line. After a good stir we filled the first four bottles.

Then we moved on to the 75% W15 / 25% RHST. We siphoned W15 up to the 75% line in the second jug and filled the remaining 25% with RSHT. Again, we gave it a good stir and bottled that blend.

We continued through all three blends and bottled some of each wine by themselves.

As I mentioned before the lees did get stirred up in the W15 so I wound up with more unblended wine than I would have like. The cloudy W15 was siphoned into a sanitized one gallon jug and left to clear…yet again.


I did find that the two yeast strains produced not only different flavor and aroma profiles, but they also behaved quite differently with the same clarifier.

I was really surprised to see just how different these two wines really were. My expectation was that only a trained and discerning palate would have been able to tell the difference. However, the samples I tasted all along the way proved that the yeast accounts for vast differences in flavor, aroma, color, and clarity.

Even the chemistry between the two differed. However, the pH and TA did come back into alignment as the wines reached their fully fermented state.

There is one last thing to do with the five Rieslings I’ve created. Host a blind tasting!

That’s right, I will be hosting the first ever Winemaker’s Academy Wine Tasting. With the help of a few friends we’ll taste all five wines next to each other to see which one the group likes best but also whether or not they too can pick up on the differences in flavor and aroma.

  • RCGoodin

    So, how did the tasting go? Would you recommend one yeast over the other?

    • Hi RCGoodin, great question! The tasting was a lot of fun. My wife and I had some friends over and we went through all five wines blind. I wrote quite a bit about it in this article entitled The First Winemaker’s Academy Wine Tasting.

      In the end it turned out that I was the only one who really liked the RHST Riesling. To me the peach overtones were much nicer than the citrus / grapefruit flavors the W15 created. However, I will say that I was the only one out of the four of us that preferred the RHST.

      In the end it comes down to personal taste. Both yeasts produced great wines its just that my palate favored the RHST.

      Are you thinking of doing a split fermentation?

  • Pauline Whalley

    Hi Matt, read your article with interest. Have you tried doing this with a red wine kit? My colleagues at work and I are relatively new to wine making and have been making wine from a variety of kits, but I find that the whites seem more successful in taste than the reds, the reds seem to lack body and mouthfeel, although I am hoping a period of ageing will improve this.

    • Hi Pauline! I hope you found the article series helpful.

      To date I have not tried this with a red wine kit. I too have had less luck with the reds as I have with the white wine kits. That being said I haven’t tried the high end red kits that include the grape skins. I think this could do a lot for a red wine kit. Have you tried one of these yet?


  • Pauline Whalley

    Hi Matt,
    Haven’t tried a high end kit as yet, but it’s on my to do list. However I am considering ageing in an oak barrel to see what effect this would have. I have some reds ageing in bottles, watch this space! What are thoughts on oak ageing?

    • Oak aging can do amazing things for your wine! Oak is often referred to as “the winemaker’s spice cabinet”. You can add so much more depth and character to a wine this way.

      I would suggest trying your hand with oak adjuncts to get you started. Barrels tend to be quite large, quite expensive, and require a bit of work to maintain. Oak adjuncts allow you to experiment with different toasts levels and different origins (French, American, Hungarian, etc) much more easily and at a fraction of the cost. A bag of cubes might run you $10 and will treat a carboy or two. Once you purchase a barrel though you’re sort of stuck with whatever toast and origin of oak you bought.

      Here’s an article that you may find helpful Oak Products Explained. In the second paragraph is a link to another article that may also be useful.

      Cheers Pauline!

  • Adan

    Hi Matt. I’m looking into doing a split fermentation like this from a wine kit soon! When you added the clarifying agent after the degassing, I was wondering whether you split the packet equally between the 2 carboys, or if you purchased an additional additive? I’m assuming I’d just split up the contents of the clarifying pack, but not too sure…

    • Hi Adan, when I use the first clarifier I just used a measuring cup to add half to each batch. It wasn’t too scientific.

      When I clarified that wine though I learned a valuable lesson: make sure your wine is completely degassed before adding the clarifier. This is not what the kit directions say to do, they want you to do both at the same time.

      It took me two attempts to degas the wines and when I made my second attempt I stirred up everything that the clarifier had already settled out. It didn’t clear on its own after that so I had to add another clarifier to knock out the haze.

      So why are you doing a split fermentation? Testing yeast or something else?

      Cheers! -Matt

      • Adan

        Thanks for the tip Matt! I’m sure the advise will help a lot when I make this wine next week.

        I just want to experiment with the different effects and aroma-flavor profiles of the yeast on the wine. I’m planning on doing a blending at the end too, like you had set up, to see what the best combination of the two is. I’m trying to get the most out of that kit investment!