Choosing The Right Wine Making Yeast

Choosing The Right Wine Making Yeast

There are many factors that go into choosing a wine making yeast. This is the second most important decision you’ll have to make next to picking the grape varietal to make your wine from. Choosing the right yeast is important for two reasons. First, different yeasts produce different flavor and aroma profiles to finished wines. This has to do with how the yeast processes the must when it’s digesting the sugars and nutrients. The second reason your choice of yeast is so important is that not all strains have the same alcohol tolerance. Many wild yeasts have tolerances of only five to six percent alcohol. Other strains specifically cultivated for wine making may have alcohol tolerances upwards of 18% or more. While this topic has been covered here before we’re going to dive into the specifics of how to do it right. So let’s get to it! Choosing a Wine Making Yeast Step One: Pick Your Flavor Profile The first step in choosing a wine making yeast is to figure out what flavor profile you’d like to have. The stellar folks over at More Winemaking provide a great free resource called the Yeast and Grape Pairing Guide. This guide breaks down what yeast strains give what flavor and aroma profiles for different grape varietals. Open up the guide and look for the varietal of wine you’re looking to make. For each varietal they list the most common yeasts used along with the different flavors and aromas that can be expected from using them. You’ll notice that some yeasts are not meant to be used on their own. They’ll say something like “good for adding _____ to a blend”. This may be because that particular strain does not offer very much flavor but really packs in the aromas. These yeasts are best paired with another strain in either a mixed fermentation or a split fermentation. Here’s a quick look at the difference between the two. A mixed fermentation is where you pitch more than one yeast strain at the same time in the same must. A split fermentation is where you ferment the same varietal grape must with different yeast strains in different fermenters keeping them separate until they’re finished. After fermentation you blend them back together. Step Two: Verify the Yeast Alcohol Tolerance Once you’ve got a handle on the flavor and aroma profiles it’s time to make sure that your yeast of choice is strong enough to completely ferment your wine. If the yeast you choose is not strong enough to finish fermenting your wine there’s a good chance it will be sweeter than you prefer. To check the alcohol tolerance of your yeast strain head over to Lallemand and check out the Lallemand Yeast Charts. In addition to alcohol tolerances they provide other important information such as nitrogen demand, how competitive the yeast is, and a few others. Be sure to book mark that table as you’ll want to refer to it at the start of any fermentation. I use it all the time to plan my wine making efforts. Step Three: Estimate the Final Alcohol Content...

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The Great Riesling Yeast Experiment (Part II)

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 save for the airlock activity. However, I recently got a chance to see, smell, and taste the two Rieslings 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 it’s 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...

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The Great Riesling Yeast Experiment (Part I)

The Great Riesling Yeast Experiment (Part I)

Yeast can have a profound affect on the final flavor and aroma profiles of a wine or so we’re told. But how much of a difference is there really from one yeast to another? To answer this question I set up the Great Riesling Yeast Experiment. In this experiment I set out to ferment one Riesling kit in two three gallon batches with two different yeast strains. To find out how I picked out my yeast strains read this. This experiment, I hope, will answer the following more specific question. How much does a yeast affect the final taste and aroma of a wine? Can you make a more complex wine by fermenting the same grapes with two different yeasts and blending them back together? Is it possible to make good wine from a kit while not following the directions? Background Yeast, as you know, is the star of the fermentation show. It is responsible for the creation of alcohol in wine, mead, and many other grown up beverages. For a long time many winemakers did not believe that the yeast used to ferment grapes mattered much when it came to the final character of the wine. They believed that as long as the grape juice was fully fermented it all tasted the same. It wasn’t until fairly recently that wine researchers started to study the effects different yeast strains can have. What they found was that it can make quite a big difference, however, they did say that it takes six months or so for that difference to show up. Today, many winemakers do split fermentations for this reason. They ferment the same grapes with more than one strain of yeast in separate containers. Then they blend these wines back together to create complexities that neither yeast on their own could create. The Yeast Experiment To answer the three questions posed above I set up the following experiment. I purchased a Winexpert World Vineyard Riesling (affiliate link) which makes six gallons of wine. To ferment this kit I selected RHST and W15 yeast strains based on their different aroma and flavor profiles (also affiliate links). These two 3 gallon batches will be fermented and aged separately for a period of a few months. Once they’ve been made into complete and independent wines I will blend them back together in varying proportions. Some bottles will contain 50% of each. Others will be blended at 25% one and 75% of the other. Lastly, I’ll bottle a couple bottles of each independently. Now that we’ve covered the parameters of the experiment let’s talk about how it’s all going down. Currently I’ve got my wines in their secondary fermentation carboys, however, I’m going to cover the first steps in the experiment here. Step 1: Inoculation To get this experiment going I hydrated the grape juice concentrate in a six gallon fermenter per the instructions with the bentonite. Once the wine was properly mixed I started the yeast re-hydration process. The kit instructions clearly state not to do this, however, as I’m not using the yeast that came in the kit I felt I needed to...

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How to Re-Hydrate Yeast

How to Re-Hydrate Yeast

Yeast, a winemaker’s best friend, and star of the show when it comes to fermenting grapes into wine. They make it all possible. With a properly hydrated yeast your fermentation will start strong and be less likely to get stuck. Which is why it’s critical to understand how to re-hydrate yeast. What is dry yeast? Dry yeast is made up of small granules that consists of live, active yeast cells enclosed in a hard shell of dead yeast and a growth medium. In order for the live yeast cells to break free and ferment your must the shell must first be broken down. This is where hydration comes in. Whether you re-hydrate yeast yourself or allow nature to take it’s course in the must what you’re doing is breaking down that outer shell. If yeast is not properly re-hydrated the individual organisms can’t function properly. Their cell walls will not be fully permeable and they won’t be able to take in sugars and release carbon dioxide and alcohol. How does yeast re-hydrate if we don’t do it? In most wine kits re-hydrating the yeast is not only not necessary, the directions clearly state “do not re-hydrate the yeast”. You just add it straight to the grape juice concentrate and water mixture. By doing this we’re trusting that the dried yeast will hydrate well enough on its own. Kit makers choose the yeast strains based on many factors but one of the key factors is its ability to hydrate on its own in the must. If you read yeast hydration instructions, however, you’ll notice that the optimal water temperature for hydration is 104-109 degrees (F). Kits instructions call for innoculation temperatures of 72-75 degrees (F). These are less than optimal conditions for the hydration of yeast which is why kits only come with certain strains. How Re-Hydrating Yeast Affects Fermentation Hydrating your yeast at 104-109 degrees (F) helps break down that crusty outer layer and allows the live cells within to break free and begin multiplying. In just a few minutes your yeast population is already starting to explode. Contrast this with pitching dry yeast in a cool must. Without that heat it takes longer to break down the outer shell. This is why you only see evidence of fermentation two days or so into the wine making process. If you re-hydrate the yeast that comes with a wine kit you’ll likely see evidence of fermentation within a few hours. The rapid population growth speeds up fermentation because there are more of the little guys sooner. Another benefit of such a rapid population growth is that the yeast can dominate the environment much more easily. Keeping undesirable strains or other bacteria from getting established in your must. How to Re-Hydrate Yeast This process can vary slightly depending on the brand of yeast and the strain. However, here is the general process I’ve followed for quite a few re-hydrations. Heat 2 cups or so of water to 104-109 degrees (F). Pour 50 ml of the heated water into a dry sanitized container. Add the dry yeast to the water and stir for thirty seconds. This breaks up any clumps so...

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The Epic Rise and Tragic Fall of a Yeast Empire

The Epic Rise and Tragic Fall of a Yeast Empire

The unfermented must is a vast and plentiful breeding ground for yeast. Food in the form of dissolved oxygen and sugar abounds. For the right strain of yeast this is the perfect place to establish a thriving empire. The winemaker sets the yeast in motion. She hydrates the yeast, preparing them to conquer this new found domain. Once the yeast is awakened they are transplanted to this new land. The Lag Phase The first order of business is for the newcomers to get the lay of the land. The yeast acclimates to its new surroundings and environment. This is called the lag phase because there is not a lot of visible activity. The only evidence that anything is going on is an occasional bubble rising to the surface. After one to two days, however, our invaders have adapted to their new land and it is time to conquer it! The Rapid Growth Phase The yeast is population is still small but because there is plenty of food they begin to multiply at a feverish pace. The population explodes at a logarithmic pace during this phase. Evidence of their activity can now be seen in the form of vigorous bubbling. They’re now producing carbon dioxide at a staggering rate as a result of consuming their primary food source dissolved oxygen. Eventually the population reaches a peak. They’ve been producing carbon-dioxide is in such a huge quantity that it begins to saturate their new dominion. At the same time with the airlock in place on the fermentation tank there is no longer a source of oxygen to replenish what has been consumed. Something must give! As the population reaches a point where there is no longer enough dissolved oxygen to support new yeast they cease to multiply save to replace fallen yeast on the front line. However, with the booming population they’ve created the yeast eventually runs completely out of food. This marks the end of the rapid growth phase. The Stationary Phase Now that the yeast has asserted its dominance over the known lands inside the fermentation tank, the population is maxed out, and the food has run out the yeast must change tactics. Yeast, as it turns out, is a well adapted invader that can do what few other micro-organisms can. They switch to a different food source! At this point they shift from consuming dissolved oxygen to consuming sugar. Yeast can live in both aerobic environments (with oxygen) and anaerobic environments (without oxygen). Other micro-organisms simply perish once their food source has run out. While there is plenty of dissolved oxygen the yeast produce mostly carbon dioxide. However, when yeast switches to consuming sugar they not only produce carbon dioxide but alcohol as well! The Decline Phase While the yeast is still going strong it is starting to decline for two reasons. On the one hand food is becoming scarce but at the same time their waste product, alcohol, is starting to accumulate to levels too high for them to withstand. Whether the lack of food or the concentration of alcohol kills of the yeast depends upon the strain of yeast used to ferment the wine. More resilient strains can...

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