The Importance of Yeast Starters

The Importance of Yeast Starters

Pitching yeast into a wine must can be very stressful for these micro-organisms upon which we rely for the production of alcohol. Exposing yeast to changes in temperature, sugar levels, as well as sulfite and nutrient levels causes them stress. If the stress is too much to bear they may go into shock or die off. Creating a yeast starter is the best way to reduce shock and ensure a healthy population is introduced to your wine. Our job as a winemaker is to make this transition as easy on the yeast as possible so that fermentation gets underway with a healthy and active yeast population. This article assumes you are pitching your own wine yeast and not relying upon wild yeast to make your wine. In the yeast life cycle, the first phase is concerned with growing the yeast population. Once they reach critical mass alcoholic fermentation gets underway and our must is made into wine. The stronger the initial population introduced to our must, the quicker this first phase will go. An active and healthy yeast population is also better able to keep unwanted spoilage micro-organisms at bay. When competing for the same resources (i.e. sugar) wine yeast are quite aggressive. Dry active yeast is the most common form available to winemakers. Just like baking yeast, it is a powder which contains little granules of live yeast. The outside of the granule is a crust of dead yeast cells and food which protects and feeds the living yeast cells inside this crust. Obviously they’re not thriving in those granules as they are provided with only enough food to sustain them in a dormant state. Tossing dry yeast into a wet environment full of sugar and nutrients and likely at a differenent temperature is an abrupt change in environment. It can take a day or two for the yeast to adjust before the growth phase really starts to take off if pitched this way. There are better ways to introduce a yeast to a must and we’ll talk about two of them here. The first method is to simply hydrate the yeast so they are out of their crust and available to start consuming sugar. The second method involves creating a yeast starter. It begins with hydration but takes things much further by growing the population in a starter before adding it to the must. These soft transitions that allow the yeast to acclimate without dying and hit the must fully active and ready to rule the fermentation of your must. Hydrating Wine Yeast As the name implies, hydrating is merely getting the yeast out of the crusty granule and loose in water. It involves heating water to a specific temperature and dissolving the yeast in it. This wakes them up and gets them ready to start eating. Once they are awake again and free to roam they will need food (sugar) within a very few minutes to survive. Ideally a hydrated yeast is moved to a must within 5-10 minutes and with a temperature differential between the yeast and the must of less than 10F (5C). The...

Read More

Controlling Wine Fermentation Speeds

Controlling Wine Fermentation Speeds

The speed of a fermentation is a function of many different variables. Once you understand these variables you can manipulate them to slow down or speed up a fermentation. Most wine makers agree that a slow fermentation is better. The thinking goes that the wine will hold on to more of the varietal characteristics as well as any delicate flavors and aromas created during fermentation. More aggressive fermentations tend to blow all varietal character out the airlock, so to speak. Despite the stated benefits of a slow fermentation, there may be times when you need to speed things up. For instance, if your fermentation has been slowing down and you’re affraid it may become stuck, this would be a good time to get things moving again. Another possibility is some constraint on the winemaker’s time such as a trip or something. With all of this in mind let’s explore the major factors that affect how fast wine ferments. Fermentation Temperature This is a pretty obvious driver of fermentation activity. As you know heat is a catalyst and when applied to a fermentation the yeast will ferment must more quickly. Cool the wine down and the rate of fermentation will also slow down. There are, of course, limits to how far you can go both on the warmer and cooler sides of the spectrum. Temperature is something we’ve often discussed here at Winemaker’s Academy. Here are a couple related articles: The Effects of Fermentation Temperature on Wine How to Control Your Wine Fermentation Temperature – WMA009 Raising fermentation temperatures is decidedly easier than lowering it. Kurt recently shared a great method for controling fermentation temperatures you should probably check out. To cool a wine you either need an ice bath or some sort of chiller (check out the podcast above for more information). Your best bet is to ferment your wine in a cool room (60-65 F / 15-18 C) and use a heating system as needed. Nutrient Levels Yeast nutrients is an additive which provides nitrogen and ammonium phosphate. These help the yeast stay healthy and active. Much like you and I do better when we’re getting all the right vitamins and minerals so too does yeast do better with nitrogen and ammonium phosphate. Nutrients are required for the yeast to do their job but they don’t make for a good catalyst for speeding up or slowing down a fermentation. I recommend using the amount specified in your wine making recipe, or if you’re not following a recipe 1 teaspoon of yeast nutrients (affiliate link) per gallon of must is what LD Carlson suggests. According to professional winemaker John Garlich, yeast nutrients are like candy to yeast. They focus on eating that while it’s in abundance because it’s easier to process than sugar. However, when it runs out they can have trouble switching gears into consuming sugar. Listen to this interview with John for more information Wine Making Chemistry with Bookcliff Vineyards – WMA015. I don’t recommend adding extra nutrients to speed up a fermentation nor should you reduce the nutrients to slow things down. I recommend adding an appropriate...

Read More

Help My Wine Smells Like Bananas

Help My Wine Smells Like Bananas

There is an incredible amount of aromas one can detect in a wine. Some are fruity some aren’t. As you can well imagine some smells are okay and other signify that something has gone awry. Recently Emmett, a Winemaker’s Academy member, wrote in with the following problem: During degassing of my kit, I noticed my wine smelt like bananas. Its a Cabernet Sauvignon so needless to say, banana isn’t in that wines sent profile. Any ideas on where this may be coming from? I know that wines like Beaujolais Nouveau will sometimes have Banana like aromas, but I’ve never heard of it connected with a Caberney Sauvignon. Causes of Banana Odors in Wine It is certainly possible to pick up banana flavors from the fermentation process. As Emmet points out, Beaujolais is known to have banana aroma and flavors as a result of carbonic maceration. Other wines may also exhibit these aromas if they contain Isomyl Acetate or Ethyl Octanoate, both of which are naturally occuring biproducts of the fermentation process (read more here). As long as these chemicals are in small enough concentrations the wines will be fine to drink and the banana may even add a bit of a pleasing twist to the flavor profile. In higher concentrations, however, these wines may be undrinkable. There are two main causes of banana odors in wine outside of what can occur naturally. The first cause is cool fermentation temperatures and the second is spoilage. Let’s look at each in a little more depth. Cool Fermentation Temperatures According to Master of Wine Debra Meilburg, “Banana-like aromas appear in wine when grapes are fermented at excessively cool temperatures.” (read the entire article here) So if your fermentation dipped below the recommended temperature range for your yeast, banana aromas may ensue. As you know, when yeast digest the sugars and nutrients in a wine must they alter them. Chemical compounds in grapes called stereoisomers are taken in by the yeast where they are subjected to enzymes used to digest sugars. This interaction changes the stereoisomers and makes them take on flavor and aroma characteristics of other fruits. When yeast is under stress, such as when temperatures get too hot or cold, the yeast will produce off flavors. Just like you and I can’t do our best work if we’re not comfortable, yeast will struggle with an extreme environment. Banana odors are one example of an odor that can be produced by stressed yeast. Spoilage The other possibility is that your wine is contaminated with a spoilage micro-organism. When acetobacter contaminates a wine it converts the alcohol into acetic acid (vinegar). In the presence of 1-pentatol (a rather unpleasant form of alcohol) the acetic acid will mix with it and produce amyl acetate which smells like artificial banana flavoring. Unfortunately for our friend Emmet, this was the case. What started out as a mild banana odor gradually gave way to vinegar odors. Somehow his wine was exposed to acetobacter and, perhaps due to stress on the yeast, 1-pentanol was likely present. The two combined to give the banana odors. Over time, however, the acetobacter converted...

Read More

Wine Making Chemistry with Bookcliff Vineyards – WMA015

Wine Making Chemistry with Bookcliff Vineyards – WMA015

http://traffic.libsyn.com/winemakersacademy/wma015.mp3Podcast: Play in new window | DownloadSubscribe: iTunes | Android | RSS Wine Making Chemistry with BookCliff Vineyards Wine chemistry is a complex subject. There are so many things to measure, balance, and think about that it’s hard to know when to do what and decide what’s really important. To help us navigate this complex subject Holly Wells and John Garlich of BookCliff Vineyards have come on the show to walk us though the entire wine making process… from a chemistry perspective. We start with the grapes on the vine and discuss when to harvest and how to tell if the time is right. From there we cover each and every step along the way up to bottling your wine. Even if you are primarily a kit winemaker you’ll learn a lot from this interview. John was a home winemaker before he started BookCliff Vineyards and he shares a lot of tips that will help winemakers of any scale. To learn more about BookCliff Vineyards please visit: http://bookcliffvineyards.com/ Also, the BookCliff Vineyards’ Facebook page can be found here and here is a link to their Twitter profile.   Resources & Products Mentioned Refractometer pH meter* analytical scale (measures 1/100th of a gram, if you can find it John recommends 1/1000th of a gram accuracy) Holly’s resources available through the Core Enology Group Resource Page   *Digital pH meters require several calibration reagents as well as storage and cleaning solutions. Be sure to read the section on recommended additional products for more...

Read More

Oak Products Explained

Oak Products Explained

Oak has long been used to add flavor and complexity to wine. In addition to barrels there are a number of oak products on the market you can use to make wine with instead of having to deal with the expense and upkeep of a barrel. Before we get into the oak products let’s talk a little bit about the various aspects of oak and what it can do for you. You may also be interested in reading How Oak Affects Wine. That article goes into how oak from different places in the world impart different nuances to your wine. Flavors From Oak The following are some of the more prominent flavors you can get from using oak: vanilla caramel coffee oak spices smoky / campfire In addition to the flavors listed above oak also adds tannins to the wine. There are a two things that can greatly impact the flavor that oak imparts on your wine. These are the age of the oak itself as well as the toast of the oak. Oak Age Before the oak goes into a barrel or other oak product it is aged. They stack the oak outdoors and let it sit anywhere from several months to three years or so. The longer it sits the higher the quality, however, the cost goes up too. The gold standard for barrels is oak that has been weathered for 36 months. During its time outdoors the oak dries out Toast When barrels are made the oak staves are arranged around a flame that heats and “toasts” the wood. This process carmelizes sugars naturally present in the wood. The toast of the oak can range from barely being visible to being completely charred. The most common toast levels are light, medium, medium plus, and heavy. Lightly toasted oak retains much of the “woody” type flavor. Often a light toast will impart more tannins and green wood flavors. A heavy toast is the most drastic toast you can put on oak. It results in a smoky flavor. One of my favorite Zinfandels has a stronger smoky taste that makes it seem like you’re drinking your wine in front of a campfire. While I can’t confirm they use a heavy toast I would presume it is. Medium plus is somewhere between medium and heavy toasts. This is the darkest toast most wineries use, at least from what I’ve seen. Oak Products There are several diffent types of oak products you can use to impart these flavors on your wine. Dust Basically this is toasted oak that has been made into sawdust. The particles are very small which means the surface area of oak is maximized. This oak product is what is most commonly included with wine making kits. Because the particles are so small they impart flavor quickly. If you were looking for a boost of oak flavor before bottling you could add oak dust and within a week or so it will have imparted just about everything it has to offer. When you first add the dust it will float. Over time and as it interacts with...

Read More

How Terroir Affects Wine Making

How Terroir Affects Wine Making

What is Terroir? Terroir is a French term (pronounced terwah) and translates literally as “land” or “local” depending upon who you ask. In the world of wine though it takes on a far more complex meaning. One that is difficult to fully describe or even just wrap your mind around. The simplest definition I can find is “a sense of place”. Meaning that if a wine is said to be showing it’s terroir it is displaying characteristics of the specific locale the grapes were grown. What makes this so difficult is separating out the differences between two Chardonnays that are due to terroir versus differences caused by different wine making process. To get a better idea of what this terroir concept is all about let’s take a look at some of the factors that affect a wines terroir. The following list is by no means complete, it’ll just give us a good place to start from. Factors That Affect Terroir vineyard slope slope direction soil conditions nutrients in the soil (minerals) climate (singular weather events are not considered terroir) neighboring plants microclimates (pockets of cool air for example) use of wild yeast instead of inoculated yeast fermentation temperature proximity to mountains or bodies of water Winemakers can play with the following things to emphasize or mask the effects of terroir: pruning irrigation time of harvest oak (exposure time, type of oak, toast of oak, age of staves at the time the barrel was made, how many years the barrel has been used) It takes some trial and error to determine what sort of terroir a given vineyard has to offer and more time still to figure out how best to showcase it through the manipulation of the factors listed above. Minerality, for example, may come shining through the finished wine if the correct yeast is used. More on this later. The effects of a good slope are more difficult to understand or pinpoint as a contributing factor to a wine’s character. Tiny nuances in any of the factors that affect terroir can change the character of the finished wine. Because of this certain terroir areas can be very small. In fact some winemakers believe that the terroir in one specific spot will produce a wine of a given character and a patch just ten or twelve feet away will produce an entirely different character even if the same varietal occupies both areas. Largely it is believed that terroir is most influential in France. However, after listening to many hours worth of interviews with wine makers, I am discovering that many California winemakers know of areas that produce specific characteristics which can be attributed to terroir. How do they know? Well, a small producer will harvest their vineyard in lots and process the wine as they go. If one 500 gallon tank came from lot 2 and the next 500 gallon tank came from lot 3 and the two taste differently after fermentation it is likely terroir. This is true, of course, only if all other variables are held constant (such as yeast strain used, fermentation temperature, etc). The Trouble...

Read More
Page 1 of 512345