Notes from Iridesse Wines

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Archive for October, 2007

Yeast, Yeast, and More Yeast!

Posted by Genevieve Rodgers-Llerena on October 29, 2007

Yeasts are really the unsung heros of our civilization. Without yeast there would be no wine – perish the thought – only grape juice. There would be no cider, no beer, no vinegar (it’s a derivative of the three aforementioned beverages), no bread, no pizza, and the list goes on. I think you could make a case that there indeed would be no professional sports. Sure high school and college sports would not be gravely affected, but if I’m going to pay to see grown men (who make more money in a year than most people will ever see in a life-time) kick, hit or pass a ball around, I want – no need – a beer. Pizza is a close second. Really life as we know it would be radically different without the humble yeast.



So, what do yeasts really do? Here’s the simplified version: Yeasts breakdown (will call it eat) sugar and nutrients and produce alcohol, carbon dioxide, volatile metabolites, heat and more yeasts. They are the vital ingredient for turning grape juice into wine. It’s easy to point to alcohol production as the key byproduct of yeast activity, which is exactly what the government does. But you would be missing one of the yeast’s most amazing accomplishments – volatile metabolites. These are the esters, sulfur compounds and volatile fatty acids that make wine more flavorful than the grape juice it is derived from. No one sits around with friends expounding on the wonderful mouth-feel and aroma of grape juice; but there are thousands of websites devoted to those aspects of wine. Many of the compounds that give wine its flavor, aroma, color and mouth-feel are released or modified by the yeast during fermentation.

Wine makers choose yeast based a variety of attributes. The first thing a winemaker does is determine which yeasts are suitable for the wines that she is making. Yeast strains have been isolated to compliment different grape varietals, because of the different volatile metabolites that they create, and their ability to ferment in varying levels of alcohol and temperatures. Next a winemaker needs to determine what qualities should be enhanced or reduced in the wine. For example, a winemaker making Cabernet Sauvignon may choose BDX (Bordeaux Red) if she is worried about color loss or to enhance aromas. If the Cab had to be picked a little earlier than optimal, or if it has nice spicy aromas, she might pick CSM instead. Personally, I like to break up the fruit into two or more lots and use different yeasts in each tank. This way I can develop more complexity in the finished wine when the tanks are blended together. I get most of my yeast from Vinquiry as they have a nice selection. Here’s the link if you want to know more about available yeasts .


I would be remiss if I didn’t also mention the natural, or native yeast, fermentation method. Many wineries are using this method for fermentation, and while it may seem Nouveau, it has been used for several millennia. For a natural fermentation the wine is not inoculated with a commercial yeast, hence the name natural. The winemaker allows the yeasts that are present on the fruit to carry out the fermentation. On the surface this sounds like a very straightforward and simple way to make wine. It’s very inexpensive and after all isn’t this the way wine has been made for thousands of years? Well yes, BUT… When wine is inoculated with a commercial yeast, that yeast dominates the fermentation from the very beginning to the very end. They have been isolated because they are hardy in very inhospitable environments, when the must is at low temperatures and high in sugar and when the must is at high temperatures and high in alcohol, and also because they produce flavors and aromas that are pleasing. During a natural fermentation yeasts of several different genera are active with different types of yeasts dominating during different stages of the fermentation process. The hope is that in this mix of yeasts there are those that hardy both at the start, in high sugar, and at the end, in high alcohol, and that they produce a wine that is pleasing. But, there is no guarantee that this will be the case. And, there are few things more terrifying than a fermentation that stops before the wine is dry. This is where the winemaker earns her keep.

So there you have it, a very brief introduction to yeast. Please remember them when next you have a glass of wine, or a slice of pizza.


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Rain? Yikes!

Posted by oenophilus on October 10, 2007

Genevieve & I were minding our own business last night, sipping a gorgeous artisan red vermouth on the rocks, watching the brilliance of Hugh Laurie on House, when she asked the question that every winemaker and winegrower dreads hearing during Harvest. “Is that rain?” Yes, indeed-ee, Ma’am. It was pouring down like it hadn’t rained hard for months….Wait. It hadn’t rained hard for months. We have had the traditional Northern California dry summer, right after a very dry winter. It was time for a good rain.

Unfortunately, many growers still have fruit on the vine. Usually by the time the first hard rain hits, most of us have picked our grapes, gotten them through their first fermentation, and had them safely tucked away for their “long winter’s nap.” How does this affect the grapes? How does this affect the wines yet to come? Well that comes with more Depends than a keg party at the Old Soldiers’ Home.

Depends on what? When we are patiently waiting for wine grapes to finish ripening, we are waiting for a number of factors: flavors, acids, sugars, and pickers. Rain can adversely affect all of these factors. The plant sucking up a lot more water will cause the grapes to swell, thinning their skins. Rain will also dilute flavors, lower sugar levels, lower acid levels, and make it very hard to pick the fruit. Is that the end of the great wine the vintner had planned on making? Depends. Maybe the sugars were already too high and the plant can process the water, restore the flavors and balance the acids before the sugars soar again. How fast can pickers get into the vineyard so the plants don’t move all the water into the fruit? Depends. If you had a lot of rain on a very steep clay slope, the pickers can’t safely climb up and down the hill until the ground dries out. If your vineyard is on a valley floor, it may be prone to flooding and the tractors following the pickers can’t get in to haul the fruit out. If you have a small vineyard and rely on a vineyard management company to pick for you, guess whose phone was ringing off the hook last night and early this morning for every client left to get picked? Whole lotta Depends here. Noble Rot

Another extremely important factor is mold and rot. Sweet grapes have already attracted all sorts of creepy spores that are just waiting for conditions to be right to them to populate, grow, and do the nasty on your PHAT bunches of grapes. What are the right conditions? Wet, warmish, still air, tight bunches, thin skins, and a little time all contribute to grapes rotting away. You don’t need a CSI team ducking under yellow tape to analyze this. These grapes look and smell Yucky! You wouldn’t want to get these anywhere near your mouth. In a very small number of select instances, the dominant fungus will be Botrytis Cinerea as “Noble Rot”. In some varietals, this will produce magical flavors that drive many of us to a maddened neurotic passion that is brought on by the great dessert wines resulting from a proper handling of this icky fruit. If you are not already a convert, you MUST try Sauternes, Baumes de Venise, Tokay Aszu, Trokenbeerenauslese, Amarone, and a new bunch of late harvest or “Botrysized” dessert wines from North America.

For the most part, winegrowers are working themselves into a frenzy today and winemakers are getting ready for fruit. We are all watching the weather to hope that we get a strong breeze to dry out the grape bunches. We also hope that it gets hot and sunny enough to speed things along, not just gets warm and humid to make the rot spores feel right at home. Is the 2007 vintage in danger? Get real. We are SO past the days of stuffed-shirt pundits making broad swath declarations of quality that have no meaning on reality. Every Grower and Vintner will do their best with what they are given to get you the best wine that they can possibly make. Let’s wait to unscrew some caps and pop some corks in a couple of years to see what the Rains of October 9, 2007 meant to Northern California wine country.

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