The Science Behind Great Wine


May 16, 2016 Blog » Learn About Wine » The Science Behind Great Wine

What makes a great wine… great? By understanding the processes involved with making a great wine, you’ll be able to identify a great wine based on your own tastes. It doesn’t matter if you’re a collector or a novice to the world of wine, a solid foundation provides the basis of how to find great quality (regardless of price).

The Science Behind Great Wine

The Science Behind Great Wine

Carlo Mondavi and I sat down to discuss the grape selection and winemaking processes for a presentation. The goal of the presentation was to point out the most important facets of what defines a great wine so attendees would know what to look for when seeking great wine. We decided it was a good idea to share the concepts within to all 🙂

NOTE: Carlo Mondavi is the grandson of Robert Mondavi; partner in Continuum Estate on Pritchard Hill in Napa Valley; and founder of Raen Winery that specializes in Pinot Noir wines from the Sonoma Coast. By the way, the Mondavi family is no longer associated with the Mondavi wine brand, which is owned by Constellation.

 

What makes great wine…great?

What makes great wine... great?
We came up with a list of 4 pillars that essentially summarize what makes a great wine:

  1. Great grapes
  2. Great winemaking
  3. Longterm vision
  4. Art

“Making good wine is a skill, making fine wine is an art” -Robert Mondavi

Grapes and Winemaking: We can all agree that you need high quality ingredients and exceptional preparation skills to make outstanding sushi (imagine Sukiyabashi Jiro in Jiro Dreams of Sushi) so it’s easy to accept that this same idea also applies to great wine.

Longterm Vision: There are many intriguing new wineries and winemakers, but the great ones have one thing in common: they think big. As soon as the winery’s founder considers that their winery may continue to exist after they’re gone, they think differently about how they develop their brand and, ultimately, how they make wine.

Art: There’s this undefinable x-factor to great wine that’s hard to quantify in a scientific manner. Art is also a very personal choice that really comes down to the eye of the beholder. Of course, the more educated you are at understanding the craft of art, the more sophisticated/nuanced your taste will become. Winemakers, like artists, follow different ideologies and these core competencies are indeed reflected in the wine.

Grape Growing and Wine Making for Great Wine

Since art is a personal choice, we’ll focus on the quantifiable aspects (Grapes and Winemaking) and leave the fun part of seeking the art-side of wine for you to explore.

“You can make bad wine with great grapes but you can’t make great wine with bad grapes.” -Robert Mondavi

Grapes Terroir and Vintage

When you simmer down all the many processes involved in growing great grapes, there are essentially two areas of consideration:

  • Terroir: Terroir is essentially mother nature’s influence on grape growing and includes the climate, soils and other aspects dealing with the natural world.
  • Vintage: This area involves the choices that humans make to facilitate grape growing throughout a single year/vintage (i.e. pruning, irrigation, soil treatments, pest management, harvest timing, etc).

 

Terroir

What is Terroir in wine
The word “terroir” can mean many things to different wine experts so, for the sake of simplicity, we’ve defined terroir to reference a region’s climate, soils and flora.

People talk a lot about soils and climate when it comes to wine, but there’s a third component that scientists are now beginning to understand more: Flora.

What is Flora?
Flora includes all the living plants/funghi in a given area. This includes everything from trees, sagebrush, grasses, and flowers, all the way down to microbes like yeasts and bacteria.

“You can find 50,000 yeast particles on a single wine grape”
-Carlo Mondavi

 

Climate

Climate not only includes what’s happening with weather on a grand regional scale, but also references small differences from place to place. There are really 3 levels of detail that can be observed with climate:

  1. Macroclimate
  2. Mesoclimate
  3. Microclimate

 

Macroclimate

Macroclimate
The figure above was used with permission by the author, Dr. Gregory V. Jones (Jones, 2006; Jones et al. 2012).

From the work done by Dr. Gregory Jones, an Environmental Scientist at Southern Oregon University, we’ve learned that different grape varieties are suited for different macroclimates. Very simply, a macroclimate includes the average temperature and degree days (sun irradiance) of a particular region during the growing season. Based on the chart above, we can very quickly see that certain grape varieties are better suited to certain climates (e.g. Pinot Gris in a cool climate or Sangiovese in a warm climate). From this information we can identify larger regions (such as Napa Valley) that are better suited for certain wine varieties based on their average seasonal climates.

 

Mesoclimate

Mesoclimate wine
A closeup map of Sonoma and Napa Valley which are located just north of San Francisco, CA in the North Coast AVA. Full map available here

If you dial in a step deeper from the macroclimate, you’ll be able to notice subtleties between wines from different vineyards within a single region. Mesoclimate refers to climatic differences in an encompassing region such as distance to a river (where it may be cooler and foggy in the morning) or the location of a vineyard on an elevated slope. The influence of mesoclimates is partly why Napa Valley has been chopped up into 16 different sub-AVAs (American Viticultural Areas).

Here are some basic questions that pertain to a vineyard’s mesoclimate:

  • Is the vineyard on a slope?
  • Is the vineyard in a valley?
  • Is the vineyard close to a large body of water (lake, ocean, river)?
  • Which direction does the vineyard face?

 

Microclimate

Microclimate

Finally, microclimate goes all the way down to the individual vine. Perhaps there is a part of a vineyard that is shady during certain parts of the day or there’s airflow in one part of the vineyard and not another. Microclimates are what influence a single vine to produce quality grapes.

Technology: In Northern Italy a cooperative called Cavit in Trentino developed a region-wide monitoring system called PICA . The system monitors changes and gives growers (through iphone messaging) immediate vineyard management actions. For the time being, PICA is a proprietary tool, but as growers develop more advanced technology we’ll see active farming based on microclimates.

 

Soils

vineyard soil types
Forget terms like Goldridge, Kimmeridgian, and Jory… what matters in soil is drainage, pH, soil depth and soil temperature.

What really matters about a soil is how the fertility of the soils affect the vines throughout the growing season. There are 4 fundamental soil compositions based on particle size:

  1. Clay: Known for producing rich, structured wines
  2. Sand: Known for producing wines with higher aromatics and slightly lighter color intensity
  3. Silt: A harder to manage (viticultural-y speaking) soil that can produce highly vigorous vines which deliver more herbaceous flavors, but when managed it can produce wines in a style very similar to clay.
  4. Loam: Typically found in valley floors and is not typically associated with fine winemaking due to high productivity (unless blended with higher levels of clay/sand).

What’s interesting about the soil types listed above is that if you look at all the finest, most structured, age-worthy red wines, they almost all grow on clay-dominant soils (Rioja, Pomerol, Napa Valley, Paso Robles, Tuscany, Coonawarra, Burgundy). Beyond this, the most highly appreciated aromatic wines (like German Riesling and Beaujolais) grow in sandy/rocky soils.

Complexity in soils = complexity in wine
When managed properly, vineyards with diverse soil types tend to produce wines with more complexity.

Shallow and/or Infertile soils
A controversial topic of soil quality has to do with soil depth. Carlo Mondavi observed how Pinot Noir vines with shallow soils (on hillside vineyards) spend more energy during the growing season on fruit development and less towards vigor (making green leaves). The reduction on energy spent in leaf development resulted in wines with less herbaceous character. And, while some may argue that herbaceous notes in some wines adds complexity, many of the finest wines do grow on infertile soils.

 

Vintage

Vintage Wine
Each vintage starts the moment you pick grapes until the next harvest in the fall.

All the processes and preparations made throughout the year leading up to, and including, harvest define the job of viticulture or “wine growing.”

“great wine is grown, not made”

 

Harvest

Harvest Wine Grapes Timing Ripeness
Terms in figure: Brix is the measure of sweetness in grapes. pH, in this image, shows an estimated level of acidity in a resulting wine made with these grapes. pH is logarithmic and inversely related to acidity so, a wine with 3.5 pH has an acidity level 5 times higher than a wine with a pH of 4.

Timing is the most important consideration for harvest. Once grapes are picked, they do not continue to ripen. In cooler regions, winemakers need to consider weather changes and pick before heavy rains. In warm climate regions, timing the harvest improperly (even by a few days) can mean the difference between a fresh and fruity wine and a flabby, overripe wine.

phenolic ripeness in wine grapes
Ripeness involves more than just sweetness of grapes.

It’s important that sugar levels are high enough for harvest, but then there’s also phenolic ripeness. Phenolic ripeness pertains to the condition of the tannin in the seeds (catechin) and skins (epicatechin) of the grape. We talk about this style of ripeness often when describing a wine as having “sweet tannins.” Grapes with less ripe seeds and skins result in more astringency and bitterness in a wine.

Some grape varieties have lower tannin naturally and winemakers may pick them a little more green to add texture and acidity to a wine (this is commonly practiced with Pinot Noir). Other grape cultivars have high tannin (such as Cabernet Sauvignon and Nebbiolo) and are better to be picked when the phenolic ripeness in the seeds and skins is higher.

 

Wine Growing Practices

viticulture sustainable
Great vineyards lean towards the sustainability side of the spectrum.

If you step back and look at a winery’s vineyard as a whole, you’ll see their growing practices are somewhere on the scale of sustainability. The very best wineries with long term vision are sustainable. And while most of us think of sustainability as an environmental consideration, it also involves social and economic aspects. Each of these 3 aspects of sustainability (Environmental Responsibility, Social Equity and Economic Viability) work together and produce a slow increase of profitability to maintain the winery, land and community.

What is Permaculture? Permaculture is an agricultural system that is sustainable and self-sufficient. It involves planning for ecological and environmental design so that the resources available on a plot of land can be stored and used to sustain the land. This type of farming practice involves observing and working with natural conditions to fight obstacles in farming (pests, rot, etc). It is the ultimate goal of sustainability to be self-sufficient, but it’s not always possible. This is why different types of sustainability certifications exist so that we may understand what protocols a winery follows.

You can read more about the other different types of sustainability certifications and what they mean here.

 

Winemaking

Winemaking practices
Even after the fermentation is complete, a wine continues to change as it ages.

After the grapes are harvested, the process of making wine begins. This is where the winemaker has several choices which can affect the resulting style of wine.

The first choice is perhaps the most important and least talked about: Yeast. Yeast adds its own set of flavors to wine. Yeast aromas are referred to as Secondary Aromas and can range from yeasty, beer-like aromas to buttermilk, and even earthiness (mushroom). While most wine is produced with commercially controlled and manufactured yeast, many of the finest wines in the world are made with natural yeast (from the region and winery’s natural flora). Natural yeast fermentations can be much more difficult to manage but, if the vineyards and winery have a healthy yeast population, the end result is a complexity in the wine.

 

Winemaking Processes: Punchdowns and Pumpovers

Pump overs and punch downs winemaking
Grape skins rise to the surface of the fermentation chamber and a few techniques have been developed to reintegrate them into the wine.

The process of punchdowns and pump overs is to reintegrate grape skins and seeds into the fermenting juice so that the proper levels of phenolic extraction can be made. You could relate this process to stirring the grinds in your french press. Of course, different grape varieties need different levels of extraction to develop positive flavor characteristics (and not the bitter, astringent or sulfur-like aromas). Generally speaking, the Bordeaux varieties of Cabernet Sauvignon, Merlot, Malbec and Petit Verdot do better with higher intensity extraction (e.g. pump overs) and lighter varieties (such as Pinot Noir, Syrah and GSM blends) do better with more delicate extraction.

 

Winemaking Processes: Fermentation Temperature

Fermentation Temperature
Just as making a proper cup of tea requires the proper temperature (maybe between 160–175º F / 70–80º C), wine needs to be fermented at the right temperature too.

As yeasts eat the grape sugars and metabolize them into alcohol, the temperature of the fermentation increases. This increase in temperature causes volatile aromas to burn off and this isn’t necessarily a good thing. You can assume, for the most part, that red wines with more floral notes are often fermented at lower temperatures (flower aromas are usually the first to go), which means the winemaker was trying their best to preserve these volatile aromas in the fermentation. When temperatures get too high, wines will exhibit less fruit flavors and more earthy or baked flavors. And, while this is not necessarily a bad thing (a chocolaty Malbec anyone?), it suggests that not all the original aromas in the wine were preserved.

NOTE: You’ll note a few winemakers using whole clusters of grapes in their fermentation. The inclusions of stems will naturally decrease the temperature of the fermentation.

Aging wine oak concrete tank
When the wine is finished fermenting it spends time in a vessel to settle and/or age. Certain aging vessels introduce oxygen which alters the chemical state of the wine and changes the flavors.

After the fermentation is complete, the winemaking still has a ways to go. The choice of aging vessel plays a crucial role in the development of a wine.

  • Tank: Stainless steel is meant to preserve the original flavors as much as possible. This style of settling is most commonly used for white wines where floral and herbal aromatics are of utmost importance.
  • Concrete: Concrete storage vessels may breathe more than stainless while still maintaining a cool temperature. Wines aged in concrete have a higher level of preserved fruit characteristics, while still seeing the benefits of oxygen ingress (for red wines, this can include softening bold tannins). Some believe that concrete adds a textural sensation of minerality, but this hasn’t yet been fully proven.
  • Oak: Oak aging not only increases oxygen interaction in the wine but, when barrels are new and toasted (“toasting” is essentially torching and caramelizing the inside of the barrel to create flavors), they add flavors too. The flavors created include vanilla, clove, smoke, sweet tobacco and cola and are caused by aroma compounds from the oak.

 

Aging: Reductive vs Oxidative

Reductive vs oxidative wine
The choice of aging vessel is really where the winemaker makes a visionary/artistic choice about their wine. Some producers try to preserve the wine’s natural character as much as possible by using neutral (used) barrels which do not add oak flavors or by aging wines for extended periods of time to soften the wine’s characteristics (acidity, tannin, etc). The choices the winemaker makes during aging, might be the best place to start when developing your own preferences.

 

Fining and Filtering

fining and filtering in wine
Another choice in the winemaking process is whether or not wines are fined and filtered. Wines often have a little bit of a hazy color due to dissolved amino acids in the wine. Fining agents bind to these proteins and they drop out of the wine, leaving it clear. By the way, most fining agents are a protein of some kind (casein from milk, egg whites, fish bladders, etc). Nearly all white, rosé and sparkling wines are fined/filtered in some way but not all red wines. Filtering essentially does the same process of fining but with filters that have microscopic holes.

Proponents argue that fining/filtering clarifies and stabilizes wines and opponents believe that by not filtering their wines they provide them with added texture and structural elements for age-worthiness. The main issue with unfined and unfiltered wines is that consumers do not like cloudiness in their wines, particularly in white, rosé and sparkling wines.

 

Bottling

Screw caps vs corks
By now, winemakers have observed success for long term aging for both corks and screw caps.

When it comes to bottling, many believe that wines with screw cap closures are not as high quality as wines enclosed with corks. This isn’t true. Many high-end producers choose natural corks, but there are many turning to screw caps as a more reliable method (screw caps do not cause cork taint). In fact, low quality agglomerated corks tend to be more problematic than screw caps. Our one takeaway is that both methods are suitable for fine winemaking.

Happy Searching and salut!


SUBSCRIBE TO GET FRESH WEEKLY WINE STORIES
Do you like this post?


By Madeline Puckette
I'm a certified wine geek with a passion for meeting people, travel, and delicious food. You often find me crawling around dank cellars or frolicking through vineyards. Find me at @WineFolly