While far from a new practice, gravity flow winemaking seems to have experienced a resurgence over the last decade or so in the United States. Before pumps and power, the most efficient way to move wine from vessel to vessel was to use the natural force of gravity and a nice slope. You could say that it’s an old world technique that is discovering a renaissance in the new world of winemaking. The question is “why?”

Pinot Noir

A handful of winemakers are utilizing gravity flow to move their wines, believing that this gentle method will help preserve the delicate flavors and aromas that may otherwise be lost by the use of abrasive pumps. Not all grape varietals will respond in the same way to this technique.  Not surprisingly, the most responsive varietal to this gentle handling is sensitive Pinot Noir.  When produced with a reverence for what Pinot Noir can achieve, this wine can deliver some of the most subtle, mysterious, and enchanting characteristics in the aromas and flavors.

To capture those ethereal qualities in the bottle is the lifelong goal of the Pinot Noir winemaker. I am a proponent of this gravity flow technique: I’m a former math instructor-turned full-time winemaker. My four-tier gravity flow winemaking facility opened in 2005 and is the result of 20 years of winemaking and farming the “heartbreak” Pinot Noir grape. Designing and building a facility that would do this finicky grape justice was a dream that I’ve had for many years. While building our Russian River Valley facility in Sonoma County, we discovered that to construct a multi-tiered facility is significantly more costly than creating a single level winery. Such dedication to producing a certain type of varietal may seem over the top, but all one has to do is taste the resulting product and then it all comes clear.

The four-tier gravity flow winemaking system

• Crush Pad: Harvested grapes are brought up to the top tier at the rear of the winery. A forklift empties the bins directly into a destemmer set above the fermentation tanks into which the destemmed grapes fall. After sorting and destemming, grapes fall into the fermentation tanks below on the press pad.
• Press Pad for Fermentation: Fermentation begins here. Activities on this tier include cold soaking, punching down, fermentation, and pressing. All juice from this level including free run and press wine drains into settling tanks on the cellar level.
• Cellar: Juice flows into settling tanks or directly into barrels for storage and aging in the cellar.
• Bottling Level: Once this gently-handled wine has matured and is ready for bottling, it is pushed with nitrogen back into the settling tanks for blending or cold stabilization and a hose is run from the tank down to the bottling level to flow the wine into the bottling line system.

Four tiers of a gravity flow system (image courtesy of Language Artisans)

Sustainability for the Love of the Grape

Intern David McDowell helps Pinot Noir into a tank at the top of the hill at Moshin Vineyards

Another benefit of the gravity flow method is the savings in energy usage. Combined with the generation of electricity from the solar system installed in 2008, a gravity flow system contributes to the movement toward sustainability at Moshin Vineyards. In 2009, Moshin also installed an in-house nitrogen-producing generator, alleviating the need for multiple deliveries of heavy tanks that often leaked nitrogen. Other sustainable practices include the biodynamic farming of our newest vineyards: all grape waste is composted and we use the diatomaceous earth and cotton filter pads in the vineyard for weed control.

For large public events at Moshin, compostable plates and utensils are utilized: the overall “greening” of the winery is a continual work in progress. Does this extra care for the grape handling and sustainability make a difference? Does your homegrown, nurtured tomato taste better than the one from the supermarket that was bred for shelf-life rather than enjoyment?

Wineries using gravity flow systems in California

Wineries using gravity flow systems in Oregon

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[Rick Moshin grows grapes and makes wine at Moshin Vineyards in the Russian River Valley region of Sonoma County.]

– photos by Amber Moshin

Would you build a house without first having a plan and knowing the kinds of construction materials you would use? When vineyard managers plant rootstocks, choose grapevine scions, and implement a vineyard management system without thoroughly understanding the soils in which these plant materials will grow, they do much the same thing. Detailed soil maps created prior to vineyard establishment help the vineyard manager and winemaking team analyze the important soil chemical and physical properties in order to make wise decisions in the vineyard.

Viticulture Implications of Soil Formation

The soil distribution and variability within a particular vineyard eventually lends complexity to the resulting wine. Because of the variability of the soils, a vineyard manager needs a map to these various soils to fully understand how a particular vineyard works.

Soil survey reports produced by the United States Department of Agriculture (USDA) are widely available for much of the nation and provide general soil maps and soil descriptions for a region. However, for most intensive viticulture uses, these reports provide only general reconnaissance information, which must be supplemented by detailed soil maps and complete site-specific chemical and physical soil characterizations. Earth and soil scientists working with private vineyard management companies produce these detailed soil maps to help a vineyard start well once it’s planted.

Cropley soil (Vertisol) at Halter Ranch Vineyard: High water-holding capacity, high montmorillonite clay content (>50% clay); pH 6.5 in topsoil and pH 7.5 in subsoil.

Soil, the medium in which plants grow, is a natural body on the surface of the earth. It is a mixture of rocks and minerals, organic matter, water, and air, all of which occur in varying proportions in the mix. The rocks and minerals are usually weathered and fragmented. Soils have distinctive layers, called horizons, which are the products of earth’s environmental forces acting upon materials that are deposited or weathered in place by geological and atmospheric processes.

The characteristics of a soil are determined by the interaction of the following elements:

• The chemical, physical and mineralogical composition of the parent material
• The climate in which the soil material has accumulated and has existed since accumulation
• The relief, or topography, which influences the local, or internal, environment of the soil, its drainage, moisture content, aeration, susceptibility to erosion, and exposure to sun and wind
• Biological forces that act upon the soil material, such as the plants and animals living on and in the soil
• The length of time the forces of development have acted on the soil material

Better Understand a Vineyard through Soil Maps

The first vineyard characterization task is to map the soil variability and soil distribution on the landscape. It has long been recognized that soils differ relative to variations in parent material, climate, landscape topography (relief), biosphere (plants and animals), and soil age. Soil variability on small vineyards may depend on differences in soil parent materials or landform changes in slope steepness and aspect. Until recently, soil mapping has been accomplished solely with the use of stereo aerial photographic base maps and topographic quadrangles. Relatively new remote sensing methods such as high-resolution aerial orthophotography, infrared aerial photography, and satellite imagery enable the soil mapper to detect relative soil water contents and other surface properties indicating soil variations. However, knowing soil properties to the depth of the root zone is important because it is the entire soil-root environment that ultimately determines the quality and management requirements for a given plant. A team creating the maps will excavate soil pits to determine soil variations with depth and to sample the soils for geochemical analyses.

Cropley soils at Halter Ranch exposed by a soil pit in the Adelaida District, Paso Robles AVA

When describing soil textures within a vineyard, it is important to not only identify the soil textural classes but also the soil parent material rock types and the amounts of rock fragments within the soil profiles. Related soil properties like saturation percentage should also be determined to aid in irrigation system design.

Soil texture information should also be supplemented with data regarding soil organic matter content and soil chemical properties, such as pH and plant essential nutrient concentrations. Soil organic matter and humus contents (i.e., highly decomposed organic matter) will modify the general effects of soil mineral texture by causing soil structure formation, increasing soil water holding capacity and increasing cation exchange capacity (CEC). The interrelationships among all these soil properties should be considered when making vineyard management decisions.

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Paso Robles: An American Terroir

In 2007, Dr. Tom Rice produced with Tracy G. Cervellone a definitive study of the Paso Robles AVA from the perspective of vineyard soils and significant climatic factors influenced by geology. Paso Robles: An American Terroir begins with a cataloguing of the soils in evidence throughout this AVA as well as a quick recounting of the wrinkles in geological time that track the emergence of the parent material resulting in the soils that now host so many vineyards in this dynamic region. Following an introduction to the terra of Paso Robles as a whole, Dr. Rice and Cervellone narrow their focus to the various districts demarcated within the AVA.  By surveying the types of wines produced by vineyards and wineries in each district, the authors make the connection clear between the wines produced from a particular plot of land and the soils beneath the vines with the cycles of weather in a vine’s environment.

Like modern-day Cistercian monks, who were some of the first viticulturalists to record their observation of everything related to the experience of a grape vine and how each factor might influence the resulting wine, the authors of Paso Robles: An American Terroir present their evidence for how Paso wines came to be, at least as far as soils and climatic factors.  Soils certainly do not determine everything about a particular wine: terroir contains the idea of everything in the grape’s environment, such as the smoke from an August wildfire that permeated Central Coast vineyards while the vines were heavy with fruit.  However, soils certainly exert an influence on the life and health of the vine, which links to the quality of the harvested fruit and, in the end, of the finished wine.

For more information, visit www.pasoterroir.com.

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[Dr. Rice teaches soil science at California Polytechnic State University-San Luis Obispo.]

– photos by Tom Rice, Ph.D.

Author of the immortal phrase “In wine there is truth” and one of the earliest writers to describe grape cultivation and winemaking practices as well as the concept of terroir, Pliny the Elder appears to have appreciated the floral loveliness of wines produced from Malvasia grapes. Although he may not call them “Malvasia,” Pliny gives high accolades in his first-century encyclopedia Natural History to the sweet, aromatic wines of southern Italy, a description that could reference both the Malvasia fruit and the resulting wine. Modern day viticulture scientists share a kindred link with Pliny, even as they employ the most advanced equipment and cutting-edge techniques for studying grapevine genetics.

While the exact origin of the Malvasia family of grapes remains a mystery, modern DNA testing indicates that this was one of the earliest vines cultivated. In 2007, the American Journal of Enology and Viticulture published a paper by several French viticulture scientists that identified shared genetic patterns within a collection of Malvasia specimens at the Domaine de Vassal Grape Germplasm Repository. In their paper entitled “Relationships and Genetic Diversity within the Accessions Related to Malvasia Held in the Domaine de Vassal Grape Germplasm Repository,” Thierry Lacombe et al. attempted to outline the genetic relationships among the vast collection of Malvasia-named grape vines held by L’Institut National de la Recherche Agronomique (INRA) in Paris.

In the repository, these scientists examined 70 Malvasia-associated accessións (or selections) using ampelography and Simple Sequence Repeat (SSR) DNA analysis. They were attempting to determine the potential number of individual Malvasia varieties in existence in order to identify how many of these selections were the same cultivar and how many were genetically distinct. The researchers were trying to reduce some of the confusion that results from so many different vines being named “Malvasia.”  This exhaustive study produced several interesting findings. For one, of the 70 accessións studied, it was determined that there were actually 49 distinct varieties. This research determined that, although there are many vines that have “Malvasia” in their names, most are not actually related by genetic code or parentage. This helps explain the inconsistency in the characteristics of wines that share the name “Malvasia.”

Of the 70 selections, 73% were white-skinned grapes and only eight selections were considered aromatic varieties, including Malvasia Bianca. The vast majority of Malvasia grapes are not aromatic. This research proposed that four subgroups of Malvasia exist: specimens in each subgroup were found to be genetically more similar to members of their subgroup than to specimens in the other subgroups. This research also demonstrated that the aromatic subgroup of Malvasia shares portions of gene sequences with the powerfully scented Muscat d’Alexandrie grape, which further explains the highly aromatic character displayed by the Malvasia Bianca cultivar.

The study also revealed that there is no clear common denominator among the Malvasia accessións. The name “Malvasia” is not directly based on origin or determined traits.  Rather, Malvasia is more of a generic name applied to many grape varieties growing in the Mediterranean Basin than it is a group of grape varieties that are closely related genetically. Ultimately, this research illuminated how not all Malvasias are (genetically) equal and that only the most fragrant wines can be produced from the aromatic subgroup of the Malvasia family.

– by Ken Volk

Ampelography is the science of determining grape vine varieties by leaf shape, growing habits, and physical morphology