A fermentation vessel is the container where maceration and fermentation take place. Stainless steel tanks, oak tanks, oak barrels and a variety of plastic bins are common fermentation vessels.

Plastic and stainless steel are practical for several reasons. Both can be easily cleaned and sterilized to prevent contamination from microbial growth. Because of their size, plastic bins are also handy when fermenting smaller amounts of grapes and can be placed in temperature controlled rooms or have plates inserted to control temperature. Stainless steel tanks can have thermostats and insulated jackets attached to control the temperature of the fermentation but are inefficient for small lot winemaking. Oak barrel fermentations are thought to smooth bitter tannins and create a softer more supple wine. However, they are expensive, difficult to clean and are prone to bacterial contamination.

Summary: Whites are fermented in barrel or in stainless steel while reds are fermented in plastic bins, stainless steel or, increasingly, oak.

Destemming is the process of removing berries from the stems. In the vineyard, grapes are harvested as whole clusters. When the fruit arrives at the winery, it is sorted for quality and can be sent through a destemming machine. The destemmer removes the fruit from stems with minimal rupture of the grape skins. Fermenting with whole berries creates a lighter-bodied style of wine that accentuates fruity characteristics.

Depending on the ripeness of the stems, the winemaker will choose the amount of stems, if any, to be included in fermentation. When green, stems can impart vegetal notes and accentuate bitter tannins. However, when used correctly, stems can add complexity to some wine styles. As the stems become more mature and brown, in a process known as lignification, they can contribute structure, weight and texture to certain varietals, most notably those made in a Rhone style.

If the stems aren't ripe, the winemaker may still be able to take action in order to achieve the characteristics associated with stem inclusion. Depending on the quality of the grapes, the winemaker can crush additional fruit or add tannins directly to the must to obtain the desired flavor and texture profile.

Several wine styles skip the destemming process altogether. This is typically done for white wines that undergo whole cluster pressing and some red wines, such as Beaujolais Nouveau, that are fermented whole cluster in an effort to highlight fruitiness and soft structure.

Summary: High quality white grapes usually aren't sent through the destemming machine while most red wines are. Some red wines will keep a portion of whole clusters to emphasize fruit and structure.

After the grapes are sorted, they can be sent through a machine called a crusher. The crusher splits open grape skins to release a portion of their juice and expose the skins. This allows the juices have more contact with the grape skins during fermentation. Because the skins contain so many of the interesting color, flavor and tannin components, crushed berries result in much greater extraction. Crushing may break some seeds and release bitter compounds into the wine, so it is important to evaluate seed ripeness and crushing levels in the process.

Leaving whole berries limits juice/skin contact and creates a lighter-bodied wine emphasizing fruity characteristics. Depending on the fruit and style of wine being made, winemakers will often use a portion of whole berry and crushed fruit during fermentation to achieve the desired balance of fruit characteristics and structure.

Summary: Crushed red grapes create more extracted styled wines than whole berries. White grapes are rarely crushed.

Sulfur Dioxide (SO2) is commonly used during the winemaking process as a tool to prevent bacterial spoilage and oxidation.

Sulfur adjustments are typically made during key periods when the grapes or wine are at greatest risk for spoilage. For red wine, SO2 is first added after the destemming/crushing process. During this initial stage, concentration levels of between 20 to 50 mg/L are used to inhibit bacterial growth and prevent wild yeast strains from starting fermentation. Because white wines rarely go through the destemming and crushing process, they have SO2 added immediately after the grapes are pressed.

SO2 is also added just after malolactic fermentation and is maintained at a level (e.g., 25 parts per million) throughout the life of the wine. SO2 levels that are too high can increase the bitterness while bleaching color from a wine. Without SO2, wines would typically oxidize and/or be attacked by microbes. Note that organically labeled wines do not use SO2 and tend to not age more than a year or two.

Summary: SO2 is a necessary part of winemaking. 99.99% of wines made in the world use SO2 to protect them.

After red grapes have been sorted and sent through the crusher-destemmer, they are kept around 10˚C degrees for several days. The cool environment prevents spontaneous fermentation from taking place. During the cold soak, the grapes are punched down to increase extraction of color and other water-soluble phenolic compounds from the skins. The cold soak helps emphasize brighter fruit notes and darker color. It should not be used for grapes that have significant color and do not require an emphasis on fruitiness (e.g., some clones of Cabernet Sauvignon or wines that are too fruity).

Summary: A cold soak will emphasize fruitiness and color in the resulting wine but is not appropriate for wines that are too fruity.

To achieve extraction in fermentation requires contact between the fermenting juice and the skins that tend to float to the top. The more contact and mixing up, the more extraction there is (think about a teabag in a cup of water). In small lot winemaking, especially with thick-skinned varietals as Cabernet Sauvignon, it can be difficult to get enough mechanical mixing to maximize extraction. Color or tannin extraction enzymes can be added during fermentation to help break down skins for more extraction without being too aggressive with the fermenting must (note that this is an especially good idea if the seeds are still a little green and tannic).

Summary: High extraction goals, especially for thick-skinned varietals in small fermentation vessels, can more easily be met with enzyme additions.

Tannins are phenolic compounds present in skins and seeds of grapes. They are responsible for tactile sensations and are perceived as a drying sensation on the mouth and insides of the cheeks. The winemaker works to create a balance of fruit and textural components while minimizing the tannic elements associated with bitterness. Tannin levels vary widely by varietal (Pinot Noir has relatively little tannin, while Cabernet Sauvignon has a lot) and are influenced by the climate in which the grapes are grown.

Grapes grown in cool climates typically feature more muscular tannins, while warm climate grapes tend to have softer tannins that favor earlier drinking. Near the end of the growing cycle, grape tannins can soften - this is highly desirable in cool/mountain climate fruit, but may make warm/valley climate fruit a little too soft. If tannins are too soft, a wine can benefit from a tannin adjustment. Tannins can be added thru whole cluster inclusion (see above) or adding enological tannins that have been created from grape skins. Note that while oak barrels also add tannin, they tend to impart a "drying" tannin that will stick out unless balanced with enough grape tannin.

Summary: For riper styles of wines where the grapes have softer tannins, tannin additions can help create a more structured, complex and age able wine.

Yeast is the catalyst for fermentation in wine production. A member of the fungi kingdom, this single-celled organism feeds off sugars present in grapes and produces alcohol and CO2 as by-products of this process. In addition to creating alcohol, yeast strains can influence the aroma and flavor of wine.

There are many strains of wild or "native" yeast present on the grapes as they come from the vineyard. Some are good, some are dangerous to the wine. The winemaker can choose to ferment with these native yeasts for more natural winemaking. Proponents believe that the resulting wines are more complex but their impact on the finished wine is not predictable. Native yeast often creates more volatile acidity and stuck fermentations are not uncommon.

Alternatively, the winemaker can choose to use commercial cultured yeast that has been proven to have specific results in the finished wine. Proponents of cultured yeast strains point to a cleaner fermentation, control over the finished product and lower probability of stuck fermentations as advantages.

There are middle ground practitioners that start with native yeast and then add a large amount of cultured yeast near the end of the fermentation to ensure that it completes. Very little real-world research has been done to compare these techniques.

There are dozens of cultured yeast strains available depending on which varietal and style of wine you creating. Please consult with your winemaker to help determine which yeast strain best suits your needs.

Summary: Non-interventionalist winemakers will choose native yeasts, while those focused on consistency will choose cultured yeasts.

The skins and seeds of grapes are included with the juice during red wine fermentation. As the fruit macerates and fermentation commences, the CO2 created by the fermentation causes skins to rise to the top and form a cap. To extract color, tannin, and other flavor compounds present in the skins, the cap is broken-up and pushed back into the fermenting wine to increase contact between the skins, seeds and juice. Breaking up the cap also helps maintain the health of the fermentation by regulating the temperature and promoting microbial stability. The process introduces oxygen, which helps maintain a healthy fermentation. The three common techniques of cap management typically used are Punch Down, Submerged Cap and Pump Over.

Punch Down
Punch downs are a technique of cap management where a hand tool (or a pneumatic device for larger lots) that resembles a five-foot potato masher is used to push the cap back into the fermenting wine. This process typically takes three to five minutes and is performed twice to five times per day. This is an effective technique for thinner-skinned varietals but is very time-intensive and if not done gently, can break seeds, releasing bitter tannins into the wine.

Submerged Cap
Submerged caps are a technique of cap management in which a physical barrier is placed directly into the fermenting wine to keep the cap submerged beneath the surface while allowing gas to escape. This technique provides constant contact between the cap and the juice, so a continuous extraction can occur without the harsh tannins sometimes found using punch downs. Because submerged caps allow very little oxygen for the fermentation, they are often used in conjunction with pump overs to prevent hydrogen sulfide odors from developing.

Pump Over
Pump overs are a technique of cap management in which juice pumped from near the bottom of the fermentation vessel is sprayed over the top to break-up and keep the cap moist. Typically the operation is performed to allow at least one or two complete turnovers in the juice. During the height of fermentation, pump overs usually take place several times per day. The frequency decreases as fermentation nears completion and desired levels of extraction are reached.

Summary: For red wines, keeping the cap mixed up creates more extraction. There are multiple techniques and even hybrid approaches.

Many of the compounds responsible for a wine's color, tannins and flavor reside in the skins, stems and seeds of the grape. Depending on the varietal and style of wine being made, the winemaker will employ different techniques to achieve the desired level of extraction. Decisions regarding fermentation temperature, cap management, crushing, destemming and the use of enzymatic additions help determine the level and type of extraction that will occur. Typically "extraction" refers to red wines.

A lower level of extraction results in a red wine that is lithe on the palate, has restrained color and more approachable bright fruit characteristics. These wines don't require lengthy aging and are great for social occasions. A medium level of extraction brings more complexity, tannic structure and darker color. Some of the simple fruity aromatics (that come from the juice) are traded off for more complex aromatics that are only extracted from the skins of the grape. Highly extracted red wines are all about power - teeth staining color, heavy tannins and downplayed aromatics that sometime require several years of aging to be the most enjoyable.

Summary: In winemaking, you can shoot for power, elegance or a compromise of the two.

The fermentation temperature has an impact on the style of wine produced and the extraction level of color, tannin and flavor. White wines are usually fermented at cooler temperatures than red wines. The cooler temperatures decrease the activity level of yeast, resulting in a slower and longer fermentation that can last several weeks.

Red wines fermented at cool temperatures between 22˚C and 24˚C, display approachable fruit-forward qualities that are lighter in color. Fermentations between 24˚C and 29˚C bring forth a greater balance between fruit and tannin to create a more refined wine. Hotter temperatures between 29˚C and 35˚C speed up the fermentation and extract more, making for wines with more tannin and color extraction. If the fermentation becomes too hot, yeast cells can actually die off, resulting in off-flavors and a stuck or unfinished fermentation.

Summary: Hotter fermentations favor bigger, more extracted wines while cooler fermentations favor more aromatic and elegant wines.

Extended maceration is a technique used with red wines in which the skins and seeds of the must are allowed to remain in contact with the juice after fermentation is complete. The extended contact, which can last between 5 days and several weeks, produces smoother, more velvety tannins in wine. This is often done with Bordeaux varietals or Rhone varietals that have significant tannin levels. However, there is typically some loss of fruitiness and color in the process.

Summary: Extended maceration creates a velvety mouthfeel and softer tannins, but fruitiness and color are modestly compromised.

Grapes are pressed in order to separate the juice from the skins. White grapes are pressed soon after they arrive at the winery before fermentation takes place. Because of the high sugar content at picking, the juice is sticky and makes pressing more time consuming. Red wines are pressed after fermentation when most of the juice is easily released.

There are several different types of presses available for the winemaker to use. Membrane presses, that make use of a large inflatable air bladder, are preferred because they extract a high proportion of juice while still providing a gentle force on the grapes. This prevents seeds from breaking during the process, which would cause bitter flavors to be extracted into the wine. Basket presses, which use "grape on grape" pressure, are also very gentle, but can be inefficient.

During red wine production, many winemakers will separate the easily released free run juice from the press juice. Depending on the style of wine being created, the winemaker may use all free run or blend in a portion of the press wine for more structure.

Free run refers to the juice released from grapes during the crushing process. As the grapes are split, juice seeps from the pulp. Free run is also created from the weight of the grapes while they are sitting in a bin. Grape clusters on top gently press clusters at the bottom, causing the skins to split open and release juice.

After red wines have completed fermentation, free run juices are siphoned off and the remaining must is pressed.

Press Juice/Wine
The liquid obtained from pressing is referred to press fraction juice or press wine. Press fraction contains more grape solids and tannins than free run juices. The first press fractions are typically very high quality comparable to free run, but may lack the necessary supportive tannin usually obtained with pressing. Medium press wines tend to have more structure and can be added to the free run if it is low in structure. As higher levels of pressure are applied, press fractions can exhibit more aggressive or bitter flavors as skins tear and seeds break. These hard press fractions are typically put into their own barrels and not blended in with the wine.

Summary: All wines are pressed. Lighter pressings tend to have higher quality than harder pressings, but a blend of them may be necessary to create balance.

Malolactic fermentation, also referred to as secondary fermentation, uses bacteria to transform muscular malic acids (think green apple) into smoother tasting lactic acids (think milk). The process reduces the wine's acid content and helps create a creamier textural quality in the mouth. With the exception of very light styles, like Beaujolais Nouveau or Dolcetto, all red wines undergo malolactic fermentation.

Summary: Nearly all red wines go through malolactic fermentation.

Stainless Steel
Stainless steel is used as a fermentation vessel for a variety of reasons. Steel is non-reactive, so unlike wood, it doesn't impart any flavors into the wine. This characteristic is beneficial for white wine styles and rosés that wish to accentuate crisp acidity

Winemakers, who want to add more body to a white wine, can create a blend from juices fermented in stainless steel and oak barrels. The winemaker will set up trials containing different percentages of stainless/oaked wines until the desired weight and acidity level is achieved.

Stainless steel also has the benefit of coming in many sizes and can have insulation jackets and thermostats attached to better control the fermentation and aging temperatures. Steel vessels are easily cleaned, so build up of harmful bacteria is minimized.

Oak
Oak barrels are the traditional vessel associated with wine production. Oak imparts flavors and textural qualities that provide layers of complexity to a finished wine.

New oak is used to describe barrels that are being used for the first time in wine production. They impart a greater amount of sensory character to a wine as the charring inside the barrel is exposed to wine for the first time. The aromas and flavors are leeched into the wine during the fermentation and aging process. Each time a barrel is used, the amount of flavors available will diminish.

Used oak is the term given to barrels that have already undergone wine aging. Depending on the varietal and style, the maker may chose to use a barrel that has already been used to age or ferment wine. A significant portion of the aromas and flavors that a new barrel can impart are no longer available in used barrels, so they are often chosen to provide more subtle wood character to wines during aging. After several uses, typically 3-4 years, the barrel no longer imparts any flavors and is called neutral oak.

For single barrel lots, Crushpad has created a "zebra barrel" which is a blend of new and used oak.

Summary: New oak imparts more dramatic tones and is good for red wines with lots of tannins. Each time a barrel is used there are fewer characteristics imparted into the wine.

When sitting in a new oak barrel for an extended period of time, wine picks up flavor and textural qualities from the wood. Our winemaking team can monitor the oak influence on your wine to ensure that it doesn't become over-oaked. The barrel rotation program may be used to move your wine into a neutral oak barrel once the desired level of oak characteristics have been achieved.

Summary: If you are concerned about your wine being over-oaked, it is recommended that you use the barrel rotation program.

French Oak
France is one of the main producers of oak barrels for use in wine. The forests are mostly located in the center of the country and barrels are named for the primary region the wood comes from, but may also be named for the specific forest the wood is harvested from. Two of the prized regions are Tronçais, a government owned forest north of Moulins and Bertranges in the Nevers region. Many of today's coopers tend to mark their oak "bois de centre" or "Center of France." Winemakers generally use French oak for its subtle contributions when making wines in a European style.

American Oak
Wood for American oak barrels is harvested primarily in the Midwest region of the country, from the states of Missouri, Ohio, Kentucky, and Arkansas. American oak is thought to impart more dramatic notes associated with the wood such as vanilla, dill and coconut. American oak species have a tighter wood grain due to an increase in tyloses, the woody growths that seal the pores in the growth rings. American oak barrels are less expensive than their French counterparts as the tighter grains allow the wood to be processed by sawing rather than splitting, resulting in less waste.

Eastern European Oak
Oak harvested from Hungary and Slovenia is increasingly becoming a more popular alternative to either American or French oaks. Oak from this region is considered to be very similar in character to French oak, with slightly more assertive wood tannins, but typically costs much less. The forests are located mainly in the provinces of Baranya, Somogy, Zala, Borsod-Abauj-Zemplen, Heves, and Veszprem.

Summary: Oak can have a significant impact on a wine. French oak is associated with elegance. American oak is believed to impart power and Eastern European woods are considered a blend of the two.

French Oak
France is one of the main producers of oak barrels for use in wine. The forests are mostly located in the center of the country and barrels are named for the primary region the wood comes from, but may also be named for the specific forest the wood is harvested from. Two of the prized regions are Tronçais, a government owned forest north of Moulins and Bertranges in the Nevers region. Many of today's coopers tend to mark their oak "bois de centre" or "Center of France." Winemakers generally use French oak for its subtle contributions when making wines in a European style.

American Oak
Wood for American oak barrels is harvested primarily in the Midwest region of the country, from the states of Missouri, Ohio, Kentucky, and Arkansas. American oak is thought to impart more dramatic notes associated with the wood such as vanilla, dill and coconut. American oak species have a tighter wood grain due to an increase in tyloses, the woody growths that seal the pores in the growth rings. American oak barrels are less expensive than their French counterparts as the tighter grains allow the wood to be processed by sawing rather than splitting, resulting in less waste.

Eastern European Oak
Oak harvested from Hungary and Slovenia is increasingly becoming a more popular alternative to either American or French oaks. Oak from this region is considered to be very similar in character to French oak, with slightly more assertive wood tannins, but typically costs much less. The forests are located mainly in the provinces of Baranya, Somogy, Zala, Borsod-Abauj-Zemplen, Heves, and Veszprem.

Summary: Oak can have a significant impact on a wine. French oak is associated with elegance. American oak is believed to impart power and Eastern European woods are considered a blend of the two.

Toast During the construction of barrels, coopers heat the staves so that they can be shaped. This toasting process creates sensory characters in the wood that will be imparted into the wine during fermentation and aging. The cooper's individual style, along with the degree of toasting, determines the type and depth of characteristics that will find their way into a finished wine.

Toast Level (Low) Lower toast levels impart more subtle characteristics associated with oak into the finished wine. The more restrained approach is ideal for many white wine varietals and lighter reds such as Pinot Noir.

Toast Level (Medium) Barrels with a slightly higher toasting level will impart more smooth textural and distinct flavor characters into a wine. Some makers create dramatic full-bodied white wines using a medium level of toast. Medium toast imparts more complex sensorial elements to red wines aged in the wood. New textures emerge and aromas associated with spice, clove and wood play a more dominant roll.

Toast Level (High) High toast levels in barrels are usually associated with big red wines like Cabernet Sauvignon, Syrah and Mourvèdre. The higher toast level compliments the assertive tannic structure of the grapes to bring forth some sweet characters that help smooth these grapes.

Summary: Low levels of toast are best when trying to impart more subtle characters.