GuildSomm Expert Guide to Winemaking

Question 1

Who is André Tchelistcheff?

Answer 1

André Tchelistcheff was America’s most influential post-Prohibition winemaker. Tchelistcheff is most notable for his contributions toward defining the style of California’s best wines, especially Cabernet Sauvignon. Called the “dean of American winemakers”, industry pioneers, such as Rev. John Staten of Field Stone Winery, Robert Mondavi, Louis Martini and Rob Davis of Jordan Vineyard & Winery, and Rick Sayre of Rodney Strong Wine Estates, considered him their mentor.

Question 2

In winemaking, what does MOG stand for?

Answer 2

Materials other than grapes

Question 3

What is the primary rootstock (approximately 80%) in Champagne’s vineyards that is also seen as a majority in Cognac production?

Answer 3

41B

Question 4

While all aspects of the growing environment impact fruit composition what are the two most critical?

Answer 4

temperature and water availability are the most critical

Question 5

Where is the Klosterneuburg Must Weight (KMW) or Babo scale used?

Answer 5

Austria, Italy, Eastern Europe

The Klosterneuburg Must Weight (KMW) or Babo scale, used in Austria, Italy, and Eastern Europe, attempts to account for this overstatement by applying a factor of roughly 0.85 to the Brix scale, which assumes that 15% of the solids are non-sugar.

Question 6

In the EU, potential alcohol is estimated using the official conversion ratio of —- grams per liter sugar yielding 1% ABV.

Answer 6

16.83

In the EU, potential alcohol is estimated using the official conversion ratio of 16.83 grams per liter sugar yielding 1% ABV. The actual conversion ratio depends on the efficiency of the yeast and typically ranges from 16.5 to 17.5. If all of the sugar was converted to ethanol, 15.7 grams per liter sugar would yield 1% ABV. In reality, yeast converts only 90 to 95% of sugar to alcohol, and the rest is converted to other biproducts of fermentation, including glycerol and fusel alcohols.

Question 7

What type of solution does Baumé use? In which countries is the Baumé scale used?

Answer 7

Baumé is another specific gravity measurement used in France, Spain, and Australia. It is analogous to Brix but uses a salt (sodium chloride or table salt) solution as opposed to sucrose as the reference. While salt is not an intuitive choice, it is convenient since Baumé is an estimate of the potential alcohol, where a juice at 14 degrees Baumé is likely to have a final alcohol concentration of about 14%. Baumé is converted to Brix by multiplying by a factor of 1.8.

Question 8

Which sugar scale uses specific gravity? What countries is this scale used in?

Answer 8

The Oeschle scale. It is used in Germany and Switzerland.

Specific gravity (closely related to density) is perhaps the most fundamental scale used to estimate sugar content, and its use seems to be gaining in popularity. The Oechsle scale, used in Germany and Switzerland, is mathematically related to specific gravity.

Question 9

Which is the primary organic acid that occurs naturally in grapes?

Answer 9

Tartaric.

Others are Malic and citric acid.

Lactic, succinct an acetic acids are formed during fermentation and are present in wines at low concentrations.

Question 10

What are the two parameters for measuring acidity?

Answer 10

pH and titratable acidity.

The perception of sourness is most determined by the wine’s titratable acidity—wine with a high titratable acidity (TA) tastes more sour. Wine’s perceived texture is affected by pH. High pH (low acid) wines may seem soapy, while low pH (high acid) wines are perceived as having “harder” tannins. Additionally, pH affects a wine’s hue and the efficacy of sulfur dioxide, with lower pH wines requiring less SO2 for microbial stability.

Question 11

Water is considered to have a neutral pH of 7. Wine generally has a pH between ______?

Answer 11

3 and 4

Technically, pH is a measure of the concentration of hydrogen ions (or protons) in a solution. The pH scale is logarithmic, so wine at a pH of 3 has 10 times the acidity of wine at a pH of 4.

Question 12

Phenolic compounds add which attributes to a wine?

Answer 12

henolics are an important class of compounds that lend color, flavor, and texture to wine. Tannins and Anthocyanins are two examples.

Phenolic compounds are important for agreeability and play a key role in odxidation chemistry.

Question 13

What are the three groups phenolic compounds are generally divided into?

Answer 13

Flavonoids, non-flavonoids, and tannins

Question 14

What compound is largely responsible for the bitterness in wine?

Answer 14

Catechins are small polyphenols that are extracted mostly from seeds and stems (though also from skins) and are largely responsible for bitterness in wine. While the concentration of catechin in wine is low, they are significant in wine as they are a major constituent of tannin.

Question 15

How do catechins and tannins relate to each other?

Answer 15

Tannins are large molecules that impart astringency and bitterness in wine. From a strict chemistry standpoint, they are characterized by their ability to bind with protein, which explains the astringency perception they induce—tannins react with proteins in the wine drinker’s mouth. Tannins are often regarded as a single component in wine but can be more accurately thought of as a cohort of distinct compounds of different lengths and configurations made of catechin “building blocks.” The structure of catechins and tannins favors reactions among each other, as well as with anthocyanins. Smaller tannin “units” polymerize, or bind together, forming longer chains. These bonds are also easily broken, so at the same time that bonds are forming, others are breaking apart. Tannins’ ephemeral behavior makes them difficult to measure or study in a meaningful way, and for this reason, knowledge about their behavior is evolving as scientists develop better tools to study them.

Question 16

What are Anthocyanins?

Answer 16

Anthocyanins refers to a family of pigmented compounds responsible for the vibrant color of young red wine. Their extraction from the skins of red grapes begins as soon as the berries are crushed, and they immediately start binding with tannins and other compounds to create more stable pigments sometimes referred to as polymeric pigments. During fermentation, they continue to be extracted from the skins and depleted by polymerization. After pressing, the concentration of anthocyanins decreases as they are converted to polymeric pigments. After a year or so, the color of red wine is driven by the concentration of polymeric pigments.

Question 17

Do Anthocyanins extract rapidly in the beginning of the red wine fermentation or towards the end?

Answer 17

Anthocyanins extract rapidly at the beginning of fermentation.

During red wine fermentation, winemaking techniques are used to extract phenolics from the grapes. Anthocyanins extract rapidly at the beginning of fermentation. Tannins and catechins are more soluble in alcohol than water, so their rate of extraction is faster toward the end of fermentation. Phenolic compounds can improve quality and ageability, but over-extraction of tannins and catechins results in wines that taster bitter, hard, and closed. In particular, high levels of catechin can lend an unpleasant bitterness.

Question 18

Does astringency increase or decrease over the lifetime of a wine?

Answer 18

Decreases.

Question 19

What metric is most commonly used to determine the date of harvest?

Answer 19

Sugar concentration as it determines the wine’s potential alcohol.

In addition to sugar, winemakers typically monitor the pH and TA (titratable acidity) of the fruit. During ripening, pH increases and TA decreases, and winemakers seek to harvest once they are in a range that will result in a balanced wine. The precise range depends on the grape variety, the intended wine style, and whether the wine will go through malolactic fermentation

Winemakers may also consider the concentration of malic acid. If malolactic fermentation is intended, it gives an indication of how the acidity will change after this fermentation. Otherwise, winemakers may prefer to delay harvest until the malic acid concentration is below a particular threshold, since a high concentration of malic acid can lend an overt green apple character to the wine.

Question 20

What are typical grape chemistry’s at harvest (Brix, pH, Titratable Acidity) for Sparkling, White and Reds

Answer 20

Sparking: Degrees Brix: 17-20, pH: 2.9 - 3.2, Titratable Acidity (g/L tartaric acid): 8-12

White: Degrees Brix: 19-25, pH: 3.0-3.6, Titratable Acidity (g/L tartaric acid): 5-10

Red: Degrees Brix: 20-27, p`H: 3.3-4.0, Titratable Acidity (g/L tartaric acid) 4-8

Question 21

Is Champagne a whole-cluster wine style and whole cluster pressed?

Answer 21

Yes

Whole-cluster wine styles, including wines that will be whole-cluster pressed (such as Champagne) or undergo carbonic maceration, require hand-harvesting. On the other hand, harvesting by hand is slow, labor intensive, and expensive.

Question 22

What is encuvage?

Answer 22

Vatting, putting the must into the vats for fermentation

Question 23

To minimize damage, growers have widely adopted practices such as gently handling and keeping the fruit cool and intact. What impact do cool temperatures have on the fruit?

Answer 23

Low temperature slows the rate of oxidation reactions and microbial growth. Cool fruit is easier to process as it is less prone to unintentional crushing. In regions with cool daytime temperatures fruit is harvested in the morning. In warm regions, night harvesting has become standard.

Question 24

What are the implications of handing grapes gently? Are white or red grapes in arguably greater need for gentler handling?

Answer 24

Gentle handling of grapes reduces unwanted oxidation and extraction. Oxidation is responsible for juice browning and loss of aroma and flavor compounds. For this reason, crushing is minimized until just before fruit is put into the fermentation vessel. Gentle handling is particularly important with white grapes, whose flavors are driven by delicate aroma compounds, and for styles of wine where skin contact is not desired. Gentle handling avoids pulverizing stems or seeds that may contribute bitter and green flavors to the must.

Question 25

A winemaker may take an oxidative approach to fruit processing and handling - what does this technique entail and what are the benefits to this?

Answer 25

Winemakers may take an oxidative or reductive approach to fruit processing and handling. Reductive handling aims at preserving aromatics and fruit flavors and preventing browning. With reductive handling, dry ice (carbon dioxide) and other inert gas and sulfur dioxide may be used generously during fruit processing to protect the must from oxidation. This technique preserves fruit and floral flavors and delicate aromatic compounds, including thiols.

Question 26

What are thiols?

Answer 26

A thiol is an organosulfur compound that smells fruity in tiny amounts, but in larger amounts it smells like garlic and is considered a wine fault. Thiols are also a building block of earthiness

Question 27

In some white wine styles there can be intentional oxidation or hyper-oxidation of the juice. What is this and why is it practiced?

Answer 27

With intentional or hyper-oxidation, the juice turns brown initially but clarifies thought fermentation. This allows the most susceptible compounds to be oxidized and discarded as lees, resulting in a finished wine that is potentially less fruity but more resilient against post-fermentation oxidation.

Question 28

What is sous voile aging?

Answer 28

“under vail” aging, referring in Jura to aging under flor

Question 29

What is the only varietal used in Vin Jaune?

Answer 29

Savagnin

Question 30

In Jura, what does ouillé refer to?

Answer 30

A non-oxidative style of winemaking or “floral” style.

Question 31

Is sorting generally more extensive for red or white grapes?

Answer 31

Sorting is more extensive for red grapes or fruit that will see skin contact, since fruit that is pressed right away has less time to extract bad flavors.

Question 32

What is Laccase?

Answer 32

An oxidation enzyme produced by botrytis.

Laccase causes rapid oxidation that is not deterred by sulfur dioxide or alcohol, unlike other enzymes. Botrytis imparts a specific flavor profile (ginger and saffron, accompanied by oxidation) that is generally considered a flaw in dry wines, though some wines are defined stylistically by the presence of botrytis, including Savennières, Austrian Smaragd styles, and some wines from Alsace. Under ideal, dry conditions, botrytis infection results in noble rot, a condition that defines some important sweet styles including Sauternes and Tokaji.

Question 33

In white wines, what does whole cluster pressing result in?

Answer 33

Whole-cluster pressing minimizes skin contact, resulting in clearer juice with fewer skin-derived compounds, including phenolics that may cause bitterness. The stems act as a press aid, improving juice yields and clarification. White wine that has been whole-cluster pressed is often considered to be higher quality, though this depends on stylistic intent. It tends to result in a clean, bright, and delicate style, while wines from destemmed and/or crushed fruit can be more textured. Whole-cluster pressing is required for many styles of sparkling wine, where skin contact is undesirable.

Question 34

Of the following red winemaking processing options, which is the most traditional?

• Destemmed and crushed
• Destemmed but not crushed (whole-berry fermentation)
• Not destemmed and crushed (fermentation with stems)
• Not destemmed or crushed (whole-cluster fermentation, carbonic maceration)

Answer 34

Destemmed and crushed

Crushing begins the extraction process sooner, and because sugar is not trapped inside the berries, it is more available to the yeast. This can result in a faster, warmer fermentation. When tank space is at a premium, minimizing the time in tank is logistically beneficial. Stylistically, traditional fermentation avoids flavors contributed by carbonic maceration or stem inclusion.

Question 35

What is carbonic maceration?

Answer 35

Carbonic maceration is an intracellular fermentation that occurs inside intact berries in the absence of oxygen. This fermentation is mediated by enzymes naturally present in the grapes and does not require yeast or bacteria. Once the alcohol level inside of the berries reaches 2%, the enzymes are denatured, and the fermentation stops.

In strict carbonic maceration, carbon dioxide is added to a tank of whole clusters to displace oxygen and ensure an anaerobic environment, and the tank is sealed. The clusters remain intact and enzymatic activity takes place inside the berries. While little color is extracted from the skins, color from the skins is transferred into the pulp. After one to three weeks, the grapes are pressed sweet, and the wine completes primary fermentation off skins via the action of yeast. The resulting wines are simple, light, fruity, and often low in tannin and color.

Question 36

What does semi-carbonic maceration refer to?

Answer 36

Semi-carbonic maceration, often used synonymously with whole-cluster fermentation, refers to the practice of including a percentage of whole clusters, ranging from a small amount to 100%, in the fermentation. Juice in the bottom of the tank begins fermenting traditionally and produces carbon dioxide that induces carbonic maceration inside the intact clusters. The clusters may be broken down through cap management or foot-treading throughout the fermentation. Including whole clusters yields a slower, cooler fermentation, since stems create air channels that allow heat to dissipate and because sugar is released and consumed by the yeast more slowly. Some sugar typically remains trapped inside the berries and is released at pressing.

Question 37

Which varieties is semi-carbonic maceration more common with?

Answer 37

Pinot Noir and Syrah

Question 38

What does stem inclusion contribute?

Answer 38

Stems increase the concentration of phenolic compounds (especially catechins) and potassium. When stems are included, the resulting wine is often lighter colored and more tannic, with a higher pH and lower alcohol.

Some winemakers are partial to stems, while others believe that they contribute green, herbaceous, or bitter flavors to the wine. For this reason, they may be either avoided or included only when they have certain characteristics—for example, brown stems but not green.

Question 39

What do pectolytic enzymes do?

Answer 39

Pectolytic enzymes breakdown pectin and may be added to speed up the extraction process.

These enzymes help break down the grape skins, facilitating the extraction of color, tannin, and flavor. This is particularly important when logistics limit the duration of time allowed on skins. Similarly, pectolytic enzymes may be added prior to pressing to facilitate extraction and increase yields.

Question 40

Is extraction from the skins common in white wine making.

Answer 40

Extraction from the skins is limited and even avoided in white winemaking, as it can lend unpleasant bitter or green, leafy flavors, but there are instances where some skin contact is desirable. Skin contact can be used to increase the concentration of varietal aromas or phenolic extraction, resulting in a more textured wine. This can be accomplished through a short maceration on skins lasting from 2 to 48 hours.

For white wines that are intended to be light, fresh, and easy drinking, skin contact is typically avoided. A short maceration of a few hours may be used on Chardonnay to improve the wine’s structure and ageability. Aromatic grapes like Muscat and Gewürztraminer are good candidates for longer skin contact, but they also have bitter skins, so a winemaker must be careful to avoid over-extraction.

Question 41

What is saignée?

Answer 41

Saignée involves macerating on skins for a short time before bleeding juice off of the tank.

Saignée is a red-winemaking technique that concentrates must. Soon after processing, a small portion of juice is removed from a tank containing red grape must to increase the proportion of skins, and hence the concentration of the resulting wine. This juice may be made into rosé, but because it came from grapes intended for red wine, it is typically sweeter and has a higher pH than juice from grapes picked expressly for rosé and may require adjustment to yield a balanced wine.

Question 42

What is the range of duration of skin contract for red wines?

Answer 42

Red winemaking involves a longer period of skin contact, typically 10 to 21 days, though some fermentations remain on the skins for only 3 or 4 days and others may macerate for several months, referred to as extended maceration. During fermentation, extraction is increased through cap management techniques.

Question 43

What is cold soaking? When does it happen? Why do people practice it?

Answer 43

Prior to fermentation, red wines may be held uninoculated at cold temperature for anywhere from a few days to a couple of weeks in a process known as a cold-soak. During this time, fruit enzymes break down the grape skins, beginning the extraction process, and the populations of native yeast (favored over Saccharomyces at cold temperature) build slowly.

Some winemakers believe that cold-soaking increases color extraction, though this is debatable and depends on fruit composition.

Question 44

What is thermovinification?

Answer 44

Thermovinification and flash détente are niche techniques that accelerate the extraction of red grapes by exposing them to very high heat for a short period of time. This technique is NOT used in quality winemaking.

The must is heated to between 140 to 180 degrees Fahrenheit for a period of 30 minutes to 24 hours, with higher temperatures requiring less time. The must is often pressed directly after heating, and fermentation proceeds off of skins.

Question 45

What is pressing?

Answer 45

Pressing separates the juice (or wine, in the case of reds) from the skins and seeds and marks the end of the process of extraction from the skins.

Question 46

What is a winemakers press cut?

Answer 46

A winemaker’s press cut dictates when the juice coming out of the press will be diverted from light press to heavy press. This is a key decision in white winemaking, as the nature of the wine depends not only on what is extracted but also what is not. Winemakers seek to maximize the volume of the light-press juice, while avoiding unpleasant attributes that would lower its quality

Question 47

Is light or heavy press wine considered to be of lower quality?

Answer 47

Heavy-press wine is generally regarded as lower quality and is frequently fined or filtered to remove undesirable characteristics prior to fermentation. It can be an interesting blending component.

Question 48

Is most of the wine free run in red or whites?

Answer 48

Reds because reds are fermented with skins. With reds, most of the wine is free run, with press wine representing less than 20% of total volume Free run for whites is just the very minimal amount that comes off before pressing.

Question 49

What are the two broad categories of presses?

Answer 49

Batch and continuous

With a batch press, the press is loaded, the grapes are pressed, and the pomace is emptied out of the press. In continuous pressing, grapes are loaded into the press and pomace is expelled continuously. While continuous presses are sometimes used in high-volume winemaking, batch presses are preferred for quality.

Question 50

Is a batch press or a continuous press used for quality?

Answer 50

Batch

Question 51

What is currently the most common type of press?

Answer 51

Pneumatic press. They are gentle and provide good quality and high yields.

Pneumatic presses are more time consuming to load and clean than basket presses but often have a larger capacity and are less time intensive overall. For this reason, they are often preferred by larger producers. There are several types of pneumatic presses, but all have a horizontal cylindrical tank with perforated screens or internal drains that allow juice to escape.

Question 52

When is a tank press used?

Answer 52

In reductive winemaking.

A tank press is a fully enclosed membrane press ( a press with the inflatable bladder is located along one side of the tank and grapes are compressed against the other side.) that allows the winemaker to exclude oxygen for very reductive winemaking. This may be preferred for bright and clean white wine styles with delicate aromas, like popular styles of Sauvignon Blanc.

Question 53

What is débourbage?

Answer 53

A clarifying process by letting the wine sit over night, settling the solids at a cold temperature followed by a racking or decanting of the juice off of the solids that have settles to the bottom of the tank.

Question 54

What is bentonite used for?

Answer 54

Bentonite (a clay generally derived from volcanic ash) may be added after pressing to help clarify juice prior to racking. Here, bentonite acts as a setting aid, helping to remove grape solids, yeast, bacteria, pectin and proteins. It attracts proteins through electrostatic forces. It is not soluble in juice and will be removed during racking.

Question 55

Is chaptilization allowed in California?

Answer 55

No. Must may be enriched through the addition of grape concentrate. (That said, winemakers I na ll region are prone to bending the rules (says guildsomm))

Question 56

What’s the most common method for reducing potential alcohol?

Answer 56

Adding water to must. (this is is typically done in a tank prior to fermentation).

In many regions, the addition of water for the purpose of reducing alcohol content is not legal. However, it is typically permissible to use a “reasonable” volume of water for making additions, which gives winemakers a loophole to adjust the must. Alternatively, vines may be irrigated just prior to harvest, which is effectively a water addition, albeit less precise than adding water to the tank.

With red wine, water added prior to fermentation increases the capacity for extraction from the skins, whereas water added after fermentation is just a dilution.

Question 57

What is the most common type of acid used as an additive to balance a flabby wine?

Answer 57

Tartaric. Tartaric acid is typically used to adjust acidity since it is stable (that is, it cannot be broken down during fermentation) and found naturally in grapes.

Malic, citric, and sulfuric acids are also used occasionally.

Because lactic acid bacteria convert citric acid to diacetyl, reminiscent of popcorn butter, an addition of citric acid can enhance the buttery character of a wine.

Question 58

Through fermentation, do a wine’s pH and TA change or remain constant?

Answer 58

A wine’s pH and TA change throughout fermentation (especially for red wines) and aging, which makes it difficult to predict the ideal addition prior to fermentation, though this is learned through experience. Winemakers often make an addition prior to fermentation and might make a smaller adjustment after malolactic fermentation is complete.

Question 59

When salts are added, how do salts reach with tartaric acid, what is the result?

Answer 59

If acidity is too high, a wine can also be deacidified. There are several methods, all involving adding salts that react with tartaric acid to form tartrate salts that settle out of the wine. (However, the presence of tartrate salts in a wine does not imply that the wine has been deacidified.)

Question 60

What is Saccharomyces cerevisiae?

Answer 60

Saccharomyces cerevisiae is an alcohol-tolerant yeast that dominates most alcoholic fermentations

Question 61

What is Oenococcus oeni?

Answer 61

Oenococcus oeni is a lactic acid bacteria frequently responsible for malolactic fermentation

Question 62

If a winemaker chooses to inoculate with a yeast what is their most likely choice?

Answer 62

Saccharomyces cerevisiae or, less often, Saccharomyces bayanus

Saccharomyces are well adapted to the conditions of fermentation; they are alcohol tolerant and capable of finishing a fermentation, with some strains able to withstand alcohol concentrations of 16% to 17%— a unique characteristic. To ensure that fermentation finishes, it is important that a strong population of Saccharomyces is established early in the course of fermentation. Stress induced by low levels of nutrients can cause the yeast to produce high levels of reductive aromas or result in a stuck fermentation.

Question 63

In most cases, are non-Saccharomyces yeasts capable of completing fermentation?

Answer 63

No. In most Cales, non-Saccharomyces yeasts are not capable of completing fermentation.

Question 64

What is the dominant yeast species at the beginning of fermentation?

Answer 64

Kloeckera apiculata.

Kloeckera and Candida are more cold-tolerant than Saccharomyces, so the practice of cold-soaking favors them.

Question 65

What are the two categories of bacteria that are present in wine?

Answer 65

Lactic acid bacteria (LAB) and acetic acid bacteria.

Lactic acid bacteria are key in winemaking because they are responsible for malolactic fermentation.

Question 66

Which is the most desirable lactic acid bacteria for completing malolactic fermentation?

Answer 66

Oenococcus oeni is the most desirable, since it is relatively alcohol and low pH-tolerand and less likely to produce high levels of volatile acidity and other wine taints.

Question 67

How do LAB (Lactic Acid Bacteria) participate in autolysis?

Answer 67

LAB participate in autolysis by producing enzymes that break down dead yeast cells.

Question 68

What does acetic acid bacteria do?

Answer 68

Acetic acid bacteria (AAB) converts alcohol to acetic acid (vinegar). Although useful in vinegar product AAB are considered spoilage organisms in wine.

Question 69

Towards the end of fermentation at dryness Brix can measure in a negative degree (-1), (-2), why is this?

Answer 69

Ethanol is less dense than water.

In a healthy fermentation, dry wines generally begin in the range of 18 to 25 degrees Brix. Toward the end of fermentation, the readings become negative, since ethanol is less dense than water. At dryness, the Brix reading may register around −2 degrees Brix. At the same time, the temperature increases throughout most of fermentation and may begin to decrease toward the end.

Question 70

What is pied de cuve?

Answer 70

A portion of yeast-rich, already fermenting grape must that may be used to inoculate a fermentation (as with using a sourdough starter for baking).