Improving wine balance with varietal blending

Wine blends are constructs of two or more varietals, and/or micro/macro-climates, and or clones, and/or juice types (press or free-run) that are implemented by the winemaker to, among other reasons, overcome wine deficiencies or defects, improve balance, or enhance complexity. I have previously discussed blending and wine complexity and will cover wine balance and blending in this post.

According to Dr. Bruce Zoecklein, Head of the Enology/Wine Chemistry Group at Virginia Tech, wine can be broken down into the three sensory categories indicated in the table below.

                              Wine Sensory Components

Structure                                  Texture                               Flavor
Sweet                                       Light (delicate)                   Nutty
Acid                                         Rich (dense)                       Earthy
Astringency                                                                         Herbal
Bitterness                                                                            Smoky
                                                                                            Spicy
                                                                                            Berry
                                                                                            Tropical Fruit
                                                                                            Apple*
                                                                                            Citric*
                                                                                            Pear*
* Found mainly in white wines
Source: Derived from Figure 1 of Matching Food and Wine.

As regards the structural components, Dr. Zoecklein argues that a balanced relationship must exist between the tastes of sweetness, on the one hand, and acid, astringency and bitterness on the other, in order to yield the perception of a quality wine to the taster.  The preferred relationship is captured in his Palate Balance Equation (Zoecklein: Components of Red Wine Mouthfeel):

           Sweet ⇄ Acid + Phenolics (Astringency and Bitterness),

where

          Sweet = Carbohydrates + Polysaccharides + Ethanol,
          Acid = Population of organic acids, and
          Phenolics = Skin, seed, and stem phenols + barrel phenols + enological tannins + volatile  phenols.

Based on the foregoing equation, an increase in the sweetness element will lead to a reduction of the taster's perception of acidity and phenolics; and the reverse is also true.  Dr. Zoecklein sees this balance, or harmony, as a key indicator of wine quality and, in that, he is joined by Wines and Vines and Crushpad Blog, among others. According to Chris Stamp, writing in Wines and Vines, "... a balanced wine is a wine in which the various components work together to provide a pleasing taste."  According to Richard Leahy, writing in Crushpad Blog, wines that are in balance tend to stay that way while wines that are out of balance tend to grow moreso over time.

How does balance relate to quality? If, for example, a wine has insufficient sugar in relation to its acids and phenols, it will present as harsh and acidic and will retard the evolution of flavors in the mouth of the taster. A wine with too much sugar, on the other hand, will be flabby and cloying and will not refresh the palate. The sweetness of sugar also balances out the bitterness of phenols. Alcohol adds to the sensation of sweetness in a wine. It also adds a thickness. Too much alcohol and the wine can present as hot, lead to a reduced perception of wine aroma, and can impart a sense of intoxication.  For a winemaker doing business in the US, there is an approximately $.50 difference in the taxes paid per gallon of produced wine if the alcohol level goes beyond 14.001%.

The winemaker needs to know the acid content of the grape and must in order to: decide when to harvest; determine pre-fermentation must treatment; monitor wine stability; and comply with US TTB requirements of 0.5% minimum acid levels. Red table wines generally range between 0.6% and 0.7% TA as levels below 0.4% render the wine susceptible to infection and spoilage. A second method for measuring the acidity of a wine is through observation of its pH (potential of hydrogen) level. The pH level of a wine affects the way it is perceived by the wine drinker as well as its reaction to micro-organisms. Low-pH wines are generally viewed as sour and render tannins more astringent but they also limit micro-organism growth.

Grape tannins provide color, flavor, structure, and texture to the wine and serves a preservative function. Tannin affects wine balance in the following ways:

• The lower the tannin levels, the greater the amount of acidity the wine can support; conversely, the higher the tannin levels, the lower should be the acidity
• High-acid, high-tannin wines tend towards astringency
• Too much tannin results in wines that are heavy on the palate, lacking in finesse, and possessing a rough finish
• Increasing alcohol content increases the intensity of bitterness and decreases the sensation of astringency
• Low alcohol levels will result in dominant acidity and astringency and harsh, thin wines
• Lowering wine pH increases the astringency of the tannins.

To summarize, acid gives wine a tartness and freshness while countering the effect of sweetness and magnifying the astringency of tannins. If a wine has too much acid it will be puckery and sour; too little and it will be flat, flabby, and dull. If a wine has insufficient sugar in relation to its acids and phenols, it will present as harsh and acidic and will retard the evolution of flavors in the mouth. If the wine has too much sugar, it will be flabby and cloying and will not refresh the palate.

Hopefully the normal grape-growing and alcoholic fermentation processes would have produced a balanced wine but if an imbalance were brought about by an insufficiency or excess of any of the elements described above, the winemaker may choose to blend with a varietal that addresses the imbalance. The following are examples of varietals which contribute to balance-enhancement in selected wine blends (Stenwreth MW, Tong 15; finewineconcierge.com; winelit.slsa.sa.gov.au)

• In the Langhe region, Barbera is used to tone down the tannins of the mighty Nebbiolo
• In California, Petit Sirah is used to add structural backbone to Zinfandel
• Petit Verdot adds freshness and firmness to blends
• Malbec, Merlot, and Carmenere soften the tannins of Cabernet Sauvignon in Bordeaux blends
• Cabernet Franc adds freshness (among other features) in Bordeaux blends
• Pinot Noir adds body and structure (among other characteristics) to Champagne
• Chardonnay adds freshness to Champagne
• Mazuelo adds structure and freshness (among other features) to Rioja wines
• Graciano adds acidity to Rioja wines
• Canaiola adds sweetness to Chianti and tempers the harshness of Sangiovese.

©Wine -- Mise en abyme

Wine balance: Napa's Phoenix

In the early 1970s, Napa wines exhibited characteristics that were close enough to wines from France that a group of leading French experts famously (Judgement of Paris) could not differentiate between the wines from the two regions and awarded top honors, in both the red and white flights, to the wines from Napa.  Somewhere along the way the paths of these two regions diverged (some would say that Napa lost its way) and Napa wines became known as fruit, alcohol, and oaken bombs that were too extracted and dangerous to food.  A sense abounds, however, that the tide is beginning to turn and that a vanguard of the winemakers who jumped off the deep end are beginning the long swim back to join those who had the courage and foresight to mann the shore batteries against the onslaught of sweet.  We examine the forcing factors in this post.

Source: beltwayfinewine.com

According to Greg Byrne (Wine surges in popularity ..., Santa Fe New Mexican, 7/15/09), in the 1970s and 1980s, many Napa wineries picked too early in an attempt to emulate the wines of Bordeaux.  The standard practice was to harvest grapes based on sugar ripeness -- pick at 23.6 degrees Brix in order to yield 12.6% alcohol in the fermented wine.  After many years of pursuing this path -- a path, according to Byrne,  littered with overly tannic, underripe, harsh wines -- Joe Heitz (Heitz Cellars) began to agitate for producing wines based on what the climate allowed rather than what Bordeaux was producing.  In the early 1990s, then, hang time became the buzzword as winemakers pursued riper fruit and the wine style changed for the better.

Writing about this same period, John Gilman (California Classicism, The World of Fine Wine (TWoFW), Issue 35, 2012) saw two waves of winemaking which, by the end of the 1970s, had placed California winemaking squarely on the map:

1960s                                          1970s
Heitz                                           Joseph Swan
Ridge                                          Sterling
Mayacamas                                Chateau Montelena
Mondavi                                      Clos du Val
Chalone                                      Joseph Phelps
Schramberg                                Stag's Leap Wine Cellar

The two men agree that Humpty Dumpty fell off the wall but disagree as to the forces that dislodged him.  According to Byrne, the lack of rain in Napa in September and October allowed for much longer  hang time and phenolicly ripe fruit.  It also brought along, however, higher sugar levels, lower acidity, darker color, and richer flavors.  By marrying this style of wine with young oak, the Napa winemaker was now promoting power and exuberance over elegance and finesse.  Byrne feels that too many winemakers went too far down this path.

While Bryant saw viticultural practices, as it related to phenolic ripeness, as the Napa problem, Gilman sees the problem as the industry's pursuit of cellar-based technology solutions aimed at closing the "Bordeaux gap" (and the creation of winemaking superstars who, from time to time, read their own reviews).  In addition, phylloxera had caused widespread replantings in the 1990s and cellar manipulation was used to paper over resulting problems such as young juice in the mix, improperly sited vines, and the pursuit of high yields by the growers in order to meet high demand.

Adding fire to the flame was Robert Parker assigning high scores to these wines and an indolent, self-centered, unquestioning public snapping up the wines at every turn, based exclusively on these scores.  This created a vicious cycle with existing wineries adjusting their wines in pursuit of points and new entrants applying the formula from day one.

Regardless of the proportions, these factors had combined to push the industry to a "bad place" by the end of the 1990s.  Gilman has characterized that place: high-alcohol wines made from late-picked fruit, vinified with residual sugar, sprinkled with winemaking additives, and matured in expensive new oak.  "Phenolic ripeness became the mantra behind which this was all concealed."  Alcohol levels had gotten so high that a number of post-fermentation mechanisms were created for mitigation purposes; likewise, technical solutions were employed to address acid deficiency.

A number of factors point to a sea change but, before we address those, let us take a look at the winemakers who did not respond to the siren song of imbalance.  The figure below is a compilation of wineries who continued to make wines the old-fashioned way, with words like balance, elegance, finesse, and food being their north stars.  The winemakers on this list, plus some others he refers to as "neo-classicists" (James Johnson Vineyards, Philip Togni, for example), remain today, according to Gilman, "at the top of their games and are currently fashioning some of the greatest wines in their illustrious histories."

A number of writers have been making the case that California winemakers are beginning to see the light and are moving to more balanced wines.  The writers mentioned in this article definitely fall into this camp.  Byrne sees the pendulum as swinging back to finesse, acidity, and varietal character.  Gilman views the wines being crafted by the old-liners and the neo-classicists as "classic, old-school wines crafted for the cellar and destined to evolve gracefully."  You can also add Alice Feiring to the mix.  In a June 2012 article in the Daily Beast (Big? Jammy? Not Anymore! California ...) she cites examples of winemakers who have, for one reason or the other, made the switch from powerful to more food-friendly wines.  She makes the point that grass roots organizational activity is also forcing the industry to re-examine its position.  Case in point, the In Pursuit of Balance initiative spearheaded by Rajat Par (celebrity sommelier and winemaker) and Jasmine Hirsch, Director of Marketing for Hirsch Vineyard.  Hirsch is quoted in the article as saying that one of the drivers of the move to balanced wines is a maturing of the American wine palate and an associated quest for greater subtlety and complexity.

The perceived waning influence of Robert Parker is cited as another reason for this shifting wine style.  Parker preferred the style of wine which came to be characteristic of Napa and winemakers and customers heeded his cry.  With the financial crash, collectors who pursued this type of wine were wiped out and began looking for less expensive alternatives.  They even started looking in places like Chile and Argentina, for crying out loud.  Paralleling the fall of Parker's traditional base was the rise of the Millenial's as serious players.  In contrast to Parker's traditional base (i) their tastes' were eclectic and (ii) they did their own research , drawing on friends, acquaintances, blogs, and critics who had been laboring in the shadows.  Parker's pronouncements still move product but the echo chamber is becoming smaller with the passage of time.

How does a winemaker get on this train?  According to Gilman: (i) steer clear of high alcohol; (ii) keep ripeness in check; (iii) keep new oak in check; and (iv) produce structured wines with balance and complexity.


© Wine -- Mise en abyme

Diurnal temperature shifts and wine quality

Diurnal temperature range (DTR) refers to the difference between the highest daytime temperature and the lowest nighttime temperature.

Source: http://apollo.lsc.vsc.edu/classes/met130/notes/chapter3/daily_trend4.html

As it relates to wine, many estates/regional promoters tout the fact that their estates are located in areas of high diurnal variation because of, as they see it, the benefits conferred on grapes grown in the region.  For example, washingtonwine.org states "One of the greatest natural phenomena for growing grapes which end up balanced between ripe sugars (which will equate to alcohol in the wine) and crisp acidity is a difference between day time and night time temperatures ..."  The site goes on to say that Washington State has some of the most dramatic fluctuations in the world with differences of as much as 40℉ between the high day and low night temperatures.  The organization sees the cool evenings as preserving malic acid in the grape which "translates through fermentation to wine and adds freshness and balance."  It should be noted here that the organization sees wine balance as a mediation between sweetness and acidity, a position that runs counter to the definition that has been established on this blog.

Concha y Toro, one of the leading Chilean producers, sources grapes for its Don Melchor label from the Puente Alto vineyard in Maipo Valley.  According to the winery's website (conchaytoro.com), "It is the sharp diurnal temperature differences that assist tannin ripening and the development of aromas as well as fixing exceptionally high quantities of polyphenol compounds in the grape."  In their discourse on the benefits of high diurnal variation, Concha y Toro focuses exclusively on its perceived benefits for the secondary metabolites versus the primary metabolite arguments of washingtonwine.org but, in both cases, the argument is "high DTR is beneficial for the grape and its end product, the wine."  That is not a universally held position.

There is a second school of thought which decries significant DTRs and views balanced wines as a product of balanced temperatures.  The principal of this school is John Gladstone (Wine, Terroir, and Climate Change) but philosophical adherents are sprinkled throughout the industry (see, for example, Climate and the ripening process, wine business.com, August 2007; What makes LI wines "cool", Suffolk Times, March 31, 2011).  The basic tenet of this school is that a low temperature range during the growing season creates wines of the best quality and that sites with this characteristic tend to be in maritime or high-latitude locations.

According to adherents, the factory that is the vine operates on all cylinders during the daytime with the presence of light allowing for photosynthesis and the accumulation of sugars into the berry.  Photosynthesis ceases with the onset of darkness, but, according to this school, if the nighttime temperature does not fall below a certain level, respiration and flavor and tannin synthesis will continue, resulting in more rapid and complete phenolic ripening of the fruit at lower sugar levels.  Diurnal variation in arid regions, according to this school, allows production of high levels of sugar during the daylight hours and the cool nights take the vines out of the effective metabolic range.  This slows the phenolic ripening process thus allowing the accumulation of higher sugar levels over the longer ripening period and an unbalanced wine.

At this moment let us take a step back and look at what is known regarding temperature effects on berry development:

Higher temperatures

• increased rate of sugar accumulation
• increased rate of organic acid degradation
• inhibition of anthocyanin development

Lower temperatures

• reduction in the rate of sugar accumulation 
• reduction in the rate of organic acid degradation.

We also know that phenolic ripeness is highly temperature dependent (Mark Greenspan, wine business.com) and that phenolic ripening processes will operate sub-optimally or shut down as you move further away from the optimal (Mark Greenspan; Louisa Hargrove, Suffolk Times).

Based on the foregoing, the following Greenspan adages still hold true:

• In arid regions, cool nights are essential for the prevention of rapid acid metabolism
• Different wine styles are produced in high-DTR versus narrow-DTR areas
• Areas with narrow-DTRs generally gain phenolic ripeness at lower sugar levels than do their high-DTR counterparts

© Wine -- Mise en abyme

Available mechanisms for ameliorating tannin-associated wine imbalance

In a previous post on tannins and wine balance, I noted that too much tannin results in a wine that is heavy and rough on the palate and lacks finesse.  Further, if combined with high acidity, the wine will be astringent.  While low levels of tannin may result in an early drinking wine, it may compromise color stability, mouthfeel, and the aging potential of the wine.  This post looks at the tools available to the winemaker to increase/decrease tannin levels as desired.

Increasing Tannin Levels

Tannin levels can be elevated by manipulating aspects of the winemaking process to extract more tannin from a given batch or by adding exogenous tannin during the winemaking process.

The primary integral process for elevated tannin extraction is maceration.  The length of the maceration, and the controlling temperature, are two very important variables in determining tannin extraction levels.  The longer the duration, the higher the levels of tannin and anthocyanin extracted. The higher the temperature (within limits), the higher the tannin extraction rate.  With the higher levels of phenolic compounds that result from post-fermentation maceration, the greater the potential for phenolic polymerization and wines with a softer mouthfeel.

While maceration can be used to extract tannin from both skin and seed, warm processing is a method wherein a quick, hot fermentation is applied to allow extraction of tannin from the skin while minimizing seed contact.

Exogenous tannin addition can be oak (or like products) or powdered.  In the case of oak, the wine is either placed into oak barrels or oak powder, chips, or planks are placed into the container in which the wine resides (The role of oak tannin was discussed in the preceding post.).  Powdered tannin is the end product of mechanical action on grape seeds or various types of wood.  A recent study by Washington State Enologist Jim Harbertson and Australian Wine Researcher Mark Downey called the efficacy of the latter approach into question.  Their key findings were: (i) most of these additives are 12%-48% tannin and (ii) had limited or negative impact on wine quality.  They concluded that the addition of powdered tannin was an unnecessary expense.

Retarding Tannin Levels

"Cold soak" is a method that is utilized in the winery to extract anthocyanins from the grape skin while restricting the level of tannin extraction.  Anthocyanins are more soluble in grape juice than in alcohol so soaking the solids in the juice at 45℉, or lower, will retard the initiation of fermentation while allowing the extraction of color from the skin and limiting the tannin extract.

Fining is a method of clarifying or chemically stabilizing wine using agents that are insoluble in the liquid, have the ability to bind with suspended particles, and are heavy enough to fall to the bottom while retaining the attracted material.  Tannins have an affinity for proteins and protein fining agents such as gelatin, egg white, and isinglass are used to remove tannin from the wine in this manner.  The fined wine is racked off the bottom-resident particles.  Care has to be taken that the wine is not over-fined as the result may be wines that lack complexity, depth, and viscosity and have diminished aging potential.

      ****************************************************************************************************

In addition to raising or lowering tannin levels, tannin-associated wine imbalance can be addressed by actions taken in relation to the other elements of the balance equation.  For example, reducing the acidity levels in high-tannin, high-acid wines will reduce the level of astringency in the wine.  In addition, increasing the level of alcohol in a wine will increase its bitterness but will also reduce the sensation of astringency.  Astringency is also decreased with increasing wine pH.

Hopefully the winemaker will be presented with grapes with the appropriate amount of tannins to ensure the production of balanced wines but if he/she is presented with an excess or surfeit of tannins, the above mechanisms are available for amelioration.

© Wine -- The View From Orlando

The role of tannins in wine balance

Wine quality, as perceived by the consumer, has a number of elements, an important one of which is wine balance.  I have defined wine balance in a previous post but will reproduce Dr. Bruce Zoecklein's (Virginia Tech Enologist) Palate Balance Equation here to highlight the included elements.

              Sweet ⇄ Acid + Phenolics (Astringency and Bitterness).

I have treated the sweet (alcohol) and acid elements of this equation in prior posts and will focus on the phenolics element in this post.  The placement of phenolics (tannin) and wine balance in the quality assessment framework is indicated by the arrow in the figure below.

So what are tannins?  According to the indefatigable Dr. Zoecklein (Enology Note #116), tannins are "a heterogeneous group of phenolic compounds" with properties to include: astringency (caused when the tannin binds with protein in saliva; evidenced by mouth pucker and a bitter aftertaste); bitterness; the ability to react with ferric chloride; and the ability to bind with proteins.  A key characteristic of phenols, according to Dr. Zoecklein, is the ability to associate with (polymerize, in scientific lingo) themselves and other compounds thus yielding larger molecules.  The degree of polymerization (an actual metric) tends to increase with the passage of time.

There are two main types of tannins: hydrolizable and condensed (more properly called proanthocyanidins).  Hydrolizable tannins are found in the bark of oak and other plants and are formed in the growing tree for the purpose of food storage. These tannins are called hydrolizable because they can be broken down into smaller components in the presence of an acid or water.  Condensed tannins are insoluble and are found in tea, pomegranates, and the seed, skins, and stems of grapes.

Grape tannins are a combination of compounds (cathecin, epicathecin, epigallocathecin) which link up in chains and of which at least two need to be present for the compound to be termed a tannin. Seed tannins weigh, on average, 3.5 - 5mg per berry while skin tannins weigh in between 0.5 and 0.9 mg.  Seed tannin polymers are shorter than skin tannin polymers (the longer the tannin chain the higher the astringency) yet seed tannins are perceived by winemakers to be harsher, greener, and more astringent than skin tannins and that is evidenced in the way that the berry is handled once it enters the winery.  Oak tannins are astringent in tree matter and need to be seasoned and toasted -- as a part of the barrel treatment -- in order to increase their usefulness.

Grape tannins accumulate during the first period of berry growth with skin tannin synthesis beginning earlier than seed tannin synthesis and then ending with the conclusion of the first phase of growth. Seed tannin synthesis continues into the early period of berry ripening before concluding.  Both skin and seed tannins continue to mature during the berry ripening phase.

Tannins release is a function of how the grapes are handled in the winery.  Tannins are not desirable in white wines so white wine grapes are pressed lightly and there is no contact between the juice and skin.  In the case of red wines, tannins are desirable for color, mouthfeel, and aging and there is extensive skin contact. The amount of tannins released are a function of skin thickness (Cabernet Sauvignon, Nebbiolo, and Syrah are thick-skinned and thus release more tannins than do thin-skinned varieties like Pinot Noir, Gamay, and Cabernet Franc), the length of maceration, and the number of cap punch-downs to which the must is subjected.  Skin tannins release early and easily (as they are water soluble) but then plateau.  Seed tannin release is slow, steady, and long and requires alcohol as a solvent.  Once grape tannins are in solution, 80% of them undergo one or the other of the structural changes listed below:

• Tannin-tannin linkages
• Oxidative change
• Acid-catalyzed reactions
• Bind with anthocyanins (color compounds) to form polymeric pigments that ensure long-term color stability
• Formations that provide structure and mouthfeel to wines.

Grape tannins provide color, flavor, structure, and texture to the wine and serves a preservative function.  Oak tannins play an essential role in wine maturation in that they: (i) promote oxidation products (react with oxygen in the presence of a transitional metal to release activated oxygen which, in turn, oxidizes alcohol to acetaldehyde);  (ii) produce astringency; and (iii) aid in the removal of off-notes.  Tannin-anthocyanin complexes sediment out of wines as they age resulting in browner, less tannic wines.

Tannin affects wine balance in the following ways:

• The lower the tannin levels, the greater the amount of acidity the wine can support; conversely, the higher the tannin levels, the lower should be the acidity
• High-acid, high-tannin wines tend towards astringency
• Too much tannin results in wines that are heavy on the palate, lacking in finesse, and possessing a rough finish
• Increasing alcohol content increases the intensity of bitterness and decreases the sensation of astringency
• Low alcohol levels will result in dominant acidity and astringency and harsh, thin wines
• Lowering wine pH increases the astringency of the tannins.

The winemaker has a number of tools at his/her disposal to increase/reduce tannin levels as required and I will discuss those tools in a follow-up post.

© Wine -- The View From Orlando

The role of alcohol in wine balance

Wine balance is one of the important measures of wine quality and attainment of said balance, according to Dr. Bruce Zoecklein (Virginia Tech oenologist), requires the harmonic functioning of each element in the Palate Balance Equation reproduced below. The arrow on the figure following the equation illustrates where balance and alcohol fall within the wine quality assessment framework.

              Sweet ⇄ Acid + Phenolics (Astringency and Bitterness).

Fortunately for wine drinkers, the structure that grape vine plants have evolved for the protection and nourishment of their genetic-material-carrying seeds, also serves as the raw material for the drink of their choice.  At harvest, the vitis vinifera berry has the following composition (Murli Dharmadhikari, Director and Enologist, Iowa State University Extension):

• Water (70 - 80%)
• Dissolved solids
• Sugar (primarily glucose and fructose; 150 - 200 g/L if ripe)
• Organic acids
• Phenolic compounds
• Nitrogenous compounds
• Aroma compounds
• Minerals
• Pectic substances (primary role is cementing plant cells together).

The dissolved solid of interest herein is sugar so we will focus exclusively on that topic for the remainder of this post.

Sugars exist in the grape vine as sucrose (a one-to-one bond of the single-molecule sugars glucose and fructose) and are transported to the berry from the vine where it is metabolized.  As the berry develops (see figure below), the vine-sourced sucrose decreases in volume and is replaced by carbohydrates from surrounding leaves.  Once in the berry, sucrose is separated into its constituent parts by the enzyme invertase.

As the figure below shows, xylem flow (water and nutrients from the roots) to the berry stops shortly after veraison but the flow of nutrients from surrounding leaves (via the phloem) continues through the bulk of the ripening phase.  As the figure shows, the sugar, measured in °Brix (the sugar-content metric used in the US; % sugar by weight), begins to accumulate in the berry post-veraison as sugar consumption declines.  The sugar content at berry maturity can range between 12 and 28% with the optimal level for harvest falling between 19 and 25 Brix.

Grape berry development (Source:www.extension.org)

In a 1966 study, W. Mark Kliewer of UCDavis concluded that the following sugars resided in a mature grape berry: Stachyose, Manninotriose, Raffinose, Melibiose, Maltose, Sucrose, Galactose, Glucose, and Fructose.  With the exception of glucose and fructose, all of the sugars are found in minute amounts and do not contribute in any way to the sensory characteristics of fermented wine. 

Glucose is a 6-carbon-atom sugar resulting from the breakdown of sucrose by the berry and is the first sugar to be broken down by the yeasts during the fermentation process.  There is 5 times more glucose than fructose in the berry at the beginning of the ripening stage but the levels are about equal at the time of harvest due to rapid fructose accumulation in the later stages of berry development.  Through its participation in the development of glycosides, glucose plays a role in the flavors of wine based on the interaction of those glycosides with phenolic compounds such as anthocyanins and terpenoids.  Fructose is twice as sweet as glucose and is a key component in the sweet sensation of wine.  Depending on the time of harvest, the ratio of glucose to fructose in the berry will vary: In an unripe berry, glucose will be dominant; at the ripening stage, the levels will be even; if the grape is over-ripe, fructose will dominate; and if the grape is ripe, the levels will vary depending on whether the variety is high-fructose (e.g., Chardonnay and Pinot Blanc) or high-glucose (e.g., Chenin Blanc and Zinfandel).

Wine is a result of using yeasts (Saccharomyces) in an anaerobic (oxygen-free) environment to convert the sugars from the pressed grape juice into ethanol in the two-step process illustrated in the figure below.  The first step -- glycolysis -- results in the 6-carbon glucose being split into two 3-carbon pyruvate molecules.  In the next step --- alcoholic fermentation - four atoms of oxygen and two atoms of carbon leave the pyruvate, resulting in acetaldehyde which is converted into ethanol.

Alcoholic fermentation (Source: http://alcoholicfermentation.net/) 

Wine is never fermented completely dry as sugars such as xylose and arabinose survive the fermentation process unscathed.  The amount of alcohol produced as a result of fermentation is directly related to the amount of sugar present in the juice initially.  The conversion ratio is ºBrix x 0.55 = alcohol in wine (Dr. Dharmadhikari).  Residual sugar is the measure of sugar solids remaining after alcoholic fermentation and is stated in g/L.  For dry wines the residual sugar ranges between 0.2 and 0.3 g/L while the measure for sweet dessert wines ranges between 5 and 15 g/L.

In wine, the sweetness of sugar balances out the bitterness of phenols.  Sweetness is perceptible by humans at around 1% of volume but that perception is dependent on the size of the sugar molecule. Both fructose and glucose are single sugar molecules and are perceived as sweet by humans because they fit neatly into the receptors on the tongue.  Carbohydrates, on the other hand, are long chains of sugars, do not fit neatly into the receptors on our tongues, and are not perceived as sweet.

As stated previously, wine balance is viewed as a key indicator of wine quality.  If a wine has insufficient sugar in relation to its acids and phenols, it will present as harsh and acidic and will retard the evolution of flavors in the mouth.  In such a case the winemaker may choose to add sugar (chaptalize) in the form of cane sugar (sucrose in cane sugar is inverted by the enzymes present in the wine and converted into glucose and fructose) or corn sugar (dextrose which will be fermented quickly by the yeasts).

Alcohol adds to the sensation of sweetness in a wine. It also adds a thickness. Too much alcohol and the wine can present as hot, lead to a reduced perception of wine aroma, and can impart a sense of intoxication.  For a winemaker doing business in the US, there is an approximately $.50 difference in the taxes paid per gallon of produced wine if the alcohol level goes beyond 14.001%.  If the winemaker believes that the wine would benefit from de-alcoholization, there are three methods available to him/her: reverse osmosis, spinning cone, and adding water.  These methods will be discussed in greater detail in a subsequent post.

Hopefully the normal grape-growing and alcoholic fermentation process would have produced a balanced wine but if an imbalance were brought about by an insufficiency or excess of alcohol, the winemaker has tools available to address the problem.

© Wine -- The View From Orlando

The role of acidity in wine balance

Now that I have provided a contextual framework for wine balance, I can return to the promised discussion of acidity, one of its constituent elements.  As a refresher on acid's relationship to balance, Dr. Bruce Zoecklein's (Virginia Tech oenologist) Palate Balance Equation is reproduced below. The arrow on the figure following the equation illustrates where balance and acidity fall within the wine quality assessment framework.

              Sweet ⇄ Acid + Phenolics (Astringency and Bitterness).

Acids play an important role in the cellular and metabolic functions of the grape berry and in the color and texture of the fermented wine.  The precursors of acid are formed in the leaves of the grape plant and are transported to the berries where they are synthesized to acids.  Acid accumulation begins at the start of berry development and continues unabated until the beginning of the ripening process.  Acid levels tend to vary acording to the controlling temperatures of the growing region; in warmer regions acid is used up during respiration, resulting in lower acidity levels in the fruit at harvest.  Conversely, acid levels are higher and sugar levels lower in cooler-climate growing regions.

The primary acids found in grapes and fermented wine are tartaric, malic, and citric acids as well as the tartaric and malic derivatives potassium hydrogen tartrate (cream of tartar) and potassium hydrogen malate.  Tartaric acid -- which occurs in nature in fruits such as grapes, bananas, and tamarinds -- represents between 50% and 66% of the acid content in a ripe berry and, as such, controls the acid content in the finished wine.  The tartaric acid level falls off as the grape ripens but not as much as in the case of malic acid.  Crystallized tartaric acid precipitates out of the wine during fermentation and can form crystals on the underside of the wine bottle cork if the wine is stored below 50ºF.  Tartaric acid is resistant to attack by wine microbes (and thus lends ageability with lower spoilage risk to the finished product) and is the winemaker's material of choice if/when a decision is made to add acid to a wine.

Malic acid is the second most important contributor to grape acid levels with amounts ranging between 23% and 40% of the total acid content.  The grape utilizes malic acid during respiration at a rate higher than for tartaric acid, leading to a higher ratio of tartaric-to-malic acid at harvest than at the earlier stages of fruiting.  Unlike tartaric acid, malic acid can be metabolized by a number of organisms and winemakers take advantage of this fact to to reduce wine acidity through malolactic fermentation, a process wherein the bacteria convert the hard malic acid to the softer lactic acid and carbon dioxide.  Malolactic fermentation increases the wines aging potential as the bacteria that metabolize the malic acid also scavenge remaining nutrients and, in so doing, reduce the potential for future microbial spoilage.  Malolactic fermentation occurs post-alcoholic-fermentation and is automatic for most red wines and selected whites.

Acetic acid is produced during fermentation by the conversion of ethanol to acetic acid by a species of  Acetobacter or from the actions on glucose by selected anaerobic bacteria.  The acid is present in most wines at levels of approximately 0.5 g/L and is detectable by humans as a pungent odor at levels of 1.0 g/L and above.  The legal limit for acetic acid in wine is 1.2 g/L in California and 1.4 g/L elsewhere in the U.S.  Acetic acid boils off when heated and as such is referred to as volatile acidity.

The winemaker needs to know the acid content of the grape and must in order to: decide when to harvest; determine pre-fermentation must treatment; monitor wine stability; and comply with TTB requirements of 0.5% minimum acid levels.  Total acidity is the sum of the hydrogen ions of both fixed and volatile acids that are present in the wine and, as such, is the most accurate representation of acid concentration.  Total acidity is difficult to measure accurately, however, and so the more easily measurable titratable acidity (TA) is used as its proxy.  Acids and bases neutralize each other to water so the acidity of a liquid can be approximated by determining the amount of an alkaline solution that is required to neutralize it to water.  The acidity level revealed in this manner is called the substance's titratable acidity.  Red table wines generally range between 0.6% and 0.7% TA as levels below 0.4% render the wine susceptible to infection and spoilage.

A second method for measuring the acidity of a wine is through observation of its pH (potential of hydrogen) level.  The higher the number of hydrogen ions (H+) in a liquid, the more acidic it is while the higher the number of hydroxide ions (formed when an oxygen ion bonds to a hydrogen ion and represented as OH-) in the liquid, the higher its alkalinity. The pH scale (illustrated below) runs from 0-14 with acidic solutions falling below 7,

Source: epa.gov

7 as a point of neutrality, and alkaline solutions falling between 7 and 14.  A change of 1 unit on the scale represents a 10-fold change in pH.

The pH level of a wine affects the way it is perceived by the wine drinker as well as its reaction to micro-organisms.  Low-pH wines are generally viewed as sour and render tannins more astringent but they also  limit micro-organism growth.  Higher pH provides a more favorable environment for micro-organism growth and reduces the functionality of sulfur application.  White wine pH ranges between 3.0 and 3.3 while red wine pH falls between 3.3 and 3.5.  Low pH values are often correlated with high TAs and vice versa.

To summarize, acid gives wine a tartness and freshness while countering the effect of sweetness and magnifying the astringency of tannins.  If a wine has too much acid it will be puckery and sour; too little and it will be flat, flabby, and dull.  As stated previously, wine balance is viewed as a key indicator of wine quality.  If a wine has insufficient sugar in relation to its acids and phenols, it will present as harsh and acidic and will retard the evolution of flavors in the mouth.  In such a case the winemaker may choose to de-acidify using potassium bicarbonate or calcium carbonate or dilute the wine with water or a low-acid wine.  If the wine has too much sugar, it will be flabby and cloying and will not refresh the palate.  In such a case the winemaker may choose to acidify the wine by adding tartaric, malic, or citric acid.

Whether naturally obtained or engineered, appropriate acidity is a key element of wine balance.

© Wine -- The View From Orlando

Wine balance as a quality measure

According to Dr. Bruce Zoecklein, Head of the Enology/Wine Chemistry Group at Virginia Tech, wine can be broken down into the three sensory categories indicated in the table below.

                              Wine Sensory Components

Structure                                  Texture                               Flavor
Sweet                                       Light (delicate)                   Nutty
Acid                                         Rich (dense)                       Earthy
Astringency                                                                         Herbal
Bitterness                                                                            Smoky
                                                                                            Spicy
                                                                                            Berry
                                                                                            Tropical Fruit
                                                                                            Apple*
                                                                                            Citric*
                                                                                            Pear*
* Found mainly in white wines

Source: Derived from Figure 1 of Matching Food and Wine.

As regards the structural components, Dr. Zoecklein argues that a balanced relationship must exist between the tastes of sweetness, on the one hand, and acid, astringency and bitterness on the other, in order to yield the perception of a quality wine to the taster.  The preferred relationship is captured in his Palate Balance Equation (Zoecklein: Components of Red Wine Mouthfeel):

           Sweet ⇄ Acid + Phenolics (Astringency and Bitterness),

where

          Sweet = Carbohydrates + Polysaccharides + Ethanol,
          Acid = Population of organic acids, and
          Phenolics = Skin, seed, and stem phenols + barrel phenols + enological tannins +             volatile phenols.

Based on the foregoing equation, an increase in the sweetness element of the equation will lead to a reduction of the taster's perception of acidity and phenolics; and the reverse is also true.  Dr. Zoecklein sees this balance, or harmony, as a key indicator of wine quality and in that he is joined by Wines and Vines and Crushpad Blog among others.  According to Chris Stamp, writing in Wines and Vines, "... a balanced wine is a wine in which the various components work together to provide a pleasing taste."  According to Richard Leahy, writing in Crushpad Blog, wines that are in balance tend to stay that way while wines that are out of balance tend to grow moreso over time.

How does balance relate to quality?  If, for example, a wine has insufficient sugar in relation to its acids and phenols, it will present as harsh and acidic and will retard the evolution of flavors in the mouth of the taster.  A wine with too much sugar, on the other hand, will be flabby and cloying and will not refresh the palate.   Such wines will not be perceived as quality wines by the taster.

Over the course of future blog posts I will be examining the components of the balance equation in greater detail in order to provide the reader with an understanding of the factors that the winemaker has to consider in his/her quest for balance, one of the key measures of a quality wine.