Wrestling with Heavyweights: Ripening and Place

Recently, I opened a bottle of Joseph Roty Marsannay from 2007, and its rim bore that smell of bacon fat that we associate almost exclusively with older, very fine wines from the Cote de Nuits (read: old DRC).  But there it was, out of nowhere, that old, fine scent.  Like it was making a cameo.

The 2007 Burgundy reds are moving along at a fast pace.  It makes them very useful in a restaurant.  This faster-than-usual pace is probably explained by softer-than-usual tannins.  They also don’t have much color, but the acidity is good and the best examples are gregarious and aromatic.  I remember being underwhelmed by the vintage when I first tasted the wines back in 2009.  I also remember hearing that ‘07 would be a good vintage to drink young, but I took this to mean Look, we had a weak vintage so please drink it all as soon as possible.  As it turned out, I was wrong, the vignerons were right, and they weren’t trying to pull anything.  I learned my lesson.  I should have bought more ‘07s.  I now wish my lists were stocked with them.  As far as wines from the 2000s go, their current performance is rivaled only by the upright-and-handsome ‘01s. 1 

I’ve been thinking about these wines a lot lately.  Their dynamic has grown more and more fascinating the more I’ve tasted them.  I began looking for an explanation, and the answer seemed to lie in the way they ripened.  A little digging revealed that 2007 had been an unusual growing season with unusual ripening.  The spring was very warm, kicking off such a quick start that many growers—who still bore the hot horrors of 2003 fresh on their minds—feared for the survival of their August vacations.  By the summer, however, the weather had grown cloudy and cool, and it mostly stayed that way until harvest. 2 

The 2007 season was something of a reversal of typical ripening in Burgundy.  Things usually go cool and slow until a surge of warmth toward the end of the season.  This warmth brings the fruit up to a decent level of ripeness, and producers must soon harvest before the inevitable rainstorms. 

I began to wonder how exactly this tale of ripening in 2007 explained the unusual behavior of the wines.  As sommeliers, we run into vintage descriptions like this all the time.  Their very existence assumes that we readily understand what factors like a warm spring and clouds during ripening should equate to in a wine, and why.  But the more questions I asked of other sommeliers and winemakers, the more it appeared that many had a limited grasp on the mechanics and contingencies of ripening.  I began to suspect that the topic, like most aspects of wine, might be rife with speculation.

It reminded me of sommeliers’ constant grappling with place.  So much of our arena of study is built on an assumption that wines from different places taste different, but we actually have quite a hard time fully answering the question of why.  We certainly do our best, and most of the time we do okay.  We parrot explanations of soil effects, and maybe we toss around the word mesoclimate.  But none of us actually understand the entire operation of the machine of terroir.  It isn’t our fault.  The scientific community doesn’t understand terroir, either.  It’s possible that the whole thing is just the wrong size for human beings to access it empirically. 

I set aside my very specific question about 2007 reds in Burgundy and began asking a broader, more primary question:  What is it about place that directs ripening?  Perhaps we can characterize a place by the way fruit ripens there.  I wasn’t so interested in how much the fruit ripens, mind you, but more in simply how.  It is not just a matter of must weight.  And it is a more specific feature than just climate. 3

I began calling this feature the fruit’s manner of ripening.  After all, fruit doesn’t ripen in a linear fashion.  It ripens along multiple physiological pathways, and with multiple environmental influences.  I spoke with Jason Lett of Oregon’s Eyrie Vineyards, and he described ripening as the result of three factors:  light, heat, and time.  The influence of their particular combination—as created by the particular arrangements of a given place—probably goes a long way toward explaining the character of the place’s fruit. 

The matter is hinted at regularly in our literature.  A comparison of the Mosel against the Rheingau might read something like this: 

The steep Mosel slopes present the vines to the sun, and this added exposure to sunlight—combined with the moderating effect of the narrow, snaking river Mosel—allows riesling grapes to reach an arched, luminous kind of ripeness in spite of the marginal climate.  The resulting wine is endowed with very great litheness, grace, and mineral detail.  On the other hand, the much wider Rhine River does more moderating work than does the Mosel, reflecting more sun and acting as a larger heat sink, such that the slopes of the south-facing Rheingau need not be as steep to catch extra sun, and so the Rheingau fruit achieves its greatness in a slightly different way, with more power bred in. 4

It is an illuminating anecdote, but rarely, if ever, would it go on to elaborate the full operation of these effects, and certainly never at the grape level.  And so, the account leaves us with an incomplete sense of the machine.

I wanted to find out exactly what these accounts mean to imply about ripening.  Hopefully an answer would tell me what is qualitatively different about a ripe grape in Burgundy versus, say, a ripe grape in California’s Central Coast. 5  And perhaps a sense of that difference would help me see into the essential character of those places.  At the very least, I hoped to find out what we actually know about ripening, and how it relates to place.

Solvang, California

Happy to have an excuse to get away from muggy Atlanta and into the radiant peaks and valleys of the mild California Coast, I made my way from LAX to Solvang, a compact tourist town northwest of Santa Barbara, situated on a Santa Ynez hilltop.  Solvang is that ilk of town that makes a concerted, ongoing effort to express its cultural roots (in the case of Solvang those roots are Danish).  Solvang does so with occasional outcroppings of traditional Nordic costume, a bevy of candy shops, and a convenient selection of novelty restaurants with names like Bit ‘O Denmark and The Red Viking. 

I would be staying in Solvang as I visited with Joe Davis, of Arcadian Winery, and Bob Lindquist, of Qupé, in the Santa Maria Valley. Davis is well attuned to the subtleties of his region.  He tends vines and makes wine from vineyard sites all over the Central Coast, from down in the Santa Ynez Valley all the way up to Monterey.  And Lindquist has been an unwavering producer of mostly Rhone varieties for three decades.  In both cases, they are winemakers who hold the old world in high esteem and who are proud of the ways that the favorable climate of their own place allows them to pay homage.  At the same time, however, their wines still differ notably from their European counterparts.

To explain those differences I might be tempted to start with soil, a subject that is transfixing but that neither sommeliers nor plant scientists actually understand very well on a physiological level.  We know that differences in water retention and nutrient levels count for something, and that they can also have an effect on ripening, but the ways in which basic mineral content affects flavor in wine are still an area of mystery.  Perhaps this mystery is what attracts sommeliers, keeps us sniffing around.  Speculations about the effects of soil are well diffused into sommelier culture, but the best evidence in this very important portion of our study is mostly anecdotal, and sometimes conflicting.  Any causal connections are difficult to find.  This fact doesn’t take away from its overall salience, but it should make us cautious around general statements about soil (yes, including these).  Some empirical data is out there, but it is sparse, and difficult to interpret.  Soil is a terrific subject, but it is hard to built into a model.

On the other hand, the ripening differences between eastern France and California’s Central Coast are fairly clear.  The main difference is time.  The ripening season in the Central Coast is slower, steadier, and longer.  Imagine a curve that describes ripening activity.  For the Central Coast it would be long and relatively flat, with an extended, gently sloping tail. 

This flat, long curve is the result of a favorable combo of abundant sun without a lot of heat.  Due to the east-west orientation of many of its valleys, the Central Coast pulls cold air (and commonly also a dose of cold early-morning fog) straight off the Pacific, and as a result the overall climate of much of the region is fairly cool.  Those AVAs closer to the ocean stay especially cool, and, according to Bob Lindquist, “Our typical daytime highs during the main part of the growing season are in the 70's. We get some occasional 80's and quite a few days that don't climb out of the 60's. We only get 90's or 100's during heat waves.”  It is not unlike the temperature ranges of Burgundy.  If anything, Burgundy is the one with the warmer periods.

The Central Coast’s cool, camel-colored hillsides stay active with breezes and sunshine.  There is little pressure to pick because, unlike France, there isn’t a dependable barrage of bad weather coming in autumn (although I have heard unconfirmed rumors of occasional late-season storms that plague the Santa Rita Hills).  It is a scenario in which a much longer hangtime is natural.  Even for producers like Joe Davis, who typically harvests Pinot Noir at a relatively low 22° Brix, the season from flowering to harvest is 18 weeks, or 126 days, nearly a month longer than in Burgundy.  For those producers who harvest at higher must weights, say 26° or more, it can be longer still.  

The sheer length of this ripening allows a thorough, more comfortable use of the grape’s mechanisms.  It produces fruit that retains acidity but often also shows a certain agreeably mature quality.  The kind of tension that one might usually expect from a cool climate (and which Burgundy wines typically possess in spades) is generally absent. 

For its part, Burgundy’s ripening is more difficult.  The best sites are said to rely heavily on cool morning sun, an effect created by the mostly east-facing aspect of the slope.  Most seasons involve bouts of cloud cover followed by the aforementioned surge of ripening in the later, warmer part of the season.  Burgundy’s curve would be shorter and steeper than that of the Central Coast, and it would cut off abruptly a bit after the surge, since there is usually some pressure to harvest. 

I was already familiar with this distinction of ripening style between the two places, but I had not yet connected it at the berry level.  On my second afternoon in the Central Coast, Joe Davis picked me up in airy Solvang, his young son Max in the back seat.  We passed a number of large signs promoting split-pea soup, and more than a couple of tasting rooms that claimed to be As Seen in Sideways.  Davis drove me around the Santa Ynez Valley, stopping the SUV intermittently at vineyard sites, and diverting for an occasional “boonie cruise”. 6  We discussed ripening mechanisms along the way.  I had spent most of my time on the plane reading about grapevine physiology, a topic that kept me surprisingly riveted, so I was primed for the conversation.  Through that conversation (and a few jargon-rich academic journal articles) I began to see the grape as a small, complex metabolic machine, one whose end goal is ripeness. 

The Ripening Machine

It may help to remind you what a berry is.  A berry is a way for a vine to move its seed somewhere else.  And if I were to use a functional description of ripening, it would be:  the method by which a vine makes its fruit attractive to a seed disperser, like a bird or a deer.  It is to the plant’s advantage to make the fruit desirable, so the plant fills the grape with energy in the form of sugar and attractors in the form of aromatic phenols and bright pigments.  Immature grape berries, on the other hand, are highly concentrated with acidity and tannin, low in sugar, and low in aromatics and color.  This ensures that dispersers are not likely to eat these berries before the seeds inside of them are viable. 7

As the seed matures, the berry becomes more alluring using the three physiological processes of photosynthesis, respiration, and secondary metabolite maturation.  These processes all work along different axes, and have different environmental influences.  Their goal, however, is the same.


Photosynthesis is the means by which a plant produces energy for later use.  To be more specific, it is the plant taking light energy from the sun using chlorophyll in the leaves and converting it into chemical energy in the form of sugar.   The process also forms two by-products, water and oxygen.  Pores on the underside of the leaf called stomates release the oxygen, and it soon becomes part of the breathable atmosphere.   Before fruit-set, sugars are sent to a number of locations on the plant, often accumulating as starch, particularly in the roots.  After veraison, however, which is a key turning point in the life of the grape and really the beginning of true ripening, any new sugars made from photosynthesis are sent into the grape.  These sugars begin to accumulate in the vacuoles of the cells of the pulp, which also begin to swell with water.  Photosynthesis continues to place sugar in the pulp of the berry throughout the ripening process.  Brix, Baumé, Oechsle, and any other measure of must weight are then in a sense also a measure of this activity. 

The rate of this activity increases with temperature, so that in warm conditions a berry will accumulate sugar faster than in cool conditions (and therefore potential alcohol levels will rise faster, too).  The effect stalls, however, at 95˚F, as the stomates close up, effectively shutting down the plant.  The fruit may begin to lose water mass, and berry desiccation may result.


Respiration is the process by which the plant releases energy from storage in compounds like sugars and acids.  In a sense respiration is just the opposite of photosynthesis.  It is the act of using oxygen (which is brought in through the stomates) to break up complex carbon bonds, thereby metabolizing usable compounds into energy, and generating carbon dioxide and water as byproducts.  Sommeliers commonly associate lower acidity with very ripe wines and wines from hot vintages.  Respiration is the reason why.

I spoke with Professor Douglas O. Adams, a specialist in grapevine physiology at UC Davis, and he helped walk me through some of the technical details of the process. After veraison the vine begins to focus its respiration on malic acid instead of sugar.  Both tartaric and malic acids exist in high concentrations at veraison, but as the berry swells, the concentration of these acids declines.  The overall level of tartaric acid in the berry stays nearly the same, but malic acid begins to be respired out, or burned up and used as energy.

Adams gave me a picture of this activity within the grape: “At veraison tartrate [or tartaric acid] is distributed evenly from skin to pulp.  Malate, however, is high in the skin, low in the vasculature, and exists in a gradient in the pulp, with a high concentration at the center near the seeds.  By harvest there is a flatter gradient of malate, with a lower, even level of distribution from the skin to the center.”  As the berry ripens, then, the acids are working toward uniformity within it.

Like photosynthesis, respiration accelerates with heat, and this is why malic acid levels may drop quickly in a warm environment, while in a cool environment acid levels typically remain high. 8  Light intensity, on the other hand, seems to have no effect on acid levels. 9  This fact that would seem to at least partly explain why cool morning sun seems to be so valuable for many varieties, particularly a fast-ripening  grape like Pinot Noir.  

Striking the right relationship of balance between falling acidity and rising sugars might be the winemaker’s primary challenge.  As we were rolling along next to Stolpman Vineyard, Joe Davis pulled the SUV over onto a dusty shoulder.  He demonstrated with his hands how photosynthesis and respiration have “an inverse relationship, but not directly inverse”.  In other words, the two work in opposite directions, and they are influenced by the same accelerant (heat), but they are influenced at different rates.  Anticipating that moment where the two are in balance requires the winemaker to maintain a keen sense of both processes.

Secondary Metabolite Maturation

The third dimension of ripening is difficult to label, as it is not really one single process but a collection of small chemical developments, many of which are not well understood.  I am calling it secondary metabolite maturation but I might just as easily use the more common umbrella term of physiological ripening.

This is a very complex array of chemical activities.  It is probably this aspect of ripening that (along with the alchemic, transformative powers of fermentation) most accounts for the intricate chemical life of a wine solution.  Even if a full description of these activities and compounds were possible, I wouldn’t be the one for the job.  I’m not able to wield terms like isovaleraldehyde or 1-propanol with any authority, nor would these terms be likely to translate to your experiences. 

There are, however, a few classes of compounds worth noting.  Most are within the general category of secondary metabolites, compounds the grape produces beyond those—like sugar or amino acids—that are directly necessary for the survival of the plant.  The building blocks for these compounds arise early in the berry’s development, before veraison.  Not much is known about this very crucial phase. 10

It is clear, however, that before veraison tannins accumulate in a single cell layer of the skin and another layer under the seed coat.  Compounds called hydroxycinnamic acids also form at this time.  They are precursors to volatile phenols, and they exist in both the pulp and the skin. 11  They are particularly important to white wine quality, since they are the most abundant kind of phenolic compound in free run juice. 12

Also forming in this period are methoxypyrazines, the compounds we commonly encounter in certain grapes as grassy or green vegetal aromas, especially those of the Sauvignon family.  The ongoing decline of pyrazines in the grape after veraison is likely related to sunlight levels in the cluster. 13

After veraison, anthocyanins accumulate in red grapes.  Anthocyanins are pigmented compounds that account for the color of red wine.  They also contribute aromas and flavors.  Although they may form without the aid of sunlight, extra sunlight does appear to enhance their accumulation.  Their accumulation does not seem to be related, however, to an increase in heat, as was shown by a study of Yakima Valley Merlot grapes in which bunches were shaded, heated, sun-exposed, and cooled, and done so in every possible combination.  In fact, the study showed that very high temperatures actually inhibited anthocyanin development. 14

Late in the ripening process many more aroma and flavor compounds begin to accumulate.  During this late phase of ripening we find the development of glycosides.  Glycosides act as precursors for the later development of more complex aroma and flavor compounds.  With time they will become unbound and express themselves.  Their period of development is called gustation15

Maturity or richness of flavor seems to be related to the extended and ongoing development of secondary metabolites. 16  It is difficult to separate the effects that light and heat have on nurturing these compounds, although light does seem to play the greater role.  Time seems to have an effect here, too.  Some of these compounds may form of their own accord over time and aren’t influenced heavily by either light or heat.  Their chemical world, their encouragement, and their contribution to wine, seems to be an area that remains fairly dim, and about which there is much to be learned.

A Walk-Through

Perhaps—given our three central influences of light, heat, and time, combined with our three dimensions of ripening—a walk-through of general scenarios may still be possible, in spite of all the associated unknowns.

On one fairly intuitive extreme, it seems that ripening in the presence of both plenty of sun and plenty of heat will cause sugar levels in a given plant to increase more quickly than in a cooler environment.  Heat will also lead to an increased rate of respiration, which will lead to a drop in malic acid levels.  If this occurs then one risks being forced to harvest before secondary metabolites have had a chance to form properly, and an imbalanced wine may result.  If one waits for greater physiological ripeness, then the risks are high alcohol and low acid.  The scenario seems obvious enough.

Sunlight without high temperatures will allow for sugar accumulation, but at a slower rate.  At the same time the sun will also provide anthocyanin development in red grapes and possibly encourage other aromatic and flavor compounds.  Respiration will occur slowly, so malic levels will stay relatively high.  The cooler temperatures mean a lower rate of both photosynthesis and respiration, allowing for more time on the vine, which in turn allows a denser population of secondary metabolites to form.  This description of what happens in a cool, sunny place with a long hangtime (like the Central Coast) seems fairly satisfying.

But how do we describe the kind of ripening that happens along a more compressed curve, like that of Burgundy?  One winemaker described this kind of ripening as “more violent”.  These wines appear to show more tension.  Accounting for this tension requires a little speculation.  For me, the effect seems closely related to a greater perception of tannin, but it could also have something to do with a shorter period of secondary metabolite development. 

If we assume that this tense quality is related to the tannic character of a wine, then we raise a very important question:  what is it about place and ripening that influences tannin in a wine?  Red wines from Burgundy, particularly those from the Cote d’Or, are dependably a far more tannic experience than Pinot Noirs from California.  And yet the California wine has probably stayed on the vine longer, and had more time for its tannins to develop.

This question of tannin development brought me to a wall.  I actually lost sleep over the question (when I revealed this fact to my traveling companions I was sorely mocked).  It just seemed to be such a crucial point, an issue that cut directly to the heart of many discussions, even beyond ripening manner, into issues of Old-World vs. New-World dispositions.

Faced with this question, I traveled north up the California coast looking for answers in Sonoma County.  I went to Sebastopol on a warm afternoon to Littorai, where I pressed winemaker Ted Lemon until he told me that his Pinot Noir grapes actually have more tannin, and that the sense of Burgundy as more tannic is probably related to more punchdowns (three per day, versus Lemon’s one or two).  A protracted, twisting drive at altitude from the Redwood Highway out to the remote growing sites of Peay Vineyards, which lie among the tall alpine landscape of the far-flung northern coast, garnered a different take from Andy Peay.  He called it a matter of longer tannin chains forming during hangtime.  Implicitly, these would be silkier in texture than shorter, presumably less-mature, tannins.  Ross Cobb, winemaker at Hirsch Vineyards, from whose redwood-dotted landscape the cool and foggy Pacific is visible, suggested I think about extracted levels of catechin, one of the bitter molecular building blocks of tannin.  He also listed soil type as a probable contributor.

The Trouble with Tannin

It turns out that one of the more challenging physiological stories to tell is the behavior of tannin.  Science has not yet described what promotes formation of tannin pre-veraison, nor their molecular lengthening during ripening.  We don’t even know where exactly in the berry tannin is made.  We know it ends up concentrated in a layer of the skin and in a layer under the seed coat, but we do not know where it is synthesized. 

Professor Adams told me that tannin levels are largely fixed at veraison, (although, like tartaric acid, they decrease in concentration as the berry grows) and that during ripening tannins form longer molecular chains.  In the lab, their lengths are measured by mean degree of polymerization (mDP).  Seed tannins tend to create shorter chains than do skin tannins, and late in ripening many of these tannins oxidize, turn brown, and bind to the seed coat.  This likely diminishes their extractability to some extent. 

Professor Adams then reversed most of what I thought I already understood about tannin.  “I did a study in which I found that in every case where tannins were described as either green, or unripe, short-chained, or astringent, there was always more tannin present in the wine,” he said.  He went on to describe another study, conducted in France, where it was found that in every case where tannins were longer chains they were also found to be more astringent.  This is the opposite of what many of us have been taught, that long-chain tannins are silkier and more “mature”, and that this behavior continues in a bottle as wine ages and the tannins soften.  In reality, Adams continued, “The French study showed that tannin chains form longer and more astringent linear chains of subunits in the berry, but in a wine solution the polymerization is different.  In solution we see cross-chain linkages.”  The complex shapes taken on by cross-chain linkages of tannins likely accounts for the different sensory characteristics over time.

This was an arresting revelation, but it also saddled me with a problem.  If this is the case, if tannin levels by weight are largely fixed at veraison, and the mDP increases with time, forming longer, more astringent chains, then what accounts for the prevailing misconception that riper wines are less tannic?  And could an explanation of this phenomenon provide a clue to why wines of fruit that ripened in a compressed manner feel more tannic, more tense?  Could it tell us why Cote d’Or Burgundy is so tannic?

Jeremy Seysses of Domaine Dujac, a domaine that has never feared the full embrace of Cote de Nuits tannin, told me that he didn’t believe the difference had to do with the amount of tannin in the grape, but how much of that tannin was extractable.  “I think that many US Pinots are picked so ripe that they are picked after their peak in extractability.  Past a certain point, it becomes very hard to extract anything but seed tannin from a grape skin.”  Seysses also pointed out that his sites with the greatest diurnal shifts also seem to have the hardest tannins to extract, and that this effect may play out in the California wines, as well.

Professor Adams offered three theories to deal with the question.  The first theory suggests a sensory explanation.  Adams proposed that perhaps wines with lower pH cause us to perceive tannin as more astringent, while fruit that spends more time on the vine typically has a higher pH.  This riper fruit also tends toward a higher polysaccharide content, and polysaccharides may also do the opposite work of making tannins feel less astringent.

Adams’ other two theories both harmonize with Seysses’ sense of decreased extractability in riper grapes.  In one theory, tannins in the skin become increasingly bound to plant cell walls:  “Tannins are known to interact very strongly with plant cell walls making them insoluble and unextractable into wine. Grapes continue to soften during ripening so perhaps there are additional binding sites created for tannins as the berry continues to ripen.”  The next theory adds an extra feature,  “Recent work shows that plant cell walls bind larger tannins more tightly than small ones. Perhaps the riper fruit presents more cell wall material to the fermentation that is capable of selectively binding the larger (more astringent) tannin.”

Adams went on to point out that this topic is an emerging area of research, and that he suspects in five years science will understand these and other processes related to ripening in a much keener way.

Aspectual Shapes

If we begin to understand more about what happens in the berry before veraison, then perhaps we will begin to better understand ripening, as well.  Perhaps that will aid our understanding of place.  Even with this help we are unlikely to unlock all the doors.  Just as the topic of place is rife with contingencies, so ripening has its share.  Soil type, farming methods, training, and canopy management all may have their own impact upon ripening, and describing their effects could fill many more articles like this one.

The answer to my original question about 2007 red Burgundy remains unanswered.  It seems that there is just too little known about what directed the vintage’s key features of low tannin and pre-veraison development.  One feature seems to make sense, however.  The lighter color is likely due to long periods of cloudiness during ripening.

The endowment of a place’s character to its wine will probably always remain a mystery.  Places are analogous to human personalities in a way.  They are at once both impossible to fully describe and they make for a totally unsatisfying synopsis.  There seems to be no appropriate level of description.  It is as if the complexity of their character allows them to resist any summary.  And so we must rely on the encounter, the experience of the thing, and the aspectual shape that it casts in our mind, in order to define it. 

It is an understanding that goes beyond empirical data.   And empirical data is something that many winemakers are comfortable to live without.  As long as it works, it works.  I think of someone like Bob Lindquist, who, in his L.A. Dodgers t-shirt, ventured almost no physiological or chemical speculations, and whose greatest contribution was a willingness to say, “I don’t know”, a capability that is far too rare in our business.  I think of the fact that he, without the aid of a high-powered explanatory arsenal, continues to craft some of the Coast’s most beautiful things.

For now it seems that a complete knowledge of the topic isn’t possible.  I also don’t think it’s totally necessary.  It may be enough just to see how it could work. 





1 The 2002s are just barely opening the door.  2003 is, well, 2003.  2004s are very hit-and-miss, and erring toward green.  2005 won’t even look at you; it is a ball of unresolved introspective issues, and in need of therapy.  2006 is still a little loud.  2008 is still a bundle of nerves.  2009 seems dazed, in a beefcake way.  And, so far, the 2010s are primary and large.

2 Robinson, Jancis. “Burgundy 2007—The Verdict”. Jancis Robinson. 24 January, 2009  <http://www.jancisrobinson.com/articles/a200901193.html>.

3 Pick times would still be an obvious consideration, but even for those producers in the Central Coast who harvest at 22° Brix, which is roughly equivalent to Burgundy in a moderate vintage, the differences in fruit character are clear.

4 My own approximation, not the work of an actual wine writer.

5 Assuming grape variety (and probably clonal selection) remains constant, that is.

6 Max Davis’s term for 4-wheeling

7 Kennedy, James, “Understanding Grape Berry Development”, Practical Winery and Vineyard Journal, July/August, 2002.

8 I asked Adams what directed acid levels before veraison, particularly of tartaric, since these levels remain fairly fixed, but he said that there seems to be at least a genetic determinant.  This may suggest that clones could also play a significant role in differing acid levels associated with various places, but the effect doesn’t seem to have been fully described.

9 Winkler, A.J., et al.  General Viticulture, University of California Press, 1974, p.156.

10 Kennedy, James, “Understanding Grape Berry Development”, Practical Winery and Vineyard Journal, July/August, 2002.

11 Ibid.

12 Adams, Douglas O., “Phenolics and Ripening in Grape Berries”, American Journal of Enology and Viticulture, 57:3, 2006.

13 Kennedy, James, “Understanding Grape Berry Development”, Practical Winery and Vineyard Journal, July/August, 2002.

14 Spayd, S.E. et al., “Separation of Sunlight and Temperature Effects on the Composition of Vitis Vinifera cv. Merlot Berries”, American Journal of Enology and Viticulture, 53:3, 2002.

15 Kennedy, James, “Understanding Grape Berry Development”, Practical Winery and Vineyard Journal, July/August, 2002.

16 Clearly, pick times and extraction technique could also affect richness of flavor, irrespective of place.  The human factor should really never be ignored.  For this reason, that which is traditional or common to a place may also be called a component of terroir.