Category Archives: storage

Sep 11 NO comments
aging, anthocyanins, aroma, chemistry, cherry wood, enology, fermentation, flavor, maceration, oak barrel, oak chips, phenolics, research, Sangiovese, skins, storage, wine chemistry, wine quality, wine research

Examining the Influence of Cherry Wood Barrel Aging on Red Wine Color



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Oak aging is a very common practice in winemaking, particularly in wines destined for a higher quality designation.  In general, with oak aging (and other wood aging, for that matter), the contact between the wine and the wood promotes an influx of compounds into the wine which often has a positive influence on the complexity of the wine, as well as the intensity of the nose and palate.  Even more important, the small pores within the wood influence the rate of oxygen diffusion into the aging wine, with has a significant effect on color stabilization, as well as the phenolic composition of the finished beverage.

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Color

Let’s focus on color for a bit (or, well, for the remainder of this post).  The color of wine can tell you many things, including its age, how it may have been stored, and also its potential overall quality.  Color in wine comes primarily from its anthocyanin content, which originates from the skins of grapes.  In red wine, the skins of the grapes remain in contact with the must (unfermented wine) for a period of time, which is known as maceration, which extracts more and more anthocyanins (among a barrage of other compounds) the longer the skins sit with the juice.

Once these anthocyanins are extracted from the skins into the grape must, their concentrations decrease over time due to several chemical reactions, including polymerization, oxidation, precipitation, as well as absorption by yeast.  Some of the by-products of these chemical reactions between anthocyanins and other compounds in the wine can provide a greater resistance to bisulphite bleaching and pH changes, which is important in regards to the sensory characteristics of the finished wine.

What does wood aging and color have to do with one another?

As I mentioned just previously, anthocyanins can react with other compounds in the wine, which can alter color, in addition to other quality factors in the beverage.  Since aging in wood barrels ads an influx of wood-related compounds into the wine, these can interact with anthocyanins and ultimately change the color and overall quality of the finished wine.

What type of wood are you talking about, anyway?

To date, most of the studies examining the influence of wood aging on wine have focused on French and American oak barrels, which are undoubtedly the two most common types of wood used in this type of aging.  These types of barrels have been used for generations, and are the traditional woods of choice when aging wine or other distilled beverages.  However, more and more alternatives to the traditional French and American oak barrels are being used, partly for variety, but more importantly for cost-savings.  These alternatives include chestnut, acacia, cherry, and ash (to name a few); all of which cost markedly less than traditional French or American oak barrels, and also give unique sensory characteristics to the finished wine which are becoming more desirable among consumers.

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Cherry wood, in particular, has been found to contribute to the complexity of wine, by significantly increasing the cherry and red fruit notes to the wine, as well as increase the overall acceptance of the wine.  Studies have shown that cherry wood promotes a more oxidative environment for the wine, which suggests a shorter aging period lest one be left with a wine that suffers from too much oxygen exposure (which is not good!).

The study published last year in the Journal of Agricultural and Food Chemistry, the results of which I will present shortly, aimed to take this known information regarding cherry wood aging and anthocyanins and examined the impact of cherry wood aging on the oxidative changes of color and pigment in red wines.  In a nutshell, they wanted to know how does cherry wood aging affect the color of the red wine, and how does it compare to red wine aged in more traditional French oak barrels?

How did they do it?

 The red wine used for this study was 80% Sangiovese and 20% Merlot from the 2008 vintage by Marchesi de Frescobaldi in Tuscany, Italy (Sieci, to be more specific).  Wines followed a traditional vinification protocol, including 20 days of maceration (skin contact with must).  After alcoholic fermentation, the wines underwent spontaneous malolactic fermentation.

The barrels used were two 225L medium toasted barriques of French oak and cherry wood, as well as a larger 1000L cask made of cherry wood with light toasting.  All aging conditions were performed in triplicate.  Barriques and casks were made with staves that had been seasoned for 24 months.  A 1000L stainless steel tank was used as a control.

An aging length of 4 months was chosen, due to the nature of the experiment.  This experiment was testing anthocyanin changes over time, so the experiment was carried out long enough so that the total anthocyanins would significantly decrease or disappear all together.  This magic number turned out to be 4 months.  It is important to note that even though the anthocyanin content significantly decreases during this time, the sensory contribution of the cherry wood does not decrease during this time period.

General enological parameters (titratable acidity, pH, etc), dissolved oxygen, pigment, and color were measured for all wines using various analytical techniques.

What did they find?

  • The authors found many results in this study, but I’ll just share a few of them for space considerations.  Please feel free to ask if you’re wondering about any particular result that I may not have mentioned.
  • Dissolved oxygen stabilization was a function of the wood surface-to-wine volume ratio, with the smaller casks (225L) having a higher dissolution rate than the larger casks (1000L).
  • Dissolved oxygen levels were similar in wines aged in French oak barrels than cherry wood casks.
  • During the first month of aging, wine in cherry wood casks showed a higher SO2 reduction trend than in French oak casks.

o   In wines aged in cherry wood casks, the free SO2 levels were lowest, compared to the French oak casks.
  •  Total phenolic content was similar between wines aged in cherry wood versus wines aged in French oak casks.

o   This result contrasts another study that found a significant decrease in polyphenols in cherry wood-aged wines after 3 months of aging.  The researches cite differences in experimental methods as a possible explanation of this discrepancy.
  • Tannins increased for all wines in all aging conditions.
  • Wines aged in cherry wood saw faster reductions in anthocyanins than wines aged in French oak.

o   The total pigment in the larger casks (1000L) was twice that of the smaller casks (225L).
  • After 4 months of aging, wines aged in cherry wood casks had the lowest percentage of acylated anthocyanins compared with all other storage treatments.
  • Wines aged in cherry wood casks showed large variations in the pigment profile of the wines at any given point in the aging process, indicating that wines aged in cherry wood casks may more significantly change from the initial anthocyanin content present in the wine than wines aged in other wood casks.
  • Cherry wood aging promoted the highest levels of adduct formation over time compared with other aging conditions.
  • Wines aged in cherry wood had the highest levels of color intensity compared to wines aged in other conditions.
  • After 2 months, wines aged in cherry wood possessed deeper colors, as well as a “redder” tint than the other aging conditions.

o   After 2 more months, this redness decreased in shade, resulting in all wines sharing similar coloring regardless of aging condition.
  • French oak barrels did not contribute to wine color as much as cherry wood barrels.


What does this all mean?

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According to the results of this study, the use of cherry wood barrels/casks in the aging of wine significantly influenced the color and pigment of red wine (in this case, Sangiovese/Merlot blend).  Also, the anthocyanin content of wines was affected by the type of wood used for aging, with the cherry wood barrels/casks losing nearly all ρ-coumaroylated pigments by the end of the 4 month experimental aging period.  According to the authors (and I agree), more work needs to be done to explore this result further: by examining the role of wood porosity and/or phenolic composition of cherry wood.

Due to the significant decrease in anthocyanins and pigments by the end of the 4 month aging period, it is recommended that wines aged in cherry wood barrels/casks are kept for relatively short periods of time or if longer age times are more feasible, then the use of larger barrels with lower wood-surface to wine-volume ratios should be utilized.

 Of course, wines aged in cherry oak barrels with yield wines with a different aroma/flavor profile than wines aged in traditional oak barrels, so the decision to choose one type of barrel over another should not be simply based on  anthocyanin content alone, as discussed in this post.  One must take into consideration all the differences between wines aged in alternative wood barrels and traditional oak barrels (including economic differences) before jumping to any conclusions as to which barrel is right for them or their winery.

 I'd also be curious to see how cherry wood aging affects other wines, including both red and white wines.  Will we see the same results?  Will some wines age better in cherry wood barrels than others?

What do you all think of cherry wood to age wine?

Have you ever tasted a wine aged in cherry wood barrels?  I have to admit, I have not, but I would certainly be interested in trying one to compare between that and the more traditional aging methods.

I’d love to hear what you all think of this topic!  Please feel free to comment below!  (Note: If you do not see the comments section, be sure you are in the post URL and not just on the main page).
I am not a health professional, nor do I pretend to be. Please consult your doctor before altering your alcohol consumption habits. Do not consume alcohol if you are under the age of 21. Do not drink and drive. Enjoy responsibly!
May 15 NO comments
aging, antioxidants, bottle, chemistry, contaminants, fining agents, model wine, phenolics, research, storage, trade, USA, wine quality

Evidence for Damaging Effects of Heat Exposure on Wine During Transport and Storage and Recommendations for Protection



It is well known that long term heat exposure is detrimental to the quality of wine, specifically its sensory characteristics and ability to age.  Excessive heat can also alter a wine’s physical and chemical stability, such as showing a cloudy or brownish appearance and leaking bottles.  To date, most of the evidence for the damaging effects of heat on wine storage is anecdotal, with very little concrete scientific evidence backing up the claims.

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A bottle of wine being transported from winery to consumer risks many abusive shipping processes along the way, including excessive heat exposure.  This risk is exacerbated at times by high shipping costs, limited availability of refrigerated shipping containers, and general ignorance.  Many winemakers have even adjusted their production techniques in order to protect their bottles of wine from heat exposure, including deliberately oxidized and fortified; red wines that underwent extended maceration; and distilled wines.  Nearly all commercial white wines are heat stabilized during the winemaking process, so that heat exposure does not result in a visual change in the wine (haziness).

Even if heat exposure doesn’t damage the wine per se, the ageing characteristics will be changed following a certain time of elevated temperatures.  Specifically, heat exposure can prematurely release glucose-bound flavor precursors, decrease the levels of protective free sulfur dioxide, and cause an increase in browning.  The sensory character could be changed as well, though due to rapid heating and specific reactions of the many compounds in wine, it’s not certain that the “ageing” due to increased heat exposure would be the same as if that wine were aged for a comparable amount of time at a more traditional storage temperature.  It is likely that at least the subtle differences attributable to terroir would be lost.

One potentially hazardous consequence of increased heat exposure to wine while in storage is the formation of ethyl carbamate (EC).  Based on experiments with rodents, it has been shown that there is a probability of a carcinogenic effect of EC in humans when exposed to high concentrations of the compound.  In wine, EC is formed from its precursor, Urea, which is naturally present in wine from 100μg/L to 100mg/L.  Urea can be released by wine yeasts during or at the end of alcoholic fermentation, which then can spontaneously react with alcohol to produce EC.  This reaction between Urea and alcohol to make EC has been shown to accelerate exponentially when excessive heat is applied.  Therefore, excessive heat during storage of wine is a great concern.

The study presented today used EC levels as an indicator of wine quality in order to demonstrate the chemical changes that occur in wine during transport and storage.  The goal of the study was to provide wine makers and producers with information on how to properly handle their wines in regards to transport and storage as they work with transport companies, distributors, wholesalers, and retailers in order to minimize the exposure of their wines to excessive temperatures during this transitional period.

Methods

The wine used for this experiment was a model wine, containing 10mg of urea, 5g of potassium bitartrate, 3g L-malic acid, 1.1g potassium monohydrogen phosphate, and 150mL ethanol, brought to volume by adding de-ionized water.  The resulting pH was 3.5.

Temperatures were tracked and recorded using Dickson SP100 dual-channel temperature data loggers.  An internal temperature sensor recorded the air temperature inside the test package, and an external thermistor was placed inside a wine bottle filled with de-ionized water.  Temperatures were recorded every 15 minutes.

The test packages were created by loading a standard 12 bottle case with one bottle of model wine, one bottle of de-ionized water containing the thermistor, and the rest of the case fitting the data logger.

Test packages were shipped via truck or rail, in standard non-refrigerated containers with non-insulated walls.  Wine cases were assembled onto pallets, with the top of the pallets covered with thermal blankets (fabric quilts or plastic/metal bubble wrap) for insulation.

Test packages were placed in the shipping container in three different positions per shipment: one above the thermal blanket, one in the front of the pallet below the blanket, and one in the back of the pallet below the blanket.

There were 26 individual shipments containing a total of 47 test packages monitored in the summer and fall of 2000 during 13 different shipments throughout the US.  Wines were shipped via truck or rail from winery warehouses in California to wine distribution centers in Georgia, Texas, New York, California, New Jersey, Illinois, Florida, Missouri, Louisiana, and North Carolina.  Upon arrival, test packages were removed from their pallets and returned to California via USPS Priority Mail for chemical analysis.  Wines were in transport for a total of 1 to 3 weeks.

Upon return to California, wines were sent to ETS Laboratories for chemical analysis.  EC was analyzed by gas chromatography and mass spectroscopy.

Heat exposure of wines was calculated by integrating the temperature data for each 15 minute intervals and comparing them to ideal cellar storage conditions.

Results

  •       Temperatures ranged from -13oC to 44oC in the top (unprotected) position.

o   The freezing point of table wine is -5oC.
o   Volume expansion of table wine from 13oC to 44oC is 0.9% or 7mL per 750 mL bottle.
o   Normal headspace volume at bottling is between 4 and 7mL.
  •       There was a 2 to 4oC temperature difference between the temperature of the air in the storage space and the temperature of the liquid inside the bottle.

o   Therefore, the heat capacity of the glass protects the wine from short-term temperature spikes.
  •       Temperature changes during 1 day in the unprotected top position ranged from 4oC to 21oC.

o   This temperature fluctuation could result in significant volume expansion of the wine which could affect the structural integrity of the closure and glass.
  •       There were significant temperature differences between test packages, depending upon where in the container the test package was located.

o   All extreme temperatures occurred in the top location that was unprotected; indicating that wine shipped without additional protection (i.e. blankets) will be more prone to extreme heat exposure and variation between bottles in a single shipment.
  •       EC formation in model wines was found to be between 2 and 94 μg/L during the shipping period tested.

o   This resulted in a 10-fold increase in reaction rate every increase of 19oC.
  •       Heat exposure to the wines significantly increased the effective bottle age and wine shelf life.

o   The true age of the wine jumped forward by 18 months (1.5 vintages).
o   This accelerated aging will likely lead to different wines in terms of sensory characteristics than what they would be under normal aging conditions.

Conclusions

The results of this study showed that extreme heat exposure has potentially damaging effects on the stored wines.  However, current commercial shipping technologies can be sufficient in protecting wines against heat damage, as long as certain rules and procedures are applied each time.  For example, the use of insulation in shipping containers is critical in protecting wine against excessive heat.  Since wine bottles are heavy, they are usually packed at the bottle of the shipping container, which leaves a good amount of headspace above it.  As this study showed, the headspace is prone to excessive heat fluxes, so by insulating the shipping containers, this increase in temperature of the headspace can be hampered.

One concern about these protective measures is that the cost is too much to bear for wineries.  According to the authors of this study, the additional cost for different transport options, including special refrigeration units or protective blankets, usually adds no more than 0.1% to the production cost of even the most inexpensive wines.  Those red wines that are heavily extracted and considered to be very precious are actually the ones that are least apt to be damaged by heat exposure, due to their high abundance of protective phenolic compounds.

One part of the system that this study did not cover that could cause significant damage to the wines due to heat exposure is the time when wines are moved from small un-insulated delivery trucks to the consumers’ doorstep (or some other similar end of transport situation).  There isn’t too much that can be done at this point, other than packaging the wines in protective/insulating case boxes and not shipping during the hottest months of the year.  Overall, however, damage to wines caused by excessive heat exposure can be avoided mostly by ensuring proper protection in the shipping containers during transport and storage.

One thing I’d like to see a similar experiment with actual wine instead of model wine.  Since “real” wine contains many more compounds than the model wine in this study, do the chemical reactions therein change how the wine is affected by the heat?  The authors alluded to the fact that a heavier wine with higher levels of phenolic compounds would suffer less than other wines, so it would be nice to see this backed up with some data.  Also, were the EC fluctuations found in this study enough to be harmful to humans if consumed?  Or did the levels remain below any sort of threshold level?

I’ve love to hear what you all think about this topic.  Please feel free to comment below (no html tags, please).


Source: Butzke, C.E., Vogt, E.E., and Chacón-Rodríguez, L. 2012. Effects of heat exposure on wine quality during transport and storage. Journal of Wine Research 23(1): 15-25.






I am not a health professional, nor do I pretend to be. Please consult your doctor before altering your alcohol consumption habits. Do not consume alcohol if you are under the age of 21. Do not drink and drive. Enjoy responsibly!
May 08 NO comments
consumer preference, economics, high-end wines, marketing, psychology, research, storage, wine label, wine preference, wine quality

Is Wine Bottle Weight Associated with Wine Quality?



Just looking down the aisle at the wine shop, you all know that there are a lot of different wines to choose from.  Most of the time one does not know much about the quality and thus have to make their purchase decisions based on other factors such as brand name, price, labeling, and advertisements.  One study found that consumers focus on two main attributes when making their purchasing decisions: 1) the shape/size/color of the bottle, and 2) the type of closure and label.  To date, most of the studies have focused on the impact of labeling on purchase intention, and very few have examined the effect of bottle shape/size.

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With other types of products, studies have shown that consumers associate heavier products with better quality.  Some may think that as a result of this finding, if it applies to wine, could fool consumers into thinking the wine is a higher price/quality, when perhaps maybe it is not.  Wine bottles come in a wide variety of sizes, with weights varying from 300g to 900g (empty), with an average of 500g.  One of the few studies examining bottle weight and effects on consumers found that consumers did associate heavier bottles with higher quality wine. 

One more psychological study examined consumer preferences with vodka and found similar results.  By taking a heavy glass bottle and a lighter glass bottle and filling them with the exact same amount of vodka, those participants in the study that noticed the weight difference preferred the heavier bottle, since it was perceived as being more expensive/better quality.  The main problem with this study was that there was no statistical analysis performed, so one can’t be sure if these results were “real”.

So, does the weight of the bottle really give an indication of the price and quality of the wine inside?  The cost of the bottle itself is something to consider: lightweight bottles are weaker (generally) and more likely to break during transportation, so often times stronger bottles would be preferred.  Consumers often believe that for higher quality wines, the increased cost of glass in a stronger bottles is small when compared to the risk of breakage.

There were five overall goals for the study presented today: 1) to determine if there is a correlation between bottle weight and price; 2) to determine if there are correlations between bottle weight and vintage, color, and country of origin; 3) to determine the variation in the marketplace in regards to weight; 4) to determine if there are any correlations between bottle weight and whether the wine is “old world” style or “new world” style; and 5) to determine if consumers make any associations between bottle weight and price or quality.

Methods

The study was performed in a wine shop in Oxford, England.  Over 500 bottles were weighed with a kitchen scale with the main characteristics of the wine inside noted. 

To determine consumers’ opinions on bottle weight and price/quality, online questionnaires were sent out to wine experts, people in educational agronomy and food technology departments, as well as the general public (all in Spain).  In the email sent out, it was noted that the purpose of the questionnaire was to collect information about general wine consumption, preference, and wine knowledge.  Participants were asked to determine their level of expertise with wine, their frequency of wine consumption, and their preferred variety of wine.  Data for any participant consuming less than one glass of wine per week was not included in the analysis.

Results

  •       In general, participants thought that the weight of the bottle had more to do with price than the quality of the wine contained within.

o   Differences were found between the three consumer groups (naïve, amateur, expert):
§  Specifically with naïve consumers (and less so with amateurs and experts), there was a trend of higher quality wines being associated with heavier bottles.
  •       The weight of the bottles were positively correlated with the price of the wines, and inversely correlated with the vintage.

o   Heavier bottle = greater price.
o   Heavier bottle = older wine.
  •        Alcohol content was positively correlated with the weight of the bottle.

o   Heavier bottle = higher alcohol.
§  Red wines had higher alcohol content than white wines.
·         Therefore, the color of the wine was significantly correlated with the weight of the bottle, though this was not found in every country of origin.
  •       There were no significant differences between New World and Old World wines in regards to wine bottle weight.
  •       Results by country:

o   Australia:  The younger the wine, the lighter the bottle.
o   France: The heavier the bottle, the higher the price, the higher the alcohol, and the older the vintage.
o   Italy: The heavier the bottle, the higher the price, the higher the alcohol, and the older the vintage. (Same as France!)
o   South Africa: The heavier the bottle, the higher the price and the older the vintage.
o   Spain: The heavier the bottle, the higher the price, the higher the alcohol.  There was no correlation with vintage.

Conclusions

In general, this very short study found that the weight of the wine bottles was strongly correlated with the price of the bottle, which varied slightly from country to country and by type of wine.  The authors did not find any direct correlations between the price of a bottle of wine and its’ perceived quality. 

One major problem with this study was that, according to the authors, the methods used did not explicitly test whether consumers actually rely on the weight of the bottle to determine price and quality.  I was slightly miffed by the fact, as I would assume that a study setting out to test a particular hypothesis would actually design the experiment properly instead of going about it in a roundabout way.  However, I suppose this study could have been more of an initial observation, the results of which could help the authors determine if more detailed analysis needs to be performed, or if they are way out in left field with their ideas.  By performing the similar questionnaires first, the authors have some idea of potentially significant outcomes, the next study of which could be designed to more explicitly test these theories. 

For example, in order to explicitly test whether consumers actually rely on the weight of the wine bottle in order to estimate price and quality of the wine within, study participants would need to actually taste and rate the same wine when served from bottles having different weights.  The authors bring up one potential issue with this design in that the shape of the bottle may also play a role in determining price and quality.  Specifically, different bottle shapes have different centers of gravity, which may give the illusion that one bottle is heavier than another, even if they are the same weight.  This variable would most certainly need to be taken into account with future research.

In a nutshell, there appears to be some correlation between bottle weight and price based on simple online questionnaires, however, to really determine if consumers associate heavier bottles with higher price and potentially higher quality, taste experiments using the same wine in different size/shape bottles must be performed.

What do you all this of this study?  Please feel free to comment below (no html tags).

Source: Piqueras-Fiszman, B., and Spence, C. 2012. The weight of the bottle as a possible extrinsic cue with which to estimate the price (and quality) of the wine? Observed correlations. Food Quality and Preference 25: 41-45.

DOI: 10.1016/j.foodqual.2012.01.001




I am not a health professional, nor do I pretend to be. Please consult your doctor before altering your alcohol consumption habits. Do not consume alcohol if you are under the age of 21. Do not drink and drive. Enjoy responsibly!
Apr 24 NO comments
antioxidants, aroma, ecology, environment, flavor, oak barrel, oak chips, phenolics, plants, research, soil, Spain, Spanish oak, storage, wine chemistry, winemaking

Influence of Geographical Location on Volatile Composition of Spanish Oak



The use of oak in wine making, be it with oak barrels or oak chips, has a significant effect on the flavor, aroma, texture, and color of the finished wine.  Traditionally, three different species of oak have been used for wine barrel fermentation and/or aging: Quercus alba L. (American oak), Quercus petraea (Matt.) Liebl., and Quercus robur L (both French oak). As a result of overcropping of the oak trees, or the harvesting off more oak trees than can be regrown for future use, in addition to the quest for more variety, new sources of oak for wine making are being explored.  Oak from Eastern European countries such as Ukraine, Russia, Romania and Hungry are starting to be used more in wine making, including similar species as used in France (Q. petraea and Q. robur) and another species used less frequently: Q. pyrenaica, which frequently hails from Spain.

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The use of oak barrels in wine making significantly influences the volatile composition of the finished wine, which in turn affects the flavor, aroma, and taste of the wine.  Studies have shown that there are quantitative differences in the volatile composition of wine made from American versus French oak barrels.  Furthermore, studies have shown that the Spanish oak, Q. pyrenaica, also shows significant differences in volatile composition of the wood, including higher levels of eugenol, guaiacol, and other volatile phenols and furanic aldehydes.  Looking at phenolic aldehydes and ketones, Spanish oak appears to retain levels between that of French and American oak. 

The amounts of these volatile compounds that are extractable from the oak wood are extremely important in determining the overall aromatic profile of the finished wine.  As a result of this, understanding the chemical composition of Spanish oak (Q. pyrenaica) is extremely important.  Studies from other oak species have shown that there is strong variability in the volatile composition of oak wood within the same species, tree, forest, stand, etc, due to various environmental and geographical factors. 

The study presented today aimed to add to the literature of oak wood volatile composition by examining Spanish oak, Q. pyrenaica, and to evaluate the effect geographical location, site, and silvicultural parameters had on them.

Methods

The sample set included 107 samples of Q. pyrenaica that were collected from several stands in three geographical locations in the northwestern Iberian peninsula (from the provinces of Ourense, Lugo, and Pontevedra).

From each tree, disks of wood were collected at a height of 1.3m above the ground.

From each of these disks, test tubes of heartwood were taken (20mm x 20mm x 40mm).

Heartwood samples were dried, then ground with a mechanical mill and sieved (<1mm) in order to obtain sawdust of a homogenous size.

Volatile compounds were isolated and then analyzed using gas chromatography and mass spectrometry. 

Results

  •       The qualitative profile of volatile compounds obtained from Spanish oak was very similar to what has been reported for other oak species.
  •       There was high variability on several levels, including the levels of individual trees, forests, and geographical locations.
  •       Q. pyrenaica samples were high in cis- and trans-β-methyl-γ-octalactone (cis- was the dominant form).
  •        Samples were high in phenolic aldehydes, including vanillin, syringaldehyde, coniferaldehyde and sinapaldehyde.
  •       Eugenol and isoeugenol were the major phenolic compounds found in all Spanish oak samples.
  •       Phenolic compounds also found in all Spanish oak samples were α-terpinol, γ-cadinene, δ-cadinene, 3-oxo-α-ionol, and vomifoliol (fruity and floral aromas).
  •       The most common semi-volatile present in the samples was β-sitosterol (antioxidant properties).


Silvicultural Parameters

  •       The most influential silvicultural parameter on volatile composition of oak samples was altitude.

o   The volatiles that were most affected were α-terpineol, eugenol, and vitamin E.
o   All correlations were negative:  the higher the altitude, the lower the concentration of volatile compounds.
  •       Organic matter and average annual temperature had some influence on volatile composition, specifically α-terpineol, vanillin, oxo-α-ionol, vitamin E, and α-amyrin.
  •       Distance from tree center, average annual precipitation, and number of trees per hectare did not influence the volatile composition of wood.


Soil Composition

  •       Volatile composition of oak in different soil types was similar.

o   Significant differences were found for the volatile aldehydes syringaldehyde, sinapaldehyde, and coniferaldehyde; and for tritperpenic compounds such as β-amyrin and derivatives and β-sitosterol (all with antioxidant properties).
o   For those compounds with important sensory influence, significant differences were found with α-terpineol, and 3-oxo-α-ionol (floral notes), and trans-β-methyl-γ-octalactone (coconut/woody notes).
  •       The greatest difference for all the above compounds were found in loamy soils.

o   Samples grown in loamy soils had the lowest levels of all of the above volatile compounds.

Geographical Location

  •       Samples from Lugo and Pontevedra were very similar.
  •       Samples from Ourense had lower levels of many volatile compounds compared to the other two locations.

o   Significant differences were found for guaiacol and vinyl guaiacol (smoky odor), syringol, eugenol (clove aroma), α-terpineol (floral odor), and coniferaldehyde.
  •       According to linear discriminate analysis, different geographical locations could determine/distinguish different chemical composition of wood samples of the same species.


Conclusions

The results of this study showed that some silvicultural parameters, such as altitude, organic matter and average annual temperature influence the volatile composition of Spanish oak, Q. pyrenaica.  Conversely, other silvicultural parameters, such as distance from tree center, average annual precipitation, and number of trees per hectare do not influence volatile composition.

Even though it was shown that Q. pyrenaica grown in loamy soils show some significant differences in regards to volatile composition compared to other soil types, linear discriminate analysis showed that soil type is a poor determinant in volatile composition of wood in Spanish oak. On the other hand, as with French and American oak, geographical location does have a significant influence on oak volatile composition, and is a good factor for volatile composition classification.

The results of this study should arm wine makers with information they need in order to make a decision on whether or not Spanish oak is right for the style of wine they wish to create, and which forest/province they should harvest the trees from.  Ultimately, however, I think the next step in this line of research would be to create a wine using barrels from Spanish oak from different geographical locations, and compare the oak volatile composition results with the finished wine volatile content as well as a sensory analysis.

What do you all think of this topic?  How many of you use Spanish oak barrels or Spanish oak chips in your wine making practice?  Please feel free to leave your comments below (no html tags, please).

Source: Alañón, M.E., Pérez-Coello, M.S., Díaz-Maroto, I.J., Martín-Alvarez, P.J., Vila-Lameiro, P., and Díaz-Maroto, M.C. 2011. Influence of geographical location, site and silvicultural parameters, on volatile composition of Quercus pyrenaica Willd. wood used in wine aging. Forest Ecology and Management 262: 124-130.

DOI: 10.1016/j.foreco.2011.03.011



I am not a health professional, nor do I pretend to be. Please consult your doctor before altering your alcohol consumption habits. Do not consume alcohol if you are under the age of 21. Do not drink and drive. Enjoy responsibly!
Apr 03 NO comments
aging, anthocyanins, antioxidants, chemistry, enology, health, oak barrel, phenolics, Port, Portugal, research, storage, wine chemistry

Examining the Anthocyanin Content and Antioxidant Capacity of Port Wines



Port wines are created from the Duoro Demarcated Region in northern Portugal, and use several varieties of grapes, including Touriga Nacional, Tinta Barroca, Tinta Roriz, Touriga Francesa, Tinto Cão, and Tinta Amarela.  One important characteristic of Port wines and Port-style wines is that the residual sugar in the finished wine is obtained by stopping the fermentation process early, by way of the addition of brandy (or other wine-based spirit).  The final concentration of alcohol, therefore, in Port wines is around 18% v/v. 

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The aging process is also a very important factor in the creation of Port wines, which includes aging in oak barrels, steel tanks, or within bottle, depending upon the style of Port wine desired.  With Ruby Port wines, they are stored in stainless steel tanks for two years in order to prevent oxidative aging and retention of color.  Late Bottled Vintage (LBV) Port wines are made from a single years’ harvest, and are kept in barrels for 4 to 6 years, obtaining a ruby color.  Tawny Port wines are made from grapes aged in barrels and blended with other grapes from other barrels (of different vintages), which result in the wine being exposed to gradual oxidation and evaporation to produce a golden-brown colored wine.  Tawny Reserve Port wines are labeled without any indication of the age, and are blends of wines that were aged in barrels for at least two years.  As a result of all these different styles of Port wines, chemical composition and color differs markedly, depending upon the winemaking and storage process for each style.

In regards to color, various phenolic compounds in wine that create the colors that we see.  Specifically, anthocyanins are categorized as contributing to the variability of the colors of wines.  Various natural chemical reactions occur amongst the different anthocyanins present within the wines, resulting in the formation of more stable pigments that create wine color, which ultimately changes it to a brick-red color in more aged wines. Not only are anthocyanins very important in regards to wine color, but they also have several potential health benefits as antioxidant agents.

Some researchers believe that due to decreases in phenolic complexity over a period of aging, wine loses its antioxidant capacity, though this hypothesis has seen mixed results.  As a result of these mixed results, and the fact that data on free radical scavenging activity (i.e. antioxidant capacity) and anthocyanin content of Port wines is limited, the study presented today aimed to examine and understand the anthocyanin content of different styles of Port wine, and also to evaluate the antioxidant capacity of these wines.

Methods

Port wines used were made from blends of Touriga Nacional, Touriga Francesa, Tinta Roriz, and Tinta Barroca, from Douro vineyards.  Grape must samples were collected from four different fermentation vats and were collected at two different times during fermentation (2 days and 3 days. 

Commercial Port wines were purchased from a market and included the Port styles of Ruby, Late Bottled Vintage (LBV), Tawny Reserve, Tawny 10, 20 year old Ports.  6 brands of each style were selected, resulting in a total of 30 wines studied.

Anthocyanins and antioxidant activities were measured for each must and each wine.

Results

  •       The most abundant anthocyanin in the musts was malvidin 3-O-glucoside (60% in weight)
  •       The same anthocyanins were found in Ruby and LBV Port wines as were found in the must.
  •       Ruby and LBV Port wines had similar anthocyanin profiles, though there were quantitative differences.

o   A lower percentage of malvindin 3-O-glucoside was found in LBV Port wines.
o   Only traces of anthocyanins were found in Tawny Port wines.
  •       Higher anthocyanin content was found in musts with 3 days of fermentation than must with 2 days of fermentation.

o   This result indicates that there is an increase in the extraction of anthocyanins during fermentation.
  •        Anthocyanin content of Port wines was much lower than the content in musts.

o   The authors claim this is likely due to the addition of the wine spirit to stop fermentation, as well as the aging process and aging “environment”.
  •       Higher amounts of anthocyanins were found in Ruby Port wines, followed by LBV Port wines.

o   These wines age in stainless steel tanks and/or sealed glass bottles, which are not exposed to air and undergo reductive aging.  This results in a much slower loss of anthocyanins than other aging methods.
  •       Tawny Reserve Port wine had trace amounts of anthocyanins present (if any), with other Tawny Port wines having none at all.

o   Since these styles of Port wines are aged in barrels, the wine undergoes an oxidative aging process due to the permeability of the barrel to the air.  This results in a much faster loss of anthocyanins than other aging methods.
  •        The anthocyanin profile of Reserve Tawny, Tawny 10 years, and Tawny 20 years was very similar, and all exhibited the lowest levels of anthocyanins out of all the Port wines.
  •       Ruby Port showed high levels of newly formed anthocyanins, and LBV Ports differed in anthocyanin content depending upon the year of production.

o   LBV Ports with 4 years of barrel aging and 6 years of bottle aging had lower anthocyanin levels than samples with shorter aging times in the bottle.
  •       Ruby Port wines showed the same anthocyanidins as found in the must, however, the levels of which were significantly lower.
  •       Tawny 10 year and Tawny 20 year had similar anthocyanidin profiles when compared with Tawny Reserve.


Antioxidant Capacity

  •       Antiradical capacity (indicative of antioxidant capacity) was dependent upon the concentration and style of Port wine.
  •       Ruby and LBV Port wines showed higher antiradical activities than Tawny Port wines.

o   This result indicates that reductive aging increases antiradical activity.
  •        LBV Port wines showed higher antiradical activities than Ruby Port wines.

o   During aging within the bottle, LBV Port wine composition changes in the reducing environment, with the oxidation-reduction potential decreasing until it reaches a minimum value that prevents any further oxidation reactions.
  •       Tawny Port wines had lower antiradical activity than all other Port styles.


Conclusions

Overall, the results of this relatively simple study indicated that the aging process is an important factor that influences the antioxidant capacity of Port wines.  All Tawny Ports showed the lowest levels of anthocyanins, while Ruby and Late Bottled Vintage Ports showed the highest levels.  Similarly, Tawny Port wines displayed the lowest antioxidant capacities, while Late Bottled Vintage Port wines displayed the highest.

The authors did not draw any other conclusions besides these facts (as well as listing some specific anthocyanins present), indicating that this paper was merely a simple stepping stone for future research to be launched.  I’d be curious to see comparisons of different blends within each style, and if there is one particular blend that has superior antioxidant capacities to the rest.  Another interesting comparison would be between Port wines and other wines that are unfortified. 

In a nutshell, it appears, however, that if you love Port wines and are looking for the Port wine with the highest antioxidant capacity (and thus theoretically, a “healthier” Port), then a Late Bottle Vintage or a Ruby Port is your best bet. 

I’m interested in hearing what you have to think about this topic.  What types of research would you like to see done in this field, based on the results of this study?  Feel free to leave your comments below!

Source: Pinho, C., Couto, A.I., Valentão, P., Andrade, P., and Ferreira, I.M.P.L.V.O. 2012. Assessing the anthocyanic composition of Port wines and must and their free radical scavenging capacity. Food Chemistry 131: 885-892.

DOI: 10.1016/j.foodchem.2011.09.072





I am not a health professional, nor do I pretend to be. Please consult your doctor before altering your alcohol consumption habits. Do not consume alcohol if you are under the age of 21. Do not drink and drive. Enjoy responsibly!