Category Archives: trade

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 04 NO comments
agriculture, Australia, book review, ecology, economics, enology, entertainment, environment, france, insects, literature, phylloxera, plants, politics, sociology, South Africa, trade, USA, Viticulture

Book Review: Dying on the Vine: How Phylloxera Transformed Wine by George Gale



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Dying on the Vine: How Phylloxera Transformed Wine, by George Gale, is a highly educational and well-written book covering the phylloxera crisis starting in the late 1800s and how the world continues to struggle with the pest even today.  For over 150 years, this tiny little bug wreaked havoc on grape vines all over the world, the details of which this book describes the steps that were taken initially in France and the lessons learned (or not learned) by other grape growing regions around the world.  This book will appeal to anyone in the wine industry, as well as ecologists, entomologists, historians, and generally anyone interested in human behavior in times of crises.

The first half of the book (Chapters 1 through 4) takes the reader on a journey through time starting from the very first discovery of what was to become known as the phylloxera crisis in France through the controversial attempts at eradicating the pest.  Was the phylloxera bug the cause of the vine death?  Or was there an unknown disease already weakening the vines that attracted the pest?  Surprisingly, this debate went on for many years, with scientific research to back up such claims at times falling far behind.

Over time, several “solutions” to the phylloxera problem were employed in France, including planting in sand, vineyard submersion, and sulfiding.  Though these methods worked some of the time, none of them were long-term strategies that would be effective against the phylloxera worldwide, nor were some of them particularly good for the environment (re: sulfiding).  Over the next few decades, the best minds at the time eventually determined that they only way to effectively stop the phylloxera from spreading all over the country and destroying all of the vineyards (and ultimately the only source of income for many families at the time) was to graft the vines onto American rootstock.

Of course, since it was ultimately discovered that imported American vines were the cause of the initial phylloxera outbreak to begin with, acceptance of this grafting onto American rootstock method caused much contention and controversy throughout the French countryside.  Over time, however, this proven method was eventually embraced by vineyards across the country, though there would always be some debate about whether or not a better method existed that would keep French vines “pure”.

Chapters 5 and 6 describe how the phylloxera spread throughout Europe, Australia, and South Africa, and details how each country took to solving the crisis.  One would think that each country would simply look at what happened with the French vines and learn from their mistakes, however, the book describes how surprisingly many of the locales would put up a “it can’t happen here” front and completely ignore any of the work done previously in France.  It was as if each location that was affected by the bug was starting from scratch, with no one wanting to believe that this disaster could happen to them.  The book provides fascinating descriptions and insight into how each country handled the situation, and makes one think about human behavior in crises and the ability (or inability) to learn from past mistakes.

Chapter 7 takes us back to France and describes how French people during this time were taking to the new American rootstock and the American vines planted on French soil.  Though many detested the “foxy” wine produced from these American vines, many people realized their choices were limited and gradually learned to enjoy the beverages.

Finally, Chapter 8 describes how phylloxera broke out not once, but twice, in California and how people in America struggled with finding a solution just as much as the Europeans, Australians, and South Africans did regarding how to handle the eradication of the bug.  From reading the book, it amazed me how much different cultures ignored the mistakes and successes of other cultures regarding the phylloxera crisis and how foolishly proud each was.

Overall, I thought this was a fantastic book and was a great read from cover to cover.  I even found myself reading each of the three appendices, which is something I wouldn’t normally do if I did not enjoy the subject matter or the author’s writing abilities.  This book made me curious as to how this crisis affected the overall psychology and health of the people involved, which is a topic of interest of many scientific research studies, including one summarized here on this blog.  Since the focus of this book was on the ecological/viticultural side of things, I knew not to expect answers to these questions; however after reading this book by George Gale, I want to know more!

If you’re at all interested in the history of wine, ecology, entomology, or just overall good writing, I highly recommend picking up a copy of this book! 

You may purchase is on Amazon by clicking on this link:  Dying on the Vine: How Phylloxera Transformed Wine

 ...or you may buy it directly from the publisher by clicking here:  Dying on the Vine: How Phylloxera Transformed Wine

Happy reading!



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 30 NO comments
agriculture, climate change, consumer preference, economics, environment, Germany, global warming, high-end wines, prices, research, trade, wine quality

The Economic Effect of Climate Change on Viticulture



Regardless of what you believe is the cause, global warming and climate change is occurring.  Depending upon where one looks around the globe, climate change affects specific areas of the world differently.  Specifically, in regards to wine and viticulture in California, studies have shown that global warming could have negative effects on the quality of wine (Pinot Noir, specifically) in the region, which would likely be reflected by lower prices.

Is it possible that some areas of the world will see positive benefits of global warming?

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The paper reviewed today, though now a couple of years old at this point, aimed to examine the economic impact of global warming on viticulture in the Mosel Valley of Germany, which lies between 49.61o and 50.34o latitude.  Within the Mosel Valley, production of grapes depends upon specific site characteristics such and steep slopes on rocky/infertile soil and specific weather conditions to allow for winter survival and successful ripening.  As a result, wine quality (as well as prices) depend upon weather and can therefore vary widely from year to year.  Due to these specific limitations and characteristics in the Mosel Valley, it is expected that temperature-induced changes due to climate change will have a direct impact on the economics on this part of Germany.

In order to study the economic impact of global warming on viticulture in the Mosel Valley of Germany, the authors used the “Ricardian” approach that has been verified and validated by other studies focusing on the effects of climate change on agriculture.  To be more specific, the authors created their three models based on different price data, including retail, wholesale, and auction prices.

Model and Data

The data this model focused on revenue and its components.  Per hectare revenue between 1997 and 2008 in each of the 5 viticultural areas of the Mosel Valley were examined (Upper Mosel, Middle Mosel, Lower Mosel, Saar, and Ruwer Valley).  Revenue is basically calculated by the product of price and crop yield, though there are some other complexities that result in deviations from this simple formula, such as how wines in the Mosel Valley are labeled and marketed. 

Basically, German wines are classified and labeled according to the natural sugar content of the grape must (unfermented) based on the Oechsle cale (oOe):  the sweeter the must; the higher the alcohol; the stronger the aroma; and finally the higher the quality.  The quality of wines increase in the following order: Quality Wine (no oOe requirement), Kabinett (70oOe), Spätlese (76oOe), Auslese (83oOe), Beerenauslese (110oOe), Eiswein (110oOe), and Trockenbeerenauslese (150oOe).  Wine prices are thereby determined by the vineyard where the grapes were grown and by the quality level.

Data for revenue per hectare are not readily available; however, they can easily be calculated by multiplying crop yield data by the average prices for each region and each wine quality level.  Wine prices by region and by quality are not readily available; however, they can easily be calculated by drawing on various wine price data using three different sources (retail, wholesale, and auction).

Wine production data by region and by quality between 1997 and 2008 was provided by the Statistical Office of the State of Rheinland-Pfalz and its agricultural commission (Landwirtschaftskammer).

A disadvantage to using retail and wholesale price data is that they refer to posted prices, not transaction prices (though sometimes they are).  Conversely, an advantage to using these data is that they cover a wide range of wine producers in the Mosel Valley.  Auction prices, while they do represent actual transaction prices, only a very small percentage of Mosel Valley wines are represented and sold, so auction prices may not be representative of the Mosel Valley region in general.

Retail price data from 1994 to 2008 came from the Gault Millau Wine Guide for Germany.  This guide contained detailed information about wine age, geographic origin, and quality classification, as well as the data to allow for the calculation of wine prices and quality levels per region.  Wholesale price data from 1993 to 2001 came from the Mainz Wine Trade Fair (Mainzer Weinbörse).  Auction price data from 1981 to 2008 came from the wine associations VDP Grosser Ring and Bernkasteler Ring.

Auction wines, though in the past represented a great variety of wines in the Mosel Valley region, primarily serve now as a showcase for a few very high quality wines.  For example, only 0.13% of wines auctioned are Quality Wines (lowest quality), while 74.1% of all wines produced in the Mosel Valley are at the Quality Wine level.  Also, 12% of the wines sold at auction are Eiswein, Beerenauslese, or Trockenbeerenauslese quality levels, whereas these quality levels only represent 0.2% of the total production of the Mosel Valley. 

According to the authors, responses of prices to temperature during the growing season are very sensitive to these higher quality wines, making it likely that these data will suffer from selection bias.  Also, the auction price data are likely to overstate the average effect of temperature on price.  In years of good weather, yield reduction is practices in vineyards production higher quality wines, therefore prices of these quality wines are already partially a result of weather.  Crop yields more fully reflect weather variation in the Upper Mosel region, where quality of wine is lower and yield reduction is seldom practiced.

Results

  •       Wine quality and price are highly dependent upon weather, as seen in other studies.

o   In more northern latitudes, warmer and drier weather are expected to yield higher quality fruit.
o   Warmer weather had a significantly positive effect on prices.
o   Higher quality wines benefitted from a warmer growing season than lower quality wines.
o   The effect of temperature increase on price was greatest in the regions of Saar and Ruwer.
  •        Auction prices were significantly more sensitive to temperature changes than retail or wholesale prices.
  •       There was a greater production of higher quality wines in warmer years.

o   Increases in temperature resulted in an increase in wine prices within each quality level.
o   Increases in temperature resulted in higher number of higher quality wines than lower quality wines.
  •       Revenue per hectare significantly increased with increasing temperatures.

o   The extent of this effect depends on which price structure one is considering:
§  Auction price data suggested increases in revenue of 63% per degrees Celsius increase.
·         Since auction data focuses mostly on high quality wines, this result is most likely an overestimate of the revenue increase due to increasing temperatures.
§  Wholesale price data suggested increases in revenue of 27% per degrees Celsius increase.
§  Retail price data suggested increases in revenue of 37% per degrees Celsius increase.

Conclusions

All three models employed in this study suggest that the vineyards of the Mosel Valley in Germany will increase in value as a result of increasing temperatures caused by climate change.  Auction prices will likely overestimate this increase, whereas retail and wholesale prices more accurately represent the potential effect of global warming on changing prices of wine. 

According to the results of the models, the authors predict that a 3oC increase in temperature would more than double the value of the vineyards in the Mosel Valley region.  A more moderate increase of 1oC is predicted to result in an increase in revenue of about 30%.

One thing that’s not certain is whether we will continue to see this trend as the future progresses, or if we are in a more transitional period with much more change to come.  The only thing we can do is to continue running these models and adjust parameters accordingly depending upon any new changes observed.

The authors described a few more limitations of the models used in this study.  The first limitation is that the model does not take into account any general equilibrium effects that may occur with the restructuring of land prices.  Specifically, if there were to be any dramatic changes in prices of vineyard land itself due to climate change, there could be consequences for the final results of the price analysis.  Another limitation presented by the authors is that the results presented represent only a small fraction of the overall appraisal of the role of climate change on vineyard and general agricultural values.  Finally, it’s possible that too high an increase in temperature would be detrimental on price, if the grapes were subsequently damaged by excessive heat.

I’d love to hear your thoughts on this topic.  Please feel free to comment below (no html tags, please).

Source: Ashenfelter, O., and Storchmann, K. 2010. Measuring the Economic Effect of Global Warming on Viticulture Using Auction, Retail, and Wholesale Prices. Review of Industrial Organization 37: 51-64.

DOI: 10.1007/s11151-010-9256-6




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!