Tag Archives: polyphenols

Comparing Biogenic Amines and Polyphenols of Grapes and Wine After Conventional, Biodynamic, and Organic Practices: Which Method is Best?

Posted on April 15, 2013 by Becca| 4 Comments

 

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Biogenic amines are carefully monitored in the food and beverage industries, since if they are taken in at too high of concentrations, they can cause significant health problems including headaches, breathing problems, and cardiac problems. Biogenic amines are nitrogen-based compounds that are derived from amino acids and include compounds such as histamine, serotonine, tyramine, tryptamine, phenylalanine, agmatine, putrescine, cadaverine, spermidine, and spermine. Many of these compounds may be formed during the fermentation processes of food and beverage production, which are caused by interactions with the microbial population in the system.

In wine, several biogenic amines have been identified, with the most common being histamine, tyramine, and putrescine, and with concentrations reported up to 50mg/L. It has been shown that polyphenols in wine actually serve to keep biogenic amine levels in check, as some polyphenols in wine have been seen targeting the enzymes facilitating biogenic amine production, thus keeping amine levels relatively low. In essence, these polyphenols are providing protection to the wine so that these biogenic amine compounds don’t rise to potentially toxic levels.

Several studies have examined whether or not certain agricultural or processing techniques affect the balance of polyphenols and biogenic amines in a variety of food products with varied results. Studies have examined conventional, organic, and biodynamic agricultural methods only to come up short in terms of general

Photo By drdcuddy (Flickr: Italia 2010) [CC-BY-SA-2.0 (http://creativecommons.org/licenses/by-sa/2.0)], via Wikimedia Commons

Photo By drdcuddy (Flickr: Italia 2010) [CC-BY-SA-2.0 (http://creativecommons.org/licenses/by-sa/2.0)], via Wikimedia Commons

observable trends. Some studies have shown that organic products have better biological activity than conventional products, while other studies have found no differences between conventional and organic agriculture and production methods. In general, it is assumed that organic and biodynamic agriculture and production methods are better for human health overall, though there is no solid scientific evidence to back that up quite yet (only mixed results).

Generally speaking, organic agriculture and biodynamic agriculture are very similar in that they both utilize composting and cover crops and prohibit the use of commercial pesticides, fungicides, herbicides, and other sorts of man-made chemicals. One major difference between the two practices is that biodynamic agriculture utilizes special preparations that use mineral and/or herbs, as well as various animal organs, which can be buried until the soil or made into a spray to apply to the foliage of the plants.

The study presented today aimed to compare conventional, organic, and biodynamic viticulture and winemaking practices for both red and white grapes and wine, and to determine if any of these methods differ from one another in terms of their polyphenol and biogenic amine content and particularly if one viticulture or winemaking method is ideal compared to the rest in terms of wine and human health quality.

Methods

Red and white grapes of the Sangiovese and Pignoletto varieties, respectively, were all grown in 2009 from vineyards in the Emilia-Romagna region of Italy. Conventional, organic, and biodynamic viticulture practices were performed for the different treatments.

Grapes were all picked on the same day from random locations throughout the vineyards and throughout the vines and clusters. 10kg of grapes were harvested from each treatment vineyard and were ground into a powder for chemical analysis.

Wine was made from the grapes at each of the treatment vineyards on site using conventional, organic, and biodynamic winemaking practices.

The following biogenic amines were measured for both grapes and wine: tryptamine, histamine, tyramine, diamine-propane, cadaverine, putrescine, spermidine, and spermine.

The following were measured for both grapes and wine: total polyphenols, individual polyphenols, anthocyanins, and antioxidant activity.

Results

Grapes

• Putrescine was the most abundant biogenic amine in all samples.
• Tryptamine was 4.7 times higher in Sangiovese grapes than Pignoletto grapes.
• Total biogenic amine levels in Sangiovese grapes were 5.5 times higher than in Pignoletto grapes.
• There were no clear trends or differences between viticulture methods in terms of biogenic amine levels.
• There were no significant differences between viticulture methods in terms of total polyphenol levels.
• Total anthocyanins were significantly higher in Sangiovese grapes compared with Pignoletto grapes (as expected).
• Total anthocyanin levels were highest using conventional viticulture methods, followed by biodynamic methods and finally organic methods.
• Catechins and stilbenes were significantly different between the Sangiovese and Pignoletto grape varieties (lower in Pignoletto grapes); however there were no significant differences between the two groups in regards to viticulture practice treatment.
• Resveratrol and trans-resveratrol were found in all samples, though cis-piceid and trans-resveratroloside were only found in Sangiovese grapes.
• Piceatannol was 2 times higher in Pignoletto grapes compared to Sangiovese grapes.
• Sangiovese grapes had 3 times greater antioxidant capacity than Pignoletto grapes.

Wine

• Biogenic amines were 3.6 times higher in Pignoletto wines compared with Sangiovese wines.
• There were no differences in biogenic amine levels between the different winemaking practices.
• Total polyphenols were 6.5 times higher in Sangiovese wines compared with Pignoletto wines.
• Sangiovese wines had the highest levels of anthocyanins and stilbenes compared with Pignoletto wines.
• Sangiovese wines had greater antioxidant capacities than Pignoletto wines.

Conclusions

The results of this study indicated that there were no significant differences in the chemical profile of Sangiovese and Pignoletto wines when treated with conventional, organic, or biodynamic viticulture and winemaking practices. The clear differences found in this study were in terms of grape variety (red versus white), and not viticulture or winemaking method, which was confirmed using Principle Components Analysis. Sangiovese grapes were found to have higher levels of biogenic amines, though none of the levels were high enough to cause a threat to human health. Conversely, after the winemaking process, it was found that Pignoletto wine had higher levels of biogenic amines compared with Sangiovese, which is likely due to winemaking technique and the interactions with the compounds present in the white must.

It seems as though reducing the levels of biogenic amines in wines may be difficult, as there are a number of factors that could be contributing to their

Biodynamic Composting. Photo credit: By Mark Smith [CC-BY-2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons

Biodynamic Composting. Photo credit: By Mark Smith [CC-BY-2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons

levels (i.e. grape variety, winemaking technique, geographical growing area, etc), though this study shows that using biodynamic or organic viticulture or winemaking methods as opposed to conventional methods will not affect biogenic amine levels.

Of course, there are many environmental benefits of using biodynamic and organic viticulture and winemaking practices, so these results are certainly not meant to deter anyone from adopting these methods. It’s simply a matter of determining what viticulture or winemaking technique will help lower biogenic amine levels in wine, and it’s clear from the results that choosing biodynamic or organic methods over conventional methods will not help in this case. I encourage biodynamic and organic agriculture and production methods, though again if one is seeking to change practices just to lower biogenic amine levels, switching to either of these won’t make a difference (but it will make a difference in other areas!).

I’d love to hear what you all think of this topic! Feel free to share comments or stories with everyone!

Source: Tassoni, A., Tango, N., and Ferri, M. 2013. Comparison of biogenic amines and polyphenol profiles of grape berries and wines obtained following conventional, organic and biodynamic agricultural and oenological practices. Food Chemistry 139: 405-413.

Posted in Chemistry, Environmental Science

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Examining Variations in Grape Phenolic Maturity and Ripeness at Harvest and How It Influences Wine Quality

Posted on March 25, 2013 by Becca| 5 Comments

 

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It is well known among grape growers and winemakers that the phenolic maturity of the grapes at harvest significantly impacts the overall quality of the finished wine. Specifically, the aroma, flavor, mouth feel, and astringency (to name a few) are all tied in with the composition of phenolic compounds in grapes and wine, thus are strongly influenced by grape ripeness or a lack thereof. Studies have found that certain phenolics in the skins of unripe grapes are less extractable and certain phenolics in the seeds of unripe grapes are more extractable than those in the skins and seeds of fully matured grapes, thus resulting in altered flavor and aroma of the finished wine.

The current demand from consumers in terms of ideal red wine characteristics are wines with a dark red color, full body, soft tannins, and ripe fruit flavors and aromas. In order to create wines with these types of characteristics, winemakers need to use fully ripened grapes, specifically those grapes that have reached “phenolic maturity”. It is because of this that there has been a lot of work done looking for a method or system to test grapes in the field to determine their ideal harvest date when phenolic maturity has been reached. There has been some progress in this field of research, however, according to the authors of today’s paper, these methods rely on the average values of a sample of grapes in the vineyard, and don’t take into account the variability of the phenolic maturity of grapes within that sample. A large variability in grape phenolic maturities could spell trouble for a winemaker attempting to create the “ideal wine” for consumers.

Agne27 at the English language Wikipedia [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/)], from Wikimedia Commons

Agne27 at the English language Wikipedia [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/)], from Wikimedia Commons

When grapes ripen throughout the season, each and every grape does not ripen at the exact same rate. A lot of factors go into this variability, from weather to vineyard management practices and even to the specific location on the cluster. As a result of this variability in ripening rates, there is the potential for there to be a large variability in phenolic maturities of the grapes at harvest, even when the average values indicate it’s about time to pick. According to the authors of today’s study, no one has ever looked at this variability (in other words, heterogeneity) of phenolic maturities in grapes, nor has it ever actually been quantified.

Thus, the goal of the study presented today was to evaluate the variability or heterogeneity of the degree of grape ripeness (degree of phenolic maturity) and how this variability affects wine quality and phenolic composition.

Methods

Grapes used for this study were Cabernet Sauvignon from experimental vineyards at Constantí owned by the Rovira i Virgili University in Spain. Grapes were studied during the 2007 and 2008 vintages and were harvested from the two central rows in this experimental vineyard.

600 grapes were collected randomly at 1, 3, 5, and 7 weeks after veraison (i.e. when the grapes start to change color) and analyzed. Sugar content, titratable acidity, pH, weight, and ripening heterogeneity of a portion of those grapes were measured.

Grapes were harvested 7 weeks after veraison for winemaking purposes and were separated into three different groups based on their densities. Grapes were then crushed, and then underwent typical red winemaking procedures (including a 14 day maceration period). After bottling, wines were stored at 15oC until ready for analysis.

The following were measured for grapes: sugar content, probable alcohol degree, titratable acidity, and pH; and the following were measured for the finished wines: ethanol content, titratable acidity, and pH. Also measured were: color intensity, lightness, chroma, hue, red-greenness, yellow-blueness, total color difference, total anthocyanin content, flavanol content (including catechins and oligomeric proanthocyanidins), total phenolic index, and astringency index.

A sensory analysis was performed on all wines by a panel of 10 “expert enologists” from Rovira i Virgili University after a 6 week storage period after bottling. Dark tasting glasses were used so the appearance of the wine color did not have any influence on the panel’s scores. Wines were compared in pairs, with the pairs being made up of two of the following: low density wine, medium density wine, and high density wine. The panel was asked to determine if they could tell a difference between the two samples and also what their favorite sample was and why.

Results

• As expected, during the growing season, sugar content, probable alcohol degree, pH, and berry weight increased, while titratable acidity decreased.
• The 2007 vintage grapes reached a greater phenolic maturity than the 2008 vintage grapes, though both years were considered “normal” years.
• Significant heterogeneity in phenolic composition and maturity of grapes was noticed from the start of the sampling period all the way through harvest.
o According to the authors, this means that are likely many unripe grapes mixed in at harvest prior to the winemaking process, which could increase bitterness and astringency due to lower sugar content, higher acidity, lower anthocyanin levels, and higher seed tannin levels, ultimately lower the quality of the finished wine.
o They suggest that these results indicate a significant influence of grape heterogeneity on phenolic composition of wine.
• As grape density increased, ethanol content and pH of wines increased, and titratable acidity decreased.
• Grape density significantly affected wine color.
o Higher density grapes resulted in wines with higher color intensity, chroma, and red-greenness as well as lower lightness levels.
o Hue and yellow-blueness levels were not consistent from year to year.
• The sensory panel was able to tell the different in wine color of wines from different grape densities just by using the naked eye.
o According to the authors, these results indicate that grape heterogeneity significantly impacts wine color.
• Grape density significantly influenced the anthocyanin content in the wines.
o As grape density increased, anthocyanin content increased (for both free and combined with flavanol forms)
o The authors noted that the presence of unripe grapes (i.e. less dense) at harvest could significantly impact the anthocyanin content of the finished wine.
• As grape density increased, proanthocyanidin concentrations and astringency increased.
o Denser grapes resulted in greater proanthocyanidin levels, which according to the authors could result in greater tannin levels, indicating a greater ability for aging than less dense grapes with lower levels of proanthocyanidins.
• As grape density increased, (+)-catechin decreased and (-)-epigallocatechin increased.
• Grape density significantly influenced proanthocyanidin monomer and oligomer concentrations.
o As grape density increased, monomers and dimers increased.
• Only 50% of the sensory panel could tell the difference between the medium and high density wines, while 100% of the panel could tell the difference between the low and high density wines.
o Overall preference was unanimous for the higher density wines, which the panel indicated had greater fruit and floral notes, as well as having better balance, lower acidity, and less bitterness than low density wines.

Conclusions

According to the results of the study and the author’s interpretations, grape ripeness heterogeneity has significantly more influence on finished wine quality than initially thought. Specifically, less ripe grapes (i.e. indicated by the lower density grapes in the study) can significantly influence the phenolic composition of the finished wine, and ultimately the overall quality of that wine. Basically, lower density grapes (i.e. less ripe grapes) lower the ethanol content, pH, anthocyanin concentrations, color intensity, total phenolic index, and proanthocyanidin concentrations, as well as increase the titratable acidity of the finished wine, resulting in an overall lower quality wine. By mixing in these lower density grapes in with the higher density grapes, the overall quality of the finished wine will most certainly be lowered some.

Agne27 at the English language Wikipedia [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/)], from Wikimedia Commons

Agne27 at the English language Wikipedia [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/)], from Wikimedia Commons

While only half of the sensory panel could differentiate between the medium and high density wines based on taste alone, 100% of the panel could tell the difference between the low and high density wines, indicating that grape ripeness heterogeneity is an extremely important factor in determining overall wine quality. Even though not all the panelists could tell the difference between the medium and high density wines based on taste alone, they were able to tell the difference based on color, so adding those two factors together could potentially decrease the overall acceptability and likelihood of purchase of even medium density (or not as many unripe grapes) wines (this was not tested—just my theory).

According to the authors, more research on grape phenolic maturity heterogeneity is needed, as well as methods or protocols for filtering out these less ripe grapes either in the field or just prior to the winemaking process. While the average phenolic maturity of the grapes may indicate it’s time to harvest, the fact that the grape to grape variability or heterogeneity is so vast indicates that there will likely be some lowering of quality if those grapes are mixed in with those truly ripe grapes.

Perhaps a method to quickly sort lower density grapes away from the higher density grapes would be most effective at reducing the heterogeneity of phenolic maturity of the grapes destined for making wine, be it through mechanical or digital means. My first thought was some sort of equipment or attachment to existing equipment that allows for density sorting in a similar manner that was done in this experiment. Those grapes with higher density would sink to the bottom of the machine, while those with less density would stay afloat, thus allowing someone to either scoop out the less dense grapes or have them funneled separately to a different container.

Overall, I thought this was an interesting study and certainly one that deserves follow up investigations based on its important findings. The entire concept of grape phenolic maturity variation and heterogeneity deserves more research, as well as applicable methods for sorting out these less ripe grapes either prior to harvest or just prior to the winemaking process in order to improve the chances of making a higher quality wine.

What do you all think of this study? Do you already employ methods for sorting out these less ripe grapes prior to winemaking? Please feel free to share your thoughts and/or experiences!

Source: Kontudakis, N., Esteruelas, M., Fort, F., Canals, J., De Freitas, V., and Zamora, F. 2011. Influence of the heterogeneity of grape phenolic maturity on wine composition and quality. Food Chemistry 124: 767-774.

Posted in Chemistry, Enology, Viticulture

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The Effect of Red Wines with Varying Antioxidant Activities on the Cardiovascular Health of Rats

Posted on March 11, 2013 by Becca| Leave a comment

 

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Thickening of the arteries, or atherosclerosis, is a disease that is often associated with complications of heart attack and stroke. It is caused by LDL cholesterol (low density lipoprotein) which enters into the inner lining of the arteries which causes vascular oxidative stress. This oxidative stress occurs via the production of too many reactive free radicals that can’t be controlled by the antioxidative species that naturally reside in the body. When unable to control simply by altering diet and exercise habits, a way to reduce the oxidative stress (and thus the occurrence of too many harmful free radicals) is needed to reduce the risk of atherosclerosis and ultimately those cardiovascular events that are triggered by this disease.

As you all know by now, if you read this blog or have read one of the countless research articles related to the topic, that wine (particularly red wine) is loaded with polyphenols, which originate in the skins and seeds of the grape though a small fraction originates from the oak barrels that the wines are fermented and/or aged therein. Red wine typically has higher levels of polyphenols present, since red wine goes through a maceration step where the skins and seeds are left in the juice for a period of time, allowing the extraction of greater levels of polyphenols. White wines do not undergo this maceration step, nor do the skins and seeds typically remain in contact with the juice for any reason (of course there are exceptions), thereby resulting in a marked reduction in polyphenols in the finished white wine.

Polyphenols are known to have high antioxidant capacities, a fact by which has been studied over and over again in the literature. In studies of red wine and its effects on cardiovascular health, several mechanisms for possible protection have been described. Some studies showed that the cardio-protective nature of the wine is related to the high antioxidant capacities of the polyphenols present in the wine, while other studies claim that the polyphenols are acting in a more anti-platelet or anti-inflammatory fashion, which increases vasodilatation (i.e. opening of blood vessels) and improves cardiac function.

The study presented today aimed to examine the antioxidant activities of red wine in the rat model, while simultaneously determining whether or not results found in vitro (i.e. outside of the body, or in other words, in test tubes and petri dishes) correlated with what is found in vivo (i.e. inside the body). The latter is important for if it were found that in vitro results did not correlate with in vivo results, then making any assumptions or formulating implications for human health from in vitro studies would be much more difficult without an in vivo component.

By Patrick J. Lynch (1999), modified by Christian 2003 (Yale University - School of medicine) [CC-BY-2.5 (http://creativecommons.org/licenses/by/2.5)], via Wikimedia Commons

By Patrick J. Lynch (1999), modified by Christian 2003 (Yale University – School of medicine) [CC-BY-2.5 (http://creativecommons.org/licenses/by/2.5)], via Wikimedia Commons

Methods

The wines used in this study were: 1) a Chilean Syrah; 2) a Brazilian Cabernet Sauvignon; and 3) an Argentinean red blend. After purchase, the bottles were opened, put into test tubes, and stored at -80oC until ready for use in the experiment.

Rats were randomly split into 5 groups: 1) control rats fed a regular diet; 2) rats fed a high fat diet and 770-1360μL water; 3) rats fed a high fat diet and 800-1380μL of red wine with low antioxidant activity; 4) rats fed a high fat diet and 790-1170μL of red wine with intermediate antioxidant activity; and 5) rats fed a high fat diet and 820-1340μL of red wine with high antioxidant activity. The dose of wine was adjusted every week (for a total of 4 weeks) according to the body weight of the rats.

After the 4 week experiment, blood and liver samples were taken from the rats and analyzed for the following: plasma fatty acid composition, malondialdehyde concentration, plasma antioxidant activity, antioxidant enzyme expression (superoxide dismutase, catalase, and glutathione peroxidase), and antioxidant enzyme activity.

Results

• Rats fed a high fat diet showed increased levels of malondialdehyde in their blood plasma.
• Rats fed a high fat diet ate less food than the control diet group, though there were no differences in weight gain between the groups.
• Rats supplemented with high antioxidant wine had the lowest malondialdehyde levels in the liver and plasma antioxidant activity compared with all other groups and the low antioxidant wine group, respectively.
• A correlation was found between in vitro antioxidant activity measurements in the wine and in vitro measurements in the blood plasma of rats.
• Catalase and glutathione peroxidase were highest in rats supplemented with the low antioxidant activity wine.
• The only difference in enzyme activities was: superoxide dismutase was higher in the high antioxidant wine group compared with the medium antioxidant wine group.
• The only differences in plasma fatty acid profiles were the following: 1) palmitoleic acid was higher in the high antioxidant wine group compared with the medium antioxidant wine group; and 2) cis-13,16-docosadienoic acid was higher in all wines groups compared with the non-wine control.
• Rats supplemented with the low antioxidant wines had increased activity in all enzymes measured compared with rats supplemented with the high antioxidant wine.
• Trans-resveratrol, quercetin, and anthocyanidin levels were highest in rats supplemented with high antioxidant activity wines.

Conclusions

The authors of this study claimed that based on the results, rats supplemented with wines with high antioxidant activities were better able to protect against blood plasma and liver oxidative stress than wines with lower antioxidant activities. They also suggested that resveratrol, quercetin, and anthocyanidins play an important role in the protection against oxidative stress due to their high abundance in the rats supplemented with the high antioxidant activity wines. It was also noted that higher levels of trans-resveratrol were associated with lower levels of malondialdehyde, which further supports the idea that this compound plays a major role in protection against oxidative stress in the body.

The take-home given by the authors was that since there are differences between rats and human in regards to their response, further studies should only focus on wines with medium to high antioxidant activities, because wine with low antioxidant activities may not provide much protection against oxidative stress and atherosclerosis than would be ideal.

Photo by Nick Savchenko: http://farm8.staticflickr.com/7160/6495446227_33a3f9dfe1.jpg

Photo by Nick Savchenko: http://farm8.staticflickr.com/7160/6495446227_33a3f9dfe1.jpg

I’d love to hear what you all think about this topic. Do you really care about the antioxidant capacity of wine? Does this factor into your buying behavior when it comes to purchasing wine? Or, is this all just interesting for science’s sake and you’re going to drink wine anyway knowing you might be getting a nice little cardio-protective bonus? Please feel free to leave comments!

Source: Macedo, L.F.L., Rogero, M.M., Guimarães, J.P., Granato, D., Lobato, L.P., and Castro, I.A. 2013. Effect of red wines with different in vitro antioxidant activity on oxidative stress of high-fat diet rats. Food Chemistry 137: 122-129.

Posted in Health

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Polyphenol Levels and Antioxidant Activities in Aged Sherry Wines

Posted on February 20, 2013 by Becca| 1 Comment

 

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The polyphenolic content and antioxidant capacity of wine has well been studied in the literature, and is a topic often discussed on this blog. It has been studied so much that we’re all aware of the fact that these characteristics vary significantly from wine to wine, depending upon many factors including but not limited to grape variety, aging time (as well as how the wine is aged), and environmental conditions. According to many studies, there is a trend of increasing concentrations of polyphenolic compounds in wine as the wine is aged for longer periods of time, though this can vary again based on the aforementioned outside forces.

The study presented today is a short one (phew, right?), examined the evolution

I, Hashashin [GFDL (http://www.gnu.org/copyleft/fdl.html), CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/) or CC-BY-SA-2.5-2.0-1.0 (http://creativecommons.org/licenses/by-sa/2.5-2.0-1.0)], via Wikimedia Commons

I, Hashashin [GFDL (http://www.gnu.org/copyleft/fdl.html), CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/) or CC-BY-SA-2.5-2.0-1.0 (http://creativecommons.org/licenses/by-sa/2.5-2.0-1.0)], via Wikimedia Commons

of polyphenol content, antioxidant content, and color in old Sherry wines. The authors also sought to determine if antioxidant activity is correlated with the age of the wine.

Methods

26 Sherry wines from vintages between 1935 and 1996 were analyzed. All wines were oloroso Sherries which were made in the oxidative method (i.e. no secondary fermentation with flor yeasts). All wines were made with the white Palomino Fino grape variety and were aged in American oak barrels. For each wine, the following were measured and analyzed: total polyphenol content, individual polyphenols, antioxidant activity, and color.

Results

• Concentrations of all parameters measured trended higher in those Sherry wines that were aged for longer in oak barrels than those aged for shorter periods of time.
• For those Sherry wines aged for longer periods of time in oak barrels, the following compounds were most prominent: hydroxymethylfurfural, furfural, protocatechuic acid, tyrosol, p-coumaric acid, and syringaldehyde.
• The highest levels of polyphenols were found in those wines aged for longer in oak barrels than those aged for shorter times.
• The oldest Sherry wines (as old as 1935) had extremely high levels of antioxidant activities.
o The authors attributed the high antioxidant levels to the aging in oak barrels, since the grapes used to create these Sherries were white grapes, and white grapes do not have very high levels of antioxidants to begin with.
• Based on the aforementioned results, the authors claim that the level of antioxidant activity is “clearly related” to the length of time the Sherry wine is aged in oak barrels.
• A strong influence of polyphenols on the antioxidant activity of the Sherry wines was found.
o Those polyphenols most highly correlated with the antioxidant activity in the Sherry wines were: protocatechuic acid, protocatechuic aldehyde, syringic acid, vanillin, and p-coumaric acid.
• SO2 levels for the Sherry wines tested were found to be between 8 and 17mg/L which correlated with the antioxidant activities of the wines, but was not statistically significant.
• Those Sherry wines that were aged in oak barrels for longer periods of time were darker in color than wines aged for not as long.
• The above relationships were all confirmed with principle components analysis and linear discriminating analysis.

Conclusions

This study was mostly “for the sake of science”, though could potentially have interesting applications in the real world. The study found that those Sherry wines aged in oak barrels for longer periods of time possessed greater levels of polyphenols and antioxidant activities (as well as darker colors). If you’re looking to maximize your polyphenol and antioxidant activity intake, then based on this study you know to go for wines aged for longer periods of time in oak barrels.

One thing I was wondering while reading this article was whether or not this type of analysis could be used for determining authenticity of wines suspected of possible fraud. I suppose the technique itself isn’t that sensitive, but it potentially be used in concert with other techniques. For example, if the aging treatment was known for the particular wine in question, then one might be able to measure the polyphenol levels and antioxidant activity to get a ballpark idea of whether or not the wine could be legit or if it could be a fraud.

If it was known that the wine was aged for a long period of time in oak barrels yet the polyphenol levels and antioxidant activities were extremely low, then red flags could be raised on the authenticity of the wine. I suspect this technique would not be very sensitive, and could thereby require other techniques to be

By Tomascastelazo (Own work) [CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons

By Tomascastelazo (Own work) [CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons

performed if the results were not clear, but I think it could be a quick a dirty test if no other options were immediately available. Of course, less invasive methods for determining the authenticity of wines are currently in development, so this technique may not be the best option for multiple reasons, but hey, I’m just thinking out loud here! :)

Can you think of other applications for this information about polyphenol levels and antioxidant activities in Sherry wines? Please feel free to leave your comments!

Source: Schwarz, M., Carmen Rodríguez, M., Guillén, D., and Barroso, C.G. 2012. Evolution of the colour, antioxidant activity and polyphenols in unusually aged Sherry wines. Food Chemistry 133: 271-276.

Posted in Chemistry

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