Tag Archives: red wine

Let’s Talk About Sex, Baby!: The Effect of Red Wine Consumption on Sperm Performance

Posted on May 15, 2013 by Becca| Leave a comment

—————————————————————————————————-

Welcome to The Academic Wino! If you are new here, please read the “About Me” page to find out more about myself and the blog. If you would like to receive free updates on articles like this by email, then sign up here or you can subscribe to the RSS feed. Also, check us out on Twitter, Facebook, Google+, and or Pinterest. Thanks for visiting!

—————————————————————————————————-

(As an aside: how many of you now have that song stuck in your head after reading the title?…ahhhhh high school memories….).

The lights are turned down low, the Barry White is softly pumping through the stereo, and you’ve got yourself a nice big glass of red wine and your lover by your side…OK, without starting to making this sound too much like a bad porno movie, I’ll let your mind wander however you’d like with that and shift into a more scientific mode…

Quite some time ago, I covered an article discussing the relationship between alcohol consumption and the success rate of in vitro fertilization. This study found that increased levels of alcohol consumption negatively affects fertilization success when consumed by either men and women, though they only considered more heavy consumption (at least 4 drinks) and did not differentiate between the different types of alcohol.

Very basically, in order to have successful fertilization, a sperm must be able to penetrate the exterior wall of the egg by producing and releasing a specific type of enzyme to break down that wall. This can either happen naturally by copulation (wah wah wee wah…) or by in vitro methods outside of the body.

See page for author [Public domain], via Wikimedia Commons

Studies have found that estrogens in both male and female reproductive systems play a critical role in fertilization success. Specifically, estrogens elicit biochemical changes in the sperm that result in the activation of the little swimmers by allowing them to bind to the zona pellucida (“wall”) of the egg and go through acrosome reactions to break down that wall and fertilize the egg. Without this activation, the sperm are just bumbling around like drunken idiots looking for a good score they’re never going to get.

In addition to estrogens, studies have also found many compounds present in the environment that possess similar sperm activation activities and capabilities. Specifically, genistein, quercetin, and 8-prenylnaringenin; all classified as phytoestrogens; have been shown to have these estrogen-like activities. Genistein is found in soy and legumes, quercetin is found in parsley and red wine, and 8-prenylnaringenin is found in hops and beer. Though these compounds may behave similarly to estrogen in terms of the ability to activate sperm for fertilization, some research has indicated that “too much” of these compounds can instead have an inhibitory effect and negatively affect fertilization success.

Myricetin is another compound very similar to quercetin, which is found in very high levels in berries, tea, and red wine. According to the study presented today, very few studies have examined the effects of these estrogen-like compounds in male human reproduction, and in particular no studies have examined Myricetin. In other studies not related to human reproduction, the effects of Myricetin have been mixed: some studies have found it has antioxidative properties, while other studies have found just the opposite. Similarly, some studies have shown Myricetin has anti-carcinogen properties, while other studies have found the compound promotes tumor growth. What about the effects of Myricetin in male human reproduction? Is it helpful? Or detrimental? To date, no studies have examined this topic.

By Gilberto Santa Rosa from Rio de Janeiro, Brazil. (be_sperm.) [CC-BY-2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons

The study presented today aimed to evaluate the effects of Myricetin in red wine on sperm biology and potential reproductive success, with potential applications for “putting it into practice”.

Methods

To collect sperm samples, donors made sweet love to a plastic cup after 3 days of abstaining from any sexual activities. Those sperm with normal volume, count, motility, vitality and morphology were pooled together and processed.

Pooled sperm samples were separated into different treatments: 10nM Myricetin; 100nM Myricetin; 1μM Myricetin; 100nM Myricetin with 1μM ICl, AbERα, AbERβ, or 10μM LY. Positive (capacitated sperm) and negative (incapacitated sperm) controls were used. Sperm were exposed to the treatments for a 30 minute period.

The following were measured after treatment exposures: sperm protein, sperm mobility and viability, cholesterol levels in sperm, acrosin activity, glucose-6-phosphate dehydrogenase activity, and Acyl-CoA dehydrogenase activity.

Results

• Stimulation with 10nM and 100nM of Myricetin resulted in a 25% and 50% increase in sperm motility, respectively.
o The 100nM result was the same as the positive control.
• Stimulation with the greatest level of Myricetin (1μM) resulted in a decrease in sperm motility compared with the control and other Myricetin treatments.
• Stimulation with 10nM and 100nM of Myricetin resulted in a 20% and 30% increase in sperm viability, respectively.
o The 100nM result was the same as the positive control.
• All Myricetin treatments resulted in significant increases of cholesterol in sperm.
o The 100nM result was similar to the positive control and the 1μM treatment was less effective than the 10nM and 100nM treatments.
• Treating the sperm samples with combinations of Myricetin and either ICl, AbERα, AbERβ, or LY resulted in the reversal of this trend and effectively rendered the sperm incapacitated.
o This suggests that Myricetin may play an important role in the activation of sperm samples at certain concentrations.
• For the 10nM and 100nM Myricetin treatments, there was a significant increase in acrosin activity compared with the controls, with the 100nM treatment showing a greater increase than the 10nM treatment.
o The 100nM treatment showed a 70% increase in acrosin activity compared with the negative controls, which was almost equal to the result for the positive control.
• The highest concentrations of phosphorylated AKT were found in the 100nM Myricetin treatment samples, which was about 5 times greater than the untreated negative control.
• 100nM and 1μM Myricetin treatments showed greater increases in glucose-6-phosphate dehydrogenase activity than the 10nM treatment, with the 100nM Myricetin treatment being the most effective.
• Stimulation with 10nM and 100nM of Myricetin resulted in a 10% and 40% increase in acyl-CoA dehydrogenase activity compared with the untreated negative control, with the 100nM treatment being the most effective.

Conclusions

The results of this study generally showed that exposure of sperm to lower doses of Myricetin improved their mobility and viability/survival, while the higher doses of Myricetin were not as effective.

In order for a sperm to fertilize an egg, it must first become “capacitated”, which allows it to produce the enzymes necessary to penetrate the hard exterior shell of the egg and increase success of fertilization. To be successfully capacitated, cholesterol levels in sperm must increase, as well as the induction of phosphorylation of specific proteins. The results of this study showed that Myricetin, when exposed to sperm at lower doses and for a short period of time, is effective in capacitating the sperm and increasing their capacity to produce the enzymes necessary to successfully fertilize an egg by inducing these same responses in sperm samples.

While the results of this in vitro (in the lab/petri dish) study are fascinating, I’m not convinced we’d see the same thing in vivo (i.e. in the body). First, this study does not take into consideration the effect of the body’s surrounding environment on this mechanism. What I mean is that when the sperm are swimming around in the female reproductive tract, they are exposed to a lot of compounds and hormones that weren’t examined in this study. How do these female hormones and compounds influence the efficacy of Myricetin on sperm performance?

Recall: Myricetin is a compound with estrogen-like characteristics. Also recall: Myricetin at the highest doses was not as effective (and sometime inhibitory) as the lower doses in sperm performance. So, think about it: what happens when you have your sperm exposed to a small dose of Myricetin but then placed in the presence of the estrogen compounds in the female reproductive tract? Wouldn’t this result in increased estrogen-like compound concentrations and ultimately reduce the effectiveness of the Myricetin? I’m not sure, but I think a study somehow incorporating a more natural environment as found in the female reproductive tract is necessary to determine how sperm performance will be altered in “real life”.

Even if Myricetin actually does perform as similarly in vivo as it does in vitro, how much wine would a man need to drink in order to beef up his sperm performance? Studies have shown that myricetin and quercetin make up 20-50% of the flavonol component of red wine, ranging from 53 to 200mg/L.

By Meister des Rasikapriyâ-Manuskripts [Public domain], via Wikimedia Commons

According to the authors of this study, one would only need to consume 1-2 glasses of red wine a day in order to achieve the Myricetin levels tested in this study. However, if the extra estrogen in the female reproductive tract interacts in an inhibitory or toxic manner with the levels of Myricetin in the red wine, sperm performance, mobility, and viability may be significantly decreased instead of increased as we saw with Myricetin alone.

I would certainly take these results with a grain of salt if I were you. It’s very possible that the interaction between the Myricetin in the red wine and the estrogen in the female reproductive tract result in a inhibitory or toxic effect on the sperm, which is something that should really be studied before any real conclusions can be made here. I do wonder if when in in vitro fertilization scenarios, a man drinking a glass or two of red wine prior to donating sperm and the fertilization of the egg outside of the female body (i.e. thus without the excess estrogen) would be as beneficial as we saw in the results of this study.

Of course, a lot more research needs to be done in this field, so certainly talk with your doctor about your alcohol consumption habits if you are trying to conceive. Maybe we’ll learn more about the interaction of red wine and sperm performance in the female reproductive tract in subsequent experiments; however this study does give some indication that red wine or at the very least Myricetin supplements could play an important role in human reproductive success (or failure).

What do you all think of this study? Please share your thoughts!

Source: Aquila, S., Santoro, M., De Amicis, F., Guido, C., Bonofiglo, D., Lanzino, M., Cesario, M.G., Perrotta, I., Sisci, D., and Morelli, C. 2013. Red Wine Consumption May Affect Sperm Biology: The Effects of Different Concentrations of Phytoestrogen Myricetin on Human Male Gamete Function. Molecular Reproduction and Development 80: 155-165.

Posted in Health

Tagged health, human reproduction, in vitro fertilization, IVF, red wine, red wine and health, reproduction, sperm performance

The Influence of Oak Chips Added at Various Stages of Winemaking on Sensory Characteristics of Wine

Posted on April 3, 2013 by Becca| 4 Comments

—————————————————————————————————-

As many of you may already know, using oak barrels in wine fermentation and aging increases wine aromatic complexity and improves overall quality. The use of oak in wine is and has always been very popular, despite the fact that it costs more money to produce an oaked wine than it is to produce a wine made in stainless steel tanks. As a result of this cost differential, some wineries as well as home winemakers have been searching for alternatives to oak barrels that give similar aromatic and quality characteristics to the finished wine without the high costs.

There is some experimental evidence suggesting that application of oak extract to the vines during the growing season may impart oak flavor characteristics into the finished wine, however, it’s a practice that is currently just in the research and development phase, and is not yet widely practiced or accepted. In recent years, the use of oak chips instead of oak barrels has become much more popular, as it has been shown that using oak chips in wine fermented and/or aged in stainless steel tanks results in finished wines that are aromatically similar to wines that are fermented and/or aged in oak barrels.

Oak chips may be added to the wine at any stage during the winemaking process, and will result in varied styles of wine depending upon exactly when the chips were added. The goal of the study presented today was to examine the sensory

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/)], via Wikimedia Commons

characteristics of one particular type of wine (Bobal) when placed in contact with oak chips at different stages throughout the winemaking process and to identify when during the winemaking process oak chip exposure will create the wine most similar to a wine kept in oak barrels.

Methods

Bobal grapes from a vineyard in the La Mancha region of Spain were used for this study and were harvested at their optimal ripening time. Grapes were separated into 7 batches and were all processed the same up until right after skin maceration. The following treatments were applied to the grape batches:

1. Control Wine: wine without the addition of oak chips.
2. Addition of oak chips during alcoholic fermentation.
3. Addition of oak chips during malolactic fermentation.
4. Addition of oak chips post-fermentation (1 week contact time).

The three oak chip treatments were split into two sub-treatments: 3g/L dose and 6g/L dose (total 7 treatments including control).

The oak chips used were a mix of French and American oak and had medium toast.

The rest of the winemaking process was pretty standard and the same for all treatments: manual punch downs, malolactic fermentation, racking, filtering, bottling, and storing. Finished wines were stored at 16-18oC until sensory analysis was performed. All treatments were performed in duplicate.

For all wines, the following were measured and analyzed: total acidity, ethanol content, pH, volatile acidity, total SO2, and free SO2.

For the sensory analysis, a carefully trained panel of 15 judges between the ages of 24 and 50 years old from the University of Castilla in La Mancha, Spain was selected. Panelists were specifically trained to analyze flavor descriptors in Bobal wines (both oaked and unoaked).

20mL of each treatment wine samples were given to the judges in standard wine glasses and covered with a watch glass in order to avoid volatile loss to the air. Sensory analysis took place in individual booths in a sensory analysis chamber. Panelists smelled and tasted the wines and recorded the aromatic and flavor descriptors they noted in each wine.

Results

• There were no significant differences between samples in regards to total acidity, volatile acidity, and pH.

Nose:
• Aromas on the nose of control wines (no oak chips added) were: red fruit, fresh, liquorish, pepper, sweet spices, leather, tobacco, and cassis.
• Wines with oak chips added at alcoholic fermentation saw a significant decrease in red fruit, liquorish, cassis, and pepper aromas.
• Wines with oak chips added at alcoholic fermentation saw a significant increase in sweet spices and woody notes at the higher 6g/L dose compared with the lower 3g/L dose.
• Wines with oak chips added at malolactic fermentation saw significant decreases compared with all wines in red fruit, fresh, pepper, and cassis aromas.
• Adding oak chips during malolactic fermentation resulted in significantly higher intensities of oak-derived aromas at the 6g/L dose compared with the 3g/L dose.
• Wines with oak chips added post-fermentation for one week were similar in character to wines with oak chips added during malolactic fermentation, however showed decreases in intensity of woody, vanilla, coconut, toast, and toffee notes.
• Wines with oak chips added post-fermentation for one week showed increases in red fruit character compared with wine with oak chips added during malolactic fermentation.
• 6g/L oak chip wines generally showed greater oak character than wines treated with 3g/L oak chips.
• Principle component analysis (PCA) grouped wines most similar to each other into two groups: 1) both wines with oak chips added at alcoholic fermentation and control wines; 2) both wines with oak chips added at malolactic fermentation and both wines with oak chips added post-fermentation for one week.
o The second group showed significantly more oak character than the first group.
o In the second group, the two wines with chips added at malolactic fermentation were greater in oak aromatic intensity than the wines with oak chips added post-fermentation for one week.

Taste:
• Control wines (no oak chips) had flavors of red fruit, liquorice, clove, pepper, leather and tobacco.
• All oak chip wines had significantly decreased red fruit flavors, with the wine treated with oak chips at malolactic fermentation having the least red fruit flavors.
• All oak chips wines had flavors of cinnamon, vanilla, wood, toast, and chocolate that were not present in the control wines.
• Wine treated with 6g/L of oak chips during malolactic fermentation had the most oak-like qualities compared with all other wines.
• All oak chip treatments reduced astringency in the wines.
• Wines treated with oak chips during malolactic fermentation had greater body than all other wines.
• Principle component analysis (PCA) grouped wines most similar to each other into two groups: 1) both wines with oak chips added at alcoholic fermentation and control wines; 2) both wines with oak chips added at malolactic fermentation and both wines with oak chips added post-fermentation for one week.
o The second group showed significantly more oak character than the first group.

Conclusions

The results of this study showed that the addition of oak chips at different times during the winemaking process resulted in finished wines with significantly different aromatic and flavor profiles. The addition of oak chips at any time resulted in wines with more oak-like character, however the amount of oak character was dependent upon the dose of oak chips as well as when during the winemaking process the oak chips were added. It was noted that astringency was also reduced when oak chips were added, and body was only affected when the oak chips were added during malolactic fermentation.

The authors suggested that any of the treatments would be acceptable alternatives to using an oak barrel, however, depending upon what style of wine

By Agne27 (Own work) [CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons

you wish to create will determine how much and when the oak chips should be added. According to the results, adding 6g/L of oak chips during malolactic fermentation produced the wine with the most intense oak flavors, however, all oak chip treatments possessed some oak-like character.

One treatment that I feel was missing from this experiment was the oak barrel treatment control. The results showed that oak chip treatments resulted in “oakier” wines compared with the stainless steel control, however, how does it compare with wines that are actually fermented and/or aged in a barrel? Is it comparable? A lot less?

It would also be interesting to see how wines made from other grape varieties are influenced by oak chip addition at different stages during the winemaking process. Will we see similar results? Or will we see different treatments emerging as the “oakier” style wines?

One other thing I would have liked to have seen is preference scores by the sensory panel. They described the aroma and flavor characteristics of each sample; however, they did not score whether or not they preferred one particular wine over another. Everyone has different tastes and preferences, of course, but it would have been at least somewhat interesting to see if the panel actually liked these wines or not.

I’d love to hear what you all think of this topic! Do you have any personal experiences you can share regarding oak chip-treated wines? What sort of future research would you like to see coming out of this study? Please feel free to comment!

Source: García-Carpintero, E.G., Gómez Gallego, M.A., Sánchez-Palomo, E., and González Viñas, M.A. 2011. Sensory descriptive analysis of Bobal red wines treated with oak chips at different stages of winemaking. Australian Journal of Grape and Wine Research 17: 368-377.

Posted in Enology

Tagged bobal wine, oak barrels, oak chips, oak in wine, oak treatments, red wine, wine quality, winemaking

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

—————————————————————————————————-

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

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

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

Tagged cabernet sauvignon, grape maturity, grape ripeness, grapes, polyphenols, red wine, wine color, wine quality

Applying Oak Extract to Petit Verdot Vines: Making Oaked Wines Without Oak Barrels?

Posted on February 4, 2013 by Becca| Leave a comment

—————————————————————————————————-

About a year and a half ago, I reviewed an article that examined the effect of the application of an oak extract to Verdejo grapes on the potential oak flavor of the finished wine, in lieu of oak barrel fermentation or ageing, or the use of oak chips in stainless steel tanks (to read that full article, click here). The main take-away from that article was that oak extract application on Verdejo grapes does, in fact, produce a finished wine that mimics the flavors and aromas of a wine that has been aged in oak barrels.

I had one reader comment: “who would want oak on Verdejo anyway?”; which is certainly a valid question! Who knows! Maybe Verdejo was what the authors had at their disposal at the time. Anyway, those same authors about a year later published a very similar experiment, however this time, focusing on a grape that is almost exclusively oaked: Petit Verdot.

By Eric 先魁 Hwang [CC-BY-2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons

Studies (and experience) have shown that grapes exposed to smoke from wild fires result in wines with a burnt or smoky flavoring. Taking this concept further, we’ve seen in the Verdejo study mentioned previously and other studies that certain compounds sprayed onto the grapes during the growing season (such as oak extract) result in wines with similar aromatic characteristics. In addition to the grapes themselves, alcoholic fermentation, malolactic fermentation, and the aging process all have influence on the aromatic profile of the finished wine.

In regards to the aging process, oak aging in particular has a significant influence on the aromatic development of the wine (compared to the stainless steel alternative). Sometimes aging in oak barrels can be problematic for some vineyards, due to the relatively high cost of a single barrel and the long periods of aging time required to produce a wine with certain aromatic characteristics. Smaller wineries may not have enough money and/or time to be able to age their wines in oak barrels for these very reasons.

One alternative approach is to use oak chips in stainless steel tanks, though this practice is still thought of as poor-quality and less desirable (though in reality, most people can’t tell the difference). Another alternative, which is the focus for today’s paper, is to instead apply oak extracts directly to the grapevine, which could result in wines retaining the characteristics of these extracts, thus eliminating the need to age the wines in relatively expensive oak barrels. This

Photo by Bernt Rostad: http://farm4.staticflickr.com/3457/3246033875_f9556cf61b.jpg

alternative is still relatively novel, and is still in a more experimental phase than a widely practiced phase.

Methods

The oak extract used was food quality French toasted aqueous oak extract from Protea France S.A.S.

The grapevines used were the Petit Verdot variety grown in La Mancha region of Spain (southeast Spain).

There were 4 different treatments used in this experiment: 1) a 25% dilution of the oak extract applied once on the 7^th day after veraison (when the grapes start changing color); 2) a 25% dilution applied 4 times; on the 4^th, 7^th, 10^th, and 13^th days after veraison; 3) an undiluted (100% concentrated) oak extract solution applied once on the 7^th day after veraison; and 4) an aqueous solution of eugenol and guaiacol standards applied once on the 7^th day after veraison. An untreated control was also used for this experiment.

Treatments were applied to 10 plants in the same row, with 5 plants left untreated between treatments in order to avoid contamination. 250mL of each treatment was sprayed on the leaves of each plant at around 7am and when the temperature was below 20^oC.

After grapes were harvested at maturation, grape yield was calculated. Winemaking took place in a multitube fermenter, which has been shown to reproduce actual cellar and winemaking conditions. Wines underwent both alcoholic and malolactic fermentation, and were done in duplicate. After malolactic fermentation was complete, wines were stored bottles at 14^oC for 8 months. Samples were taken at each fermentation step, as well as after the 8 months of storage time.

The following enological parameters were measured for each sample: yeast assimilable nitrogen (YAN), ^oBaumé, reducing sugars, alcohol degree, titratable acidity, volatile acidity, pH, malic acid, and lactic acid. All parameters were measured in triplicate. Volatile compounds were also measured and analyzed.

Results

Grapes

YAN, ^oBaumé, probable alcohol, pH, titratable acidity, and the ratio of ^oBaumé to titratable acidity of grapes from the oak extract treatments were not significantly different than the control grapes.
- YAN levels were higher and ^oBaumé, pH, and probably alcohol levels were lower in grapes treated with eugenol and guaiacol compared with the controls.
No oak lactones or 6-methoxyeugenol were found in any of the grape samples.
Furfural levels were higher in oak extract treated grapes, with the 25% dilution extract treated four times throughout veraison having higher levels than the 25% dilution extra treated only once during veraison.
The lowest levels of acetovanillone, methyl vanillate, and guaiacol were found in the undiluted (100%) oak extract treatment.
The 25% dilution extract treated four times throughout veraison and the undiluted (100%) oak extract had lower levels of 4-vinylguaiacol and 4-ethylphenol compared with the control.
Syringol was lower in oak extract treated grapes.
The eugenol and guaiacol treatment grapes showed higher levels of eugenol and guaiacol (surprise surprise), as well as furfural, 4-vinylguaiacol, 4-ethylguaiacol, and syringol.
Discriminate analysis could not distinguish between the oak extract treated grapes and the control grapes, but could distinguish a difference in regards to the eugenol and guaiacol treated grapes.

Wine

Eugenol and guaiacol treatment resulted in the wine with the lowest alcohol level.
After alcoholic fermentation, titratable acidity was higher in all treatments compared to the control, however, after 8 months, titratable acidity was the same for all wines.
After 8 months, eugenol and guaiacol treatment wines had a lower pH than the control.
After alcoholic fermentation, volatile acidity was highest for control wines and lowest for eugenol and guaiacol treatment wines.
Malolactic fermentation progressed equally in all wines.
There were no oak lactones found in the control wines.
Oak lactones were found to be present in all oak extract treatment wines.
After alcoholic fermentation, the wine with the highest levels of oak lactones was the 25% dilution that was applied 4 times throughout veraison.
- After 8 months, these levels decreased in these wines as well as the wines from the 25% dilution that was only applied once. These levels increased for undiluted (100%) oak extract treatment wines.
Concentrations of oak lactones never reached sensory perception thresholds in any of the wines.
Furfural and 5-methylfurfural levels were higher in oak extract treatment wines compared with the control wines.
- Over time, these levels decreased in all wines.
- Levels of both these compounds were below their sensory thresholds in all wines.
After alcoholic fermentation, eugenol levels were higher in oak extract treatment wines compared with the control wines.
- After 8 months, eugenol levels were actually higher in control wines than oak extract treatment wines.
6-methoxyeugenol levels were higher in oak extract treatment wines than control wines, with the highest levels in the undiluted (100%) oak extract treatment wine.
- These levels increased during malolactic fermentation in all wines.
After alcoholic fermentation, guaiacol levels were higher in all treatment wines compared with the control wines.
- These levels increased in the treatment wines after malolactic fermentation.
- After 8 months of storage, guaiacol levels were 3x higher in treatment wines compared with the control wines.
- Guaiacol levels were higher than their sensory threshold levels in all wines.
4-ethylguaiacol levels were higher in oak extract treatment wines compared with the control wines.
- Levels were found to be below sensory threshold in all wines.
Syringol levels were higher in oak extract treatment wines than in control wines (recall: this trend was the opposite in regards to the levels in the grapes).
- Levels were found to be below sensory threshold in all wines.
Vanillin, vanillin derivatives, acetovanillone, and methyl vanillate were all higher in oak extract treatment wines compared with the control wines.

Conclusions

According to the results of this study, applying oak extract on Petit Verdot grapes during veraison resulted in changes in the aromatic profile of the finished wines. Finished wines appeared to have many of the volatile compounds frequently found in wines that are fermented in aged in oak barrels. It’s interesting to note that nearly all of the oak volatile compounds were not actually present in the grapes themselves, but were present after the fermentation and storage processes. What is happening here is likely that the oak volatiles are present in grapes as non-volatile precursors, which undergo changes during the fermentation and storage processes that result in the formation of their volatile counterparts in the wine.

Photo by inspector_81: http://farm6.staticflickr.com/5165/5218552773_478a515be5.jpg

In addition to the oak extract treatments, I would have liked to have seen two more treatments: 1) fermentation in oak barrels and 2) fermentation using oak chips. It would have been interesting to compare the oak volatile compounds from the oak extract treatment wines directly to those from oak barrel fermented or oak chip fermented wines. How do the levels of the oak volatile compounds in these oak extract treatment wines directly compare with wines fermented in oak barrels or using oak chips? Sure, the levels are increased with respect to the controls, but is it enough to produce a wine that would taste the same (or similar) to a wine produced in more traditional ways?

The above being said, it would have been interesting to see a sensory analysis of these wines, in addition to the chemical analysis that they performed. How did the wines actually taste? How do they actually taste compared to wines made in a more traditional manner?

The results of this study provide some evidence that the use of oak extracts on grapevines during the veraison process yields aromatic profiles similar to that of wines fermented in oak barrels, and thereby could be a good alternative to the more expensive and time consuming oak barrel fermentation methods. However, before I can say that previous statement with complete certainty, I’d like to see a few more treatment comparisons.

How about you all? What do you think of this study? Please feel free to comment!

Source: Martínez-Gil, A.M., Garde-Cerdán, T., Zalacain, A., Pardo-García, A., and Rosario Salinas, M. 2012. Applications of an oak extract on Petit Verdot grapevines. Influence on grape and wine volatile compounds. Food Chemistry 132: 1836-1845.

Posted in Chemistry

Tagged oak barrels, oak chips, oak extract, oak in wine, petit verdot, red wine, wine quality

Tag Archives: red wine

Let’s Talk About Sex, Baby!: The Effect of Red Wine Consumption on Sperm Performance

The Influence of Oak Chips Added at Various Stages of Winemaking on Sensory Characteristics of Wine

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

Applying Oak Extract to Petit Verdot Vines: Making Oaked Wines Without Oak Barrels?

Click to vote!

Recent Posts

Categories

Follow Us!

Recommended by The Academic Wino:

Archives