Tag Archives: winery waste

Grape Seed Extracts Reduce Formaldehyde Levels in Leather Production

Posted on November 12, 2012 by Becca| Leave a comment

 

I’ve covered the topic of the recycling of wine industry a lot lately on The Academic Wino, as it is it becoming increasing more desired in the wine business to not only decrease the contaminants and potentially toxic chemicals in the environment, but to also increase the overall sustainability of the industry as a whole.  Everywhere I look there are more and more papers on the topic, and even though they vary widely in their potential applications, they all boil down to the same thing: environmental friendliness and sustainable practices.  In the European Union, there is approximately 14.5 million tons of wine industry

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waste produced from wineries within its borders, which is a lot of material that could be recycled and reused for other purposes.

Most of you are aware by now that wine industry waste contains primarily crushed grape skins, seeds, and pulp.  You also may know already that these winemaking by-products are rich in beneficial polyphenol compounds that act as antioxidants, antibacterial agents, anticarcinogenic agents, antiviral agents, et cetera.  We’ve seen research that focuses on using wine industry wastes as supplements to one’s diet; for use as supplements to the winemaking process in order to improve wine quality; for adding to processed meats to reduce carcinogenic properties; and for coming with animal manure to produce an alternative fuel source, just to name a few.

Today’s paper focuses on yet another application for wine industry waste: as a treatment in leather production to reduce toxic by-products often associated with the process.  Now, I understand that leather production in and of itself is a hot topic amongst many animal rights proponents, however, I’ll ask you to bear with me and not go down that road for now.  I am not taking any stance in this post on the use of leather for the purpose of clothing or other products, however, since this is a common practice around the world, it is important to find more “environmentally and health friendly” ways to produce it, regardless of whether or not you agree to the practice to begin with.  That issue is a whole other discussion which is not appropriate for this type of blog.

Back to the topic at hand…

One of the by-products of leather production is formaldehyde, which at certain levels can be very unpleasant to the nostrils, as well as toxic to both humans and the environments.  Something that is used in preserving dead creatures for

Formaldehyde

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science labs isn’t exactly something I would want to be in contact with for extended periods of time.  Formaldehyde is not actually used in the production of leather; however, compounds in the leather itself can react with other production agents (i.e. synthetic tanning agents, resins, etc) and produce free formaldehyde in the air around it.  This free formaldehyde can cause an array of health problems, and is known to illicit allergic responses in some individuals.

Many countries throughout the world have placed limits on the allowable levels of formaldehyde.  The European Union classifies formaldehyde as a Category 3 suspected carcinogen, with allowable levels of formaldehyde in clothes which are not in direct contact with the skin no greater than 300ppm (parts per million).  Levels of formaldehyde in clothes which are not in direct contact with the skin are very similar in New Zealand, and are even lower for children and those with sensitive skin.  Allowable levels of formaldehyde in the United States vary depending upon the context.  For example, OSHA (Occupational Safety and Health Administration) permissible exposure limits in air are 0.75ppm, short term exposure limits (over 15 minutes) are 2ppm, and action levels (over an 8 hour period) are 0.5ppm.  It is in the best interest of those working in the leather production industry, and ultimately those that are exposed to the leather once it is finished, that ways to reduce free formaldehyde in the air is of critical importance.

In a previous study performed by the authors of the current study, they found that by using Camellia sinensis and Vinca rosea, the leaves and flowers of which are utilized to make tea and therapeutic compounds, respectively, were effective in reducing the levels of free formaldehyde in leather production.  The common compounds between the two, which were likely involved in the reduction of formaldehyde levels were the tannins; as well as the polyphenolic compound catechin (part of the flavanol family) and gallic acid components.

Building upon these findings, the authors then examined grape seed extracts, which were produced from wine industry waste.  Grape seeds contain many of the same polyphenolic compounds as the species studied previously, and also include proanthocyanidin molecules which are also part of the flavanol family.  Would grape seeds also act to decrease levels of free formaldehyde in leather production as tea had?  The paper presented today aimed to examine that very question.

Methods

Vitis vinifera wine grape seeds were utilized in this study, and did not include other portions of the industry waste (such as skins or pulp). Seeds were ground and then prepared by three different methods: 1) as a powder; 2) as an extract; and 3) as an extract using a modified procedure (details omitted by cited in an unpublished document).

The source of the leather was domestic wet salted sheep skins.

Leather was produced using approved methods and was treated with each of the three grape seed treatments plus a non-grape seed control.

Experiments were repeated 3 times.

Results

  • Modified grape seed extract treatment resulted in leather with the lowest levels of free formaldehyde.
    • All three grape seed treatments (powder, plus two different extracts) reduced the levels of free formaldehyde compared to the control.
  • Even though the grape seed powder was effective, it did not completely dissolve in water.
    • This created powder residues on the leather which is likely visually unappealing to consumers.
    • Extracts did completely dissolve in water, thereby would be more desirable in leather production than the powder.

Concluding Thoughts

This was a short and sweet study, which tested the effectiveness of grape seed powder and extracts on the levels of free formaldehyde in leather production.  According to the results, all treatments made from grape seeds were effective in reducing the levels of free formaldehyde in leather production, though modified grape seed extracts were the most effective.  Even though grape seed powder was effective in reducing the levels of formaldehyde, it is not an ideal product to use in leather production, since the powder did not fully dissolve in water and thereby left a powdery residue on the finished leathers’ surface.

In their concluding statements, the authors suggested that the amount of grape seed extract used in leather production could be increased or decreased in order to further control the levels of free formaldehyde by-products.  Specifically,

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increasing the amount of grape seed extract in the leather production should further decrease the levels of free formaldehyde produced.  This statement was not supplemented with experimental evidence, thus must be taken with a grain of salt.  In theory, the prediction is plausible; however, one should not be so confident that it is correct without experimental evidence.  This would make a good follow-up experiment to the experiment presented above.

I would be curious to see how extracts made from complete grape marc (i.e. seeds, skins, and pulp) performed in the same experiment.  This may be a more realistic approach, as the seeds would not have to be separated from the marc prior to creating the extracts.

Another follow-up experiment could involve different types of leather.  Are these extracts as effective with other types of leather?  Could these extracts be utilized in the production of synthetic leathers somehow?

In general, this study provided yet another interesting use of wine industry wastes, though certainly more work needs to be done to further optimize the process.

What do you all think of this study or this topic in general?  Please feel free to leave your comments!

Sources:

Bayramoğlu, E.E. 2013. Hidden treasure of nature: PAs. The effects of grape seeds on free formaldehyde of leather. Industrial Crops and Products 41: 53-56.

“Proposed Government Product Safety Policy Statement on Acceptable Limits of Formaldehyde in Clothing and Other Textiles”. Ministry of Consumer Affairs, New Zealand.  http://www.consumeraffairs.govt.nz/pdf-library/publications/Acceptable-Limits-of-Formaldehyde-in-Clothing-and-Other-Textiles.pdf  Accessed 11/10/12.

“OSHA Fact Sheet: Formaldehyde”. Occupational Safety and Health Administration, United States. http://www.osha.gov/OshDoc/data_General_Facts/formaldehyde-factsheet.pdf Accessed 11/10/12.

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Grape Stem Extracts: An Example of Utilizing Winery Waste for a More Sustainable Industry

Posted on November 5, 2012 by Becca| Leave a comment

In this age of changing climate, there is an ever present push to find more ways to be more environmentally friendly and sustainable in all industries and settings.  If you’re at all familiar with the content here on The Academic Wino, you’re probably already well aware of the fact that the wine industry is no different in regards to this quest for sustainability.  To be specific, there have been quite a large number of studies now at this point examining the utilization

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of wine industry waste into other functional products, instead of simply discarding the waste to wreak havoc on the environment.

Though there are certainly more studies than I have been able to present on this blog, here are some examples of what has been done so far in regards to utilizing wine industry waste:

As you can see from just the headlines of these posts, there have been many applications examined for wine industry waste in nearly every possible use imaginable.  Most research to date has focused primarily on the grape pomace (a.k.a grape marc), which is made up of the leftover skins and seeds of the grapes after pressing.  One major source of wine industry waste that has been examined very little is the grape stems.  Prior to pressing, during the sorting process, stems are separated from the grapes and discarded.  To date, very few studies have examined what, if any, nutritional value these stems have, and can they be utilized for other purposes instead of being discarded and adding to the significant environmental issues associated with industry waste.

The study present to you all today aimed to add to the small list of literature

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related to the utilization of grape stems by examining their antioxidant activity and the possible applications for their use as natural antioxidants for the betterment of human (or animal) health.

 

 

 

Methods

Grape stems were supplied by the Spanish winery, Antonio Nadal S.L., Mallorca.  Stems were collected from the Vitis vinifera grapes, Manto Negro (red) and Prensal Blanc (white).  Stems were collected during the destemming process and prior to grape pressing.

Stems were dried, ground, and stored at -20oC until ready for use.  Ground stems were prepared into extract using acetone and also ethanol (two separate extracts).  There were a total of 4 extracts tested: 1) red grape stems with acetone; 2) red grape stems with ethanol; 3) white grape stems with acetone; and 4) white grape stems with ethanol.

The following were measured and analyzed in stem extracts:  total polyphenols, flavanols, and antioxidant capacity.

Results

  • The author reports high polyphenolic concentrations in all grape stem extracts.
  • Total polyphenol concentrations were higher in red grape stem extracts than white grape stem extracts.
  • Grape stem extracts prepared with acetone had higher concentrations of total polyphenols than grape stem extracts prepared with ethanol.
  • Concentrations of flavanol were higher in red grape stem extracts than white grape stem extracts (same pattern as with total polyphenols).
  • Grape stem extracts prepared with acetone had higher concentrations of flavanols than grape stem extracts prepared with ethanol (same pattern as with total polyphenols).
  • Flavanols made up 70% of the total polyphenol content of the grape stem extracts.
  • The author reports high antioxidant capacities in all grape stem extracts, with the red grape stems extracts having higher antioxidant capacities than the white grape stem extracts.
  • Antioxidant activity was significantly correlated with total polyphenols and flavanols.

What does this all mean?

Overall, this study found that red grape stem extracts prepared in acetone have the higher levels of total polyphenols, flavanols, and antioxidant capacities than all other extracts.  The authors stated that all four extracts had high levels of these three things, though if one were to create a hierarchy of what is contains the highest to lowest levels (keeping in mind the low levels are still relatively high), it would be the following:  red grape stem extracts with acetone > red grape stem extracts with ethanol > white grape stem extracts with acetone > white grape stem extracts with ethanol.

This was a very simple study that showed straightforward results (i.e. none of their results contracted one another and were similar to those of other studies).  However, I would have liked to see them compare the grape stem extracts with

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grape seed extracts, grape pomace extracts, grapes themselves, and finished wine.  The authors claim that the total polyphenol and flavanol levels as well as antioxidant capacities of all the grape stem extracts were high; however, they didn’t have any type of control to prove it.

I am guessing that they were comparing the levels they found in their grape stem extracts with the levels found in the literature, however, I know from experience that comparing your numbers directly with the numbers of another study may be problematic, as there are almost always differences in regards to methods or individual researcher techniques that may alter the results from study to study.  I would be more confident in the results had there been a control to which they were comparing.

Assuming the analysis is correct, it seems as though grape stems may be potentially useful as supplements benefitting human health, or potentially other applications that utilize products high in total polyphenols or antioxidant capacities.  By recycling the entire grape and not just the skins and seeds, the wine industry may come one step closer to being more sustainable and friendlier to the environment than ever before.

Source: Llobera, A. 2012. Study on the Antioxidant Activity of Grape Stems (Vitis vinifera). A Preliminary Assessment of Crude Extracts. Food and Nutrition Sciences 3: 500-504.

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Enzymatic Extracts from Wine Industry Waste May Provide Cardiovascular Benefits in the Rat Model

Posted on October 18, 2012 by Becca| 2 Comments

Wine industry wastes are a topic we’ve covered a few times before on The Academic Wino.  We’ve discussed papers on how water waste from the wine industry may be used as an alternative biofuel or biogas as well papers discussing how grape seed extract could be used as a meat preservative.  Grape pomace has also been investigated as a potential protein supplement for Tilapia fish, and in humans, grape pomace has been investigated as a potential supplement to help those suffering from diabetes.

Grape pomace, or marc, can be problematic in the environment when it is accumulated in large quantities.  Recycling grape pomace may provide the winery with economic gains by creating new products from it, in addition to protecting the environment from further damage or industrial pollution.  Grape pomace is full of bioactive polyphenolic compounds which could be beneficial for products aimed at providing some sort of health benefits for animals or humans.  Since the vast majority of these polyphenolic nutrients are located in the skins and seeds of the grapes, the grape pomace; which is basically pressed

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skins and seeds left after the winemaking process is complete; is a huge source of nutrition that could be utilized in a sort of functional food or “nutraceutical” (think ‘vitamin’ or ‘supplement’).

Polyphenolic compounds have previously been extracted from grape pomace by way of organic solvents, which themselves may be a health risk and also concerning for environmental contamination.  One alternative that has been designed for this purpose is enzymatic extraction.  This method results in a more environmentally-friendly water-soluble by-product which is nontoxic.

These polyphenolic compounds that are found in wine are well documented to be beneficial to human health, including (but not limited to) cardiovascular benefits, antioxidant properties, and anticarcinogenic benefits.  Studies have shown that grape seed extracts also possess similar health benefits as wine, and have been shown to have cardiovascular and vasodilator benefits in the rat model.  Specifically, grape seed (and skin) extracts improve vascular function by increasing nitric oxide (NO), a vasodilator and antiplatelet factor, to the vessels endothelial cells.

Though grape seed extracts and grape skin extracts have been frequently studied for their potential health benefits, no studies have actually examined entire grape pomace extract to determine its ability to provide health benefits to animals or humans.  The goal of the study presented today was to chemically characterize grape pomace extract using enzymatic extraction methods, and to test its effects on the vascular system of rats.  The results could provide information regarding the usability of grape pomace as a functional food or dietary supplement for protecting against cardiovascular diseases.

Methods

Grape pomace consisted of pressed Verdejo grapes from Yllera wineries in Rueda, Valladolid, Spain, which contained the skins, pulp, seeds, and stems.  Polyphenolic compounds were extracted using an enzymatic extraction process then completely dried.  The extract was then lyophilized to a fine red powder.  For every 100 grams of wet pomace, 12 grams of lyophilized extract was made.

The grape pomace extract was analyzed for the following: total protein, crude fat, phytochemical content (kaempferol, quercetin, procyanidin and catechin), oxygen radical absorbance capacity (ORAC), and DPPH radical scavenging activity.

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Male rats were used and were fed a normal laboratory diet.  For the testing vascular function, the thoracic aorta, and second- or third-order branches of small mesenteric arteries were isolated.

For vascular function, the following for measured/analyzed: mechanical activity, relaxation and contraction, NO involvement, and O2- production in arterial sections.

Results

  • The enzymatic extraction process increased the carbohydrate and protein content of the pomace extract.
    • The insoluble fibers, cellulose, hemicellulose, and lignine, all decreased after extraction.
    • Pectin concentrations increased after extraction.
    • There was an overall reduction in fat content after extraction.
  • Polyphenolic compounds present in the extract included kaempferol, catechin, quercetin, and procyanidins B1 and B2.
    • Only trace amounts of resveratrol, gallocatechin, and anthocyanidins were found.
  • The antioxidant activity (ORAC) of the grape pomace extract was 4238.9 +/- 731.0 nmol TE/mg.
  • Addition of grape pomace extract elicited relaxation in the endothelium-intact vasculature of rats.
    • After removing the endothelial layer, this relaxation (a.k.a. vasodilation) was no longer observed.
  • When exposed to nitric oxide synthase inhibitors, vasodilation of the arteries was significantly reduced.
    • The NO synthase inhibitors prevented the synethsis (production) of NO, which had a negative effect on the vasodilatory properties of the blood vessels.
      • After adding grape pomace extract, this inhibitory effect was reversed.
    • After adding the α-adrenergic agonist Phe, concentration-dependent contractions were induced.
      • Exposure to grape pomace extract reduced the maximum concentration elicited by Phe.
  • ET-1 and DETCA, both of which are known to promote the vascular production of O2-, elicited and sustained a contraction in the rat aortas.
    • By exposing the aortas to grape pomace extract, these vascular contractions elicited by the ET-1 and DETCA were reduced.
  • After 3 hours, there was a significant increase in O2- production brought on by ET-1.
    • Grape pomace extract prevented this significant increase in O2- production.

Conclusions

First and foremost, this paper showed that processing grape pomace using an enzymatic extraction process may serve as a good mechanism for extracting the beneficial polyphenols from grape pomace and potentially other foodstuffs which may be recycled into functional foods, dietary supplements, or other

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uses.  The antioxidant activity of the grape pomace extracted in this manner was at similar levels to pomaces extracted using more traditional chemical methods.

Exposure of rat vasculature to grape pomace extract resulted in a reduction in superoxide anion elicited by ET-1.  At the same time, the vascular contraction caused by ET-1 was reduced due to grape pomace exposure.  Exposure to grape pomace also prevented O2- production in the vasculature of the rats.

What do these results suggest?

The authors of the study state that these results are the first of their kind showing the vascular vasodilatory properties of grape pomace extract.  According to the authors, it appears as though grape pomace extract (processed by enzymatic extraction) induces endothelium-dependent vasodilation and reduces vascular constriction brought on by NO-dependent mechanisms.

In plain English, it seems as though like grape seed and grape skin extract, grape pomace extracts also possess significant health benefits, in particular cardiovascular benefits.  Of course, this study focused on the rat model, therefore to be certain similar results will be seen in humans, clinical research trials would need to be performed.

I would also like to see a study that directly compares the vasodilatory properties of blood vessels after exposure by grape pomace extracts produced from traditional organic solvent methods with extract produced from enzymatic extraction methods.  Does one extraction method result in an extract with superior health benefits to the other?  Or is this simply a matter of environmental soundness (which is extremely important in and of itself).

Using the information gathered from this study, what sorts of studies would you like to see performed in the future?  What is the next step?  Do you have any other ideas for using grape pomace that have not been investigated yet in the scientific literature?

Please leave your comments!

Source: Rodriguez-Rodriguez, R., Justo, M.L., Claro, C.M., Vila, E., Parrado, J., Herrera, M.D., and de Sotomayor, M.A. 2012. Endothelium-dependent vasodilator and antioxidant properties of a novel enzymatic extract of grape pomace from wine industrial waste. Food Chemistry 135: 1044-1051.

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Using Dehydrated Grape Marc Waste to Improve Wine Quality: A More “Natural” Approach?

Posted on September 26, 2012 by Becca| 10 Comments

Producing a quality wine is of utmost important to winemakers, and arguably the most important goal in the industry as a whole.  There are many factors that influence quality in a wine, many of which are related to the chemical composition of volatiles and phenolic compounds, both which influence the sensory and overall quality characteristics of the finished wine.  Viticultural management and winemaking techniques can play a role in altering the concentration of these compounds, in addition to any biochemical reactions that may occur during the fermentation and aging processes.

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In addition to volatile compounds, which are associated with the aroma and flavor of wine, color plays an equally important role in wine quality.  In the “average” wine and poorer quality wines, color tends not to last as long as it does in higher quality wine.  In other words, color tends to degrade faster in average and low quality wines than it does in high quality wines.  This decline is tied in with an overall decline in the concentration of polyphenols in wine, which act to prevent oxygen degradation and other harmful reactions.  As a result of this, many average and lower quality wines must resort to adding greater quantities of SO2 and ascorbic acid in order to make up for the decrease in polyphenols that otherwise protect the wine.

With the increased push for more stringent ingredient labeling on wine bottles, and a general increased interest in producing more organic and/or sustainable wines, the use of more natural additives to protect wines again oxygen degradation or other “ailments” is of growing importance.

One potential candidate for a natural alternative to SO2 or ascorbic acid for the purposes of maintaining wine quality is waste grape marc from the juice industry and has been recently been studied for this purpose.  In the juice industry, grape marc (i.e. the skins and seeds waste) are collected after only a short period of maceration time (4 days touching the juice) than the maceration time of red winemaking.  This means that this marc has not yet been stripped of much of its chemical structure and components, indicating their possible ability to be reused and recycled instead of going to waste.

The goal of the study presented today was to determine if this grape skin waste in its dehydrated form could act as a new winemaking technique for increasing or maintaining color and for protecting the wine against phenolic and aromatic degradation prior to bottling.

Methods

Grape marc wastes were of Vitis vinifera grapes of the Bobal variety (red), and a mixture of the white variety Airén (70%) and an unknown red variety (blend hereby referred to as “AMIX”).  Marc was collected from a juice concentrate factory in Castilla-La Mancha (Julian Soler, Cuenca, Spain).   Marc was collected, frozen, then thawed, dried, then ground after the removal of seeds and stalks.  Four grape skin marc treatments were made for this experiment: 100% Bobal, 100% AMIX, 75% AMIX & 25% Bobal, and 50% AMIX & 50 Bobal.

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Two aged and two young wines were provided by a local winery.  Young wines were meant to correspond with bulk commercial wines with a shelf life less than or equal to three years.  Young wines were made using traditional methods, and with 5-10 days of maceration and fermentation in stainless steel tanks.  Wines were blends of grapes found in the area, including Tempranillo, Cabernet Sauvignon, Merlot, etc.  Aged wines were created similar to young wines, except these underwent a longer maceration time (10-20 days) and were aged for at least 6 months in American oak barrels.

All wines had a pH between 3.5 and 3.9, and alcohol content between 13.5 and 14% vol.  Wines were bottled in amber bottles with synthetic cork closures (4 bottles of each wine made).

For maceration with the grape skin marc treatments, wines were macerated with 5g/L of the treatment over 3 days at 18oC.  After maceration, grape marc treatments were removed with a strainer and the wines were stored in crystal bottles at 18oC.  Analysis of the wines occurred immediately after maceration, then at 3 months and 6 months post maceration.

Color parameters (anthocyanins) and total phenolic compounds were analyzed using UV-vis spectrophotometry.  Individual phenolic analysis occurred using HPLC-DAD.  Finally, volatile compounds were measured using SBSE-GC-MS.

If you want to know more details about the methods, please ask!

Results

Color

  • The addition to grape marc in wines significantly impacted the color intensity and shade of all wines (both aged and young).
    • Bobal showed the highest color intensity increase, which AMIX showed the lowest.
    • The extent of color intensity increases were dependent upon the type of grape used to make the dehydrated grape marc powder, though all grapes led to an increase in color.
      • These results indicate the addition of grape marc waste prior to bottling may improve the color in both aged and young wines.
  • All grape marc treatments cause a decrease in shading, which is indicative of higher quality.
    • The Bobal treatment appeared to be the most effective in reducing shading in wines.
    • The mixture of Bobal and AMIX treatments were not as effective in reducing shading in wines.
  • Color intensity increased over time in all wines.
    • Bobal wines showed the highest increase over time.
  • Shade values increased over time (degradation in quality) compared with controls.

Total Phenols

  • Total phenols significantly increased after grape marc treatment.
    • Bobal treatment showed the highest increase, followed by the mixtures of Bobal and AMIX.
    • Increases were higher in aged wines than young wines.
    • Total phenols evolved over time in the same pattern for grape marc treated wines as control wines.
    • All wines treated with grape marc had significantly higher total phenol levels than control wines
      • Total phenol levels were similar for all grape marc treatments, with no one treatment performing better than the rest.

Anthocyanins

  • Grape marc treatments resulted in an average increase of 50mg/L of total monoglucoside anthocyanins.
    • Bobal produced the highest levels of anthocyanins, while AMIX produced the lowest.
    • Anthocyanin levels decreased over storage time.
      • AMIX and the mixture with more AMIX showed the lowest decrease in anthocyanins.
      • The amount of anthocyanins present depended upon the grape marc treatment and on the age of the wine.
  • Even though anthocyanins decreased over time, the anthocyanin content in grape marc treated wines was always higher than control wines, and remained significantly higher by the end of the experiment.

Low Molecular Weight Phenolic Compounds

  • Treatment with grape marc significantly increased the levels of low molecular weight phenolic compounds in all wines.
    • Mixtures of red and white marc appear to have increased these values the most, compared with white or red varieties by themselves.
      • The authors concluded that mixtures of grape marc could be good strategy for balancing phenolic compound deficiencies in wine.
      • Also, using different mixtures of grape marc could allow winemakers more control over aroma and flavor profiles of their wines by adjusting the proportion of one particular skin over another.
  • The primary low molecular weight phenolic compounds released by the grape marc were gallic acid, catechin, epicatechin, and resveratrol.
    • Caffeic and coumaric acids increased more in young wines than aged wines.
    • Resveratrol increased more in young wines.
  • After 6 months of storage, all wines treated with grape marc had higher levels of low molecular weight phenolic compounds than controls.
    • Grape marc mixtures with greater levels of white grape skins produced wines with the highest levels of low molecular weight phenolic compounds.

Volatile Composition

  • After grape marc treatment, the volatile compound β-ionone significantly increased in wines.
    • The Bobal treatment resulted in the greatest increase of β-ionone.
    • After grape marc treatment, β-damascenone and nerolidol decreased in all wines.
      • Even though β-damascenone levels decreased, they were still above their odor thresholds, thus maintaining their floral and fruity characteristics.
      • 1-hexanol (herbaceous tones) remained unchanged after grape marc treatment.
      • After grape marc treatment, increases in isoamyl acetate (banana tones) were noted.
      • Wood-derived compounds remained unchanged after grape marc treatment.

What does this all mean?

Overall, the results of this study indicate that using dehydrated grape skins/marc from the juice industry may be a important tool for increasing the quality characteristics of average or lower quality wines prior to bottling.   Specifically, after the treatment with dehydrated grape skins, color and total phenolic content increased in all wines, as well as anthocyanins and low molecular weight compounds, all of which are important contributors to wine quality.  The volatile component of the wine was only moderately affected, indicating that if particular flavor profiles are desired, then the winemaker must be deliberate in exactly which variety of grape(s) is used in creating the dehydrated grape skin treatment.

I found the results of this study very fascinating, and important in the quest for finding more natural alternatives to preserving or increasing quality in the winemaking process.  One thing that is missing from this study, however, is the sensory analysis of the treated wines.  Does dehydrated grape skin treatment affect the flavor and aroma of the finished wine?  Based on the results from the volatile compound analysis, the answer should be yes, however, I would have liked to see the accompanying sensory analysis for confirmation.

In lieu of space, I won’t go on regarding more specific results or implications; however, I’d love for you all to help me continue the discussion in the comment section below.

What do you think of the study results?

What implications to you see for this type of treatment application?

Is there testing that you would like to have seen that was not performed?

Do you think the treatment of grape marc waste is, in fact, a natural approach?  Or something different?

Please feel free to leave your comments/questions for discussion!

Source: Pedroza, M.A., Carmona, M., Alonso, G.L., Salinas, M.R., and Zalacain, A. 2013. Pre-bottling use of dehydrated waste grape skins to improve colour, phenolic and aroma composition of red wines. Food Chemistry 136: 224-236.

DOI: 10.1016/j.foodchem.2012.07.110

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!

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