Category Archives: Environmental Science

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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The Environmental Impact of Producing a Single Bottle of Wine in Nova Scotia, Canada

Posted on March 5, 2013 by Becca| 3 Comments

 

Climate change is a very real threat that has many industries concerned over how their businesses with be affected. More importantly, it’s this changing climate that has and continues to push many industries into developing better ways to function that has less environmental impact as well as developing ways to function under altered conditions. Prior to making any change, businesses and industries must step back and take a look at their current environmental footprint, and how their business practices and procedures impact the overall health of the environment.

When considering the wine industry, there has been a lot of work focus on the micro-scale of within the winery or vineyard, and what sort of a carbon footprint or environmental impact is left after all is said and done. However, outside influences that also heavily contribute to the overall carbon footprint or environmental impact have largely gone ignored; factors by which if one really wishes to improve their overall environmental impact, they need to take into consideration. These outside influences include, but are not limited to,

By James Ellison (Flickr: Gaspereau Vineyards, NS) [CC-BY-2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons

By James Ellison (Flickr: Gaspereau Vineyards, NS) [CC-BY-2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons

greenhouse gas emissions (think the emissions of machinery or transport vehicles), and total energy use (think all the gas, oil, or electricity that is used to create and distribute the product).

The Academic Wino reviewed one study in particular that examined the overall environmental impact of wine distribution in the United States, which is an important piece of literature examining the energy expenditure of the shipping and distributing side of the wine industry. However, a model incorporating both the distribution side of the industry as well as the grape growing and winemaking side of the industry is needed in order to get an accurate picture of the overall environmental impact of the wine industry as a whole. (See Part I and Part II here for the review of that piece of literature).

Life Cycle Assessment (LCA) is a tool that is used to determine the environment impact associated with a particular product “from cradle to grave”. In other words, using complex mathematically modeling, LCA takes into consideration the positive and negative energy inputs and outputs from the very beginning to when an individual product is first made, all the way through when that individual product is sold to the consumer. In terms of wine, the LCA starts from when the grapes are first grown (either starting from the planting of the vine or the start of the growing season the spring, depending upon the model), through harvest and winemaking, then finally through bottling, storing, shipping, and purchase by the consumer.

The study presented today used LCA to determine the energy inputs and environmental emission of one complete life cycle of one standard sized 750mL wine bottle, from grapes grown and wine made in Nova Scotia, Canada all the way through the recycling of the bottle, which could have potential implications for other vineyards and wineries trying to minimize their carbon footprint on the world.

Methods

The mathematical model created included the “material and energy flows associated with”: growing the grapes, making the wine, making of the bottle, transporting the wine to the store, the consumer transporting the wine home, refrigeration of the wine, and the recycling of the bottle. Also included was energy associated with the vineyard equipment, as well as the emissions related to pesticides. Energy related to the following was also included: corks, sugar, labels, and heat-shrink capsules. Only the energy related to transport of the following items were included: yeasts, filtering agents, clarifying agents, bacteria, enzymes, and antioxidants. Water consumption was not included in the model, as the data were not available. The authors note that irrigation is not needed in Nova Scotia due to ample rain during the growing season, so omitting the water component may not be as bad as it would be if a lot of water was required for irrigation.

For space considerations, I will omit some of the details on the breakdown of exactly what went into the model and under what conditions, but if there is a certain item you’d like me to elaborate on or you have questions as to whether it was in the model and what assumptions were outlined for the model, please feel free to comment and I’ll clarify that for you.

The following categories were examined during the analysis: “abiotic resource depletion potential, freshwater acidification potential, eutrophication potential, global warming potential, stratospheric ozone depletion potential, aquatic eco-toxicity potential, terrestrial eco-toxicity potential, photo-oxidant formation potential, and cumulative energy demand”.

Three different scenarios were tested to evaluate how each would alter the life cycle assessment of the bottle of wine, and if one scenario were superior over

By Patrick Heusser, www.x8ing.com (own work, www.x8ing.com) [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

By Patrick Heusser, www.x8ing.com (own work, www.x8ing.com) [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

any others in regards to improving the energy usage or carbon footprint of the bottle. The following scenarios were tested: 1) an organic viticulture scenario; 2) a lighter bottle scenario; and 3) an increased transport distance and new transport mode scenario. Again, due to space considerations I’m leaving out the specific changes made to create these scenarios, but once again, just ask if you have specific questions regarding any one of them.

Results

This paper is chock full of interesting results, though I will just highlight some of them.

• Taking into account the energy and emissions of all categories related to producing and distributing a bottle of wine, the two categories with the highest relative impact were vineyard activities and consumer shopping.
• Recycling of the glass bottle and refrigeration at home contributed very little to the life cycle impact of a single bottle of wine.
• In regards to the vineyard activity category, the majority of the impacts were associated with nutrient management activities and fuel usage.
o The trellis system itself was responsible for half of the vineyard activity impacts (related to toxicity) due to the energy and emissions required for making the steel posts and the use of chromium copper arsenate to preserve the wood.
• Most of the categories were impacted mostly by the manufacturing process related to that particular category.
• Consumer shopping represented between 8% and 58% of the total life cycle impacts of a single bottle of wine.
o Nearly all of this was a result of the use of the car to pick up the bottle at the store and bring it back home.
• The glass bottle impact (between 3% and 24% of the total life cycle impacts) resulted mostly from the electricity used to create the bottles.
• Winery impacts were mostly derived from the electricity needed to run all of the equipment (note: Nova Scotia electricity is primarily coal-fired) as well as the ethanol emitted during fermentation.

Scenarios

• Organic viticulture practices only improved the life cycle impacts of 3 of the categories by 0.14% and 3%.
o Organic viticulture practices resulted in an increase in the following categories: freshwater acidification potential, eutrophication potential, and global warming potential.
o Organic viticulture significantly decreased the aquatic eco-toxicity potential and the terrestrial eco-toxicity potential as the toxic wood preservatives were no longer used in this scenario.
• Creating bottles that are 30% lighter than the typical bottle results in an improvement in life cycle category impacts between 2% and 10%.
o These improvements were found mostly from the reduced energy and emissions needed to produce the lighter bottle, though some of it was found in the transportation of the bottle from winery to store as well.
• Using a larger shipping truck reduced the life cycle impacts of a single bottle of wine. Using a ship or a larger transport truck was more environmentally friendly than using a small “domestic” transport vehicle.
o It was more environmentally friendly on a per bottle basis to ship a bottle of wine from Nova Scotia to Australia on a container ship than it was to ship a bottle from Nova Scotia to Vancouver in a small transport truck.

Conclusions

According to the results of this study, in regards to the environmental impact of the life cycle of a single bottle of wine produced and sold in Nova Scotia, improvements on carbon footprint and emissions would be most felt in the vineyard practices (i.e. grape growing) and consumer shopping areas. While the electricity required to produce the wine and many of the materials needed for the production of the wine and the bottle itself, improving upon the vineyard practices and the consumer shopping experience will produce the most significant results.

In regards to vineyard management practices, the results indicated that most of the energy and emissions comes from nutrient usage. The authors of the study suggested that switching to or incorporating organic fertilizers or using methods to increase nutrient-uptake efficiencies by the plant could result in significant

By Huhu Uet (Own work) [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-3.0 (http://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons

By Huhu Uet (Own work) [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-3.0 (http://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons

improvements in emissions from this area. The authors noted that simply switching to manure would not be an appropriate solution, as they found that manure emits significantly more nitrous oxide, ammonia, and nitric oxide than synthetic fertilizers, and that the nitrogen in manure is not as easily taken up by the plants.

In regards to the consumer shopping experience, the authors noted that a consumer driving 5km to the store to buy a single bottle of wine had a greater negative environmental impact than the vineyard practices and winemaking practices combined. The authors suggest that trying to avoid these consumer car trips by implementing more direct-to-consumer shipping options (where a more efficient transport truck would be used) as well as car-pools or purchasing multiple bottles at a time could reduce the emissions produced from this category.

Finally, using lighter weight bottles would significantly reduce the environmental impact of a bottle of wine, thus incorporating these into a winery’s arsenal would likely be effective in reducing the negative environmental impact produced by that particular winery.

It is important to keep in mind that these results are based on the wine industry in Nova Scotia, which is a relatively small industry. Thus, some of the factors may be different when scaled up to a wine region with significantly greater production and output. It would be interesting to apply this same model using data from larger wine regions to see if the same trends hold, or if other categories or management practices were more or less efficient when scaled up.

I’m leaving out a lot of details in this study, so if there is any clarification that you need or you have additional questions, please feel free to ask. Do you think the authors missed any important potential emissions creators in this model? Please leave your comments!

Source: Point, E., Tyedmers, P., and Naugler, C. 2012. Life cycle environmental impacts of wine production and consumption in Nova Scotia, Canada. Journal of Cleaner Production 27: 11-20.

Posted in Environmental Science

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Is Soil Dryness Responsible for Early Grape Ripening in Australia?

Posted on January 29, 2013 by Becca| 1 Comment

 

Climate change, be it brought on by anthropomorphic sources or the natural cycle of the earth (I’m not trying to start that debate), is continuing to be touted as having a significant influence on agriculture and also viticulture worldwide.  Scientists have been predicting that growing and ripening seasons are likely to change in some places, while some (if not all, eventually) will find that the variety of grapes traditionally grown in their region will no longer survive there and other varieties of grapes will have to be planted in order to keep up with the changing environment and climate.

In Australia, studies have found that many grapes varieties in 11 of 12 grape growing regions have been ripening earlier in time periods between 35 and 115 years.  It was noted that these early ripening years were correlated with increases in temperature.  One study in particular by Webb et al (2012) surmised that the earlier ripening in these regions was quite possibly due to temperature increases, soil drying, and/or changes in vineyard management techniques.

By Amanda Slater (originally posted to Flickr as Barossa Valley. SA) [CC-BY-SA-2.0 (http://creativecommons.org/licenses/by-sa/2.0)], via Wikimedia Commons

By Amanda Slater (originally posted to Flickr as Barossa Valley. SA) [CC-BY-SA-2.0 (http://creativecommons.org/licenses/by-sa/2.0)], via Wikimedia Commons

The author of the study presented today (White 2013) claims that there are several issues with the conclusions that Webb et al (2012) came up with.  First, he claimed that the data Webb et al (2012) used was for areas of land around 2500 hectares, whereas the vineyards they were analyzing were significantly smaller at 0.2 to 16 hectares.  The “behavior” of any given piece of land can be radically different even at relatively close distances.  Assuming the environmental information ascertained from a 2500 hectare plot is similar to a random tiny vineyard of no more than 16 hectares in size could be dangerously inaccurate, resulting in missed data or other important hydrological and geographical information unique to that particular vineyard or area.

White (2013) also noted that the soil data used by Webb et al (2012) was for the entire continent of Australia and not for any one particular vineyard site.  Again, similar to the concept described above, the soil in one particular area may be radically different from the soil in another, thus using the average for an entire continent may lead to inaccurate results.

Next, White (2013) noted that the water data used by Webb et al (2012) did not include data from regions by which some of the study vineyards were located.  This may have resulted in some loss of data and loss of result accuracy.

Finally, the last beef that White (2013) had with the study by Webb et al (2012) was that they only used growing season rainfall totals, whereas White argued that the more appropriate variable would be the annual rainfall total.  Just because the vines are dormant in the winter does not mean that the rainfall occurring at that time has no influence on the growth and development of the vine the following spring and summer.

Focusing on Soil Dryness

One of the claims Webb et al (2012) made is that earlier ripening could be due to increased soil dryness.  As a result of the aforementioned flaws in the study design, White (2013) sought to examine this claim further, to either confirm or refute the hypothesis based on more accurate data.

Soil moisture can be simply defined as the balance “between rainfall and actual evapotranspiration, with a variable small surplus in winter going to drainage” (White, 2013).  In other words, the soil will be moist or dry depending upon how much rain it got, plus the amount of moisture that is lost through evapotranspiration (think moisture lost due to heat to the atmosphere) with a small amount draining into the water table far below the surface.  As air temperatures increase, potential evapotranspiration increases.  In other words, as air temperature increases, more water is lost from the plant to the atmosphere.

By Tomas Castelazo (Own work) [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-3.0 (http://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons

By Tomas Castelazo (Own work) [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-3.0 (http://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons

It is important to note that as temperatures and carbon dioxide increase, plants have a mechanism to conserve their water by closing their stomatal pours on the leaves.  By closing the stomata, the amount of water that is lost by the plant to the atmosphere decreases and remains within the plant and within the soil around the plant for survival.

So in reality, as White (2013) noted, for most vegetation in areas that are known to have low rainfall or suffer from near drought-like conditions, the decrease in water loss by the plant is directly affected by increased temperatures and increased carbon dioxide, thus counteracting the potential loss of water to the atmosphere had these stomatal closing mechanisms not been in place.  Hydrological research also found that catchment runoff (i.e. runoff from the higher elevations to the lower elevations)  increases with increasing carbon dioxide, thus supporting the idea that as temperatures and carbon dioxide increase, water is not lost into the atmosphere but is in fact retained in the plant and in the soil around the plant.

Due to the results of this research in plant physiology and catchment hydrology as mentioned just previously, White (2013) concluded that annual rainfall may be a good surrogate for soil moisture when the measurements of soil moisture are not readily available.  The overall goal of the study was to determine if trends in annual rainfall confirmed or refuted the theory that soil drying has an effect on earlier ripening in grapes based on the conclusions made by Webb et al (2012).

Briefly, the annual rainfall data and the grape ripening data from 5 different grape growing regions in Australia and over an 11 year moving average were analyzed using a linear mathematical model.

Conclusions

The results of the study found that 3 out of 5 grape growing regions showed positive annual rainfall trends (i.e. increased annual rainfall over time), while 2 out of 5 regions showed negative annual rainfall trends (i.e. decreased annual rainfall over time).  Only one of each was statistically significant.  According to White (2013) the model results are consistent with the data collected from those same regions in Australia during those same time periods.

Since there was a significant increase in annual rainfall during this 11 year period, White (2013) said it was not possible that soil drying would be contributing to the early ripening found at vineyards throughout the region.  In fact, if anything, the soil was getting wetter while the grapes were ripening earlier!

At the site that did see a significant decrease in annual rainfall, there was actually no change in grape ripening found in previous studies.  So, if Webb et al (2012) were correct in their assumption, this site should have seen either no change in annual rainfall plus no change in ripening date, or a decrease in rainfall plus an earlier ripening date.  Since neither of these scenarios played out, White (2013) ascertained that soil dryness was not contributing to earlier ripening in the grapes of Australia.

Based on these results, White (2013) expressed confidence that soil dryness did not influence the date of ripening for grape varieties in Australia.  In fact, it is likely that there are other factors involved that are significantly affecting this date, with the more likely culprits, according to White (2013), being vineyard management practices and increased air temperatures.  According to White (2013), vineyard management practices had changed around this time period, which is something that should be significantly considered as a major player in earlier grape ripening.

Personally, I don’t lay the blame on any one factor in particular.  I think many different factors act in concert to speed up the ripening process of these grapes, and thereby more complex mathematical models taking more of these factors into consideration should be tested.

I’d love to hear what you all think!  Please feel free to leave your comments!

Source: White, R.E. 2013. Has soil drying contributed to earlier grape ripening in wine regions of southern Australia? Australian Journal of Grape and Wine Research 19 (1): 123-127.

Posted in Environmental Science

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Examining the Phenolic Content and Antioxidant Capacity of Grape Leaves: Possible Implications for Recycling and Sustainability in the Wine Industry

Posted on January 16, 2013 by Becca| Leave a comment

 

The majority of research papers published focusing on wine industry wastes or wine industry by-products have focused primarily on grape marc or grape pomace.  However, in the spirit of sustainability, should we only be considering the fruits themselves as the only source for recycling in the wine industry?  Of course not!  Not only can the fruits (in the form of skins and seeds, primarily) be recycled into other uses, such as for medicinal purposes or for use in other industries (i.e. leather production, food preservatives, additives to wine, etc), but also the water waste produced from wine making as well as the grape leaves from the vines can be utilized and reused for other purposes.

In regards to grape leaves, research has been more limited compared to research on grape pomace.  Studies have shown that the juices obtained from grape leaves can be used for many medicinal purposes due to several biological activities including antibacterial, antifungal, anti-inflammatory, and antiseptic properties.

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

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

Grape leaves are also used frequently as food in Greek cuisine, as well as additives in other foods due to the leaves known antioxidant properties.

The ability to recycle the whole plant, and not just from grape skins and seeds, is just another step toward sustainability for the wine industry as a whole.  By reusing and recycling all parts of the plant, the amount of potentially toxic waste entering the environment is dramatically reduced.

The article presented today examined the antioxidant properties of grape leaves in order to confirm if grape leaves are appropriate for use in other industries.

Methods

Leaf samples were collected in July of 2006 from an experimental vineyard in Sendim, Bragança in NE Portugal.  Twenty varieties of Vitis vinifera were studied: 9 white and 11 red.  Each variety was grown in two adjacent rows, all of which underwent the same viticultural treatments (no irrigation or soil treatments).  5 plants in the center of the two rows we selected for each variety, and 4 leaves were harvested from each plant.  Leaves were freeze-dried and then ground into a powder for further analysis.

The following were analyzed for the leaf samples: phenolic content and antioxidant activity (total reducing capacity, reducing power, and scavenging ability).

By user:yelod - wikimedia commons משתמש:ילוד - ויקיפדיה העיברית (Own work) [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

By user:yelod – wikimedia commons משתמש:ילוד – ויקיפדיה העיברית (Own work) [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

Results

  • Extraction yields were greater for red varieties than white varieties.
    • For whites, the highest yields were found in Chardonnay and Samarrinho.
    • For reds, the highest yields were found in Alicante, Bouchet, Bastardo, and Trincadeira.
  • All samples contained the following compounds: trans-caffeoyltartaric acid and trans-coumaroyltartaric acid (both hydroxycinnamic acids) as well as myricetin-3-O-glucoside, quercetin-3-O-glucoside, quercetin-3-O-galactoside, and kaempferol-3-O-glucoside (all flavonoid glycosides).

Why are the leaves be so high in phenolic content?

The authors speculated that the grape leaves were likely rich in polyphenols, specifically flavonoids, since these compounds are known to act as UV filters.  The UV protection characteristic of flavonoids functions to protect the plant cells (particularly chloroplasts) from the damaging effects of UV rays.  In effect, flavonoid function as a part of the plants’ defense mechanisms against harmful UV rays, thus their high levels in the leaves of the plants.

  • Total phenolics were found to be higher in the leaves of red varieties than the leaves of white varieties.
    • For red varieties, Tinto Cão had the highest levels of polyphenols whereas Mourisco had the lowest (3.5 times different).
    • For white varieties, Codega had the highest levels of polyphenols, whereas Gouveio had the lowest.
  • For all leaf samples, quercetin-3-O-glucoside and quercetin-3-O-galactoside made up 64-73% of the total phenolics.
  • Grape leaves appear to have higher polyphenol levels than grapes themselves.

Antioxidant Capacities

  • White varieties had higher antioxidant capacities than red varieties.
    • The white varieties showing the highest reducing capacity were Viosinho, Rabigato, Côdega, and Malvasia Fina.
    • The red varieties showing the highest reducing capacity were Tinto Cão and Alicante Bouchet.
  • In regards to reducing power, for white varieties, Côdega showed the strongest levels, with Chardonnay and Samarrinho following behind it.
    • For red varieties, Tinto Cão, Rufete, and Touriga Francesa showed the strongest levels.
    • Both Côdega (white) and Tinto Cão (red) showed similar levels, thus there was no clear difference between red and white varieties in terms of reducing power.
  • In regards to scavenging activity, there were no clear differences between red and white varieties.
    • For white varieties, Malvasia Rei showed the highest scavenging activity.
    • For red varieties, Tinta Gorda showed the highest scavenging activity.

Why did the varieties with the highest polyphenol content not have the higher antioxidant capacities?

It is typically thought that those items possessing high polyphenol levels will also have high antioxidant capacities.  However, the results of this study found nearly the opposite.  The authors speculated that this result was likely due to the fact that it isn’t all about polyphenols.  There is clearly some other compound or compounds that are interacting with either the polyphenols or other compounds to determine antioxidant capacity.

Conclusions

The results of this study indicate that grape leaves are good sources of polyphenols and antioxidant capacity to be utilized in a multitude of industries.

By Philip Larson (originally posted to Flickr as DSC01975) [CC-BY-SA-2.0 (http://creativecommons.org/licenses/by-sa/2.0)], via Wikimedia Commons

By Philip Larson (originally posted to Flickr as DSC01975) [CC-BY-SA-2.0 (http://creativecommons.org/licenses/by-sa/2.0)], via Wikimedia Commons

It was also clear from the results that there was no relationship found between total polyphenol content and antioxidant capacity.  According to the authors, this is likely due to the involvement of one or more other compounds acting either alone, or more likely in concert, with polyphenols or some other compound to affect the antioxidant capacity of the leaves.  These results suggest more work needs to be done to tease out what is the mechanism behind antioxidant capacity in grape leaves.

Overall, this was a straightforward study that clearly shows that grape leaves are an excellent source of polyphenols that could be utilized for multiple industries.  By recycling not only the grapes themselves but also the grape leaves, the wine industry can move one step closer to a more globally sustainable industry.

Source: Fernandes, F., Ramalhosa, E., Pires, P., Verdial, J., Valentão, P., Andrade, P., Bento, A., and Albert Pereira, J. 2013. Vitis vinifera leaves toward bioactivity. Industrial Products and Crops 43: 434-440.

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