The Phenolic Composition of Cabernet Sauvignon Wines in China: Demonstrating Terroir Effects

Phenolic compounds, which are found in grapes, can significantly influence the aroma, flavor, mouthfeel, color, and overall quality of a wine.  These compounds are found naturally in grapes, however can also be synthesized throughout the fermentation and aging processes.  As a result of this, there are many factors that can influence the phenolic composition of a wine, including but not limited to; grape variety, environmental influences, and winemaking techniques.  For wines that are single variety based and not aged after fermentation, the phenolic composition of the wine is highly dependent upon the grape and the conditions in the vineyard. 

Specifically, this is what the term “terroir” embodies: it is the definition of the geographical and environmental origin of the grapes that include characteristics such as soil type, climate, and topography, and who all those things combine to affect the composition and quality of a wine.  Favorable terroir conditions can produce very high quality grapes, which is a critical starting point for a good wine.  By understanding how terroir affects the phenolic composition of grapes, vineyards managers or winegrowers will have a greater understanding of how to manage and maintain the grapevine that will produce high quality wines.

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There is a lot known about terroir effects on grapes and wine throughout many portions of the world, however, there is little known that specifically compares individual phenolic compounds of single varietal wines from different winemaking regions, and even less so known about these effects in the newer wine regions of China.

The wine regions of China are very ecologically diverse, considering they are spread all over the vast country.  The Yunnan Zone can be found at altitudes between 1900 and 2400m above sea level; the Gansu Qilian Zone is located next to a desert; the Ningxia Helan Zone is past the mountains; the Yantai Shandong Zone and Changli Hebei Zone are by the sea; and finally the Huailai Hebei Zone is located in a cooler climate.  It is because of these regional differences that there is great potential for regional terroir effects in wines produced from Chinese grapes. 

The goal of the study presented today was to analyze the differences in phenolic composition in Cabernet Sauvignon vines from different winegrowing regions in China.

Methods

 5 growing regions in China were studied: Deqin of Yunnan (YNDQ); Yuquanying of Ningxia (NXYQY); Yuma of Ningxia (NXYM); Qilian of Gansu (GSQL); Changli of Hebei (HBCL); and Yantai of Shandong (SDYT). 

Cabernet Sauvignon vines were studied, since they are easily found growing in all wine regions of China.  Grapes were harvested at their full-ripened state and were in strict accordance with local wine production technical rules.  Wines went through alcohol and malolactic fermentations, but did not age afterward. 

In each growing region, two to four wineries were chosen and about 1000mLof fresh wine from each winery was collected from at least two different fermentation processes.  To ensure only regional terroir characteristics were at play, all wines from each growing region were pooled.  Each wine sample was studied in triplicate.

Anthocyanin phenolics were analyzed, as well as non-anthocyanins including flavan-3-ols, flavonols, hydroxybenzoic acids, hydroxycinnamic acids, and stilbenes.  Anthocyanins were quantified by using malvidin-3-O-glucoside as a standard, and flavanols, flavonols, hydroxybenzoic acids, hydroxycinnamic acids and stilebenes were quantified by using catechin, quercetin, gallic acid, caffeic acid, and resveratrol, respectively.

Results

Anthocyanins

• 24 anthocyanins were identified in Chinese Cabernet Sauvignon wines.

o   All 24 were found in each Chinese growing region studied.

•  Wine from the YNDQ region had the highest levels of anthocyanins.
• Wines from GSQL and NXYQY regions had significantly lower levels of anthocyanins (due to very low delphinidin derivatives).
• Cyanidin-3-O-glucoside and peonidin-3-O-glucoside were 5 times higher in YNDQ wines than wines from any other region.
• Wines from HBCL had the highest levels of malvidin-3-O-glucoside and malvindin-3-O-(6-O-acetyl)-glucoside.
• There were significant differences in anthocyanin levels between wine regions in China.

Flavan-3-ols

• 16 flavan-3-ols were found in wines from all Chinese growing regions studied.
• SDYT region displayed the highest levels of flavan-3-ols.

o   Concentrations in this region were nearly double that of GSQL and YNDQ wines.

o   This region also showed the highest levels of gallocatechin and procyanidin dimers.

•  Wines from GSQL and YNDQ had the lowest levels of total flavan-3-ols.
• NXYM wines had the highest levels of epicatechin.

o   These levels were nearly 30 times greater than levels found in YNDQ wines.

• The highest levels of catechin were found in YNDQ wines.
• SDYT wines had the lowest levels of catechin.

Flavonols

• 10 flavonols were found in Chinese wines from the growing regions of study.
• Highest levels of flavonols were found in YNDQ wines.

o   These levels were nearly 4 times greater than levels found in GSQL wines.

• YNDQ wines had much higher levels of quercetin derivatives than wines made from other wine regions in China.
• Higher kaempferol levels were found in NXYM wines.
• YNDQ wines had the highest levels of dihydroquercentin-O-hexoside, while GSQL wines had the lowest levels.
• YNDQ wines had higher levels of dihydroquercentin-O-rhamnoside, quercentin-3-O-glucuronide, and myricetin compared to all other regions.
• Wines from NXYM and YNDQ had higher levels of kaempferol-3-O-glucoside than all other regions.

o   These values were double those found in GSQL and HBCL wines.

Hydroxybenzoic Acids

 

•  3 hydroxybenzoic acids were found in Chinese wines.
• Highest levels of total hydroxybenzoic acids were found in SDYT wines, and the lowest levels in NXYM wines.
• SDYT wines had significantly higher levels of gallic acid, while NXYM wines had the lowest levels.

Hydroxycinnamic Acids

• 4 hydroxycinnamic acids were found in Chinese wines.
• GSQL and NXYQY wines showed the highest levels of total hydroxycinnamic acids.

o   These levels were nearly 5 times more than levels found in YNDQ wines.

• GSQL wines had nearly 9 times more caffeic acid than YNDQ wines and 5 times more ethyl ρ-coumarate than wines made from NXYM and NXYQY grapes.
• All wines had the highest percentage of gallic acid to total hydroxycinnamic acids.

Stilbenes

• SDYT had the highest levels of stilbenes, while YNDQ wines had the lowest levels.
• Trans-resveratrol was the most abundant stilbene in all wines, though was significantly variable between regions.

o   SDYT wines had nearly 7 times more trans-resveratrol than YNDQ wines.

Regional Similarities

•  Cluster analysis revealed that wines from the Helan mountain of Ning-Xia (NXYM, NXYQY) and GSQL regions were similar in regards to their phenolic composition.
• Wines from HBCL and SDYT regions were similar in regards to their phenolic composition.
• The YNDQ wines were different in regards to their phenolic composition than from all other regions.

Conclusions

According to the results of this study, the differences in phenolic composition of Chinese wines in this study indicate that the accumulation of phenolic compounds in grapes is strongly influenced by terroir effects.  Going further, those regions that were geographically closer to one another had wines that were statistically similar to one another in regards to their phenolic composition than regions that were geographically isolated or further away.  NXYQY, NXYM, and GSQL, all of which were similar in phenolic composition, are all located in the drier area of Western China with a cool-warm climate.  HBCL and SDYT were found to be statistically similar to each other in regards to the phenolic content of wines, and were both located in the wetter areas of Eastern China with a warm climate.  Finally, YNDQ was found to be different from all other regions in regards to phenolic composition of wine, and was located on the plateau valley zone of Southwest China with a warm-arid climate.

Overall, these results clearly show terroir effects, and confirm that different regions in China, like other regions around the world, produce grapes that result in wines with statistically different phenolic compositions.  Terroir effects were found to be similar for wines from the Helan mountain of Ningxia and Qilian of Gansu; for wines from Changli of Hebei and the Yantai of Shandong; and finally with the wines from the Deqin of Yunan having significantly different terroir effects from all other regions.

This knowledge of terroir effects in China should give viticulturalists and winegrowers the knowledge necessary for maintaining and caring for vines from each particular region, as well as giving the winemakers knowledge necessary for creating a high quality wine made from grapes with very specific phenolic profiles.  By applying the knowledge gained from this study, grape growing practices and winemaking techniques may be adjusted accordingly in order to optimize wine flavor/aroma quality in China, at the very least with Cabernet Sauvignon grapes.

I’d love to hear what you all think of this topic!  Please feel free to comment below (any unauthorized html tags will be promptly removed).

Source: Li, Z., Pan, Q., Jin, Z., Mu, L., and Duan, C. 2011. Comparison on phenolic compounds in Vitis vinifera cv. Cabernet Sauvignon wines from five wine-growing regions in China. Food Chemistry 125: 77-83.

DOI:  10.1016/j.foodchem.2010.08.039
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