Analyzing Regional Aroma Characteristics of Wines with GC-MS

A recent study investigated the differences in regional aroma characteristics among spontaneously fermented Cabernet Sauvignon wines produced from seven sub-regions of Shangri-La, China. The volatile compositions and typical aroma profiles of these wines were comprehensively analyzed by using headspace micro-extraction coupled with gas chromatography-mass spectrometry (HS-SPME/GC-MS), odor activity value (OAV), and olfactory evaluation. The findings could enhance our understanding of the unique environmental factorsaffecting wines within Shangri-La, thereby providing valuable reference for further producing high-quality wines with distinctive regional characteristics, the scientists wrote. An article presenting these findings was published in Scientific Reports (1).

The Shangri-La wine region in China exhibits great potential for producing high-quality wines with distinct regional characteristics due to its complex climate and landform, with previously studies revealing the significant variations in the biodiversity patterns of indigenous yeasts in spontaneously fermented Cabernet Sauvignon wines from different vineyards within this region (2). Further investigation demonstrated that some of these indigenous yeasts shown unique aroma production behaviors in synthetic grape juice fermentation (3). Considering the crucial role of yeasts in the formation of volatiles present in wine, the researchers believe that great variations of volatile compositions among these spontaneously fermented wines could be expected (1).

Because contemporary trends in winemaking place greater emphasis on the microbial terroir (a French term used to describe the environmental factors that affect a crop's phenotype, including unique environment contexts, farming practices, and a crop's specific growth habitat [4]) and challenge the utilization of commercial S. cerevisiae yeast starters, interest has grown in the employment of spontaneous fermentation (a process where the sugars of the grapes are naturally fermented by the yeasts present on the grapes rather than adding starter cultures) to authentically express the unique flavors linked to the geographical origin of the grape (5,6).

Grapes from seven vineyards exhibited varying degrees of ripeness, with reducing sugar concentrations ranging from 186.74 to 265.95 g/L, titratable acidity ranging from 3.42 to 8.55 g/L, and pH values ranging from 3.26 to 3.97. A total of 59 volatile compounds, including 20 esters, 19 alcohols, 7 carbonyl compounds, 5 terpenes, 5 fatty acids, 1 C13-norisoprenoid, and 2 others (2), were identified in seven spontaneously fermented Cabernet Sauvignon wines. Based on their OAVs, six alcohols, seven esters, two terpenes, one C13-norisoprenoids, and three volatile fatty acids were identified as key volatiles. The principal component analysis showed the distinct compositions of these 19 key volatiles among the 7 regional wines. The olfactory analysis revealed the certain differences in the aroma profiles, particularly “tropical fruit,” “dried fruit,’ “vegetal,’ and “sweet” across these regional wines (1).

This study confirmed that spontaneously fermented Cabernet Sauvignon wines produced from seven sub-regions of Shangri-La exhibit distinctive volatile compositions and aroma profiles, the authors wrote. This may largely be attributed to the unique metabolic behaviors of certain indigenous yeasts involved in spontaneous fermentation. Further studies are needed on the correlations between microbial community succession and flavor compound formation during grape berry development and fermentation will provide more valuable information of the terrior in this region (1).

Cabernet Sauvignon red wine and grapes. © The Little Hut - stock.adobe.com

References

1. Sun, Q.; Cui, R.; Zhao, Y. Regional Aroma Characteristics of Spontaneously Fermented Cabernet Sauvignon Wines Produced from Seven Sub-Regions in Shangri-La of China. Sci. Rep. 2024, 14 (1), 24566. DOI: 10.1038/s41598-024-76353-6

2. Zhao, Y.; Sun, Q,; Zhu, S,; Du, F.; Mao, R.; Liu, L.; Tian, B.; Zhu, Y. Biodiversity of Non-Saccharomyces Yeasts Associated with Spontaneous Fermentation of Cabernet Sauvignon Wines from Shangri-La Wine Region, China. Sci Rep. 2021, 11 (1), 5150. DOI: 10.1038/s41598-021-83216-x

3. Zhao, Y.; Sun, Q,; Tian, B.; Zhu, S.; Du, F.; Mao, R.; Li, S.; Liu, L.; Zhu, Y. Evaluation of Four Indigenous Non-Saccharomyces Yeasts Isolated from the Shangri-La Wine Region (China) for Their Fermentation Performances and Aroma Compositions in Synthetic Grape Juice Fermentation. Journal of Fungi 2022, 8 (2),146. DOI: 10.3390/jof8020146

4. Terrior definition. Wikipedia. https://en.wikipedia.org/wiki/Terroir (accessed 2024-10-30).

5. Mas, A.; Portillo, M. C. Strategies for Microbiological Control of the Alcoholic Fermentation in Wines by Exploiting the Microbial Terroir Complexity: A Mini-Review. Int. J. Food Microbiol. 2022, 367, 109592. DOI: 10.1016/j.ijfoodmicro.2022.109592

6. Francesca, N. et al. The Wine: Typicality or Mere Diversity? The Effect of Spontaneous Fermentations and Biotic Factors on the Characteristics of Wine. Agric. Agric. Sci. Proc. 2016, 8, 769–773. DOI: 10.1016/j.aaspro.2016.02.064