Finding Markers for Wine Aroma

Scientists in Portugal have been investigating important molecular and biochemical changes that occur when grapes are growing to find out how they affect wine aroma. In a study recently published in PLOS ONE, the scientists performed genetic analysis combined with metabolic profiling data collected using gas chromatography–mass spectrometry (GC–MS) to highlight key markers.¹

The research group selected three Portuguese elite cultivars as the model for their study – Trincadeira, Aragones (Tempranillo in Spain) and Touriga Nacional. There has been a recent interest in these specific cultivars because of their potential in the production of highly aromatic wine. According to the paper, increased knowledge of metabolic pathways that result in grape ripening will contribute to the maintenance of good wine aroma in the face of changing climates.

There are two main stages in the ripening of grapes. The first stage is characterized by the production of tannins and hydroxycinnamic acids, whereas the second stage is characterized by production of soluble sugars, anthocyanins and flavour-enhancing compounds.

A multi-faceted approach was taken to the analysis of the samples collected. Genetic analysis determined the effect of gene expression on the ripening of the grapes using reverse transcription–polymerase chain reaction (RT–PCR). This technique directly relates gene expression to environmental conditions. This data was linked to metabolomic profiling data collected using GC–MS. Gas chromatography coupled to electron ionization time-of-flight mass spectrometry (GC–EI–TOF-MS) quantified the concentrations of compounds such as fatty acids, phenylpropanoids and sugars. Headspace GC–EI–MS was performed to quantify volatiles.

The results of the study showed a distinct metabolic profile of compounds that were produced before and after ripening in addition to distinctive gene expression profiles. This research therefore provides candidate molecular and metabolic markers of pre-ripe and ripe berries in the three Portuguese cultivars studied, according to the authors.

Reference
1. P. Agudelo-Romero et al, PLOS ONE, 8(4) e60422 (2013).

Further Reading
“Bugs Boost Wine Aroma”, The Column9(1) http://www.chromatographyonline.com/lcgc/Bugs-boost-wine-aroma/ArticleStandard/Article/detail/802950