Wine Chemistry and Flavor: Looking into the Crystal Glass

Abstract

Over the past century, advances in analytical chemistry have played a significant role in understanding wine chemistry and flavor. Whereas the focus in the 19th and early 20th centuries was on determining major components (ethanol, organic acids, sugars) and detecting fraud, more recently the emphasis has been on quantifying trace compounds including those that may be related to varietal flavors. In addition, over the past 15 years, applications of combined analytical and sensory techniques (e.g., gas chromatography-olfactometry) have improved the ability to relate chemical composition to sensory properties, whether identifying impact compounds or elucidating matrix effects. Many challenges remain, however. This paper discusses some of the recent research aimed at understanding how viticultural and enological practices influence grape and wine volatiles. In addition, the challenges in linking composition to sensory properties will also be reviewed. Finally, future advances in linking grape, yeast, and human genomics to wine chemistry and flavor will be briefly discussed.

Origins of Grape and Wine Aroma. Part 1. Chemical Components and Viticultural Impacts

“…The origins of wine aroma and bouquet (here referred to collectively as aroma) have been of major interest over the last century, with advances made through the development and use of modern analytical techniques coupled to hybrid analytical/sensory methods (Guth 1997b, López et al 1999, Francis and Newton 2005, Polášková et al 2008, Ebeler and Thorngate 2009) and through multivariate statistical comparisons with descriptive sensory analysis (Noble and Ebeler 2002, Lee and Noble 2003, 2006, Escudero et al 2007, Sáenz-Navajas et al 2010. The combination of analytical and sensory methodologies has been particularly important in resolving effects of interactions of aroma compounds with the nonvolatile matrix (Pineau et al 2007, Robinson et al 2009, Sáenz-Navajas et al 2010) as well as with other volatile compounds (Atanasova et al 2005, Escudero et al 2007, Pineau et al 2009).…”

“…The major groups of aroma compounds found in wine are monoterpenes, norisoprenoids, aliphatics, higher alcohols, esters, phenylpropanoids, methoxypyrazines, and volatile sulfur Newton 2005, Ebeler andThorngate 2009). Numerous studies have investigated the composition of specific grape cultivars in an effort to better understand the origins of varietal aroma (Sefton et al 1993, Schneider et al 2002.…”

Genetic Analysis of the Biosynthesis of 2-Methoxy-3-Isobutylpyrazine, a Major Grape-Derived Aroma Compound Impacting Wine Quality

“…Wine flavor is the result of a complex mixture of volatile compounds in the headspace of the glass that induces feelings of pleasure at the brain level (Shepherd, 2006). During the last 40 years, over 800 volatile molecules have been formally identified in wines, in concentrations ranging from hundreds of milligrams per liter down to a few picograms per liter (Ebeler and Thorngate, 2009;Styger et al, 2011). Among all of them, a relatively limited number of compounds, called varietal (or primary) aromas, play a crucial role in wine flavor and typicality.…”

Origins of Grape and Wine Aroma. Part 2. Chemical and Sensory Analysis

“…Modern commercial GC-MS instrumentation combines compound ionization, resulting in unique mass spectral fragmentation patterns, with high-resolution separation of the resulting ions, and selective and sensitive mass detection. Numerous reviews discuss various aspects of wine composition with an emphasis on the role that GC-MS analysis has played in contributing to current knowledge in the field of wine and grape chemistry (Schreier et al 1976, Ebeler 2001, 2012, Ebeler and Thorngate 2009, Hayasaka et al 2005, Polášková et al 2008.…”

“…Therefore, we have chosen to focus on selected recent applications to demonstrate the power and types of information that can be obtained with current analytical and sensory approaches. The reader is also referred to several reviews for more detailed discussions of selected topics (Francis and Newton 2005, Lesschaeve 2007, Plutowska and Wardencki 2008, Polášková et al 2008, Ebeler and Thorngate 2009, Muñoz-González et al 2011, Ebeler 2012.…”