Grape volatile organic compounds: analysis, biosynthesis, and profiling

Important contributors to grape quality are secondary metabolites, that will consequently define the wine quality and consumer acceptance. Secondary metabolites that influence the aromatic profile of grapes are volatile organic compounds (VOCs). Over the years, several hundred VOCs have been identified in grapes and wines, ranging from trace amounts up to several milligrams, belonging to the classes of terpenoids (monoterpenes, sesquiterpenes, and norisoprenoids), volatile phenols, methoxypyrazines, and aliphatic compounds. In grapes these compounds are influenced by numerous factors, such as grape variety, climate, and vineyard management practices. Thus, the analysis of grape VOCs, including sample preparation, identification, and quantification, is important to understand the influence of individual compounds in the aromatic profile. The biosynthetic pathways and genes involved are still not fully elucidated due to the large number of genes and precursors that participate in VOC metabolism and contribute to the complexity. Our aim is to provide an overview of volatile compounds synthesized in grape berries, explore their biosynthetic pathways, and discuss the analytical methods used for their identification and quantification.