Published: February 24, 2011 r2011 American Chemical Society 2543 dx.doi.org/10.1021/jf104141f | J. Agric. Food Chem. 2011, 59, 2543–2553 ARTICLE pubs.acs.org/JAFC Analytical and Sensorial Characterization of the Aroma of Wines Produced with Sour Rotten Grapes Using GC-O and GC-MS: Identification of Key Aroma Compounds Andr  e Barata, † Eva Campo, § Manuel Malfeito-Ferreira, † Virgílio Loureiro, † Juan Cacho, § and Vicente Ferreira* ,§ † CBAA, Laboratory of Microbiology, Instituto Superior de Agronomia, Technical University of Lisbon, Lisboa, Portugal § Laboratory for Aroma Analysis and Enology, Arag on Institute of Engineering Research (I3A), Department of Analytical Chemistry, Faculty of Sciences, University of Zaragoza, Zaragoza 50009, Spain ABSTRACT: In the present work, the aroma proﬁles of wines elaborated from sound and sour rot-infected grapes as raw material have been studied by sensory analysis, gas chromatography-olfactometry (GC-O), and gas chromatography-mass spectrometry (GC-MS), with the aim of determining the odor volatiles most likely associated with this disease. The eﬀect of sour rot was tested in monovarietal wines produced with the Portuguese red grape variety Trincadeira and in blends of Cabernet Sauvignon and sour rotten Trincadeira grapes. Wines produced from damaged berries exhibited clear honey-like notes not evoked by healthy samples. Ethyl phenylacetate (EPhA) and phenylacetic acid (PAA), both exhibiting sweet honey-like aromas, emerged as key aroma compounds of sour rotten wines. Their levels were 1 order of magnitude above those found in controls and reached 304 and 1668 μgL -1 of EPhA and PAA, respectively, well above the corresponding odor thresholds. Levels of γ-nonalactone also increased by a factor 3 in sour rot samples. Results also suggest that sour rot exerts a great eﬀect on the secondary metabolism of yeast, decreasing the levels of volatiles related to fatty acids and amino acid synthesis. The highest levels of γ-decalactone of up to 405 μgL -1 were also found in all of the samples, suggesting that this could be a relevant aroma compound in Trincadeira wine aroma. KEYWORDS: sour rot, wine, aroma, ﬂavor, Trincadeira, GC-O, GC-GC, ethyl phenylacetate, phenylacetic acid, γ-lactones ’ INTRODUCTION Fruit rots often determine harvest date and inﬂuence grape quality in warm and humid grape-growing regions. 1 The cause of grape sour rot, appearing 3-4 weeks before ripening, is the combined activity of three groups of factors: (a) primary factors (insects, birds, diseases such as mildews, grape berry moth attacks (Lobesia botrana), mechanical and physiological injuries), which damage the berry skin; (b) secondary microorganisms (bacteria, yeasts, and other fungi) that penetrate the broken skins of the injured berries; and (c) secondary insects (Drosophila ﬂies and beetles) quickly attracted by the rotting and fermenting grapes, enhancing the process and accelerating its spread throughout the entire cluster. 2,3 Sour rot is characterized by the main role of yeasts in the rotting process. The most frequently isolated yeast species from sour rot-damaged grapes are Hanseniaspora uvarum, Candida stellata, Metshnikowia pulcherrima, Candida krusei, and Kloeckera apiculata, 4,5 and Zygoascus hellenicus and Issatchenkia occidentalis. 6 Other microorganisms, especially the bacteria Acet- obacter, are involved in sour rot infection. Among the transfor- mations carried out by acetic acid bacteria, the most important is the oxidation of ethanol into acetic acid. Indeed, sour rot owes its name to the strong and pungent odor of acetic acid (vinegar) present on rotten grapes and is characterized by grape pulp browning, disaggregation of the internal tissues, detachment of the rotten berry from the pedicel, and grape dropping. 5,7 In hot climates, Botrytis cinerea has occasionally been isolated from grape sour rot. 8 However, sour rot development is not dependent on B. cinerea infection, 9 in contrast to the predominant role of this fungal pathogen on bunch rot in regions with relatively cool fruit-ripening conditions. Sour rot aﬀects both crop yield and wine quality. It is commonly accepted between winemakers that the viniﬁcation of damaged grapes is associated with the production of low- quality wines with weak storage/aging potential. The diverse group of organisms involved in sour rot is known to alter fruit composition as a result of the production of high levels of a wide range of metabolites including acetic acid, glycerol, ethyl acetate, ethanol, acetaldehyde, and galacturonic and gluconic acids. 10-12 In the late 1970s, Loinger et al. 13 tried to clarify for the ﬁrst time the consequences of sour rot on wine quality, investigating the eﬀect of the disease on the sensorial characteristics of wines from the Semillon grape variety. This study showed that clusters with 20-40% rotten berries resulted in a clear and marked reduction in wine quality, whereas wines from clusters with 80% rot were totally rejected. Later, Zoecklein et al. 10 determined the inﬂuence of sour rot on white Riesling must monoterpenic composition. Sour rot had no inﬂuence on free or bound volatile terpenes, but did alter the terpene proﬁle by reducing monoterpene alcohols, whereas monoterpene oxides increased. Trincadeira is a neutral Vitis vinifera L. red native grape variety widely planted in Portugal, 14 highly susceptible to Received: October 22, 2010 Accepted: January 30, 2011 Revised: January 5, 2011