Influence of viticulture practices on grape aroma precursors and their relation with wine aroma.

BACKGROUND: The effects of two different operations in the vineyard (basal leaf plucking and head trimming) on the synthesis of aromatic precursors in the grape and their impact on wine aroma have been studied and compared with a control sample. The study was carried out over two consecutive years with four different varieties. Glycosidic precursors were analysed in grapes and volatile compounds were studied in the wines. ANOVA studies were performed to study the effect of the vintage, variety and treatment for each of the compounds released from their precursors. RESULTS: Regarding treatment, the highest values in the concentration of free aroma compounds were achieved in the leaf plucking grapes, except for Chardonnay. Significant and positive correlations between aromatic precursors of terpenes present in grapes and their released form in wines were found for all varieties. For norisoprenoids, significant and positive correlations were exclusively found for Chardonnay and for phenols and vanillins in the year 2010 the correlations were high in three of the four varieties studied. CONCLUSION: In the assays of the 2 years, more precursors were synthesised in Merlot, Gewurztraminer and Tempranillo grapes if the vineyards were plucked.

Glycosidically bound aroma compounds and impact odorants of four strawberry varieties.

This paper reports the determination of glycosidically bound aroma compounds and the olfactometric analysis in four strawberry varieties (Fuentepina, Camarosa, Candonga and Sabrina). Different hydrolytic strategies were also studied. The results showed significant differences between acid and enzymatic hydrolysis. In general terms, the greater the duration of acid hydrolysis, the higher was the content of norisoprenoids, volatile phenols, benzenes, lactones, Furaneol, and mesifurane. A total of 51 aglycones were identified, 38 of them unreported in strawberry. Olfactometric analyses revealed that the odorants with higher modified frequencies were Furaneol, γ-decalactone, ethyl butanoate, ethyl hexanoate, ethyl 3-methylbutanoate, diacetyl, hexanoic acid, and (Z)-1,5-octadien-3-one. This last compound, described as geranium/green/pepper/lettuce (linear retention index = 1378), was identified for the first time. Differences with regard to fruity, sweet, floral, and green aroma characters were observed among varieties. In Candonga and Fuentepina, the green character overpowered the sweet. In the other two strawberry varieties sweet attributes were stronger than the rest.