AGING PATTERNS OF VARIETAL VOLATILE PROFILES OF WHITE WINES: A CASE STUDY ON 18 ITALIAN VARIETAL WHITE WINES

Abstract

During wine aging many compositional changes take place. In particular, aroma undergoes dramatic modifications through a wide range of reactions that to date are only partly understood. Italy owns one of the largest ampelographic heritages worldwide, with over three-hundred different varieties. Among these, many white grapes are employed for the production of dry still white wines. Some of these wines are consumed young while others are more prone to aging. For many of these wines, the aging patterns related to volatile composition are still unknown.

An extensive survey was conducted on 18 monovarietal Italian still white wines with the aim of elucidating the behaviours of different volatile compounds during aging. In particular, a range of volatile compounds including terpenes, norisoprenoids, benzenoids and volatile sulfur compounds was investigated. A total of 108 different samples were analysed, including Nosiola, Vermentino, Müller-Thurgau, Greco di Tufo, Garganega, Lugana, Erbaluce di Caluso, Pinot Grigio, Cortese, Arneis, Albana, Pallagrello, Falanghina, Fiano, Ribolla Gialla, Vernaccia, Gewürztraminer, Verdicchio. All wines were adjusted to 30 mg/L of free SO2 and submitted to an accelerated aging protocol involving storage for 30 days 10 °C, 40 °C and 60°C in oxygen-free environment. Volatile compounds were analysed by means a combination of analytical methods based on SPME-GC-MS.

During aging some common trends were observed, among which a decrease in linear terpenes and an increase in bicyclic terpenes, non-megastigmane norisoprenoids and volatile sulfur compounds. From a quantitative point of view, the extent of these transformations varied significantly according to wine type. Besides Gewürztraminer, which was generally rich in terpenes, other wine types such as Vermentino Verdicchio and Lugana showed peculiar terpene patterns, for example accumulation of above-threshold levels of the bicyclic terpene 1,4-cineole. Regarding non-megastigmane norisoprenoids, Falanghina and Vermentino were found to accumulate high levels of TDN and vitispirane, which was not observed in other wines. Greco accumulated during aging the highest amount of DMS, showing an average content above the odor threshold. Müller-Thurgau, Nosiola and Vermentino also showed concentrations of DMS above the odor threshold after aging. In addition, the latter varieties also showed high accumulation of methanethiol.

As most of these patterns were not seen in young wines, this work highlights the important contribution of aging to the expression of aroma characters that are specific to the identity of individual varieties or wine types.