DNA and type of grain: which factor does better explain sensory differences of sessile and pedunculate oaks?
Abstract
Sessile oak and pedunculate oak have shown several differences of interest for enological purposes. Tannic and aromatic composition among sessile oak or pedonculate oak has been well studied. Sessile oak is generally more aromatic than pedunculated, while the later is more tannic. This scientific point of view is rarely applied to classify oak in cooperages. Most coopers use the type of grain to distinguish wide and thin grain. While the former leads to barrels with less aromas and more tannins, often oriented to alcohols, the later is more aromatic and convenient for wine ageing. Does the traditional cooper grading by grain have a link with species in the chemical expression of oak? A protocol has been built to monitor the effect of the two species from the tree to the barrel, and the wine aged in them. In this study the first results observed during the yard seasoning are presented. Several oak trees from the same plot in the Forêt Domaniale de Saint Palais, France were studied. Recent developments of DNA tests can identify oak species or hybrid (instead of morphological determination that can be approximate). DNA tests were performed on each tree to identify their species. After excluding hybrids, only pure sessile oak and pure pedunculate oak were considered and separated into two batches. Staves were split from each oak batch, classified according to their type of grain and put in the yard for 24 months of seasoning. Chemical, sensory and also wood microflora analyses have been made at the beginning (T0), after 6 months (T6), after 12 months (T12) and after 18 months (T18) of seasoning. Among the sessile oak, two groups can be distinguished. The former is extremely rich in lactones whereas the later is poorer and can be considered as a “neighbor” of pedunculate oak that is poor in lactones but richer in tannins. Pedunculate oak is homogeneous whether its grain is tight or wide. Sessile oak seems to be impacted by the type of grain. The richer group is related to only thin grain while the poorer is made of mainly wide grain. Tastings on oak shavings showed that sessile oak has spicy, fresh and pastry aromas whereas pedunculate oak was acetic. Moreoever the later showed a more important and varied microflora. These first three steps of the yard seasoning have shown that the grain have a true effect on the aromatic composition of sessile oak. Are these differences kept along yard seasoning, barrel making and wine ageing?
Issue: Macrowine 2016
Type: Poster
Authors
*Chêne & Cie