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Chemical characterisation of oak wood with aim to optimise its using in wine-making


Author: Andrei Prida
Degree:doctor of engineering
Speciality: 05.18.07 - Technology of alcoholic and non-alcoholic drinks
Year:2004
Scientific adviser: Boris Găina
doctor habilitat, professor
Institution: National Institute for Winegrowing and Winemaking
Scientific council:

Status

The thesis was presented on the 10 September, 2004
Approved by NCAA on the 23 December, 2004

Abstract

Adobe PDF document0.47 Mb / in romanian

Thesis

CZU 663.2.54:633.872

Adobe PDF document 12.20 Mb / in romanian
212 pages


Keywords

oak, specie, origin, gc-ms, hplc, ellagitannins, volatile substances, electronic tongue, seasoning, toasting, chips, wine aging, spirit maturation

Summary

The objective of this thesis is to elucidate certain elements relating with oak use in enology : relations between chemical composition and characteristics of wood (origin, specie, “grain”...), certain cooperage practices (seasoning, toasting), as well as influence of oak on chemical and organoleptical properties of wines and spirits.

It was shown that in single forest site limits “specie” effect predominate at ecological conditions of vegetation, the most relevant indexes for species differentiation being castalagin, vescalagin, eugenol, cis et trans-whisky-lacton. The correlation between ellagitanin content and annual ring width was established for the oak specie Quercus robur. Two naturally occurring groups of Quercus petraea oaks were found: rich and poor in whisky-lacton (its content is similar to pedunculate oak). Identified for the first time in oak the 3,4,5 –trimethoxybenzylaldehyde and 3,4,5 – trimethoxybenzylalcohol are found to be the markers of American oak. Their contents are 5-10 times higher in American oak than in European species. The chemical composition of Eastern European wood is close to French oak however differs by higher level of eugenol and vanillin. «Electronic tongue » methodology allows quantification of sensorial and analytical properties of oak extracts, as well as control of natural seasoning of wood. Toasting until 48 hours at 1500C provides to accumulate biopolymer degradation compounds, whereas the principal oak extractives are not destructed. This process stands at the base of enological oak chips processing. The wine-stave wood interaction takes place in the layer of the first 10 mm, whereas the most active penetration is observed till the first 4 mm of barrel wood. Comparing organoleptical sensations, oak wood tannins were found to be at intermediary place among the other enological tannins. Oak and chestnut tannins could be differentiated using ratios of different isomeric forms of ellagitanins (vescalagin, castalagin, roburins A-C) and concentration of ellagic acid content.

Using of Moldavian oak chips allows elaboration of quality wines, oak extracts and brandies and good management of their production.