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A new technology for imparting oak character to wine: application to a New Zealand chardonnay wine

An analytical method using gas chromatography combined with mass spectrometry in selected ion mode (GC/MS-SIM) was developed to monitor the levels of aromatic woody compounds present in a New Zealand Chardonnay wine at the part per billion level. This technique was also used to determine the levels of compounds present in oak wood. Sensory evaluations of experimental wines were carried out by experienced winemakers. Each assessment was complemented by the chemical analyses to provide an overall impression for the wines. The combination of winemaker’s perception and chemical determinations were employed with all wine ageing and wooding trials carried out as part of the project. A selection of ageing containers were chosen to monitor the ageing profiles of a Chardonnay wine under different conditions. New French oak barrels are the preferred ageing containers by the winemakers at Morton Estate Winery; especially those from Seguin Moreau and Dargaud & Jaegle. New French oak releases extractable compounds at a rate which is considered desirable. Wines which were aged in new French oak were described as ‘elegant’ and showed ‘crisp, fresh oaky character.’ Wines aged in used barrels and stainless steel scored lower in the sensory evaluations. New French oak barrels contain elevated levels of aromatic compounds on the interior surface of each barrel due to thermal modifications which occur during the toasting process. The levels of these compounds are lower in used oak barrels. It was found that heating used oak wood in an electric kiln increased the levels of aromatic compounds in the wood. Wrapping the oak in foil allowed longer toasting times and produced higher levels of thermal degradation products. These same products are considered desirable in higher quality wines. The rates of release of extractable compounds from wood into ethanolic solutions and the effect of surface area was investigated. Toasted oak cubes of a particular dimension were found to release these compounds at a rate similar to that of new French oak. These cubes were suspended throughout the body of the wine using a new technology called the ‘oak necklace.’ The oak ageing trials over the 1993, 1994 and 1995 vintages provided encouraging evidence that Chardonnay wine exhibiting new oak character can be achieved using this new technology.
Type of thesis
The University of Waikato
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