Abstract
Flavour plays an essential role in wine quality. The understanding of flavour chemistry and perception can provide
deeper knowledge on wine characteristics from specific regions. Due to climate change and modern breeding, Denmark
becomes an emerging winemaking country where some early ripening cool-climate grape cultivars have been grown.
However there is little knowledge on the flavour properties and potential of Danish wines. The overall aim of this
project was to investigate the sensory characters and chemical composition of wines from different cool-climate grape
cultivars and co-fermentations. Such systematic studies on the flavour characters of wines can contribute to a rational
development of local wine styles.
The flavour characters of commercial young mono-varietal Danish white wines from the Solaris cultivar were firstly
studied. Conventional descriptive sensory analysis showed that several wines were characterised by floral and fruity
flavours, such as banana, peach/apricot and strawberry, while the remainder were mainly described by less desirable
flavours for white wine, such as chemical, cheese and rooibos/smoke. Partial least squares regression of the sensory and
instrumental analyses showed that acetates and ethyl esters of short straight-chain fatty acids were plausible contributors
to young Solaris wine aroma, and closely correlated with floral and fruity odours. Ethyl esters of branched-chain fatty
acids were less linked to pleasant flavours. Unpleasant flavours were mostly likely caused by inadequate sulphite
management, which resulted in accelerated aging, oxidation and/or spontaneous malolactic fermentation. These findings
indicated that producers in Denmark should be more cautious in their use and management of sulphite in wine making.
To develop a rapid methodology for evaluating sensory properties of wines, different variations of Napping and Flash
Profile methods were tested using model wines. It turned out that conducting Napping with panel training on either the
method (training on how to arrange samples on the sheet) or the product (familiarization with the sensory properties of
the wines) improved the outcome. The classical Flash Profile and its modified version gave a similar sample space, but
the latter made the ranking task easier for assessors. The Napping method could mainly highlight qualitative sample
differences, whereas the Flash Profile provided a more precise product mapping on quantitative differences between
wine samples. Hence, the modified Flash Profile was used in the studies on co-fermentations as a sensory screening
method.
Different indigenous non-Saccharomyces yeasts were used in co-culture with Saccharomyces cerevisiae to increase the
flavour complexity of wine. For the Solaris wine, Metschnikowia strains (M. fructicola and M. chrysoperlae) increased
acetates such as (Z)-3-hexenyl acetate, and ethyl esters of straight-chain fatty acids such as ethyl pentanoate, leading to
wines described with floral and fruity attributes. Hanseniaspora uvarum had a high production of ethyl acetate and
acetic acid, resulting in wines described by acetone and chemical attributes. Similar performances of non-
Saccharomyces yeasts were found in rosé wines from three grape cultivars Bolero, Rondo and Regent. Furthermore, it
was found that there was a grape cultivar based segregation with respected to produced wine flavour.
In summary, this PhD project increased knowledge on the flavour characters of wines in relation to cool-climate grape
cultivars and different fermentation approaches, as well as contributed to sensory methodology advances
deeper knowledge on wine characteristics from specific regions. Due to climate change and modern breeding, Denmark
becomes an emerging winemaking country where some early ripening cool-climate grape cultivars have been grown.
However there is little knowledge on the flavour properties and potential of Danish wines. The overall aim of this
project was to investigate the sensory characters and chemical composition of wines from different cool-climate grape
cultivars and co-fermentations. Such systematic studies on the flavour characters of wines can contribute to a rational
development of local wine styles.
The flavour characters of commercial young mono-varietal Danish white wines from the Solaris cultivar were firstly
studied. Conventional descriptive sensory analysis showed that several wines were characterised by floral and fruity
flavours, such as banana, peach/apricot and strawberry, while the remainder were mainly described by less desirable
flavours for white wine, such as chemical, cheese and rooibos/smoke. Partial least squares regression of the sensory and
instrumental analyses showed that acetates and ethyl esters of short straight-chain fatty acids were plausible contributors
to young Solaris wine aroma, and closely correlated with floral and fruity odours. Ethyl esters of branched-chain fatty
acids were less linked to pleasant flavours. Unpleasant flavours were mostly likely caused by inadequate sulphite
management, which resulted in accelerated aging, oxidation and/or spontaneous malolactic fermentation. These findings
indicated that producers in Denmark should be more cautious in their use and management of sulphite in wine making.
To develop a rapid methodology for evaluating sensory properties of wines, different variations of Napping and Flash
Profile methods were tested using model wines. It turned out that conducting Napping with panel training on either the
method (training on how to arrange samples on the sheet) or the product (familiarization with the sensory properties of
the wines) improved the outcome. The classical Flash Profile and its modified version gave a similar sample space, but
the latter made the ranking task easier for assessors. The Napping method could mainly highlight qualitative sample
differences, whereas the Flash Profile provided a more precise product mapping on quantitative differences between
wine samples. Hence, the modified Flash Profile was used in the studies on co-fermentations as a sensory screening
method.
Different indigenous non-Saccharomyces yeasts were used in co-culture with Saccharomyces cerevisiae to increase the
flavour complexity of wine. For the Solaris wine, Metschnikowia strains (M. fructicola and M. chrysoperlae) increased
acetates such as (Z)-3-hexenyl acetate, and ethyl esters of straight-chain fatty acids such as ethyl pentanoate, leading to
wines described with floral and fruity attributes. Hanseniaspora uvarum had a high production of ethyl acetate and
acetic acid, resulting in wines described by acetone and chemical attributes. Similar performances of non-
Saccharomyces yeasts were found in rosé wines from three grape cultivars Bolero, Rondo and Regent. Furthermore, it
was found that there was a grape cultivar based segregation with respected to produced wine flavour.
In summary, this PhD project increased knowledge on the flavour characters of wines in relation to cool-climate grape
cultivars and different fermentation approaches, as well as contributed to sensory methodology advances
| Original language | English |
|---|
| Publisher | Department of Food Science, Faculty of Science, University of Copenhagen |
|---|---|
| Number of pages | 129 |
| Publication status | Published - 2016 |
