|dc.description.abstract||The effects of varying levels of sulphur dioxide (SO₂) on the cold maceration process
was investigated with Pinot noir (Vitis vinifera L.) wine. The effects of these varying
levels on the wines composition and colour parameters were examined.
Cold maceration is a technique whereby grapes are crushed and placed at low
temperatures (4 - lO°C) in the presence 50 - 150 mgL⁻¹ SO₂. This process is believed to
provide a medium for the extraction of water soluble phenolic compounds, rather than
the alcoholic extraction employed in normal fermentations. The extraction of these
phenolic compounds was monitored from the juice through to six months of bottle age.
The changes were measured using both Spectrophotometric and High Performance
Liquid Chromatographic (HPLC) procedures.
Cold maceration wines were found to be not significantly different to the control wine in
all compositional parameters other than titrateable acidity which was found to be less
than the control for all the cold maceration wines. The unsulphured cold maceration
wine was not significantly different from the control wine in any of the spectral
measurements except natural degree of ionisation, in which it was higher, and total
phenolics, in which it was lower. These results indicate that the cold maceration process
alone does not alter the extraction of phenolic compounds. The HPLC analysis of the
wine confirmed the spectral results indicating that their were no significant differences
in the levels of extraction of anthocyanins.
The sulphured cold maceration wines were significantly greater than the control in
visible colour, colour density, total anthocyanins, natural degree of ionisation, ionised
anthocyanins and total phenolics. These results followed similar patterns with wine
ageing, at six months these wines were still significantly greater in all the measurements
apart from natural degree of ionisation. The results for the sulphured cold maceration
wines indicates that SO₂ is acting as a solvent for the extraction of phenolic compounds
The 50 mgL⁻¹ SO₂ cold maceration wine had similar colour and phenolic content to the
100 mgL⁻¹ SO₂ cold maceration wine at bottling, at six months the 50 mgL⁻¹ SO₂ cold
maceration wine still retained a similar colour to the 100 mgL⁻¹ SO₂ cold maceration
wine but had vastly reduced anthocyanin content. This indicates that for the grapes
utilised in this study the most appropriate level of addition at cold maceration would be
50 mgL⁻¹ of SO₂. With grapes of differing phenolic content the level of addition required