Research Note: Total Free Sulphydryls of Several White and Red Wines

Total free sulphydryl groups were assessed in several white and red wines. Ellman’s method was adaptedto wine samples for the determination of total –SH groups. Total –SH groups of white wines, as glutathione,were in the range of 315 to 734 and of red wines in the range of 163 to 467 mg/L. In most cases, white winesexhibited higher values than red wines. The high total sulphydryls of white and red wines indicate theirpotential contribution to wine antioxidant capacity

Decrease of Wine Volatile Aroma Esters by Oxidation

The effect of oxidation on the levels of wine volatile aroma esters was studied. Chardonnay wine wasbottled either in the presence of nitrogen or air in the headspace. Moreover, Fe II was added to the wineand the bottles were closed in the presence of air. Absorbance values were recorded at 420 nm (browningindex), while volatile esters were evaluated during storage using SPME/GC-MS. During wine storage ofup to nine months, wines bottled in the presence of air exhibited higher browning indexes and lowerlevels of several esters, such ethyl acetate, isoamyl acetate, ethyl hexanoate, ethyl octanoate and ethyldecanoate, in comparison to wines bottled under nitrogen. Addition of Fe II led to higher browning indexesand lower levels of several esters during wine storage. In addition, Fe II was added along with H2O2 toChardonnay wine and the bottles were closed in the presence of air. These additions led to wines withhigher browning indexes and lower levels of several esters during wine storage up to 40 days. The presentresults demonstrate that wine volatile aroma esters can be decreased by oxidation under semi-oxidativeand forced oxidative conditions. As a result, oxidation should be taken into account in the decrease ofaroma esters during wine storage

Protection of Aroma Volatiles in a Red Wine with Low Sulphur Dioxide by a Mixture of Glutathione, Caffeic Acid and Gallic Acid

The levels of several esters and other volatiles in Merlot-Cabernet Sauvignon blend red wines with typicalsulphur dioxide (35 mg/L), with low sulphur dioxide (25 mg/L), and with low sulphur dioxide (25 mg/L)plus a mixture of antioxidants (glutathione 20 mg/L, caffeic acid 60 mg/L and gallic acid 20 mg/L), wereevaluated at bottling, and after 18 and 36 months of ageing. Most volatiles decreased during wine storage.At bottling and after 18 months of storage, all three wines exhibited similar levels of volatiles. After 36months of storage, wines with low sulphur dioxide exhibited lower levels of many volatiles, such as ethylacetate, ethyl hexanoate, ethyl octanoate and 2-phenylethanol. On the other hand, wines with low sulphurdioxide plus the mixture of antioxidants exhibited similar levels of most volatiles in comparison with wineswith typical sulphur dioxide. The present results indicate that a mixture of glutathione, caffeic acid andgallic acid can protect esters and other volatiles in young red wine with low sulphur dioxide, and canreplace part of sulphur dioxide typically used

Winemaking Ability of Wild Yeast Strains and Comparative Volatile Profiles of Wines Fermented at 12.DEG. or 20.DEG.C.

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