Xinyi will be speaking in Session 5. Fresh Science A. Click here to see more.
Colorimetric analysis of white wine allows the determination of three fractions of Cu associated with either organic acids (fraction I), thiols compounds (fraction II) or more strongly bound thiol/sulfide species (fraction III). Cu fraction I has been linked to suppression of reductive aroma in wine. The aim of this study was to establish the combined role of Cu fractions I and II in reductive aroma suppression, and to determine the duration of their protective effect.
Chardonnay and Pinot Grigio were bottled with three Cu addition rates (0, 0.3 and 0.6 mg/L) and analysed after 0, 2, 4, 8 and 12-14 months by colorimetry for Cu fractions, and GC-SCD for the key reductive aroma compounds. Sensory analysis was performed after 12-14 months.
The results showed that Cu fraction I and II concentration decreased in all wines after 2-months of bottle aging, and the rate of decrease was wine dependent. However, all wines with Cu addition at bottling had significant Cu fraction I and II concentration remaining after 8 months. Furthermore, the combined concentration of Cu fraction I and II above 0.015 mg/L provided the best hydrogen sulfide suppression, while Cu fraction I demonstrated the best methanethiol suppression when above 0.035 mg/L. The sensory data was consistent with this analytical data, showing more prominent reductive characters in the wines without Cu fraction I and II present during bottle aging. These results illustrate the key Cu fractions required for reductive aroma suppression and provide an indication of the duration of such protection.
Dr. Xinyi Zhang started her journey of wine in 2011. After obtaining two Masters degrees in Plant Science and Viticultural and Enology from the US and Europe, respectively, she began her PhD study at the National Wine and Grape Industry Centre (NWGIC) at Charles Sturt University (Wagga Wagga, Australia) in 2016, working on the topic of the impacts of viticultural conditions and juice composition on the oxidative and reductive development of wine. Since 2020 she commenced her position as a postdoctoral researcher at NWGIC. She has been working on metal speciation quantification, reductive-oxidative development of wine after bottling, especially the metal-induced spoilage of wine for the last three years.