Project number
WW JT 22-01
Project leader
Jose-Luis Aleixandre-Tudo
Institution
South African Grape and Wine Research Institute (SAGWRI), Stellenbosch University
Project completed
2024
EXECUTIVE SUMMARY
Objectives and Rationale
The press fraction of white and sparkling wine juice is commonly kept separate as pressing time and pressing force are increased. However, the sensorial effects of the pressed juice fractions in the final wine are not well understood. This project aimed to understand the sensorial impact of different initial juice phenolic levels.
Methods
The total phenolic index (ABS 280 nm), the individual phenolic composition by ultra-performance liquid chromatography (UPLC) and the main oenological parameters of musts and wines were obtained. The ultraviolet-visible and MIR spectral properties were also measured. Triangular tests and mouthfeel descriptors were sensorially assessed in the finished wines.
Key Results
- UPLC phenolics provide an accurate representation of phenolic fraction presence
- pH is a good indicator of the pressing operation progression
- Larger sensorial differences were observed in sparkling wines
- Hydroxycinnamic acids and flavanols appeared as markers of free-run and press fractions, respectively
- Spectroscopy calibrations can accurately predict phenolic content
Key Conclusion of Discussion
Phenolic measurements (hydroxycinnamic acids and flavanols) and pH should be considered when pressing still and sparkling wines. The sensory perception of sparkling wines was more severely affected by an increasing presence of press fraction. Spectroscopy-based calibrations can be used as a monitoring tool for pressing operations.
Take Home message for Industry
Monitoring the pressing operation with a combination of phenolics and acidity measurements can aid in maintaining wine quality while optimising the must extraction yield.