The aim of the study was to evaluate the effect of PVPP on colour, polyphenol and volatile thiol content during rosé fermentation.
Project layout:
- Blends from Grenache noir and Merlot free run juice in two different ratios were used.
- The juice was fermented with 20 g/hl Zymaflor X5 and 30 g/hl Superstart at 20⁰C.
- Four different dosages of PVPP were added to the must at the end of the first third of fermentation.
- Colour, polyphenol content and volatile thiols were measured after the completion of fermentation.
Results:
- The higher the PVPP dosage used the more colour loss was observed.
- PVPP affected mostly flavanol, flavonol and anthocyanin concentrations (decreasing it with increased dosages).
- Lower dosages of PVPP (20 – 40 g/hl) increased volatile thiol concentrations compared to the control wine. The researchers hypothesised that it is most probably as a result of the early removal of polyphenols that could have potentially oxidised into quinones at a later stage during fermentation.
- Higher dosages of PVPP (60 – 80 g/hl) increased volatile thiols to a lesser extent than the lower dosages.
The significance of the study:
PVPP treatment is often used in rosé production to diminish the chances of potential problems associated with excess polyphenols. This study indicated that PVPP has an affinity for certain classes of polyphenols and that colour is decreased in a dosage dependent manner. PVPP addition during fermentation can also have a positive impact of volatile thiol concentrations.
Reference:
Gil, M. et al. (2019). Effect of polyvinylpolypyrrolidone treatment on rosés wines during fermentation: Impact on color, polyphenols and thiol aromas. Food Chemistry 295, 493-498. https://doi.org/10.1016/j.foodchem.2019.05.125
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