awri - do during grape processing - martin p. day, olav aagaard and elizabeth j. waters - 3rd july,...
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For the winemakers...TRANSCRIPT
1 The Australian Wine Research Institute, PO Box 197, Glen Osmond (Adelaide) SA 5064, Australia 2 Nomacorc SA, ZI Les Plénesses, Chemin de Xhénorie, 7,
4890 Thimister-Clermont, Belgium
Dissolved oxygen measurements during grape processing in the winery
Martin P. Day1, Olav Aagaard2 & Elizabeth J. Waters1
Introduction
. A lot is now known about dissolved oxygen (DO) in bottled wine but how much is introduced right at the beginning of the winemaking process?
. This talk is a summary of some of our observations on crushing and pressing => context of the complex phenomena happening.
Summary of talk
. Introduction . What happens when grapes are
crushed . Measurement methodology . Observations from crushing . Observations during
pressing – Normal mode
– Inert mode . DO values
after pressing . Conclusions
What happens when grapes are crushed? • Caftaric acid:1,2diphenol (catechol) forms quinone radicals with PPO in oxygen • The sulfite ion protects the must by reducing the quinone back • p-Coutaric and other phenols can also form reactive radicals •
•
Flavonoids (esp. catechins) can also form radicals and
•
•
Implications for improving crushing
. Inert the crusher ! . US patent 05/107176
granted June 1973 ! . Commercial equipment now
on market:
. LOQ of PSt3 dot ca 20 ppb
. After only a few hours, the DO has dropped to around 20 ppb !
. What implication does this have for good fermentation kinetics?
Conclusions
. Clearly grapes are exposed to a substantial amount of oxygen as
soon as they are ruptured.
. A lot more work needs to carried out to understand how and
when critical oxygen exposure occurs. . Is protecting must from oxygen really what you want?
. Technology can help -modifications seem quite simple
Thanks
. AWRI: Maurizio Ugliano, Gemma West, Mark Braybrook
. Nomacorc: Mai Nygaard, Jean-Baptiste Dievel
. Josef Chromy Wines: Jeremy Dineen
This work was supported financially by Australia's grapegrowers and winemakers through their investment body the Grape and Wine Research and Development Corporation, with matching funds from the Australian Government, and by Pernod Ricard Pacific.
The AWRI is a member of the Wine Innovation Cluster located in Adelaide.