Once the break of the cellular grape berry compartimentation occurred during the various technological operations (de-stemming, pressing, crushing, etc.), the dissolution of the oxygen in the must leads to a certain number of oxidation reactions which modify, to varying degrees, the initial chemical composition of the must. This cellular disintegration indeed puts in contact the substrates of oxidation - the native phenolic compounds of the grape -, oxygen and the enzymatic polyphenoloxidase activity (PPO) of the grape. The colour of the must then modifies, evolving towards brown tones more or less pronounced with frequently a change of its transparency and its aroma.
In rather sensitive or very sensitive musts to oxidation, a regeneration of the initial phenolic substrates occurred by a reaction of coupled oxidation, immediately followed by a new oxidation being translated by a greater consumption of oxygen. The capacity of a must to oxidise can be thus measured only by measuring finely the consumption of oxygen of this must in very controlled conditions, but also by measuring the evolution of hydroxycinnamic acids, the GRP (Grape Reaction Product) and their quinones during this oxygen consumption. It is through this methodology that we were able to measure finely the degree of oxidation of the must throughout the various technological stages of its elaboration.
We were thus able to finely quantify the level of oxidation of several white musts occurring during mechanical harvest and transport to the wineries, or during all the steps of pressing either through classical pneumatic press or through a centrifuge decanter.
Finalist of the 2013 International SIVE Awards “Research for Development”. The paper reproduced in this video-seminar was presented at the 8th edition of Enoforum (7-9 maggio 2013, Arezzo, Italy)
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