Ascorbic acid iron casse

The effectiveness of ascorbic acid in the prevention of iron casse which is exclusively caused by Fe + ions is explained by the above reactions. 

Sulfur dioxide and ascorbic acid therefore have different antioxidant properties. The first has a delayed, but stable, effect which continues over time even in the presence of a subsequent oxygenation. It cannot prevent iron casse, which rapidly appears after an aeration. The second has an immediate effect it can instantaneously compensate the damage of an abrupt and intense aeration (iron casse), but it acts only as long as the wine is not in permanent contact with air. 

The aeration of wine oxidizes iron. The amount of ferric iron formed (several milligrams per liter) can be sufficient to induce iron casse. Protection against iron casse can be ensured if the wine receives 50-100 mg of ascorbic acid per liter beforehand (Table 9.7). 

Table 9.7. Protection from iron casse by the addition of ascorbic acid before aeration (Rib6reau-Gayon et al 1977)...

Ascorbic acid effectively protects against iron casse, which can occur after operations that place wine in contact with air, such as pumping-over, transfers, filtering and especially bottling. In the same conditions, sulfur dioxide acts too slowly to block the oxidation of iron. But, if the wine must be aerated again after a treatment following a first aeration, the ascorbic acid no longer protects the wine. When a wine that has received 100 mg of... 

Table 9.8. Reduction of iron casse by addition of ascorbic acid, 48 h after the aeration cansing the haze (Riberean-Gayon et al., 1977)...

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