Mechanism of Autoxidation of Polyphenols and Participation of Sulfite in Wine: Key Role of Iron

Sulfur Dioxide and Glutathione Alter the Outcome of Microoxygenation

“…As expected, both free SO 2 and bound SO 2 reacted during MOx due to the partial release of the bound form ( Table 2). Considering that the oxygen supplied during MOx is equivalent to 20 mg/L, and that it would remove ~80 mg/L of total SO 2 if the SO 2 reacted both with quinones and H 2 O 2 , the amounts of consumed total SO 2 detected in this study confirm previous evidence that at least two mole equivalents of SO 2 were consumed during wine oxidation (Danilewicz 2011, Danilewicz andWallbridge 2010).…”

“…During the first three days of treatment, the lower values of DO detected for MLH and MHH suggest that reactions involving quinones are dominant in determining oxygen consumption, and thus GSH accelerates consumption by rapidly reacting with quinones, probably acting as "oxidation promoting nucleophiles" (Danilewicz 2011). When both preservatives are no longer available, rapid consumption of oxygen occurs due to the production of radicals by the Fenton reaction, and it is these radicals that react most rapidly with oxygen.…”

“…Sulfur dioxide prevents oxidative spoilage by scavenging hydrogen peroxide (Danilewicz 2011, Danilewicz andWallbridge 2010) and by reacting with quinones, reducing them to the catechol form (Saucier and Waterhouse 1999) or yielding sulfonates as addition products (Nikolantonaki and Waterhouse 2012). In addition, the sulfur-containing tripeptide glutathione (GSH) found in grapes has been suggested to provide a protective effect by acting as sacrificial nucleophiles for quinones (Nikolantonaki and Waterhouse 2012).…”

“…First, molecular oxygen (triplet state) cannot directly react with wine organic compounds (singlet state); however, it can accept electrons by interacting with transition metals, iron and copper ions, in the presence of catechol (Danilewicz 2011). The catechol is oxidized to a quinone, and oxygen is reduced to hydrogen peroxide.…”

Kinetics of the autoxidation of sulfur(iv) co-catalyzed by peroxodisulfate and silver(i) ions

“…[1][2][3][4][5] The role of sulfur(IV) autoxidation in the hydroxylation, epoxidation and oxidative cleavage of DNA, [6][7][8][9][10] in certain metallurgical 11,12 and food technologies, [13][14][15][16] and microbiological processes 17 generates additional motivation to study its mechanistic details. It is now understood that the process does not proceed in the absence of a catalyst in acidic medium.…”