BACKGROUND: The antioxidant capacity of an inactive dry yeast preparation (YD) was investigated by conventional analytical
methods (spectrophotometry, high-performance liquid chromatography) as well as by cyclic voltammetry in a (+)-catechin
model wine and compared with that of some of the most common antioxidants found in wine: sulfur dioxide, ascorbic acid and
glutathione.
RESULTS: Sulfur dioxide was the highest-performing substance in protecting (+)-catechin against browning, followed by
ascorbic acid and theYDpreparation. Sulfiteswere the only antioxidantwhose activitywas clearly detectable in themodel wines
after 29 days of storage.Voltammetric studies demonstrated that the antioxidant capacity of the products testedwas connected
to their intrinsic characteristics and their molar concentrations (catechin/antioxidant molar ratio).
CONCLUSION: The YD preparation displayed a certain ability to protect polyphenols against browning. The antioxidant activity
of YDs towards (+)-catechin appeared to be based on different mechanisms with respect to that of the other products tested:
the insoluble portion of these preparations (cell wall residues) might have a non-negligible role, even if the ability of YDs
to release compounds able to suppress oxidation cannot be rejected. Direct comparison of the different antioxidants led to
interesting indications concerning their mechanism of action in wine-like solution, depending on their concentration and
intrinsic characteristics.
