Abstract
In the present work, known concentration of sulfite aqueous solutions in the presence and absence of gallic acid was measured to corroborate the validity of modified Monier-Williams method. Free and bound-sulfite was estimated by differential pulse voltammetry. To our surprise, the modified Monier-Williams method (also known as aspiration method) showed to be very inaccurate for free-sulfite, although suitable for bound-sulfite determination. The differential pulse approach, using the standard addition method and a correction coefficient, proved to be swift, cheap, and very precise and accurate.
Highlights
Sulfur dioxide is the most widely spread additive in winemaking and essential as well
Equilibrium among the different molecular species is reached when SO2 is added to wine
Part reacts with compounds having carbonyl groups and is called bound sulfite, the other part, that in aqueous solution is in equilibrium with bisulfite (HSO3−) and sulfur dioxide (SO2), is called free SO2 (1) [14, 15]
Summary
Sulfur dioxide is the most widely spread additive in winemaking and essential as well. Antioxidant [1], antioxidasic [2], and antimicrobial [3, 4] effects turn sulfur dioxide into a practically essential additive in winemaking and in other food production [5]. Sulfur dioxide may be found free or bound to phenols, for example, gallic acid, aldehydes, and other organic compounds [6]. A high level of this compound brings about toxic effects [7]. Part reacts with compounds having carbonyl groups and is called bound sulfite, the other part, that in aqueous solution is in equilibrium with bisulfite (HSO3−) and sulfur dioxide (SO2), is called free SO2 (1) [14, 15]
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