Analytica Chimica Acta 458 (2002) 197–202 Removal of iron, copper and manganese from white wines through ion exchange techniques: effects on their organoleptic characteristics and susceptibility to browning P. Ben´ ıtez, R. Castro ∗ , C.G. Barroso Analytical Chemistry Department, Faculty of Sciences, University of Cádiz, P.O. Box 40, Pol. Rio San Pedro, Puerto Real, E-11510 Cádiz, Spain Received 20 June 2001; accepted 30 October 2001 Abstract Ion exchange techniques have been used to reduce the content of iron, copper and manganese in white wines. Two exchanger resins have been compared, a chelating resin, the active group of which is iminodiacetate and a Dowex, acidic cation exchange resin. The results obtained show that the technique of using exchanger resins is extremely effective in lowering the metal content of wines, although on occasions, their use alters the organoleptic characteristics of the wine. Treated wines present lower polyphenolic and aromatic profiles than the untreated wines. Polyphenolic and metallic reductions would explain why treated wines present a notably reduced susceptibility to browning. © 2002 Elsevier Science B.V. All rights reserved. Keywords: Metals; White wine; Browning; Ion exchange 1. Introduction The phenomenon called “browning” in white wines constitutes one of the principal enological problems for wine producers. In organoleptic terms, this phe- nomenon translates into a process of continuous ox- idation, a loss of aromatic freshness and, in the final stages, in the appearance of precipitates of condensed phenolic material in the bottled wine. It is known that there are certain species which par- ticipate significantly in the destabilization of wines and in their oxidative evolution [1,2]. Notable among these species are oxygen (the initiator of the process), ∗ Corresponding author. Tel.: +34-95601-6363; fax: +34-95601-6460. E-mail address: remedios.castro@uca.es (R. Castro). polyphenols (the oxidizable matter), and certain metal ions, such as Fe, Cu and Mn (activators of the pro- cess) [3–5], which are also present. There are various enological techniques in use that seek to avoid the browning of white wines by acting on one or more of these species [6,7]. Given the proven participation of the metals present in the wine in its browning, and the variability in the concentrations in which they are found in particular wines, many studies have been directed towards de- termining these concentrations but also in minimising them. Notable among the techniques that seek to re- duce the metal content of wine is the use of potassium hexacyanoferrate(II), which when added to the wine eliminates part of the iron content and significantly reduces the content of other metals that also partic- ipate in the browning of white wines and are highly 0003-2670/02/$ – see front matter © 2002 Elsevier Science B.V. All rights reserved. PII:S0003-2670(01)01499-4