Removal of sulfide-bound copper from white wine by membrane filtration

Abstract

Background and Aims: Sulfide-bound Cu in wine may act as a potential source of hydrogen sulfide. The aim of this study was to understand how the white wine matrix can influence the filterability of sulfide-bound Cu. Method and Results: Sulfide-bound Cu was formed in situ with copper(II) sulfate and sodium sulfide addition to white wine and model wines. The amount of subsequent Cu passing through membrane filters was measured by flame atomic absorption spectroscopy or inductively coupled plasma with optical emission spectroscopy. Nanoparticle tracking analysis was utilised to measure the size of particles generated after copper(II) and sulfide addition. The majority of the particles were around or below 0.2 µm, and polyethersulfone and nylon membranes remove up to 40-90 % of sulfidebound Cu from white wine. The regenerated cellulose, teflon and glass fibre membranes removed minimal sulfide-bound Cu. Conclusions: Membrane filtration removed sulfide-bound Cu by adsorption rather than by particle size discrimination. Polysaccharides and proteins were the components of white wine that most inhibited adsorption. Significance of the Study:The addition of copper(II) to wine with hydrogen sulfide results in products that cannot be removed by filtration on the basis of their particle size, but instead may be partly removed by adsorption onto membrane filters to an extent impacted by wine composition and the filtration medium.

Simplified measures of copper fractions in wine: colorimetric and filtration‐based approaches

“…between BCA addition and the eventual absorbance measurement. The results imply that the Cu not detected by the electrochemical system in wine can include a fraction of thiol‐bound Cu and is not merely Cu bound to sulfide as reported previously (Kontoudakis et al 2019a). Given that two independent instrumental techniques show their measured Cu fractions are dependent upon the same sulfhydryl wine components, this supports the assignment of sulfhydryl compounds as being particularly important to the form of Cu in wine.…”

“…Additionally, both electrochemical and SPE ICP‐OES analysis protocols required expensive instrumentation and either labour intensive sample preparation or analysis. In any case, the composition of the sulfide‐bound Cu was suggested to be a heterogeneous particle when formed in wine, predominantly composed of sulfide and Cu but with the possibility of additional wine components incorporated either internally and/or interacting with the particle surface (Kontoudakis et al 2019a). Particle sizes in model wines and white wines were found to lie within the 100–200 nm range, which meant that they were difficult to remove from wine on the basis of filtration by size, but more easily removed by filtration based on adsorption (Kontoudakis et al 2019a).…”

Antioxidant Species in Grapes and Wines via Spectrophotometric Methods: No Quenching Effects by Copper(II) and Yeast Derivative Treatments

“…e work showed that the administration of copper(II) and/or yeast derivatives to vines/grapes, as allowed by regulation for organic cultivations, does not affect the content of antioxidant species. It can be noted that the matter of copper in wine, even though white ones, was widely studied [51][52][53][54], but it was always aimed to study the mechanisms of sulfides removal, relevant to model wine systems, and never to study the possible effects by the metal on the contents of polyphenols in general, and particularly of resveratrol, quercetin, and quercetin glucoside in the real wine matrix. sulfur dioxide content (Table 2Sd), volatile sulfur dioxide content (Table 2Se), alcohol content percentage (Table 2Sf), total polyphenol content (Table 3Sa), total anthocyanin content (Table 3Sb), trans-resveratrol content (Table 3Sc), quercetin content (Table 3Sd), quercetin glucoside content (Table 3Se), wine shade and color index values (Table 3Sg), and relevant absorbance values (Table 3Sf).…”

Copper(II) and Sulfur Dioxide in Chardonnay Juice and Shiraz Must: Impact on Volatile Aroma Compounds and Cu Forms in Wine

“…A portion of the decrease in bound Cu would be due to the decreases in total Cu, and the increases in free Cu were consistent with oxygen exposure to the wine during the different wine production steps. The oxidation of wine can lead to the dissociation of the Cu-sulfide complexes (bound Cu) and regeneration of Cu(II) (free Cu) [44,45]. For the Shiraz, the HCu treatment had the highest free Cu concentration at PAF, but by PB, there was minimal difference among all samples.…”