The removal of Cu from wine by copolymer PVI/PVP: Impact on Cu fractions and binding agents

Xinyi Zhang; Nikolaos Kontoudakis; Eric Wilkes; Neil Scrimgeour; Kieran Hirlam; Andrew C Clark

doi:10.1016/j.foodchem.2021.129764

The removal of Cu from wine by copolymer PVI/PVP: Impact on Cu fractions and binding agents

Food Chem. 2021 Apr 9:357:129764. doi: 10.1016/j.foodchem.2021.129764. Online ahead of print.

Authors

Xinyi Zhang¹, Nikolaos Kontoudakis², Eric Wilkes³, Neil Scrimgeour³, Kieran Hirlam³, Andrew C Clark⁴

Affiliations

¹ National Wine and Grape Industry Centre, Wagga Wagga, NSW 2678, Australia; School of Agricultural and Wine Sciences, Charles Sturt University, Locked Bag 588, Wagga Wagga, NSW 2678, Australia. Electronic address: xizhang@csu.edu.au.
² National Wine and Grape Industry Centre, Wagga Wagga, NSW 2678, Australia; School of Agricultural and Wine Sciences, Charles Sturt University, Locked Bag 588, Wagga Wagga, NSW 2678, Australia; Laboratory of Enology and Alcoholic Drinks, Department of Food Science and Human Nutrition, Agricultural University of Athens, Athens 11855, Greece.
³ The Australian Wine Research Institute (AWRI), P.O. Box 197, Glen Osmond, SA 5064, Australia.
⁴ National Wine and Grape Industry Centre, Wagga Wagga, NSW 2678, Australia; School of Agricultural and Wine Sciences, Charles Sturt University, Locked Bag 588, Wagga Wagga, NSW 2678, Australia.

PMID: 33932850
DOI: 10.1016/j.foodchem.2021.129764

Abstract

Specific forms of Cu in wine can influence wine flavour and development. The co-polymer polyvinylimidazole/polyvinylpyrrolidone (PVI/PVP) is known to remove Cu from wine, but its impact on different Cu forms is uncertain. In this study, three Cu fractions in white wine were determined by colorimetry and two Cu fractions in red wine were determined by diatomaceous earth depth filtration and atomic spectroscopy. PVI/PVP, with either silica or chitosan formulations, reduced all three fractions of Cu measured in white wines, and sulfide-bound Cu in red wines. The inefficient removal of organic acid-bound Cu in red wines was linked to the higher pH of red wines. After PVI/PVP treatment, wines showed lower concentrations of hydrogen sulfide, but minimal changes in weaker Cu binding agents. These results demonstrate that PVI/PVP efficiently removes the least desirable form of Cu present in wine, along with its detrimental binding agent (i.e., hydrogen sulfide).

Keywords: Copper; Copper binding agents; PVI/PVP; Polysulfanes; Wine.