Removal of Volatile Phenols From Wine Using Crosslinked Cyclodextrin Polymers.

Chao Dang,Vladimir Jiranek,Kerry L Wilkinson,Dennis K Taylor

doi:10.3390/molecules25040910

Chao Dang, Vladimir Jiranek + Show 2 more

Open Access

https://doi.org/10.3390/molecules25040910

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Abstract

Volatile phenols have been implicated as contributors to off-odors associated with taints from bushfire smoke and microbial spoilage. Various methods for the amelioration of off-odors have been evaluated, but to date, they have not included cyclodextrin (CD) polymers. In the current study, two CD polymers were prepared from β- and γ-CD, using hexamethylene diisocyanate (HDI) as a crosslinking agent. Adsorption tests were performed with four volatile phenols (guaiacol, 4-methylguaiacol, 4-ethylguaiacol and 4-ethylphenol) at concentrations up to 1 mg/L. The removal of volatile phenols by CD polymers achieved equilibrium almost instantly, with isotherm tests suggesting an adsorption capacity of 20.7 µg of volatile phenol per gram of polymer. Langmuir and Freundlich models were subsequently used to fit the data. In batch adsorption tests, the CD polymers achieved 45 to 77% removal of volatile phenols. Polymer reusability was also evaluated and was found to be excellent. A comparison between volatile phenol adsorption by CDs vs. CD polymers, determined using a novel four-phase headspace solid-phase microextraction (HS-SPME) method for gas chromatography-mass spectrometry (GC-MS), suggests CD polymers offer several advantages for use by the wine industry.

Highlights

Aroma plays an important role in determining wine quality, so optimising the aroma profile of wine remains a key aim of the winemaking process
The present study aimed to evaluate the potential for CD polymers to remove four volatile phenols, guaiacol, 4-methylguaiacol, 4-ethylguaiacol and 4-ethylphenol (Figure S1), from tainted wine
The time required for CD polymers to achieve adsorption equilibrium is dependent on the sample mixture, the chemical properties of the target molecule and temperature [30,31]

Summary

Introduction

Aroma plays an important role in determining wine quality, so optimising the aroma profile of wine remains a key aim of the winemaking process. Climate change has aggravated the risk of certain off-odors occurring in wine [1]. A known source of volatile phenols associated with off-odors is Brettanomyces/Dekkera, spoilage yeast that produces 4-ethylphenol and 4-ethylguaiacol, which impart animal, horse stable, sweaty and medicinal characters at excessive concentrations [2,3]. As a consequence of the warmer ripening conditions associated with climate change, grapes and wine, tend to have less natural acidity (higher pH levels) and higher sugar concentrations, i.e., conditions which favor the growth of spoilage yeast [4]. The warmer, drier weather conditions increase the risk of bushfires occurring near wine regions, which can lead to vineyard exposure to bushfire smoke, and another volatile phenol related off-odor, commonly known as smoke taint [5,6]

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