# Removal of Volatile Phenols From Wine Using Crosslinked Cyclodextrin Polymers
The spatial arrangement of C-H bonds within each subunit of the ring-shaped CD molecule results in a lipophilic cavity (H-3 and H-5) with a hydrophilic surface (H-1, H-2 and H-4); a structure that enables CDs to form inclusion complexes with the non-polar moieties of guest molecules [21]. This binding process exists as a dynamic equilibrium in aqueous environments, and is mainly driven by non-covalent Van der Waals forces, resulting in a more stable status with lower energy when enthalpy-rich water molecules are replaced by non-polar guests [22]. The size, hydrophobicity, and conformation of the guest molecule influences encapsulation in aqueous conditions [23]. Formation of the CD-guest complex leads to a series of changes in both the physical and chemical properties of the guest molecule, including increased solubility (of insoluble compounds), protection from degradation, reduced volatility, and therefore, reduced aroma and flavor impact, as well as shifts in spectral peaks and chromatographic separation [20]. As a result of these functions, CDs have been exploited as additives by the food, beverage and flavor industries [22; 24; 25; 26]. \(\alpha\)-CD and \(\beta\)-CD are currently listed as novel foods in the US, the EU and Japan, whereas \(\gamma\)-CD is only approved in the US and Japan. \(\alpha\)-CD and \(\gamma\)-CD are both listed as novel foods by Food Standards Australia-New Zealand, whereas \(\beta\)-CD is classified as a food processing aid. A recent report suggests there are more than 200 food products containing CDs as ingredients [27]. The complexation that occurs between CDs and various aroma volatiles has been widely studied, however, there is limited literature concerning the use of CDs in wine. A key barrier to the uptake of CDs for wine production is the strict regulation of permitted winemaking additives, which does not currently include CDs. There is, nevertheless, increasing interest in developing insoluble CD polymers to broaden the applications of CDs. CDs can be polymerised with various molecules, known as crosslinkers, with these compounds containing at least two functional groups that can react with the hydroxyl groups present on the glucose subunits of CD, thereby linking the molecules in a chain structure [28]. CD polymers have been used to remove phenols and dyes from wastewater [29; 30; 31; 32], with several CD crosslinkers having been studied. [PERSON] and colleagues crosslinked \(\beta\)-CD with epichlorohydrin, and studied the sorption capability of the resulting polymer with benzene derivatives, such as phenol, \(p\)-nitrophenol, and benzoic acid [29]. [PERSON] used hexamethylene diisocyanate (HDI) and toluene-2,6-diisocyanate as CD crosslinkers, and showed adsorption of cresols, phenol and xylenol from wastewater by the polymers [30]. Other studies have used chitosan and citric acid to form phenol adsorbing CD polymers for removing pollutants from water [31; 32; 33; 34]. 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. Two insoluble CD polymers were prepared from \(\beta\)-CD and \(\gamma\)-CD using HDI as a crosslinker. Adsorption tests were subsequently conducted to evaluate the preference and capability of the polymers to adsorb volatile phenols associated with smoke taint and _Brettanomyces_ spoilage. In order to compare the removal of volatile phenols following the addition of CDs and CD polymers, a newly developed four-phase headspace solid-phase microextraction (HS-SPME) method for gas chromatography-massspectrometry (GC-MS) was employed to quantify changes in volatile phenol concentrations without interference between CD additives and internal standards [35].