Potassium metabisulphite

HPLC-grace acetonitrile, acetic acid, and methanol were obtained from Merck (Darmstadt, Germany). Milli-Q quality water was used for all HPLC experiments. Pure standards of volatile compounds, internal standard (2-octanol) and potassium metabisulphite were purchased from Sigma-Aldrich (Milano, Italy). Dichloromethane and methanol (SupraSolv) were supplied by Merck (Darmstadt, Germany), absolute ethanol (ACS grade) was obtained from Scharlau Chemie (Sentmenat, Spain) and pure water was obtained from a Milli-Q purification system (Millipore, Billerica, MA, USA). LiChrolut EN resin for solid-phase extraction (SPE) prepacked in 200 mg cartridges (3 mL total volume) were purchased from Merck (Darmstadt, Germany). Chitosan from Aspergillus niger (80–90% deacetylated, with average molecular weight of 10–30 kDa) was obtained from KitoZyme (Herstal, Belgium).

Ethanol, butanol, and mEthanol were of analytical grade (purity ≥ 99%) and purchased from Sigma-Aldrich Co. (Milan, Italy). The chemicals used, that include hydrochloric acid, formic acid, potassium bisulphite, potassium metabisulphite, 4-(dimethylamino)-cinnamaldehyde, malvidin-3-glucoside and (+)-catechin, were of analytical grade and purchased from Sigma-Aldrich Co. (Milan, Italy).