Evidence of 4-ethylcatechol as one of the main phenolic off-flavour markers in French ciders

A new HPLC method using a diode array detector was developed and validated to quantify 4-ethylphenol, 4-vinylphenol, 4-ethylguaiacol, 4-vinylguaiacol and 4-ethylcatechol in cider. The procedure was linear up to 150 mg/l for each of the five volatile phenols, precise (RSD < 2.9%) and sensitive, with limits of detection between 0.03 and 0.10 mg/l; moreover, it did not require any sample preparation. This method was applied to 11 phenolic off-flavour defective ciders. In these ciders, the main volatile phenol corresponded to 4-ethylcatechol. Moreover, the observed concentrations (maximum of 164 mg/l) indicated, for the first time, that this compound is an important phenolic off -flavour marker in cider. Then, volatile phenols concentrations were determined for 47 French commercial ciders and showed mean quantities of 3.2 (4-EC), 0.8 (4-EP), 0.1 (4-EG), 0.2 (4-VP) and 0.3 mg/l (4-VG). The majority of the tested commercial ciders presented low volatile phenol levels.