Detection Method Optimization, Dynamic Changes during Alcoholic Fermentation and Content Analysis of Brett Character Compounds 4-Ethylphenol (4-EP) and 4-Ethylguaiacol (4-EG) in Chinese Red Wines

A simple and convenient HS-SPME-GC-based detection method with high detection limit, good recoveries, highly reproducibility, minimal matrix effects and a 30-min total run time for 4-ethylphenol (4-EP) and 4-ethylguaiacol (4-EG) in red wines has been developed. The 4-EG concentration that was generated during alcoholic fermentation exhibited a biphasic trend, with an initial increase that was followed by a decrease to approximately 40-50 mu g/L after alcoholic fermentation in the winery. The content of one precursor substance (ferulic acid) strongly correlated with the 4-EG content, and the 4-EG decrease observed late in fermentation may be due to its adsorption by the yeast cell wall. 4-EP was undetectable during alcoholic fermentation in the winery. Furthermore, 4-EG and 4-EP were detected in most of the commercial wines sampled from the Chinese wine market. The regions of origin, the grape varieties, and the oak barrel aging times had strong impacts on 4-EP and 4-EG.