Treatment by fining agents of red wine affected by phenolic off-odour

Although phenolic off-odour is very detrimental for red wine quality, there is a lack of easy-to-use methods able to decrease the levels of the responsible compounds 4-ethylphenol (4-EP) and 4-ethylguaiacol (4-EG) and to improve the sensory quality of the contaminated wines. To this aim, an alternative use of fining agents (activated charcoal, PVPP and zeolite) was evaluated. Two levels of ethylphenol contamination were considered: a naturally low contaminated red wine and the same wine spiked with 4-EP and 4-EG. The impact of the treatments on desirable aroma volatiles, polyphenols and colour was also evaluated. The effectiveness in diminishing the intensity of the phenolic off-odour was assessed by descriptive sensory analysis. The activated charcoal and PVPP significantly decreased the concentrations of 4-ethylguaiacol and 4-ethylphenol in the naturally contaminated wine, while none of the tested fining agent was effective in the spiked one. Polyphenols and colour were slightly affected, to the same extent for the two treatments. Charcoal and PVPP additions negatively impacted the concentration of the aroma volatiles, especially esters, with the activated charcoal achieving a higher decrease. The sensory outcome of both treatments was the decrease in the intensity of phenolic off-odour, with charcoal achieving a higher decrease. Interestingly, in spite of the decrease in esters, also a significant increase in the intensity of red fruit odour occurred.