Reducing volatile phenols in red wines


By Karien O'Kennedy

The aim of the study was two-fold: to develop a simple, cheap and reliable method to measure 4-EP and 4-EG in red wines and to use this method to compare different fining agents for their efficacy in removing these volatile phenols from red wines. This summary will focus on the removal of the volatile phenols. 

Experimental layout

A 2012 red wine from the Duoro Valley was used. The wine was fortified with 1500 µg/l 4-EP and 300 µg/l 4-EG. Eight fining agents were used at the highest dosage recommended by the manufacturer. They were:
  • Potassium caseinate (60 g/hl)
  • Egg albumin (10 g/hl)
  • Sodium bentonite (120 g/hl)
  • Solid isinglass (4 g/hl)
  • CMC (200 ml/hl)
  • Liquid gelatine (60 ml/hl)
  • Activated carbon (80 g/hl)
  • Chitosan (10 g/hl)

Fining agents were added to 200 ml of wine in 250 ml graduated cylinders and sealed for six days. Samples were then centrifuged for 10 minutes before analysis. The newly developed method was used to analyse the wines.

Main results

  • Activated carbon decreased 4-EP by 58% and 4-EG by 56% in the wine.
  • Egg albumin decreased 4-EP by 20% and 4-EG by 17% in the wine.
  • The other fining agents had zero to very little effect on the volatile phenol concentrations in the wine.
  • With the exception of gelatine and casein, all fining agents reduced the headspace concentration of 4-EP and 4-EG (what you will smell in a glass of wine).
  • CMC, isinglass and chitosan interacted with volatile phenols in the wine and thereby reduced their vapour pressure (keeping them in the liquid and out of the gas phase), but did not remove it.
  • Of all the fining agents tested only CMC had a significant negative effect on the red wine colour. 

Significance of the study

A new method was developed and proved to be effective in measuring volatile phenols in red wines. Activated carbon is the most effective strategy for partial removal of volatile phenols from heavily affected wines. It must be noted that activated carbon also removes other volatile compounds from wine, affecting wine quality. Other fining agents such as isinglass and chitosan will not improve volatile phenol measurement in wine but can potentially improve wine aroma by reducing headspace concentration of 4-EP and 4-EG.

Reference

A simple, cheap and reliable method for control of 4-ethylphenol and 4-ethylguaiacol in red wines. Screening of fining agents for reducing volatile phenols levels in red wines: https://doi.org/10.1016/j.jchromb.2016.10.036

Image: Shutterstock

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