Antimicrobial properties of wood used for ageing wines and spirits

Abstract

This study investigated the biocidal properties, chemical characteristics and antioxidant activity of hydroalcoholic extracts obtained from wood used to age wines and spirits in the Jerez region. Extracts were prepared by ultrasound at 60 °C in 50 % hydroalcoholic solution from seasoned and unseasoned Quercus alba and Q. robur casks with different toast levels and seasoning periods. Antimicrobial activity was evaluated by disc diffusion, well diffusion and microplate dilution against relevant wine yeasts, lactic acid bacteria, and acetic acid bacteria. Total phenolic content and antioxidant capacity were also measured. Disc and well diffusion assays did not provide conclusive results, whereas microplate dilution allowed antimicrobial activity to be expressed as inhibition percentage. Yeast inhibition by the wood extracts was lower than that produced by the reference 50 % hydroalcoholic solution. In contrast, strong inhibition was observed for Oenococcus oeni (88.2 %), Pediococcus pentosaceus (99.5 %), and Lentilactobacillus hilgardii (82.7 %), exceeding the corresponding reference values of 6.3 %, 53.4 % and 59.5 %. The most active extracts came from heavily toasted American oak. No direct relationship was found between biocidal capacity and either total phenolic content or antioxidant activity. These extracts showed limited activity against yeasts but high activity against lactic and acetic acid bacteria, suggesting potential for further investigation as fermentation-control agents.