UV-C treatment: A non-thermal inactivation method for microbiological stabilisation of must and wine

Abstract

UV-C treatment is discussed as an effective and efficient method to inactivate harmful microorganisms in wine and other viticultural products. In comparison to other stabilisation techniques, the application of UV-C is thought to be beneficial to reduce energy costs and to minimize SO2 addition. The object of this work was to determine the lethal UV-C dose for harmful microorganisms such as Brettanomyces bruxellensis and Acetobacter aceti. The concept of 5-log inactivation was applied and the Weibull model was used to compare different microbial and wine parameters. Microbial relevant UV-C doses and 2-fold overdose treatments and how they affected chemical and sensory changes of wine were investigated. Riesling and Pinot noir wine, which have different absorbance at 254 nm, were individually inoculated with microorganisms at different inoculation numbers. The results showed that the Weibull model is appropriate to predict the lethal UV-C dose. Already at microbially relevant doses, UV-C treatment can lead to significant changes in the colour and concentration of aroma compounds in white wine. Higher concentrations of 2-aminoacetophenone were found with increasing UV-C doses. Hence, UV-C overdosing can cause the “atypical ageing” off-flavour in wine. However, microbially relevant UV-C doses change the sensory properties of wine more towards a typical ageing character.