Advances in wine analysis by PTR-ToF-MS: Optimization of the method and discrimination of wines from different geographical origins and fermented with different malolactic starters

tPTR-ToF-MS has been previously used to analyse the headspace of wine, but it is not fully exploited inthe field due to problems related to the high ethanol concentration. In the case of alcoholic fermentationduring bread-making, we have recently proposed improvements to the method by introducing argon inthe system in order to reduce fragmentation and formation of ethanol clusters. In this study, we optimizethe experimental setup in the case of wine by (i) boosting the sampling protocol (sample headspaceflushing and incubation); (ii) determining the optimal E/N value while using argon as carrier gas and (iii)proving that the optimized protocol reduces the effect of ethanol. The new protocol has been verified todiscriminate eight French wines coming from three different regions (Gers, Gironde, Languedoc) and, inorder to assess the applicability of the method in a relevant problem of oenological interest, we also testedit on a set of samples consisting of a red wine fermented with two different commercial preparations ofOenococcus oeni. Using principal component analysis of selected m/z signals, differentiation among winesfrom different geographical origin was achievable. Samples corresponding to the reference wine and towines inoculated with two different commercial preparations were clearly separated. Intriguingly, ourapproach suggests the selective degradation of volatile organic compounds by O. oeni in wine as newpossible feature of malolactic starter cultures in wine.