Co-inoculo di differenti lieviti e batteri lattici ed il loro impatto sull'aroma del vino

Malolactic fermentation (MLF) process is a second fermentation which usually take place after alcoholic fermentation (AF). The conversion of malate to lactate is the main effect of this fermentation but at the same time an indirectly changing of volatile aroma compounds is carried out. The achievement of MLF in cool climate like Rheingau region (Germany) is not for granted especially due to the low pH value typical of these areas. However it is clearly understood how important it could be to lead AF and MLF using co-inoculation practice. This technique allows creating the best conditions for bacteria because it represents a way to relieve the strong pH effect and other inhibition factors. The present study investigated the impact of different co- inoculation strategies on final flavour compounds in Müller-Thurgau wines from Germany. Two bacteria strains belonging to the species Oenococcus oeni and two others to the species Lactobacillus plantarum were used for the research trial. Each of the lactic acid bacteria strains was co-inoculated with one of two different yeast strains of Saccharomyces cerevisiae denominated SC-1 and SC-2. SC-1 and SC-2 were inoculated alone, with addition of lysozyme in order to avoid MLF and in combination with four different LABs. All fermentations were carried out in triplicate at 21 °C in normal bottles thereby to have enough data for statistical analysis. In total all samples were 36. Results show that treatments co-inoculated with the first yeast strain (SC-1) did not demonstrate any negative impact on the final concentration of flavour compounds. All the samples belonging to the second yeast strain (SC-2) except the controls, showed worrisome amount of volatile acidity. Slightly differences were observed in all samples combined with the strain Oenococcus oeni A-2 on final amount of cis/trans-linalool oxide. These two compounds are originated from the cyclization and oxidation of linalool (Genovese et al., 2007). Their concentrations are not so relevant in the wine and the perception threshold are not low, therefore they cannot be considered as important as linalool. Other volatile compounds such as higher alcohols, medium-chain fatty acids and esters displayed differences mainly due to the yeast metabolism. The outcomes provide that the yeast strain had the strongest effect on final wine flavour. Surely other developments can be done on this scope thereby to realize and improve the knowledge on this practice.