Technological characterisation of potential malolactic starters from Rioja Alavesa winemaking region

Technological characterisation of 22 strains of lactic acid bacteria belonging to Oenococcus oeni, Lactobacillus man and Lactobacillus plantarum species has been carried out in order to elucidate their oenological potential as malolactic starters. After analysing their behaviour against typical harsh conditions found in wine as well as their malolactic fermentation vigour, the better suitability of O. oeni strains was confirmed. These O. oeni strains were further characterised for multiple enzyme activities. Both molecular and phenotypical methods confirmed citrate catabolising ability of all strains. Glycosidase (alpha-glucosidase, beta-glucosidase, beta-xylosidase and alpha-arabinosidase) and esterase activities under different pH and ethanol concentration combinations were also quantified. All strains exhibited alpha-glucosidase, beta-glucosidase and esterase activity. Conversely, only few strains showed beta-xylosidase and alpha-arabinosidase activity. A synergistic negative effect of pH and ethanol on enzyme activity was observed under the most extreme conditions, in that way, when ethanol concentration was more aggressive, a sift to lower pH was traduced on significant enzyme activity decline. However, many strains still retained detectable activities. These results encourage the potential use of many of the characterised autochthonous O. oeni strains as an effective strategy to perform a reliable MLF and to enhance wine aroma complexity in Rioja Alavesa region.