Autochthonous Fermentation Starters for the Production of Aglianico Wines

Aglianico cultivar is among the most ancient black grape varieties native of Campania, a region of the Southern of Italy. Traditionally wines are produced by natural fermentation carried out by the autochthonous non-Saccharomyces and Saccharomyces yeasts present on the grapes and in cellar environment respectively. The aim of this work is the selection and the exploitation of new combinations of microorganisms, isolated from the native microflora of Aglianico grapes and musts, to improve the organoleptic and sensory characteristics of the produced wine. The yeasts isolated and identified by morphological, biochemical and molecular methods mainly belonged to the genera Saccharomyces, Kloeckera, Candida, Metschnikowia, Hanseniaspora and Rhodotorula. Among them two indigenous strains of Saccharomyces cerevisiae and Metschnikowia fructicula were characterized through laboratory tests and semi-industrial-scale fermentations, and selected as good candidates for autochthonous fermentation starters. The fermentations carried out with the new starters showed some positive differences compared to those carried out with commercial yeasts: in fact the selected strains efficiently completed the fermentations and positively affected the wine quality. In particular, the indigenous yeasts increased the must total acidity, reaching the expected values of pH and alcohol content, without producing excessive levels of acetic acid. They also enhanced the colour and the content of polyphenols, flavonoids and anthocyanins. HPLC analysis showed a significant increase of gallic acid, catechin and resveratrol concentrations. The results demonstrated that the two strains successfully dominated the fermentation process and contributed to improve the wines' organoleptic quality preserving the peculiarities of these typical regional wines.