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The most important oenological characteristics of high-quality sparkling wines are aromatic aspect, taste persistence, perlage, high levels of acidity and low pH. Due to hot climate and reduced rainfall that characterize Sicily region, white grape varieties such as Grillo cultivar cultivated in this area are characterized by very low concentrations of malic and tartaric acids. Grillo cultivar is characterized by an intense production of raceme grapes with low pH and high content of tartaric and malic acids. These fruits possess the chemical properties useful to increase the amounts of acids in the final wines. With this in mind, the present research was carried out to test the ability of four Saccharomyces cerevisiae strains (CS182, GR1, MSE13 and MSE41) to ferment a raceme must with a pH of 2.9 at two concentrations (14 and 16 Babo degree) of total sugars. The inoculation of the strains was performed after a preadaptation at pH 2.5. The chemical parameters and kinetics of the fermentations were monitored. The experimental sparkling base wines were characterized by a very high total acidity with 16-17 g/L of tartaric acid and 9-10 g/L of malic acids. On the other hand, ethanol was detected at low values in the range 9-10% (v/v). The base wine obtained with GR1differed in their high acidity values, whereas trials inoculated with CS182 showed more intense odors and exotic fruit. Experimental wines produced in this study represent an innovative strategy for "blending wines" to produce sparkling wines in dry Mediterranean climate.

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Catarratto is one of the most widely cultivated grape varieties in Sicily. It is an indigenous non-aromatic white grape variety. Despite its widespread use in winemaking, knowledge of the aroma and chemical and microbiological properties of Catarratto wines is quite limited. The influence of Metschnikowia pulcherrima combined with Saccharomyces cerevisiae on the aromatic expression of Catarratto wines was investigated with and without the addition of glutathione-rich inactivated yeast. The substance is a natural specific inactivated yeast with a guaranteed glutathione level used to limit oxidative processes. The aromatic profiles of the final wines were determined through analysis of the volatile organic compounds using a solid-phase microextraction technique that identified 26 aromatic compounds. The addition of M. pulcherrima in combination with the natural antioxidant undoubtedly increased the aromatic complexity of the wines. Dodecanal was exclusively detected in the wines processed with glutathione-rich inactivated yeasts. Furthermore, the presence of this natural antioxidant increased the concentration of six esters above the perception threshold. Sensory analysis was also performed with a panel of trained judges who confirmed the aromatic differences among the wines. These results suggest the suitability of glutathione-rich inactivated yeasts for determining the oxidative stability of Catarratto wines, thus preserving its aromatic compounds and colour.

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