Sustainable sparkling base wines obtained from waste matrices of the wine and honey supply chain

Abstract

The present work was performed to improve the general quality characteristics of sparkling wines produced in Southern Italy (Sicily region) as well as the sustainability of the production process. To this purpose, two novel approaches were applied during experimental winemaking: (i), the use of raceme grapes (formed from the secondary shoots) of Grillo cultivar to improve the chemical characteristics of sparkling base wine; (ii), the technological selection of potential fructophilic Saccharomyces cerevisiae strains isolated from honey by-product to improve the alcoholic fermentations and the organoleptic features of bottled wines. The racemes are typical of Grillo cugrapes and mature 20 days after the primary production. The racemes, not reaching maturation, possess a high acidity, a low sugar content and pH values between 2.5-2.8. Thus, they represent a production scrap that can be enhanced through the production of base wines for sparkling wines in warm temperate climate areas, such as the Mediterranean Basin. The experimental vineyards were subjected to a topping operation to stimulate the production of racemes. The topping operation was carried out leaving a different number of buds in order to evaluate the incidence of the budding load on the quality of the grapes and musts. The yeasts used, previously isolated from honey by-products, were subjected to the genotypic identification and technologically characterization in order to select the strains with oenological potential. Four strains (SPF21, SPF42, SPF52 and SPF159) belonging to the species Saccharomyces cerevisiae have been used as starters to ferment raceme musts obtaining base wines characterized by a remarkable and significant sensation of acidity and flavour. This is the case with the Saccharomyces cerevisiae 'galactose –' yeasts: their fructophile index is generally higher than that of the standard S. cerevisiae yeasts (known as 'galactose +'). The SPF21, SPF42, SPF52 and SPF159 strains, which belongs to GAL- group, therefore has a naturally above-average propensity for fructose. The experimental project was developed over two years at industrial level. The analysis of the chemical parameters of wines obtained through experimental vinifications showed the presence of high values of total acidity (10 g/l) and a low pH (<3). Furthermore, the base wines obtained at the end of fermentation were characterized by a discrete content of malic acid reaching a concentration of about 2.5 g/l. The presence of malic acid in the base wines is of considerable importance if a long-lasting sparkling wine has to be obtained and destined to a long aging. The present research has provided physicochemical and microbiological information on alcoholic fermentation conducted on must of Grillo racemes to produce base wines to be used for sparkling wine production. Fructophilic strains of S. cerevisiae, capable of regularly conducting alcoholic fermentation of a must with low pH and high quantity of organic acids, are of relevance for the application. At the same time, the physicochemical analyses of the base wines confirmed their suitability for the production of sparkling wine.