AN AUTOMATIC CANOPY COOLING SYSTEM TO COPE WITH THE THERMAL-RADIATIVE STRESSES IN THE PIGNOLETTO WHITE GRAPE

The complexity of the wine matrix makes the monitoring of the winemaking process crucial. Fourier Transform Infrared Spectroscopy (FTIR) along with chemometrics is considered an effective analytical tool combining good accuracy, robustness, high sample throughput, and “green character”. Portable and non-portable FTIR devices are already used by the wine industry for routine analysis. However, the analytical calibrations need to be enriched, and some others are still waiting to be thoroughly developed.

Planting grape varieties with several resistance loci towards powdery and downy mildew reduces the use of fungicides significantly. These fungus resistant or PIWI varieties (acronym of German Pilzwiderstandsfähig) contribute significantly to the 50% pesticide reduction goal, set by the European Green Deal for 2030. However, wine growers hesitate to plant PIWIs as they lack experience in vinification and are uncertain, how consumer accept and buy wines from these yet mostly unknown varieties. Grapes from four white and three red PIWI varieties were vinified in three vintages to obtain four diffe-rent white and red wine styles, respectively plus one rosé.

The online monitoring of fermentative aromas provides a better understanding of the effect of temperature on the synthesis and the loss of these molecules. During fermentation, gas and liquid phase concentrations as well as losses and total productions of volatile compounds can be followed with an unprecedented acquisition frequency of about one measurement per hour. Access to instantaneous production rates and total production balances for the various volatile compounds makes it possible to distinguish the impact of temperature on yeast production (biological effect) from the loss of aromatic molecules due to a physical effect³.

The overall quality of aged wines is in part due to the development of complex aromas over a long period (1.) The apparition of this aromatic complexity depends on multiple chemical reactions that include the liberation of odorous compounds from non-odorous precursors. One example of this phenomenon is found in dimethyl sulphide (DMS) which, with its characteristic odor truffle, is a known contributor to the bouquet of premium aged wine bouquet (1). DMS supposedly accumulates during the ten first years of ageing thanks to the hydrolysis of its precursor dimethylsulfoniopropionate (DMSp.) DMSp is a possible secondary by-product from the degradation of S-methylmethionine (SMM), an amino acid iden- tified in grapes (2), which can be metabolized by yeast during alcoholic fermentation.

The chemical profile and sensory attributes were studied in Borrigiano IGT Toscana wine (Italy), a blend of Sangiovese 85% and Cabernet Sauvignon 15% grapes harvested in September 2020, where 2-(3,4-dihydroxyphenyl)ethanol (hydroxytyrosol, HT, [1]) was added to a 750-ml wine bottle in 3 different amounts (30, 60, 120 mg) and compared with the control (no HT addition). The study aimed to evaluate whether Polyphenol-HT1®, a high purity HT (>99%) produced by Nova Mentis using biotechnology, could be used as a supplement to sulfites and how it would impact the sensory and chemical profile of this wine [2]. Each sample was prepared in triplicate.