High power ultrasound treatment of crushed grapes: beyond the extraction phenomena

The treatment of white and red crushed grapes by high power ultrasounds (US) represents an emerging technology in winemaking. In 2019, it was officially recognized by OIV through the resolution n°616-2019, and it was also approved by European Union in January 2022. The US effect on extraction mechanisms was widely studied, but more researches are needed to better understand the ultrasound effect on some specific classes of grape compounds. This research aimed to highlight at laboratory scale some specific effects of ultrasounds on some key compounds of white and red grapes. The samples were sonicated at different frequency (20-30 kHz), time (1-10 min), and power (30-90%) technological conditions used in maceration, to obtain valuable information on potential technological transferability. Valuable results were obtained regarding the release of thiols from their precursors, and the reactivity changes of unstable proteins of white wines. The experimental trails on red grape varieties allowed a maintenance of free anthocyanins and no degradative effects were highlighted. Significant and valuable effects were determined also on the tannin polymerization, with an astringency decrease. The sonication treatment of crushed grapes showed several chemical effects that contribute to decreasing the winemaking inputs and preserving the wine quality. The process conditions must be managed related to grape variety and ripeness for a precision winemakin

Determination of gluconic acid in wine using high pressure liquid chromatography with pulsed amperometric detection

The paper establishes a new HPLC method for measurement of the total content of gluconic acid (GA) in wine using a pulsed amperometric detector equipped with a gold electrode cell and an anion exchange column. A NaOH solution was used at a flow rate of 1.5 ml·min-1 as a mobile phase under isocratic conditions. Analysis took 30 min. The linearity of the method was shown up to 500 mg·l-1, with a LOQ of 2.0 mg·l-1 (10σ). Precision (as RSD%) was under 2.5 % in the usual range of GA concentration in natural wines. Accuracy was checked in comparison with the usual enzymatic method.

Aroma characterization of mold resistant basewines for sparkling wine produced in a warm-temperate area at two different altitudes

In a recent context where consumers pay an increasing attention to sustainability and eco-friendly aspects in the decision-making process, the use of the resistant varieties in the winesector have returned to the attention. In this context, the use of mould-resistant grape varietieswould be an opportunity for sparkling wine producers as it can reduced the pesticideutilization in grape management and hence production costs. However, the use of the resistant varieties to produce the base wine may be strongly infl uenceddue to its requirements for a particular balance between sugars and acidity to ensure thequality of the fi nal product. In addition, the aromatic profi le of base wine plays a crucial rolein the perception of the quality of the sparkling wine. This work aims to study the volatile composition of base wines produced from fi ve resistantvarieties (Bronner, Solaris, Johanniter, Souvignier Gris, Vinera) cultivated in two experimentalvineyards located in Trentino (IT): one situated on the valley bottom and one in the hill. Theresults were comparing with those of Chardonnay, the main variety used in this areanowadays for this product, cultivated in the same plots. The volatiles were extracted from thebase wines and the GC-MS/MS analysis allowed to quantify the aromatic compoundsbelonging to six different chemical classes: acetates, ethyl esters, alcohols, fatty acids, terpenesand norisoprenoids. Among the varieties, Souvignier Gris was characterised by methyl salicylate and 1-hexanol,while Solaris stood out for the concentration of β-damascone, acetates and ethyl esters.Bronner showed signifi cant contents of some grape-derived metabolites, such as β-damasconeand linalool. This terpene was also present in higher quantities in Solaris and Johanniter.Regarding the location, acetates and ethyl esters were higher in base wines of the valleybottom and fatty acids, higher alcohols and terpenes in the hilly plot wines

Modulation of wine sensory profile by lactic bacterial activity in a global warming scenario by different malolactic fermentation strategies

Aim. Incoming global warming imposing strategies to adapt wine chemical profile at an unknown scenario. In this sense malolactic fermentation (MLF), the biological deacidification of wines, must become a conscious choice to optimize the content in organic acids and the sensory profile of the wine. The authors present different works to understand how modulate the oenological activity of strains of Oenococcus oeni. The effect of different strategies of bacterial inoculum and correction of acidity were considered. Method. Simultaneous fermentation is an alternative strategy for managing MLF, which involves the inoculation of lactic bacteria into the grape must, instead into the wine at the end of alcoholic fermentation as traditionally practiced in winemaking. This approach has been tested in southern red wines with a high ethanol potential, withe aromatic wines, and sparkling-base wines. Furthermore, on a population of strains of O. oeni was verified the effect of the correction of grape must/wine acidity by different organic acids, in terms of MLF kinetics, cell viability and diacetyl production. Results. In the last years the focus of the selection of bacterial strains for malolactic fermentation was re-oriented from the mere ability to accomplish malic acid degradation, to the adaptability at different winemaking protocols. In this sense, simultaneous inoculum of bacteria and yeast in grape must seems to achieve different goals. In southern, high ethanol and low acidity wines bacteria results more active respect to tests performed by traditional post-alcoholic inoculum, accomplishing MLF without spoilage effects, such as volatile acidity increase. In the case of tests performed in winemaking if aromatic or sparkling base wines the simultaneous inoculum results in a higher varietal character. Tartaric, malic, and citric acid were tested to correct the low acidity of grape must/wine before MLF. Malic acid over the 2.5 g/L affected evolution of MLF, while citric acid stimulates bacterial activity and diacetyl production. The addition of tartaric acid results counterproductive at the higher value. Bacterial activity in grape must is more efficient than in wine in terms of rate and completeness of MLF. Conclusion. The acidic profile of wine is one of the key aspects in a global warming scenario, for longevity and organoleptic quality. This work offers useful information to modulate the activity of lactic acid bacteri

Evaluation of an optimized enzymatic biosensor for ethanol used in apple storage management with low oxygen stress

Ethanol has been proposed to be one of the target molecules to monitor the dynamic controlled atmosphere (DCA) technique during apple storage, measured in the squeezed juice or in the air of the storage chamber. One of the proposed commercial sensors for ethanol in apple juice is based on amperometry, after a two-step enzyme-based reaction that involves a diaphorase and an alcohol-dehydrogenase. Even though this method has been reported to overestimate ethanol, this difference is fairly fixed and it is industrially used to check the correct application of the treatment and to set the gas composition protocols when the maximum acceptable ethanol is reached. During the 2018 harvest, the ethanol concentration in juices measured with the commercial sensor appeared much higher than those usually reported in precedent years, particularly for the lower concentrations. Laboratory experiments suggested that differences between years could be due to the presence of a secondary enzyme activity present in the commercial diaphorase employed. In order to increase the sensitivity and accuracy, it has been evaluated the performance of the biosensor emploting a further diaphorase. The performances of both sensors were compared with those obtained with a gaschromatophy mass spectrometry approach after head space extraction (HS-GC-MS) in which the mass spectra was acquired in selected-ion monitoring mode. Samples belonging to ‘Red Delicious’ cv. were picked up at different temporary points from industrial storage rooms following the application of low oxygen stress. The new biosensor reduced 97% the mean difference respect to the values obtained with the GC-MS method. The difference between sensors was even clearer for samples with concentrations up to 100 mg/L, that could be used as a discriminating value for the evaluation of the technique success in ‘Red Delicious’ apple juice. The increased sensitivity of the sensor allowed a more accurate monitoring of the DCA at industrial conditions, limiting the risks linked to a false positive on the monitoring during storage