Application of UV-C light for preventing the light-struck taste in white wine

The light-struck taste is a fault occurring in white wine bottled in clear bottles and exposed to light. The defect is due to the formation of methanethiol and dimethyl sulphide responsible for like-cabbage aroma arising from the reaction between riboflavin (RF), a highly light-sensitive compound, and methionine (Met). The light-struck taste is limited for RF concentration lower than 50 \ub5g/L achieved through the choice of a Saccharomyces strain low RF-producer and the RF removal with charcoal and bentonite as fining agents [1]. Moreover, the protective effect of wood tannins has been recently showed, especially galla tannins [2]. Due to the RF sensibility to light, the UV-C light treatment was assayed. A synthetic wine solution spiked with RF (200 \ub5g/L) and Met (3 mg/L) was irradiated with UV-C light up to 2000 J/L and RF decay was monitored. A linear decrease as UV-C light intensity increase was observed. RF was lower than 50 \ub5g/L and 20 \ub5g/L for 1500 J/L and 2000 J/L treatments, respectively. The addition of tannins (40 mg/L) led to a limited RF decrease (73%) maybe due to their shading properties [3]. Even though the UV-C light treatment is not admitted by the International Organization of Vine and Wine, its application could represent a tool for avoid the risk of light-struck taste development in bottled wine. The light exposure when the redox potential is high and the combined use of tannins could limit the appearance of this fault after the wine bottling preserving the wine quality during the shelf-life

Characterisation of Vernaccia Nera (Vitis vinifera L.) grapes and wine

Vernaccia Nera (VN) is a minor Italian red grape cultivar whose oenological properties have not been investigated yet. Traditional winemaking procedures with VN can include grape drying and even triple sequential fermentations, but a rational vinification approach should be based on the grape composition. Since a comprehensive characterisation of the VN grape is still missing, the ripening of VN grapes was monitored by evaluating flavour compounds, proanthocyanidins and anthocyanins. The grapes were used to produce red wine whose chemical composition and sensory properties were assessed. Ripe VN grapes contained high amounts of extractable anthocyanins (0.88 g/kg). The most abundant anthocyanin was malvidin (56.6%), and high relative amounts of cumarate forms (11.3%) were also found. The grape skin showed a high concentration of proanthocyanidins (2 g/kg), whose degree of polymerisation was low (10.3). Epigallocatechin accounted for up to 39% of the flavan-3-ol units in the skin. Flavour compounds in the grapes included glycosylated norisoprenoids (mainly 3-oxo-alpha-ionol and vomifoliolo) and benzenoids. The VN red wine showed a high concentration of anthocyanins, but the level of proanthocyanidins (0.93 g/L) was lower than expected. The spicy flavours were the notes mostly recognised in the sensory evaluation. Our data highlight the VN grape as suitable for the production of ready-to-drink or shortly aged red wine due to its high acidity and low astringency

Oxygen Consumption in South African Sauvignon Blanc Wines: Role of Glutathione, Sulphur Dioxide and Certain Phenolics

The aim of this research was to investigate the interaction between sulphur dioxide, glutathione (GSH) andcertain phenols in the presence of oxygen in a synthetic wine and in clarified Sauvignon blanc wine. In thisstudy, the clarified wine, from which most of the phenols had been removed, was compared to syntheticwine solution, with both mediums being enriched with caffeic acid to investigate the effect of different levelsof sulphur dioxide and GSH on oxygen consumption. Moreover, thirteen young South African Sauvignonblanc wines with different levels of sulphur dioxide were oxygenated, and the oxygen consumption andphenolic and colour changes were monitored over time. The results show that oxygen consumption wasinfluenced greatly by the presence of sulphur dioxide and, to a lesser extent, by the presence of GSH,with both compounds decreasing during the course of the experiment. During oxidation, an increasewas observed in glutathionyl caffeic acid, as well as in oxidised glutathione (GSSG); however, this didnot coincide with the percentage decrease in GSH. Oxidation further led to an increase in absorbancemeasurements at 420 and 440 nm (yellow-orange colour), which were reduced by the presence of SO2. Alarge variation was also observed in the oxygen consumption of the young wines, with this rate increasingwith an increase in SO2 concentration. Positive correlations were also observed between oxygen, SO2, GSHand Cu concentrations, which were again negatively correlated with absorbance at 420 and 440 nm andGSSG concentrations

Chemical Characterization and Volatile Profile of Trebbiano di Lugana Wine: A Case Study

In this study, the volatile profile of Trebbiano di Lugana wine was determined and its chemical composition was considered to understand its potential longevity. Seven wine samples produced in different years (2005-2017) were collected by the same winery and analyzed up to 13 years after bottling. Color, total and polymeric phenols, glutathione, free volatiles and sensory characteristics were assessed. The color turned from yellow to an increased brownish hue as the aging time increased; nonetheless, it was stable up to five years from the production. Thirty-six aroma compounds were detected including higher alcohols, esters, and norisoprenoids (\u3b2-damascenone and \u3b2-oxo-ionone). While higher alcohols did not show a dependence on the different years of production, a decrease of esters was found over aging with the exception of wine produced in 2009, the latter showing higher levels of glutathione that could limit esters' hydrolysis. The perception of floral and fruity notes was dependent on the storage time with little differences up to five years after bottling. Trebbiano di Lugana wine could be suitable for aging and this aptitude might be further improved also through the proper choice of closure and packaging systems to encourage logistic and marketing strategies

Impact of Cooking on Bioactive Compounds and Antioxidant Activity of Pigmented Rice Cultivars

Pigmented rice cultivars, namely Venere and Artemide, are a source of bioactive molecules, in particular phenolics, including anthocyanins, exerting a positive effect on cardiovascular systems thanks also to their antioxidant capacity. This study aimed to determine the total phenol index (TPI), total flavonoids (TF), total anthocyanins (TA) and in vitro antioxidant capacity in 12 batches of Venere cultivar and two batches of Artemide cultivar. The rice was cooked using different methods (boiling, microwave, pressure cooker, water bath, rice cooker) with the purpose to individuate the procedure limiting the loss of bioactive compounds. TPI, TF and TA were spectrophotometrically determined in both raw and cooked rice samples. Rice samples of Artemide cultivars were richer in TPI (17.7-18.8 vs. 8.2-11.9 g gallic acid/kg in Venere rice), TF (13.1 vs. 5.0-7.1 g catechin/kg rice for Venere rice) and TA (3.2-3.4 vs. 1.8-2.9 g Cy-3glc/kg for Venere rice) in comparison to those of Venere cultivar; as well, they showed higher antioxidant capacity (46.6-47.8 vs. 14.4-31.9 mM Trolox/kg for Venere rice). Among the investigated cooking methods, the rice cooker and the water bath led to lower and comparable losses of phenolics. Interestingly, the cooking water remaining after cooking with the rice cooker was rich in phenolics. The consumption of a portion of rice (100 g) cooked with the rice cooker with its own cooking water can supply 240 mg catechin and 711 mg cyanidin 3-O-glucoside for Venere rice and 545 mg catechin and 614 mg cyanidin 3-O-glucoside for Artemide rice, with a potential positive effect on health

Effect of the grape must extraction steps on the content of varietal thiol precursors

The varietal thiols 3-sulfanyl-3-methylpentan-2-one, 3-sulfanylhexan-1-ol and its acetyl ester are the main responsible for boxwood, grapefruit and passion fruit notes of many white wines. These compounds occur in grape only as non-volatile precursors bound to S-glutathionyl- or S-cysteinyl- moieties but they are released by the yeast over the fermentation. However, the amount of these volatile compounds in wine is seldom related to the amount of their precursors in grape [1] because the lyase activity of yeast is a strain-dependent characteristic [2] and the probable contribution of hydrogen sulphide to the neoformation of the volatile thiols [3]. Fracassetti et al. [4, 5] reported massive loss of glutathione and glutathionyl- bounded varietal thiols as result of the grape juice extraction under production in industrial-scale conditions. Particularly, more than 60% of the precursors S-glutathionyl-3-sulfanylhexan-1-ol (GSH-3MH) and its aldehyde form (S-glutathionyl-3-sulfanylhexanal, GSH-3MHAl) got lost from Grillo and Catarratto bianco grape cultivars, the main Sicilian white grape cultivars, as result of the juice extraction. Such a behaviour can seriously detrimentally affect the flavouring properties of the final wine and it points out a further source of the lacking correlation between the amount of precursors in grape and volatile thiols in wine. The reasons for such behaviour were investigated in Grillo grape pressed under industrial-scale production. Must samples were collected after crashing, at draining, at pressing yield of 20%, 40%, 60% and 70%, during transfer in clarification tank, in the clarification tank and after clarification. The must was either air-exposed or air-free during the pre-fermentative steps. Thiol precursors were determined in SPE-purified must samples by UPLC-HRMS [5]. The concentration of thiol precursors detected following the crushing was comparable to the value found in grape, but it dramatically decreases (< 95%) in the must from the press loading. The concentration of thiol precursors increased as the must yield increased, and eventually equals the levels in the grape when a must yield of 60% was achieved. The final loss of thiol precursors was about 80% and 95% for GSH-3MH and GSH-3MHAl, respectively, in the must sampled at the clarification vat (the last juice fraction was excluded). Higher loss of thiol precursors was observed when the must was produced under air-free condition, whereas higher amounts were recorded in laboratory-made must, especially when sodium fluoride or EDTA were added prior the pressing. The results show that the contact of must with the grape skin leads to a loss of thiol precursors. Oxygen seems to be not involved in the oxidative loss of thiol precursor The protective behaviour of the cation-binding compounds suggests that the cations occurring on the grape skin can be responsible for the loss of thiol precursors during the pre-fermentative steps