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The development in young white wines of 2-aminoacetophenone, commonly known as atypical aging defect (UTA), leads to unpleasant notes such as mothball, wet mop, sweaty, acacia blossom, or soap. Tryptophan and indole-3-acetic acid, the most abundant auxin in plants, are considered to be the primary precursors of this compound. Indole-3-acetonitrile; indole-3-lactic acid; skatole; tryptophol and the inactivated form of the auxin N-(3-indolylacetyl)-L-alanine; N-(3-indolylacetyl)-DL-aspartic acid; and methyl-indole-3-acetate can act as potential precursors of 2-aminoacetophenone and contribute directly to UTA scents in wines. This paper investigates the distribution of 2-aminoacetophenone precursors or intermediate metabolites (n = 9) in grape berry tissues (pulp, skin, and seeds) in 12 samples of four different varieties: Cabernet Cantor, Chardonnay, Merlot, and Solaris. Chardonnay (three lots) was analyzed in more depth by evaluating precursor extraction during industrial pressing at different stages. For quantification, this study developed and validated a method using high-performance liquid chromatography coupled with high-resolution mass spectrometry. It used a pre-concentration and purification solid-phase extraction-online system and had a detection limit between 0.25 and 2 µg/L, depending on the compound. Despite significant varietal differences, indole-3-acetic acid was more abundant in seeds and skin fractions. Only ~30% of the total berry amount was extracted with free-run pressing, but ~80% was extracted at 0.6 bar. This suggests a fundamental role of pressing in managing the development of UTA during winemaking.

In this work, the anthocyanins’ profile of two hybrid grape varieties—Cabernet Carbon and Prior—grown in two experimental plots in Trentino (Northern Italy) was investigated during 2016 and 2017 harvests. The focus was on the mono- and di-glycoside anthocyanins extraction during the fermentative maceration. It was optimized an HPLC-DAD method, which allows the separation and quantification of mono- and di-glucoside anthocyanin forms (non-esterified, acetylated, and p-coumaroylated) in a single chromatographic run. Furthermore, an HPLC-DAD/HQOMS approach was used to confirm the compound identification. The skin contact fermentation was conducted for 7 days at 24 °C, punching down manually the cap twice a day. Must samples were collected every 24 h. As expected, every anthocyanin showed an initial net extraction phase described by a first-order kinetic, followed by a decrease until the end of the maceration. The analysis of the accumulation rate showed a faster increase of the di-glucoside anthocyanins concentration compared to the corresponding mono-glucoside, due to their richness in the initial grapes. Moreover, the di-glucosides concentration at the end of the alcoholic fermentation underwent a three times minor percentage decrease with respect to the maximum reached. This paper intend to improve the knowledge of the kinetics of each anthocyanin form during the maceration step, providing information about the behavior of di-glucoside compounds, never investigated before in terms of accumulation and percentage decrease.

Polyphenols, especially anthocyanins, play an important role on red wine sensory qualities and their evolution during storage. High Power Ultrasound (HPU) has been recognized as one of the most promising technologies which can be applied in winemaking processes for several purposes, and it is recently officially approved for crushed grapes treatments. The effect of ultrasound amplitude (41 and 81%) and treatment time (1, 3, and 5 min) has been studied on anthocyanins, flavan-3-ols, tannins, polymerized pigments, HCl index, and the color intensity of two finished red young wines. Anthocyanins and phenols compounds were not degraded with an increase in amplitude and sonication time, and the chromatic properties of the selected wines were preserved. Amplitude and ultrasound time were also evaluated considering their effect on evolution of anthocyanin content and phenolic stability indices during the first thirty days of storage. The higher level of amplitude (81%) induced a higher percentage decrease in tannins, 15% and 40% after 15 and 30 days of storage, respectively, compared to untreated wine which did not show a significant change during storage. HPU shows a possible chemical effect on the evolution of some analytical indices during bottling maturation, but their effectiveness could be strictly linked with the initial phenolic profile and ratios between polyphenol classes.

Atypical aging of white wines (ATA) is an off-flavour characterised by rapid loss of fruity aromas and the development of unpleasant odours. This study aims to evaluate the effectiveness of different oenological adjuvants (4-ethylcatechol, 4-methylcatechol, gentisic acid, hydroxytyrosol, ascorbic acid, glutathione, ellagic acid, gallic acid, galla tannin, ellagic tannin, quebracho, grape tannins) added to musts before fermentation for preventing the possible development of ATA. High resolution mass spectrometry made it possible to quantify and qualify free and conjugated IAA in wine at the end of the fermentation and subsequently 2-aminoacetophenone (AAP) was quantified after the force ageing period (6 days at 40 °C). Ascorbic acid was confirmed as the most appropriate antioxidant adjuvant which can be used for ATA defect prevention. With an almost comparable effect, gallotannin addition prevented AAP production to exceed 1 μg/L. A predicted model (ANCOVA) indicated that over 80% of the variability of potential AAP formation in wines was explained by the amount of precursors, grape variety and antioxidant treatment. Moreover, a suspect screening approach made it possible to study the kinetic formation and the consumption of the reaction metabolites formed during the oxidative degradation of IAA leading to AAP.

The effect of ultrasound (20 kHz, 153 &mu, m) on the prefermentation extraction mechanisms in Sauvignon Blanc grapes was studied, focusing on 3-mercaptohexan-1-ol (3MH) and 4-mercapto-4-methyl-pentan-2-one (4MMP) precursors linked to glutathione (GSH) and cysteine (Cys). The treatment determined a positive extraction trend between the duration (untreated, 3 and 5 min) and the conductivity or the concentration of catechins and total phenols, significantly differentiated after 5 min. Nevertheless, the concentration of the thiol precursors in grape juice not only remained undifferentiated, but that of 3-S-glutathionyl mercaptohexan-1-ol showed a negative trend with the treatment time applied (168 &plusmn, 43, 156 &plusmn, 36, and 149 &plusmn, 32 &mu, g/L, respectively, for control, 3 and 5 min). The divergence on the effect between families of compounds suggests an interaction between the sonication treatment and thiol precursor molecules. In order to evaluate the possible degradation properly, ultrasound was applied in a model solution spiked with 3MH and 4MMP precursors, reproducing the conditions of grapes. Except for Cys-3MH, the mean concentration (n = 5) for the rest of the precursors was significantly lower in treated samples, predominantly in those linked to glutathione (~&minus, 22% and ~18% for GSH-3MH and GSH-4MMP) rather than to cysteine (~&minus, 6%~&minus, 8% for Cys-3MH and Cys-4MMP). The degradation of precursors was associated with a significant increase of 3MH and 4MMP. The formation of volatile thiols following sonication is interesting from a technological point of view, as they are key aroma compounds of wine and potentially exploitable in the wine industry through specific vinification protocols.

Purpose The role of fermentation temperature was studied for its impact on the evolution of malolactic fermentation performed by simultaneous inoculum of yeast and bacteria in grape must. Results were discussed considering the different fermentative kinetics and the composition of obtained wines. Methods Two strains of bacteria belonging to the O. oeni and L. plantarum species were inoculated 24 h after the beginning of the alcoholic fermentation in 2 grape musts having different acidic and sugar profiles. Fermentations were conducted at 3 different temperature profiles (16/22 °C in 3 days, 18/24 °C in 3 days, 22/32 °C in 5 days). Evolution of microbiota was followed by flow cytometry and plate count. Chemical analysis of grape musts and wines were performed by instrumental approaches (FT-IR, enzymatic quantification of malic acid, GC-MS). Results L. plantarum resulted more efficient in malic acid consumption in the entire set of tests. These results are unexpected because, generally, Lactobacillus has been reported to be more sensitive to an oenological environment than O. oeni. In our experiments, O. oeni resulted inhibited by the highest fermentation temperature profile, causing incomplete malic acid degradation. Similarly, S. cerevisiae showed a higher sensitivity to environmental limiting factors in respect to what is generally known. Differences in the chemical composition of wines were observed in relation to the bacteria strain and the temperature profile. However, the statistical treatment of data identified temperature as the main variable able to influence the features of wines. Conclusions Simultaneous inoculum of yeast and bacteria in grape must is an alternative approach in the management of malolactic fermentation which showed some interesting features. However, it is necessary to consider that the dynamics of the microbial population are different to that observed in traditional winemaking and the environmental variables act against the microorganisms in a peculiar, and in certain cases unexpected, way.

Considering the carcinogenic risk to human health, it is necessary to carry out research into arsenic (As) content in agro-food products and the impact of food processing on the final content. Yeast fermentation may represent a strategy for detoxifying some widespread beverages such as wine, beer and rice wine. A preliminary study of some commercial yeast species showed different viability responses to the presence of As. Yeasts had a noteworthy detoxification capability during fermentation, reducing the initial As content by about 75 % on average (minimum–maximum: 45–92 %), making it possible to produce wines with a considerably reduced content as compared to the corresponding grape juices from naturally As-rich soils. Nevertheless, significant differences between strains were observed in relation to resistance to arsenic toxicity and As removal capability. The choice of yeast strain can determine a difference of 40 % on the As content remaining in the wine after fermentation. Arsenic content of up to 1000 µg/L did not significantly worsen the fermentation of some wine yeasts, suggesting that the use of specific yeasts may represent an effective tool for reducing As in fermented beverages.

Sulfur chemistry remains one of the most intriguing and elusive fields in wine science. In particular, the possibility for symmetric and asymmetric glutathionylated and cysteinylated polysulfides to act as latent reservoirs for H2S warrants new research on the factors influencing the formation and accumulation of these molecules. The present research studies the impact of pre-fermentative additions of commonly employed antioxidants: glutathione, ascorbic acid, and ellagic tannin. Musts from four different white grape varieties (Riesling, Pinot gris, Pinot blanc, and Johanniter) were analysed using our comprehensive HPLC-HRMS method. Seven symmetric and asymmetric glutathionylated (G) and cysteinylated (C) polysulfides (GS2C, GS3C, GS4C, GS3G, GS4G, CS3C, and CS4C) were detected in the final 48 wine samples. Finally, this work describes for the first time the impact of an accelerated ageing of wine on the polysulfides present. All variables (Must, Treatment, and Time) were shown to impart statistically significant effects (p = 0.0001) in the PERMANOVA model. The PCAs based on polysulfides present in young and aged wine explained more than 80% of the total variance for each grape variety and showed that Asc or GSH additions have tend to produce lower levels of polysulfides in the resultant wines.

The formation of ethylphosphonate (fosetyl) was investigated in wine matrices. In experimental conditions, alcoholic fermentation of grape juices spiked with phosphonic acid resulted in wines with detectable amounts of fosetyl. The ageing period adopted for these wines further increased the fosetyl content in the absence of yeast lees, thus indicating a chemical origin. A model wine assay was performed in order to study the main thermodynamic variables affecting the Fisher reaction. The results obtained allowed us to report evidence of ethylphosphonate formation in winemaking conditions, for the first time to the best of our knowledge.

Thiol compounds responsible for tropical fruit associated aroma have been extensively studied over the last 20 years. The occurrence of their non-aromatic precursors in grapes and musts is reported largely mainly for the cultivar Sauvignon Blanc. The presence of these thiols as precursors or free molecules in grape, juice, and wine has been reported in several different varieties, suggesting that they are more or less ubiquitous both for Vitis spp. and interspecific hybrids. The biosynthetic pathways resulting in these compounds are yet to be completely elucidated, but, in the meantime, industry needs to improve technological knowledge to better manage winemaking steps to enhance the variety-dependent aroma of wine. In this work, we studied the implications of the use of grape skin tannins—rich and poor in thiol precursors—on the final content of 3-sulfanylhexan-1-ol (3MH) and its acetate (3MHA) in wine and the effect in terms of sensory appreciability. The evaluation of 36 vinifications carried out in a semi-industrial scale permitted us to prove that only a tannin originally rich in precursors (High), when added to juice at the beginning of fermentation, enhanced both the concentration of precursors in the juice and the final concentration of aromatic thiols in the resultant wine. The 3MH and 3MHA developed as a consequence of the juice supplementation with tannin High and increased pleasantness and typicality of Gewurztraminer wines. A later supplementation with tannin High at the end of the alcoholic fermentation was sensorially not effective.