Influence of Different Dehydration Levels on Volatile Profiles, Phenolic Contents and Skin Hardness of Alkaline Pre-Treated Grapes cv Muscat of Alexandria (Vitis vinifera L.).

A dehydration experiment was carried out on Vitis vinifera L. cv Muscat of Alexandria (synonym Zibibbo) following the process for the production of renowned special dessert wines produced on Pantelleria island (Sicily, Italy). Harvested berries were pre-treated in a sodium hydroxide dipping solution (45 g/L, dipped for 185 s, 25 °C) to accelerate the drying process, rinsed, and dehydrated in simulated conditions (relative humidity 30%, 30 °C temperature, air speed 0.9 m/s). Three dehydration levels were achieved, corresponding to "Passolata", "Bionda", and "Malaga" stages (35%, 50%, and 65% of weight loss, respectively) of the Pantelleria denomination of origin (DOC). Grape skin mechanical properties, technological parameters, phenolics, and aroma profile varied considerably during dehydration. The most important aroma compounds for their olfactory impact, such as linalool, geraniol, nerol, and citronellol, especially in glycosylated forms, significantly increased in dried grapes compared to fresh ones, even if aroma profile modification occurred. A decrease in break skin force could have induced higher release of flavonoids. The findings showed relevant changes, allowing winemakers to better select the ratio of fresh and dehydrated grapes in the function of the final desired wine.

Relationships among electrolyzed water postharvest treatments on winegrapes and chloroanisoles occurrence in wine.

Electrolyzed water (EW) has attracted much recent attention as a high-performance, new technology for its potential use in the food industry. However, the risk of postharvest EW treatments of winegrapes destined for winemaking is the chloroanisoles formation in the final product. In the present study, we investigated the impact of postharvest grape EW and storage treatments on the occurrence of these compounds in wine, 2,4,6-trichloroanisole (TCA) being the main compound responsible for the cork taint off-flavor due to its extremely low perception threshold. The results revealed that the presence of TCA in the wines depended on the concentration of residual free chlorine in the must from the EW treatment. Particularly, TCA was not detected in wine when active chlorine concentrations higher than 0.005 mg/L were present in the must. Chloroanisole and chlorophenol levels in wine were strongly affected not only by EW but also by grape storage conditions (temperature, time, sunlight exposition). The results showed that the 24-hours grape storage at a controlled temperature of 20 °C in the dark, after EW treatment, resulted in the highest TCA concentrations in wines (7.3 ±â€¯2.7 ng/L), while storage and withering in sunlight seemed to mitigate its presence in wine. This could suggest that microbiological formation of chloroanisoles may have been influenced by the storage temperature and germicidal effect of UV light. Biochemical mechanism of chloroanisoles production in grapes and wine is unknown, but the combination of residual free chlorine on the grape surface and the controlled storage conditions in the dark may have positively influenced the bio-formation of chloroanisoles and therefore their presence in wine.

Use of density sorting for the selection of aromatic grape berries with different volatile profile.

The aim of the study was to investigate the application of berry density sorting as a tool for the selection of grapes with different volatile and precursor profiles. The study was carried out on Moscato giallo, Malvasia di Schierano, Malvasia nera lunga, and Brachetto aromatic grape varieties. Free and glycosidically-bound terpene compounds including linalool, geraniol, nerol, citronellol, and terpineol, as well as lipoxygenases activity-derived compounds, were evaluated using head space-solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) in density sorted berries (1075-1119 kg m-3). Total free terpenes changed with the berry density, while no significant changes were found in total glycosylated compounds, except for Malvasia nera lunga grapes where nerol, linalool, and geraniol contributed strongly to the increase of total contents with increasing berry density. Given that these variations were strongly variety-dependent, the possible use of density sorting equipment in winery for this aim may be less effective.

The use of chitosan as alternative to bentonite for wine fining: Effects on heat-stability, proteins, organic acids, colour, and volatile compounds in an aromatic white wine.

This investigation focuses on the use of chitosan treatment simulating a bentonite fining in order to detect any modification of the wine haze potential by simultaneously evaluating the secondary effects on untargeted fixed and volatile compounds. A significant removal of chitinases was observed after fining an aromatic white wine with 1 g/L of a fungoid chitosan. Even if the more stable thaumatin like protein fractions were not significantly affected, the heat stability of the fined chitosan wine samples were highly improved in the 55-62 °C range. Among the secondary effects of a fining treatment, a reduction of tartaric acid, malic acid, potassium and iron was showed. All the free terpenols with the exception of α-terpineol were reduced in significant amounts, whilst the glycosylated forms and the fermentative aroma compounds were not affected by a 1 g/L chitosan addition.

Volatile profiles and chromatic characteristics of red wines produced with Starmerella bacillaris and Saccharomyces cerevisiae.

The use of mixed fermentations with Starmerella bacillaris and Saccharomyces cerevisiae is gaining attention in recent years due to their ability to modulate the metabolites production of enological interest. In the present study, four of the most popular planted red grape varieties (Cabernet sauvignon, Merlot, Pinot noir and Shiraz) were fermented using the aforementioned species and two different inoculation protocols (inoculation of S. cerevisiae after 24 and 48 h from the Starm. bacillaris inoculation), in order to evaluate their impact on the volatile composition and chromatic characteristics of wines. Analysis from chemical composition showed that titratable acidity and glycerol content exhibited marked differences among wines after fermentation. For volatile compounds, mixed fermented wines using an inoculation delay of 48 h led to reduction of volatile compounds (mainly esters). A shorter 24 h delay produced wines with higher values of color intensity than pure fermented wines. The differences observed between the inoculation protocols can be explained by the growth dynamics of both species during fermentation. These findings suggest that mixed fermentations posed a great potential in reducing metabolites which are considered negative for wine quality (mainly ethyl acetate and volatile fatty acids) and with an improvement of the chromatic profile of the wines.

Impact of Increasing Levels of Oxygen Consumption on the Evolution of Color, Phenolic, and Volatile Compounds of Nebbiolo Wines.

Since the end of the last century, many works have been carried out to verify the effect of controlled oxygen intake on the chemical and organoleptic characteristics of red wines. In spite of the large number of studies on this subject, oxygen remains a cutting-edge research topic in oenology. Oxygen consumption leads to complex and not univocal changes in wine composition, sometimes positive such as color stabilization, softening of mouthfeel, increase of aroma complexity. However, the variability of these effects, which depend both on the oxygenation conditions and the composition of the wine, require more efforts in this research field to effectively manage wine oxygen exposure. The present study is focused on the evolution of the chemical composition of four different Nebbiolo wines, each of them added with 4 different doses of oxygen (7, 14, 21, and 28 mg/L total intake) during the first month of storage. In this perspective, the evolution over time of wine color and polyphenols was studied. Acetaldehyde, glyceraldehyde and glyoxylic acid were quantified by HPLC. These compounds can play a role in wine aging creating condensed colored and stable products involving anthocyanins with or without tannins. Moreover, some volatile aldehydes correlated with oxidized olfactory notes, including methional and (E)-2-alkenals, have been quantified by GC-MS. Overall, during storage a decrease of color intensity, total and free anthocyanins and an increase in polymeric pigments (in particular the contribution to the red color of pigments not-bleachable by SO2 or dTAT%) and some minor aldehydes was observed. Nevertheless, the differences in color parameters between the samples with different doses of oxygen were modest. These evidences were in contrast with an evident and detectable increase of free acetaldehyde content at increasing doses of oxygen measured after 60 days of storage. The effect of oxygen on color and production of SO2 non-bleachable pigments during aging varies with wine composition, with Nebbiolo wines appearing not very reactive in this respect, probably due to their low content in anthocyanins and high content in tannins.

Volatile profile of white wines fermented with sequential inoculation of Starmerella bacillaris and Saccharomyces cerevisiae.

Mixed fermentations with Starmerella bacillaris and Saccharomyces cerevisiae affect the chemical composition of wines, by modulating various metabolites of oenological interest. The current study was carried out to elucidate the effect of sequential inoculation of the above mentioned species on the production of white wines, especially on the chemical and aromatic characteristics of Chardonnay, Muscat, Riesling and Sauvignon blanc wines. Titratable acidity and glycerol content exhibited evident differences among the wines after fermentation. For volatile compounds, mixed fermentations led to a reduction of the total esters, including ethyl acetate, which is a compound responsible for wine deterioration. However, Sauvignon blanc wines fermented by mixed cultures contained significantly higher levels of esters and thiols, both associated with positive sensory attributes. These findings suggest that sequential inoculations possess great potential in affecting and modulating the chemical and aromatic profile of white wines, especially those produced from Sauvignon blanc grapes.

Grape VOCs Response to Postharvest Short-Term Ozone Treatments.

Ozone has been recently recognized as an efficient sanitizing agent in wine industry because of its powerful oxidizing properties. Furthermore, postharvest treatments of grapes with ozone can stimulate defense responses by synthetizing secondary metabolites against oxidative stress. In this study, the effect of postharvest short-term ozone treatments was assessed for the first time on free and glycosylated volatile organic compounds (VOCs) of winegrapes. Two different ozone concentrations (30 and 60 µL/L) and exposure times (24 and 48 h) were investigated just after treatment (fresh grapes) and after partial dehydration up to 20% weight loss (withered grapes). The study was carried out on Moscato bianco winegrapes (Vitis vinifera L.) due to the importance of terpenes in white aromatic cultivars to produce high quality wines. The results obtained showed that short-term ozone treatment caused a significant decrease in total contents of free VOCs in fresh grapes, mainly due to terpenes. Among them, linalool, geraniol, and nerol are the major aromatic markers of Moscato bianco grapes. Ozone entailed a significant decrease of free linalool contents in fresh grapes, the less stressful ozone treatment showing the smaller linalool degradation. However, the stronger and longer ozone treatment induced the synthesis of this compound probably in response to higher abiotic stress. Instead, significant changes were not observed in geraniol and nerol contents in fresh grapes. This last ozone treatment also reduced the loss of free linalool by water loss in withered grapes even though total VOCs and terpenes remained relatively stable. Furthermore, ozone seems to promote the synthesis of free (+)-4-carene and 4-terpineol in withered grapes under certain treatment conditions. Regarding glycosylated compounds, total VOCs and terpenes were less sensitive to ozone. Our findings highlight that ozone can be used as sanitizing agent in aromatic grape varieties prior to winemaking without affecting sharply the aromatic profile of fresh grapes and even improving it in withered grapes.

Oxygen availability and strain combination modulate yeast growth dynamics in mixed culture fermentations of grape must with Starmerella bacillaris and Saccharomyces cerevisiae.

Starmerella bacillaris (synonym Candida zemplinina) is a non-Saccharomyces yeast that has been proposed as a co-inoculant of selected Saccharomyces cerevisiae strains in mixed culture fermentations to enhance the analytical composition of the wines. In order to acquire further knowledge on the metabolic interactions between these two species, in this study we investigated the impact of oxygen addition and combination of Starm. bacillaris with S. cerevisiae strains on the microbial growth and metabolite production. Fermentations were carried out under two different conditions of oxygen availability. Oxygen availability and strain combination clearly influenced the population dynamics throughout the fermentation. Oxygen concentration increased the survival time of Starm. bacillaris and decreased the growth rate of S. cerevisiae strains in mixed culture fermentations, whereas it did not affect the growth of the latter in pure culture fermentations. This study reveals new knowledge about the influence of oxygen availability on the successional evolution of yeast species during wine fermentation.

Ozone Improves the Aromatic Fingerprint of White Grapes.

Ozone, a powerful oxidative stressor, has been recently used in wine industry as sanitizing agent to reduce spoilage microflora on grapes. In this study, we evaluated ozone-induced metabolic and molecular responses during postharvest grape dehydration. Ozone increased the contents of total volatile organic compounds (VOCs), which have a great impact on the organoleptic properties of grapes and wines. Among terpenes, responsible for floral and fruity aroma, linalool, geraniol and nerol were the major aromatic markers of Moscato bianco grapes. They were significantly affected by the long-term ozone treatment, increasing their concentration in the last phases of dehydration (>20% weight loss). At molecular level, our results demonstrated that both postharvest dehydration and ozone exposure induce the biosynthesis of monoterpenes via methylerythritol phosphate (MEP) pathway and of aldehydes from lipoxygenase-hydroperoxide lyase (LOX-HPL) pathway. Therefore, transcriptional changes occurred and promoted the over-production of many important volatile compounds for the quality of white grapes.

Comparison of fortified, sfursat, and passito wines produced from fresh and dehydrated grapes of aromatic black cv. Moscato nero (Vitis vinifera L.).

Moscato nero d'Acqui is an Italian aromatic black winegrape variety characterized by a low content of anthocyanins (mostly tri-substituted), a satisfactory content of high molecular mass tannins, and a fair amount of terpenes. The grapes were subjected to a postharvest dehydration process under controlled thermohygrometric conditions (16-18°C, 55-70 RH%, 0.6m/s air speed) with the aim to produce three different special wine types (fortified, sfursat, and passito) from fresh, partially dehydrated (27°Brix), and withered (36°Brix) grapes, respectively. Chemical traits of produced grapes and wines were then evaluated through spectrophotometric, HPLC, and GC-MS methods. Increased contents of skin phenolic compounds and reduced extractable contents of seed phenolic compounds were observed as dehydration progressed. Few significant differences were found in the anthocyanin profile of grapes, although the relative abundance of coumaroylated anthocyanins was higher in dehydrated grapes. The predominant free volatile compound found in grapes was geraniol, which decreased with increasing water loss, whereas the contents of major glycosylated volatile compounds increased even above the concentration effect. The changes in the phenolic composition among wines agreed with those among grape skins. Fortified wines were chromatically unsatisfactory probably due to the low content of total anthocyanins, whereas sfursat and passito wines meet good chromatic characteristics as a result of the concentration effect during grape dehydration. Fortified and sfursat wines had free aroma profiles richer in 2-phenylethanol and citronellol, whereas passito wines were mainly composed of 2-phenylethanol and 2-phenylethyl acetate, citronellol being the predominant terpenol in all the wine types studied.

Impact of post-harvest ozone treatments on the skin phenolic extractability of red winegrapes cv Barbera and Nebbiolo (Vitis vinifera L.).

Recently the use of ozone as sanitizing agent has been proposed on winegrapes in order to control mycobiota after harvest. The aim of this work was to investigate possible indirect physico-chemical effects of ozone treatment on berry skin phenolic composition and extractability. Vitis vinifera L. cv Nebbiolo and Barbera, chosen for their different anthocyanin profiles, were post-harvest treated for 24 and 72h with gaseous ozone (30µL/L). Skin anthocyanin and flavanol extractability was assessed during maceration (6, 24, 48, 96, 168 and 240h) using a wine-like solution. In our experimental conditions, ozone did not affect significantly the final extraction yield of anthocyanins (TA), proanthocyanidins (PRO), and flavanols reactive to vanillin (FRV) in Barbera, although TA and FRV extractabilities were higher in control samples than in ozone-treated samples during the first stages of maceration. In Nebbiolo, the final TA extraction yield was positively influenced by the ozone treatment (68.6, 64.2, and 59.9% for 24h ozone-treated berries, 72h ozone-treated berries and control samples, respectively). Final PRO and FRV extractability also increased in both ozone-treated samples compared to the control (+8.6-9.1% for PRO and +7.3-11.7% for FRV). No significant differences were found among treatments for individual anthocyanins in both cultivars at the end of maceration. Therefore, the use of ozone as sanitizing agent in red varieties prior to winemaking process can be considered because it did not negatively affect the extractability of skin anthocyanins and flavanols.

Metabolite profiling and volatiles of pineapple wine and vinegar obtained from pineapple waste.

Vinegar is an inexpensive commodity, and economic considerations require that a relatively low-cost raw material be used for its production. An investigation into the use of a new, alternative substrate - pineapple waste - is described. This approach enables the utilization of the pineapple's (Ananas comosus) peels and core, which are usually discarded during the processing or consumption of the fruit. Using physical and enzymatic treatments, the waste was saccharified, and the resulting substrate was fermented with Saccharomyces cerevisiae for 7-10days under aerobic conditions at 25°C. This resulted in an alcohol yield of approximately 7%. The alcoholic medium was then used as a seed broth for acetic fermentation using Acetobacter aceti as the inoculum for approximately 30days at 32°C to obtain 5% acetic acid. Samples were analyzed at the beginning and end of the acetification cycle to assess the volatile and fixed compounds by GC-MS and UHPLC-QTOF-MS. The metabolomic analysis indicated that l-lysine, mellein, and gallic acid were significantly more concentrated in the pineapple vinegar than in the original wine. Higher alcohols, aldehydes, and ketones characterized the aroma of the final pineapple vinegar, whilst off-flavors were significantly reduced relative to the initial wine. This study is the first to highlight the metabolite profile of fruit vinegar with a slight floral aroma profile derived from pineapple waste. The potential to efficiently reduce the post-harvest losses of pineapple fruits by re-using them for products with added food values is also demonstrated.

'Fortified' wines volatile composition: Effect of different postharvest dehydration conditions of wine grapes cv. Malvasia moscata (Vitis vinifera L.).

The impact of postharvest dehydration on the volatile composition of Malvasia moscata grapes and fortified wines produced from them was assessed. The ripeness effect of fresh grapes on volatile compounds of dehydrated grapes was evaluated for the first time in this study. Fresh grape berries were densimetrically sorted, and more represented density classes were selected. Dehydration of riper berries (20.5 °Brix) led to volatile profiles richer in terpenes, particularly linalool and geraniol. The effect of dehydration rate on the volatile composition of dehydrated grapes and fortified wines was also evaluated. Fast dehydration grapes were richer in total free terpenes, and the resulting wines contained greater amounts of volatile compounds. The predominant compounds were free esters, but linalool, rose oxide, citronellol and geraniol can also contribute to wine aroma, particularly for fast dehydration. ß-Damascenone can be an active odorant, although its contribution was greater in wines made from slow dehydrated grapes.

Use of response surface methodology for the assessment of changes in the volatile composition of Moscato bianco (Vitis vinifera L.) grape berries during ripening.

The changes in the volatile composition of Moscato bianco grapes were evaluated during ripening. Grape berries were sampled for five weeks (16-20 °Brix) and sorted for each date in ten density classes (1.05-1.12g/cm(3)). The highest total concentration of free terpenes was found at 19.3 °Brix; however, total concentration of the bound fraction increased significantly throughout ripening. Response surface methodology was used to assess the simultaneous effect of sampling time and berry density on the volatile composition, which was satisfactorily fitted to regression models for some key terpene compounds. Total free and bound terpenes were more affected by grape density than by sampling date. The same behaviour was observed for free and bound linalool and bound nerol, whereas the stronger effect of sampling date was exhibited for bound t-rose oxide, c-rose oxide and geraniol. The results showed that the sampling strategy impacted strongly on the aroma quality of berries.

Starmerella bacillaris and Saccharomyces cerevisiae mixed fermentations to reduce ethanol content in wine.

Decreasing the ethanol content in wine is a current challenge, mainly due to the global climate change and to the consumer preference for wines from grapes with increased maturity. In this study, a central composite design (CCD) and response surface methodology (RSM) approach was used to investigate the potential application of Starmerella bacillaris (synonym Candida zemplinina) in combination with Saccharomyces cerevisiae, in mixed (co-inoculated and sequential) cultures, to understand better the mechanism of co-habitation and achieve the objective of reducing the ethanol in wines. Laboratory scale fermentations demonstrated a decrease up to 0.7 % (v/v) of ethanol and an increase of about 4.2 g/L of glycerol when S. cerevisiae was inoculated with a delay of 48 h with respect to the inoculation of S. bacillaris. Pilot-scale fermentations, carried out in winemaking conditions, confirmed the laboratory results. This study demonstrates that the combination of strains and inoculation protocol could help to reduce the ethanol content in wines.

Impact of postharvest dehydration process of winegrapes on mechanical and acoustic properties of the seeds and their relationship with flavanol extraction during simulated maceration.

This study represents the first time that the extraction of phenolic compounds from the seeds is assessed from instrumental texture properties for dehydrated grapes. Nebbiolo winegrapes were postharvest dehydrated at 20°C and 41% relative humidity. During the dehydration process, sampling was performed at 15%, 30%, 45% and 60% weight loss. The extractable fraction and extractability of phenolic compounds from the seeds were determined after simulated maceration. The evolution of mechanical and acoustic attributes of intact seeds was also determined during grape dehydration to evaluate how these changes affected the extraction of phenolic compounds. The extractable content and extractability of monomeric flavanols and proanthocyanidins, as well as the galloylation percentage of flavanols, might be predicted easily and quickly from the mechanical and acoustic properties of intact seeds. This would help in decision-making on the optimal dehydration level of winegrapes and the best management of winemaking of dehydrated grapes.

Influence of different withering conditions on phenolic composition of Avanà, Chatus and Nebbiolo grapes for the production of 'Reinforced' wines.

The impact of postharvest withering rates on the phenolic composition of 'reinforced' wines produced with partially dehydrated grapes was evaluated. The study was performed on winegrape varieties with anthocyanin profiles differently constituted of di- and tri-substituted forms. Dehydration induced limited changes in the anthocyanin profile of berry skins. Nevertheless, the greatest abundance of total anthocyanins and their more stable forms (malvidin-3-glucoside and acylated glucosides) corresponded to the wines made from slow withered Chatus grapes, which were in turn the darkest. In contrast, the wines made from withered Avanà grapes did not meet good chromatic characteristics due to low contents of total anthocyanins and high ratios between di- and tri-substituted forms. Nebbiolo wines showed intermediate values of this ratio, and therefore of clarity and color intensity. The fast process is recommended because higher percentages of galloylated flavanols in the seeds of slow withered Nebbiolo grapes may have a negative influence on wine astringency.

Ozone treatments of post harvested wine grapes: Impact on fermentative yeasts and wine chemical properties.

Ozone represents a potent antimicrobial compound that is already proposed as a possible sanitizing agent, especially for surface decontamination of fruits and vegetables. The main objective of this study was to evaluate the effect of ozone, either in aqueous or gaseous form, on wine grape mycobiota and its impact during spontaneous and inoculated fermentations. Gaseous (32±1µL/L, 12 and 24h) and aqueous (5±0.25mg/L, 6 and 12min) ozone were tested as sanitizing treatments. A multiphasic approach was used employing culture-dependent (traditional plate counts) and -independent techniques, based on DNA and RNA amplification (PCR-denaturing gradient gel electrophoresis [DGGE] and reverse transcription PCR [RT-PCR]-DGGE), respectively. Microbiological analysis data highlighted a reduction of >0.5LogCFU/mL of the total yeasts present on grape berry surfaces after ozone treatments, mainly due to the reduction of apiculate yeasts. The chemical analysis of the wines, produced from the treated grapes, showed higher acetic acid content in the untreated spontaneous fermentations (0.52g/L) compared to the treated (ranged from 0.16 to 0.38g/L), while all fermentation-inoculated wines contained higher amounts of pleasant volatile compounds.

H, C, and O Stable Isotope Ratios of Passito Wine.

In this study we investigated the effect of the grape withering process occurring during the production of Italian passito wines on the variability of the (D/H)I, (D/H)II, δ(13)C, and δ(18)O of wine ethanol and the δ(18)O of wine water. The production of PDO Erbaluce di Caluso Passito in five different cellars in Piedmont (Italy) was considered in two successive years. Moreover, samples of 17 different traditional Italian passito wines taken at different stages of maturation were taken into account. We found that the δ(18)O of must and wine water and the δ(18)O of ethanol decrease in the case of passito wines produced in northern and central Italy using postharvest drying of the grapes in dedicated ventilated or unventilated fruit drying rooms (fruttaio), during autumn-winter. For passito wines produced in southern Italy, where the main technique involves withering on the plant (en plein air), δ(18)O tends to increase. The (DH)I of wine ethanol did not change during withering, whereas the (DH)II and δ(13)C values changed slightly, but without any clear trend. Particular attention must be therefore paid in the evaluation of the δ(18)O data of passito wines for fraud detection.