1,721,011 research outputs found
Grape VOCs response to postharvest short-term ozone treatments
Get PDFOzone 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
Volatile Compound Release from Oak Chips in Model Wine Media: Combined Influence of Toasting Degree, Size, Time of Contact, and Ethanol Content
No full textThe effects of size, toasting degree, and time of contact on the release of volatile compounds from Quercus alba (L.) chips during a simulated fermentation and post-fermentative process were studied. The results obtained indicated that the large-size chips favored the release of furfural and furfuryl alcohol, while the small ones increased the concentration of cyclotene and maltol. The interaction between chip size and time of contact showed that the small-size chips are more sensitive to the increase of ethanol concentration for the extraction rate of some compounds (furfural, vanillin, maltol, cyclotene, whiskey lactones, and eugenol) compared to the large-size ones, increasing their concentrations at the end of maceration. The toasting degree of oak chips had a different influence on the volatile compounds studied. Cyclotene and guaiacol concentrations increased with the toasting intensity, whereas the extracted concentration of all compounds increased from light to medium-toasted chips, except for eugenol, and then decreased by further increasing the toasting level for 5-methylfurfural, whiskey lactones, eugenol, and only using high-level toasted chips for furfuryl alcohol, maltol, and vanillin. A possible protection effect of the chip size toward the possible degradation or volatilization losses of furfural for high toasting degrees was observed
Effect of alternative fungicides and inoculation strategy on yeast biodiversity and dynamics from the vineyard to the winery
No full textFungi and oomycetes found in vineyards cause diseases such as powdery and downy mildew. Consequently, conventional and alternative agronomical practices are widely used prior to harvest to protect grapes. Alternative products are considered more eco-friendly and environmentally sustainable in comparison to conventional chemical products. However, the effect of these alternative products on yeast ecology, from the vineyard to the winery, is poorly understood. This study compared the effect of alternative and conventional chemical antifungal compounds (copper and sulphur based) on grapes’ mycobiota in the vineyard and during subsequent winery fermentation using culture-dependent and -independent approaches. Culture-dependent data indicated a treatment-dependent effect on the load and diversity of yeast populations on grapes. It was found that the population of Hanseniaspora uvarum was higher on grapes previously treated with laminarin and copper, compared to the other levels registered on grapes previously treated with the rest of antifungal products tested in this study (including the untreated and conventional treatment controls). Concerning, wine quality, the chemical composition was not correlated to the application of antifungal treatment in the vineyard. Understanding the effect of different antifungal products on grape and wine microbial communities may help in setting up guidelines for wine grape production. These guidelines, can be used to guarantee quality in the pursuit of a sustainable competitive advantage in the market
Impact of specific inactive dry yeast application on grape skin mechanical properties, phenolic compounds extractability, and wine composition
No full textFoliar treatments using two products based on Saccharomyces cerevisiae inactive dry yeast derivatives with specific formulations for white and red varieties were tested in two consecutive vintages on Vitis vinifera L. cv. Chardonnay, Cortese, and Nebbiolo grown in Piedmont (north-west Italy). The possible elicitor effect of the foliar treatment was assessed at harvest on the chemical composition and mechanical properties of grape berries. The accumulation and extractability of phenolic compounds in Nebbiolo grape skins were also studied. Wines were produced and analysed in terms of technological parameters, color characteristics, free volatile composition, and phenolic compounds. The treatments induced an +16 μm average increase in berry skin thickness, which makes the grapes more resistant to physical damages and pathogenous attacks. In Nebbiolo, this treatment enhanced the accumulation of anthocyanins (+33 mg/kg on average). However, the obtained results pointed out a vintage effect. In 2015, few significant differences between wines made from control and treated grapes were found. Instead, in 2016, Nebbiolo treated wines had a slightly worse chromatic quality as a consequence of lower contents of phenolic compounds, but they were richer in relative amounts of malvidin-3-glucoside
Saccharomyces cerevisiae-Starmerella bacillaris strains interaction modulates chemical and volatile profile in red wine mixed fermentations
No full textThe use of Starmerella bacillaris in combination with Saccharomyces cerevisiae is considered as a state-of-the-art biological application to modulate wine composition. This application implies a detailed understanding of yeast-yeast interactions during mixed fermentations and their effect on the composition of the resulting wines. In this context, ten commercial S. cerevisiae strains were used as partners of an indigenous, previously characterized Starm. bacillaris strain in order to get a better insight into the impact of S. cerevisiae strain employed. The different combinations of strains tested influenced the growth dynamics, the fermentation behavior and, as a consequence, wine composition in a couple-dependent manner. In addition, wines produced from mixed fermentations had significantly lower levels of ethanol, acetic acid and ethyl acetate, and showed higher amounts of glycerol, higher alcohols and esters compared to pure S. cerevisiae control fermentations. This study reveals the importance of S. cerevisiae strain choice on the chemical composition of the wines produced from mixed culture fermentations with Starm. bacillaris
Efficacy of ozone against different strains of Brettanomyces bruxellensis on winegrapes postharvest and impact on wine composition
No full textSpoilage by Brettanomyces bruxellensis is a major concern for the wine industry. The negative effect of this yeast on wine quality, that is, potentially large associate economic losses and the production of phenolic off-flavors, requires application of specific control measures. We investigated the ability of ozone to control the B. bruxellensis population on treated Barbera winegrape berries, and the impact on subsequent winemaking or fermentation. To further explore the ability of ozone treatments to reduce the B. bruxellensis population, a mix of three different strains was artificially inoculated onto the surface of grape berries. Grape berries were ozone-treated either in aqueous (6 or 12 min) or gaseous form (12 or 24 hr), crushed, then fermented to evaluate the effect of these treatments on B. bruxellensis and Saccharomyces cerevisiae growth dynamics and wine composition. Microbiological analysis revealed a significant reduction in B. bruxellensis of ~2.2 log colony forming units (CFU)/mL after treatment with gaseous ozone for 24 hr. The wines produced from grape berries previously exposed to gaseous ozone for 24 hr contained the lowest levels of acetic acid. Moreover, 4-ethylphenols were detected in wines produced from grape berries treated with water (6 or 12 min), in which B. bruxellensis population reached 5.0 log CFU/mL at the end of fermentation. Molecular analysis suggested that the three tested strains had similar sensitivity to the ozone treatments applied. This study shows the first results about the ability of ozone to control the population of different B. bruxellensis strains within the same species in the same manner
Volatile Organic Compounds in Sweet Passito Wines as Markers of Grape Dehydration/Withering/Drying Process
No full textTwenty-four sweet Passito wines from Italy were analyzed through gas chromatography-mass spectrometry. Apart from the vinification process, which was unknown, the Passito wines differed in the water loss technique used, the grape variety, and the latitude/orography of provenance. Two volatile organic compound markers, ethyl acetate and furfural, were identified, characterizing wines produced with the technique of Vin Santo, wines from sun drying, and wines from late harvest. These compounds were found at low concentrations in wines produced with grapes dehydrated in “fruttaio” (closed facility), under controlled or uncontrolled conditions. Wines from Muscat varieties had more esters and terpenes, but the wines produced from grapes dehydrated in fruttaio in North Italy, particularly those grown on high mountains, had more than Muscat wines produced in South Italy or using sun drying. Primary and secondary aroma compounds are reported for each wine. A controlled environment during dehydration, preferably at low temperature, better preserves the aroma of grapes for wine production
Ozone Improves the Aromatic Fingerprint of White Grapes
Get PDFOzone, 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
- …
