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62 WINES&VINES December 2016 WINEMAKING PRACTICAL WINERY & VINEYARD tionship between OTR, the antioxidant power of wine and time of storage can better explain these phenomena. No differences among closures for color intensity and total monomeric anthocyanins were detected for W2 wines. These wines were characterized by lower total oxygen exposure (6.5 mg/L compared to 9.8 mg/L for W1 wines), and higher content of phenolic com- pounds (3,400 mg/L compared to 2,300 mg/L for W1 wines), acting as oxygen-quenching compounds could explain this result. OTR was observed to have a significant effect on total phenolic content of W1 wines, while no differences were observed among W2 wines. Each phenolic compound had different reactivity toward the Folin-Ciocalteu reagent. 51 The results indicate that the OTR of closures can determine a variation into the chemical nature of wine phenolics. While no variation in PAs was de- tected, a significant loss of VRF of W1 high and W1 medium was detected compared to W1 low . Since vanillin reacts with free carbons C6 and C8 of the A ring of flavanols, the decrease of low molecular weight proanthocyanidins reactive toward vanillin is consistent with the minor presence of nucleophile sites on flavanol molecules due to the significant effect of OTR of closures. The fact that this phenomenon occurs only for W1 and not for W2 indicates that both TOE and the native composition in phenolics of red wine are determining factors in development of condensation and polymer- ization reactions of tannins. The SDS-PAGE analysis of human saliva after the interaction with experimental wines was performed to determine the SPI values of bottled wines. For W1 wine, the SPI was sig- nificantly lower when the bottles were sealed with closures providing high OTR. A significant decrease in SPI was detected for W2 wine. The loss of phenolics reactive toward salivary proteins positively correlated with OTR. These results are partially confirmed by the sensory rating of astringency, which is in agreement with SPI data. W1 high was less astringent than W1 low while in contrast with SPI data; W1 medium did not differ from W1 high (see "Influence of Closure on Astringency of Wines" on this page). For W2, no differences among wines were detected. The discrepancy between sensory analysis and SPI can be attributed to different reasons such as the interference of wine components, changes occurring in phenolic stimuli and sensitivity of the two analytical methods used. Regarding the interference of wine compo- nents such as tartaric acid, ethanol, fructose and mannoproteins, a recent study showed that they affect both sensory perception of astringency and SPI, and this effect depends on wine phenolics. 34 However, the entity of the effects detected were not the same for the two methods con- sidered. It is therefore likely that oxygen ex- posure can determine changes in wine phenolics detectable only by means of SPI because this analysis is more sensitive than sensory analysis to little changes in binding reactivity of tannins. Pre- and post-bottling O 2 exposure influences sensory-active phenolics of red wines Oxygen exposure to red wine before and after bottling affects the evolution of phenolics and astringency during bottle aging. This is the first time that a direct effect of a) addition of micro quantities of oxygen to a wine before bottling and, b) oxygen permeating toward closures on the reactivity of wine phenolics toward salivary proteins has been demonstrated. These effects are the function of aging time, wine initial composition (pH and phenolic composition) and dissolved oxygen level. Before applying micro-oxygenation and choosing a bottle closure, a winemaker must consider the expected consumption date of a bottled wine, the total package oxygen present at bottling and wine composition. Further studies about the influence of each wine compound on the evolution of wine astringency and reactivity toward sali- vary proteins during bottle aging are needed to improve the use of both micro-oxygen- ation and closures at specific OTRs in the wine industry. Angelita Gambuti is associate professor of wine chem- istry at the University of Naples Federico II. She holds a master's degree in chemistry and a specialization in applied biotechnology. Maurizio Ugliano is associate professor at the University of Verona (Italy), where he teaches wine chemistry and wine science. Alessandra Rinaldi of Biolaffort, France, is a researcher employed by BIOLaffort (France) enological society. She earned a master's degree in industrial biotechnology and a doctorate degree in science and technology of food- agriculture production from the University of Naples Federico II. Luigi Moio is a professor of enology at Univer- sity of Naples Federico II and chair of the oenology com- mittee at the Office International de la Vigne et du Vin (OIV). He received an honors degree in agricultural science and his Ph.D. at University of Naples Federico II. The study about the influence of closure oxygen perme- ability on wine astringency was financially supported by Nomacorc SA. References for this article are available online at winesandvines.com. Promote your wines to leading Zinfandel enthusiasts and extend your winery's relationship in the market. Join Us! We are champions of Zinfandel— America's Heritage Wine Become part of our proud legacy zinfandel.org • 530-274-4900 Zinfandel Advocates & Producers is a 501(c)(3) non-profit organization. ZAP is dedicated to advancing public knowledge of and appreciation for American Zinfandel and its unique place in our culture and history. You know how good your Zinfandel is... The mean sensory rating of astringency is shown for experimental Wines 1 and 2, which were closed with synthetic closures at low, medium and high oxygen-transfer rates. Different letters indicate statistical differ- ences (p<0.05). INFLUENCE OF CLOSURE ON ASTRINGENCY OF WINES Mean Sensory Rating 5 4 3 2 1 0 W1 low W1 medium W1 high W2 low W2 medium W2 high b ab a a a a