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The search for alternatives to sulfur dioxide (SOST99 extract preserved the wines from malolactic fermentation (MLF), maintained the quality parameters of the wines, but affected their color from the beginning of the process. Synergistic effects between ST99 and GSH were found for oxygen consumption rates, related to oxidation processes. The content of amino acids and biogenic amines was slightly affected by the treatments, but the quality or safety of the wines was not compromised. However, after 12 months of ageing in bottle, the SOST99 may be proposed as an alternative to SO

BACKGROUND: The accumulation of acetaldehyde and Strecker aldehydes during wine oxidation is detrimental to quality and often determines wine shelf-life. Knowing in advance the specific tendency of a wine to accumulate these compounds would help decision making during winemaking. An accelerated test based on a forced oxidation procedure at 45 °C (5 days) to measure aldehyde accumulation rates (AARs) is proposed and assessed by comparing results with those obtained by oxidation at 25 °C (36 days). Reactivities of aldehydes in those same wines stored in anoxia at both temperatures were also measured. RESULTS: Wine oxygen consumption rates at 25 °C are poorly correlated with those observed at 45 °C. By contrast, AARs of methional and of 2- and 3-methylbutanals measured during wine oxidation at 25 °C are equivalent to those measured at 45 °C. AARs from isobutanal and acetaldehyde are also correlated, while AARs from phenylacetaldehyde are not. Partial least squares models explaining AARs show intriguing differences regarding the apparent limiting role played by wine anthocyanins and other polyphenols in the ability of wines to accumulate aldehydes. Measured differences in aldehyde pattern are similar to those of the other Strecker aldehydes. CONCLUSION: The proposed assay makes it possible to obtain a reasonable estimate of a wine’s tendency to accumulate aldehydes, with the exception phenylacetaldehyde, in 5 days. Neither differences in aldehyde reactivity between wines nor the change in reactivities with temperature support a major role for reactivity in differentially limiting AARs during wine oxidation. © 2021 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Strecker aldehydes (SA) can be formed in wine from the degradation of Strecker and, to a lesser degree, via the oxidation of higher alcohols. The objective of this article is to assess the magnitude of the differences introduced by wine compositional factors other than amino acids and Fe, in the accumulation of SA during oxidation. Eight red, two rosé and two white wines were oxidized. The accumulation of SA was analyzed. Whites and rosés presented negative accumulations for isobutyraldehyde, and in general, these wines accumulated smaller concentrations of the other SA than red wines. Only methional and phenylacetaldehyde were accumulated in all of the wines during oxidation. 2-methylbutanal and 3-methylbutanal were accumulated in 9 out of the 12 wines, whereas isobutyraldehyde was accumulated only in 5 out of the 12. 2-methylbutanal was, on average, the least accumulated aldehyde. Methional was the aldehyde formed most homogenously. Most of the observed differences can be attributed to three factors: the pH, oxidation time and native levels of Strecker aldehydes. The influence of pH was particularly intense in the cases of phenylacetaldehyde and methional. An independent test using synthetic wines with Strecker amino acids and 4-methylcatechol with different pHs (4.2, 3.5 and 2.8) was carried out in order to verify the higher pH value, the greater accumulation in SA after oxidation process. The results strongly suggest the important role played by pH in the accumulation of SA in wine oxidation.

La presente tesis titulada “Formación, reacción y acumulación de acetaldehídos y aldehídos de Strecker durante la oxidación del vino” consta de 7 capítulos. Capítulo I: La primera tarea desarrollada en la tesis fue la obtención de un método de oxidación a temperatura ambiente, que permitiera caracterizar la cinética de consumo de oxígeno de vinos de manera muy exacta y precisa. Una de las principales ventajas introducidas por esta metodología es la posibilidad de aportar altas dosis de oxígeno, obteniéndose por ello y por primera vez, la categorización completa de la cinética de consumo de oxígeno que se ha descrito con 6 etapas o velocidades. Los modelos que relacionan la cinética y la composición inicial de 8 vinos tintos españoles revelan que el acetaldehído total, los metales (Cu, Fe y Mn), el sulfuroso libre y la absorbancia a 520 y 620 nm parecen definir estas velocidades. Capítulo II: El método de oxidación permite alcanzar por primera vez la formación de aldehídos “de novo”; ya que se aportó oxígeno suficiente para desulfitar la muestra más una dosis destinada a la formación. En todos los casos la concentración de acetaldehído y aldehídos de Strecker aumentaron. Asumiendo que el principal producto de la oxidación es el acetaldehído, se ha estimado la concentración de acetaldehído teóricamente formada que, en comparación con la cantidad acumulada experimental ha permitido obtener la concentración de acetaldehído teórico consumido – éste valor alcanzó los 46 mg/L en vinos jóvenes-. Se hipotetiza que esa concentración de acetaldehído es consumida por los polifenoles durante la oxidación, y a esos polifenoles reactivos con aldehídos los denominamos (ARPs). Los modelos que relacionan la acumulación (o acetaldehído sin reaccionar) con la composición inicial de los vinos tintos predicen que los ARPs serán principalmente antocianos y taninos pequeños. Los modelos obtenidos para los aldehídos de Strecker parecen confirmar la existencia de ARPs y sugieren que la vía prioritaria de formación de aldehídos es la degradación de Strecker a partir de sus aminoácidos precursores, y que el diacetilo (α- dicarbonilo) podría ser un precursor específico del fenilacetaldehído. Capítulo III: Con el objetivo de encontrar un método de oxidación más rápido, se incrementa la temperatura de oxidación hasta los 45 °C. La cinética de consumo de oxígeno a 45 °C es más rápida que a temperatura ambiente. Aunque con el método acelerado de oxidación se obtienen escasamente 3 velocidades, es posible obtener la mayoría de los tramos cinéticos modelizando con respecto medidas oxígeno disuelto a 45 °C. En cuanto a la acumulación de acetaldehído y aldehídos de Strecker, la concentración de 2-metilbutiraldehído, 3- metilbutiraldehído, metional y en menor medida isobutiraldehído acumulado a 45 °C son muy similares y están correlacionados con la cantidad acumulada a temperatura ambiente. Sin embargo, para el fenilacetaldehído y acetaldehído los patrones de acumulación se ven muy afectados por la temperatura de incubación. Según los modelos, la temperatura de oxidación influye en los dos procesos que afectan a la acumulación de aldehídos: formación de quinonas (α- dicarbonilo) y la reacción de los aldehídos con los antocianos (ARPs). La existencia de los ARPs comienza a estar cuestionada ya que experimentos independientes donde se dopan aldehídos de Strecker, la estabilidad de los mismos parece ser independiente a la composición polifenólica de los vinos.Capítulo IV: En este capítulo se comprueba que el diacetilo no es particularmente reactivo en la degradación de Strecker y que no es un precursor específico del fenilacetaldehído. Además, queda demostrado que la acumulación de aldehídos de Strecker depende más del pH y el tiempo de oxidación que de la composición polifenólica del vino.Capítulo V: Aunque se han probado varias estrategias en el desarrollo del método de ARPs, no sido posible obtener un índice que lo defina. El principal motivo es que la reactividad del acetaldehído de un vino es muy limitada y errática como para explicar el escaso acetaldehído acumulado durante la oxidación. El papel consumidor de acetaldehído atribuido a antocianos y taninos pequeños necesita ser reinterpretado dentro del ciclo de oxidación. Capítulo VI: El consumo de acetaldehído en extractos de polifenoles extraídos de uvas (FFAs) en condiciones anóxicas es dependiente de la concentración de dopado e independiente de la composición química de las mismas. La FFA más reactiva ha consumido acetaldehído a una ratio de 0,9 mg/L/día. La cinética de consumo de acetaldehído es rápida y se va relenteciendo con el tiempo. Esta pérdida de reactividad podría ser debida a la formación de complejos (acetaldehído-polifenol), éstos complejos “intermedios” serían lo suficientemente estables como para evitar el acetaldehído esté disponible para reaccionar irreversiblemente con el material polifenólico; y lo suficientemente lábiles como para romperse en el método de determinación con DNPH y obtenerse señal analítica. Para poder confirmar esta hipótesis sería necesario determinar el acetaldehído libre. En vinos, el consumo de acetaldehído es lento alcanzando una velocidad de 0,2 mg/L/día. La velocidad de consumo de acetaldehído se ha conseguido modelizar en función de la concentración de acetaldehído inicial, pH y edad del vino. En vinos el consumo de acetaldehído sigue una reacción de pseudo primer orden. Durante los procesos de oxidación donde el acetaldehído se puede acumular, el consumo de acetaldehído sigue siendo lento, homogéneo y prácticamente independiente de la composición polifenólica. La velocidad media de consumo es de 0,43mg/L/día. En los casos más extremos -donde hay más acetaldehído en exceso de partida-, la velocidad de consumo puede alcanzar 0,79 mg/L/día.Capítulo VI:En el último capítulo se ha demostrado que el principal destino del agua oxigenada formada en la oxidación no es la formación de acetaldehído. Los resultados sugieren que hasta un 30 % del H2O2 se emplea en oxidar otros compuestos mayoritarios del vino, un buen ejemplo serían los polifenoles. Esto explicaría por qué en los modelos donde se explicaba la acumulación de acetaldehído, los antocianos y taninos aparecieran con coeficientes negativos; ya que estos compuestos mayoritarios en lugar de consumir acetaldehído, se estarían oxidando inhibiendo por tanto la formación de este aldehído.

This study evaluates the impact on two varietal white wines from 'Chardonnay' and 'Verdejo' cultivars of different fermentative strategies: inoculation with Saccharomyces cerevisiae yeast (CT), sequential inoculation (Torulaspora delbrueckii/Saccharomyces cerevisiae) (SI), and spontaneous fermentation (SP). The wines' chemical composition was characterized by oenological parameters, organic acids, metals, major volatile compounds, ester compounds and sensory analyses. The fermentative strategy (CT, SI and SP) was found to be a key factor for assessing different styles of white wines. SI wines showed enhanced 'mature fruit' nuances and a chemical profile characterized by higher content of ethyl propanoate, ethyl isobutyrate and ethyl dihydrocinnamate. Meanwhile, the SP wines presented enhanced "stone fruit" nuances possible related to the higher contents of 2-phenyl acetate and isobutyl acetate. After a chemometric approach the above esters were identified as the markers of each fermentative strategy, independently of the variety.

By-products from the winemaking companies, specifically woody vine material, can be an interesting source of bioproducts, specifically stilbenes and related compounds, however the extraction conditions can dramatically modify the final recoveries of these beneficial compounds. The effects of microwave-assisted extraction on the recovery of stilbenes have been evaluated in this manuscript. The stability under the extraction conditions was assessed in order to define the working range. A fractional factorial experimental design was developed to analyse the influence on the extraction process of seven different extraction variables: solvent, stirring, extraction temperature, extraction time, microwave power, sample weight and extraction volume. This new method enables stilbenes to be extracted from grape stems and canes in only 5 min, with an extraction temperature of 125 °C and 80% ethanol in water as the extraction solvent. Repeatability and reproducibility were also evaluated and the resulting RSD values (n = 5) were lower than 10% for all analysed stilbenes. Additionally, stilbenes in 20 different grape stem and cane samples were determined.

The rates at which wine consumes oxygen are important technological parameters for whose measurement there are not accepted procedures. In this work, volumes of 8 wines are contacted with controlled volumes of air in air-tight tubes containing oxygen-sensors and are further agitated at 25 °C until O2 consumption is complete. Three exposure levels of O2 were used: low (10 mg/L) and medium or high (18 or 32 mg/L plus the required amount to oxidize all wine SO2). In each oxygen level, 2–4 independent segments following pseudo-first order kinetics were identified, plus an initial segment at which wine consumed O2 very fast. Overall, multivariate data techniques identify six different Oxygen-Consumption-Rates (OCRs) as required to completely define wine O2 consumption. Except the last one, all could be modeled from the wine initial chemical composition. Total acetaldehyde, Mn, Cu/Fe, blue and red pigments and gallic acid seem to be essential to determine these OCRs., This work has been funded by the Spanish MINECO (Project AGL2014-59840, RTC-2015-3379 and RTC-2016-4935-2) and partly cofunded by the European Union (FEDER). V.C. and A.M. have received a grant from the Spanish FPU and FPI programs, respectively. Funding from Diputación General de Aragón (T53) and Fondo Social Europeo is acknowledged.

The main aim of the present work is to study the accumulation of acetaldehyde and Strecker aldehydes (isobutyraldehyde, 2-methylbutanal, isovaleraldehyde, methional, phenylacetaldehyde) during the oxidation of red wines, and to relate the patterns of accumulation to the wine chemical composition. For that, eight different wines, extensively chemically characterized, were subjected at 25°C to three different controlled O2 exposure conditions: low (10 mg L−1) and medium or high (the stoichiometrically required amount to oxidize all wine total SO2 plus 18 or 32 mg L−1, respectively). Levels of volatile aldehydes and carbonyls were then determined and processed by different statistical techniques. Results showed that young wines (3 years-old bottled wines) accumulated acetaldehyde while their content in SO2 was not null, and the aged wine containing lowest polyphenols accumulated it throughout the whole process. Models suggest that the ability of a wine to accumulate acetaldehyde is positively related to its content in combined SO2, in epigallocatechin and to the mean degree of polymerization, and negatively to its content in Aldehyde Reactive Polyphenols (ARPs) which, attending to our models, are anthocyanins and small tannins. The accumulation of Strecker aldehydes is directly proportional to the wine content in the amino acid precursor, being the proportionality factor much higher for aged wines, except for phenylacetaldehyde, for which the opposite pattern was observed. Models suggest that non-aromatic Strecker aldehydes share with acetaldehyde a strong affinity toward ARPs and that the specific pattern of phenylacetaldehyde is likely due to a much reduced reactivity toward ARPs, to the possibility that diacetyl induces Strecker degradation of phenyl alanine and to the potential higher reactivity of this amino acid to some quinones derived from catechin. All this makes that this aldehyde accumulates with intensity, particularly in young wines, shortly after wine SO2 is depleted., This work has been funded by the Spanish MINECO (Project AGL2014-59840, RTC-2015-3379 and RTC-2016-4935-2) and parly cofunded by the European Union (FEDER). VC and AM-C have received a grant from the Spanish FPU and FPI programs, respectively. Funding from Diputación General de Aragón (T53) and Fondo Social Europeo is acknowledged.

Dietary fiber derived from citrus fruits was added to vinegar. Different sources and quantities of fiber and storage conditions have been scrutinized. Formulated vinegars were evaluated on the basis of their phenolic profile, volatile composition and sensory analysis. The addition of citrus fiber enhanced the phenolic and volatile profile of the resulted vinegars. Whereas lemon fiber contributed mostly to the enrichment of the polyphenolic composition, orange fiber was that which increased in a higher way the volatile composition of the vinegars. Moreover, the content of hydroxycinnamic acid derivatives and the majority of volatile compounds decreased as the dose of fiber increased. Furthermore, the judges preferred fiber-enriched vinegars, but in different quantities depending of the fiber source. This preference was mainly based on citric attribute, contributing several terpenes and ketones derived from them. The addition of citrus fiber to vinegar did not result in a marked storage-dependence.

The influence of pre-fermentative maceration and ageing factors on the ester profiles of Pedro Ximenez sparkling wines was evaluated. The pre-fermentative maceration consisted of the skin-maceration of musts at 10 degrees C for 6 h. The sparkling wines were produced following the Champenoise method. Samples were monitored at 3, 6 and 9 months of ageing on lees. Sparkling wines with pre fermentative maceration displayed higher contents of ethyl esters of branched acids and cinnamates. Meanwhile, those without maceration showed higher levels of ethyl esters of fatty acids and higher alcohol acetates. The study of statistical interactions elucidated different hydrolytic kinetics and developments in higher alcohol acetates and ethyl esters of branched acids during ageing. The application of a dual criterion based on univariate (ANOVA) and multivariate analyses (OPLS-DA) allowed us to identify new potential volatile markers related to pre-fermentative maceration and ageing time, reported for the first time in sparkling wines.

The influence of pre-fermentative maceration and ageing factors on the ester profiles of Pedro Ximenez sparkling wines was evaluated. The pre-fermentative maceration consisted of the skin-maceration of musts at 10°C for 6h. The sparkling wines were produced following the Champenoise method. Samples were monitored at 3, 6 and 9months of ageing on lees. Sparkling wines with pre-fermentative maceration displayed higher contents of ethyl esters of branched acids and cinnamates. Meanwhile, those without maceration showed higher levels of ethyl esters of fatty acids and higher alcohol acetates. The study of statistical interactions elucidated different hydrolytic kinetics and developments in higher alcohol acetates and ethyl esters of branched acids during ageing. The application of a dual criterion based on univariate (ANOVA) and multivariate analyses (OPLS-DA) allowed us to identify new potential volatile markers related to pre-fermentative maceration and ageing time, reported for the first time in sparkling wines.

A stir bar sorptive extraction gas chromatography–mass spectrometry (SBSE–GC–MS) method has been used for the characterization of the volatile composition of 26 high quality vinegars of three different protected geographical indications (traditional balsamic vinegar of Modena, balsamic vinegar of Modena, and Sherry vinegar). SBSE technique provided the identification of 113 volatile compounds, which belong to different chemical families (short-chain esters, acids, acetates and alcohols, phenols, lactones and benzenic and furanic compounds). 39 volatile compounds were never previously reported in wine vinegars. This characterization contributed to the differentiation of the 100% of the studied samples on the basis of raw material (two different types of wine, and cooked must), aging type (static and dynamic) and aging time (25 years). Furanes and terpenes together with acids and alkanes were the most discriminant variables for raw material and aging time, respectively, whereas for aging type, these ones were acetates and esters.