Aplicación de técnicas espectroscópicas vibracionales al estudio de la extractabilidad de compuestos fenólicos procedentes de subproductos enológicos.

Las características de la uva en el momento de la vendimia condicionan en gran medida la calidad del vino elaborado a partir de ellas. En regiones de clima cálido, las altas temperaturas ambientales, acentuadas en las últimas décadas por los efectos del cambio climático, originan un desfase entre la madurez tecnológica de la uva, cada vez más temprana y la madurez fenólica, cada vez más tardía, que desencadena, entre otros, problemas de estabilidad cromática en el envejecimiento. Ante esta situación se pone de manifiesto la necesidad de implementar medidas de adaptación que permitan preservar la calidad de estos vinos. En este sentido, el aprovechamiento de subproductos de la industria vitivinícola ricos en compuestos fenólicos,como pueden ser las virutas de madera cruda de las tonelerías,añadidas en etapas iniciales de la vinificación, se presenta como una estrategia enológica, nueva y sostenible, para paliar los efectos del cambio climático en la calidad de los vinos tintos.Los compuestos fenólicos de la madera, que pasarán al vino durante el proceso de maceración, junto con los compuestos fenólicos procedentes de la uva, determinarán la composición fenólica del vino y condicionarán sus características cromáticas y organolépticas. Tradicionalmente,la composición fenólica, y la facilidad de cesión de estos compuestos al vino desde diferentes matrices, se ha controlado por métodos de análisis fisicoquímicos que,en muchos casos, resultan complejos y tediosos. En las últimas décadas se han desarrollado técnicas espectroscópicas que permiten estimar de forma rápida, no destructiva y respetuosa con el medio ambiente,distintos parámetros de interés enológico. En este trabajo, inicialmente se ha evaluado el efecto que tiene la adición de chips de madera en la extracción de compuestos antociánicos del hollejo de uva tinta clasificada hiperespectralmente como uva con baja capacidadde cesión de dichos compuestos.Se ha comprobadoque la adición de copigmentos provenientes de la madera, que contribuyen a mejorar el color del vino,noalterael equilibrio de extracción de antocianos del hollejo. Se ha utilizado el análisis de imagen hiperespectral en la región del infrarrojo cercano y la regresión por mínimos cuadrados parciales (MPLS)para analizar de forma rápida el contenido total yel contenido extraíble de fenoles totales y flavanoles en semillas de uva tinta.De forma similar, se ha desarrollado un modelo MPLS para predecir el contenido fenólico extraíble en viruta cruda de roble. Se ha evaluado la capacidad dela espectroscopía NIR portátilpara estimar in situ de forma rápida el contenido fenólico extraíble delhollejo de uva y de la viruta cruda de roble. La influencia de las condiciones ambientalesen el viñedo en el momento de la adquisición espectral pueden condicionar los resultados obtenidos para los hollejos, de forma que los modelos presentan errores que comprometen su aplicación con fines predictivos. Sin embargo, en virutas de roble, los modelos propuestos para lapredicción del contenido extraíble de fenoles totales y de elagitaninosofrecen resultados satisfactorios para todos los parámetros evaluados. Así mismo, utilizando espectroscopía en el infrarrojo medio por transformada de Fourier y espectroscopíaRaman se han caracterizado muestrasde viruta cruda de madera y se han relacionado las características espectrales con la facilidad de extracción de compuestos fenólicos. De esta forma, se ha podido confirmar la relación existente entre la extractabilidad de compuestos fenólicos en viruta de madera y la composición y distribución de los componentes de su pared celular.La microscopía electrónica de barrido (SEM) aporta información topográfica complementaria que respalda la relación entre la estructura de la madera y los niveles de extractabilidad fenólica. Por último, se ha evaluado objetivamente el potencial enológico de la viruta cruda de roble, subproducto de tonelería. Para ello se ha determinado,en una situación real de vinificación en tinto, la influencia de la adición post-fermentativade virutas en la composición fenólica y la calidad cromática de vinos tintos de variedad Syrah.Los resultados obtenidos demuestran que la adición pos-fermentativa de viruta de madera cruda representa un procedimiento útil para la elaboración de vinos tintos en clima cálido, ya que produce una mejora tanto de la composición fenólica como de la calidad y estabilidad cromática.Premio Extraordinario de Doctorado U

Teaching innovation applied to laboratory practices of Analytical Chemistry

El Ciclo de Mejora en el Aula (CIMA) se ha realizado en la asignatura Química Analítica, de 1er curso del Grado en Ingeniería Química, de la Universidad de Sevilla, en concreto, en las prácticas de laboratorio. Este se ha llevado a cabo en un grupo de 12 alumnos y ha tenido una duración de 8 horas distribuidas en 2 sesiones. La intervención se ha realizado contemplando los 3 aspectos fundamentales que constituyen el sistema docente: los contenidos a impartir en el aula, la metodología docente utilizada en su aplicación y la evaluación del aprendizaje experimentado por los estudiantes. El modelo didáctico aplicado se basa fundamentalmente en el Aprendizaje Basado en Problemas con el objetivo de conseguir el aprendizaje desde una perspectiva investigativa, crítica y reflexiva. Para ello, se proponen casos y situaciones reales que permitirán a los alumnos construir el conocimiento a partir de sus ideas previas y a través de una metodología investigativa y constructivista (actividades de contraste).The Classroom Improvement Cycle (CIMA) has been carried out in the Analytical Chemistry subject, of the 1st year of the Degree in Chemical Engineering, at the University of Seville, specifically, in laboratory practices. This has been carried out in a group of 12 students and has had a duration of 8 hours distributed in 2 sessions. The intervention has been carried out considering the 3 fundamental aspects that constitute the teaching system: the contents to be taught in the classroom, the teaching methodology used in its application and the evaluation of the learning experienced by the students. The applied didactic model is fundamentally based on Problem-Based Learning with the aim of achieving learning from an investigative, critical and reflective perspective. For this, real cases and situations are proposed that will allow students to build knowledge from their previous ideas and through an investigative and constructivist methodology (contrast activities)

Estimation of Total Phenols, Flavanols and Extractability of Phenolic Compounds in Grape Seeds Using Vibrational Spectroscopy and Chemometric Tools

Near infrared hyperspectral data were collected for 200 Syrah and Tempranillo grape seed samples. Next, a sample selection was carried out and the phenolic content of these samples was determined. Then, quantitative (modified partial least square regressions) and qualitative (K-means and lineal discriminant analyses) chemometric tools were applied to obtain the best models for predicting the reference parameters. Quantitative models developed for the prediction of total phenolic and flavanolic contents have been successfully developed with standard errors of prediction (SEP) in external validation similar to those previously reported. For these parameters, SEPs were respectively, 11.23 mg g−1 of grape seed, expressed as gallic acid equivalents and 4.85 mg g−1 of grape seed, expressed as catechin equivalents. The application of these models to the whole sample set (selected and non-selected samples) has allowed knowing the distributions of total phenolic and flavanolic contents in this set. Moreover, a discriminant function has been calculated and applied to know the phenolic extractability level of the samples. On average, this discrimination function has allowed a 76.92% of samples correctly classified according their extractability level. In this way, the bases for the control of grape seeds phenolic state from their near infrared spectra have been stablished.España MINECO AGL2017-84793-C2España, Universidad de Sevilla VPPI-II.2, VPPI-II.

Valorization of American Barrel-Shoot Wastes: Effect of Post Fermentative Addition and Readdition on Phenolic Composition and Chromatic Quality of Syrah Red Wines

The influence of post fermentative addition of American barrel-shoot wastes on phenolic composition and chromatic quality of Syrah red wines has been evaluated as an environmentally sustainable alternative to the conventional winemaking for avoiding the common color loss of red wines elaborated in warm climates. American oak wood byproducts added were previously classified by hyperspectral image analysis according to the amount of phenolic compounds transferred to the extraction media. After that, wines were elaborated under different maceration conditions by applying only one proportion of wood (12 g L−1) and two different maceration procedures (simple and double addition) and were compared with a traditionally macerated Syrah red wine (CW, no wood addition). Results proved the effectiveness of the moderate postfermentative addition of oak wood byproducts to stabilize the color of wines and to provoke lower color modification along the time, producing color wines chromatically more stable for a better aging. In the case of double addition, the adsorption of the pigments during the maceration presents a stronger effect on the color than copigmentation and polymerization by cause of the copigments extracted from the woodEspaña, Ministerio de Economía y Competitividad AGL2017-84793-C

On the use of vibrational spectroscopy and scanning electron microscopy to study phenolic extractability of cooperage byproducts in wine

Wood is an important source of phenolic compounds, which can be transferred to wine during aging process, improving its properties, from an organoleptic point of view. Therefore, understanding and optimizing the extractability of phenolic compounds from wood are crucial in the oenological field. The structural composition of oak wood samples has been evaluated using Raman and attenuated total reflectance Fourier transform infrared (ATR–FTIR) spectroscopies, and their main spectral features have been linked to phenolic compound extractabilities, as measured by classic chemical analyses. To support the analysis, microscopic images of the samples were also recorded using scanning electron microscopy (SEM). The applied methodology is shown to be useful to relate the wood cell wall structure to phenolic extractability levels of wood samples. It could assist in selecting oak wood suited for improving wine quality with regard to its color or/and stability through the addiction of external copigments to wine

Study of phenolic extractability in grape seeds by means of ATR-FTIR and Raman spectroscopy

Near infrared hyperspectral imaging has been applied to grape seeds in order to select a representative subset of samples according to their spectral features in the 900-1700nm range. Afterwards, selected grape seeds have been classified according to their total phenol and flavanol extractabilities. In this way, samples were sorted in three different groups identified as low, medium and high extractability levels. In order to establish the chemical structures which can be responsible for the different extractabilities, vibrational spectroscopy has been applied to the non-extracted material after seed extractions. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) and Raman spectra of non-extracted seed material have been recorded and their main spectral features have been linked to extractabilities of flavanolic and total phenolic compounds. The vibrational spectroscopic analysis confirms that grape seed phenolic extractability is influenced by the cell wall composition (polysaccharides, lignins, pectins) and by the degree of esterification of pectins

Use of near infrared hyperspectral tools for the screening of extractable polyphenols in red grape skins

Hyperspectral images of intact grapes were recorded at harvest time using a near infrared hyperspectral imaging system (900–1700 nm). Spectral data have been correlated with red grape skin extractable poly- phenols (total phenolic, anthocyanins and flavanols) by modified partial least squares regression (MPLS) using a number of spectral pretreatments. The obtained results (coefficient of determination (RSQ) and standard error of prediction (SEP), respectively) for the developed models were: 0.82 and 0.92 mg g-1 of grape skin for extractable total phenolic content, 0.79 and 0.63 mg g-1 of grape skin for extractable anthocyanin content, 0.82 and 0.45 mg g-1 of grape skin for extractable flavanol content. The obtained results present a good potential for a fast and reasonably inexpensive screening of the extractable poly- phenolic compounds in intact grapes. Moreover, the heterogeneity of extractable polyphenols within the ripeness stage has been also evaluated using the proposed method

Linking ATR-FTIR and Raman Features to Phenolic Extractability and Other Attributes in Grape Skin

The importance of wine phenolics on the sensory characteristic of red wines is well-known. Therefore, it is necessary to control the extractability of phenolic compounds from grape skins, which depends significantly on grape ripeness and hence, on cell wall degradation. In the present study, attenuated total reflectance Fourier transform infrared (ATR-FTIR) and Raman spectra of grape skin have been recorded. Then, these spectral matrices have been studied and the main spectral features have been linked to extractabilities of phenolic compounds (anthocyanins, flavanols and total phenols). Moreover, spectral differences between external and internal grape skin surfaces also have been studied. It has been confirmed that the amount of polysaccharides and the degree of esterification of pectins have significant influence on the phenolic extractability levels of grape skin tissue

Near infrared hyperspectral imaging: recent applications in the oenological and viticultural sectors

Spanish MINECO grant BES-2012-060192Spanish MINECO project AGL2014- 58486-C2Universidad de Sevilla (España) Plan VI (VPPI-US

Assessment of Total Fat and Fatty Acids in Walnuts Using Near-Infrared Hyperspectral Imaging

“Persian” walnut (Juglans Regia L.) is one of the most consumed tree nuts in the world. It is rich in several bioactive compounds, with polyunsaturated and monounsaturated fatty acids (PUFA and MUFA) appearing at high concentrations. Walnut consumption protects against cardiovascular, carcinogenic, and neurological disorders. The fatty acid profile has usually been determined by gas chromatography, a reliable and robust tool, but also complex, polluting, and time consuming. In this study, near infrared hyperspectral imaging has been used for the screening of total fat, MUFA, PUFA, saturated, and individual fatty acids in walnuts. Five different walnuts varieties have been considered and modified partial least square (MPLS) regressions have been performed. The SEs of prediction (SEP) in external validation (ranged from 2.12% for PUFA to 13.08% for MUFA) suggest that hyperspectral imaging can be a reliable tool for controlling these parameters in a simple, non-destructive and environmentally friendly way.FCT – Foundation for Science and Technology- ref:UIDB/05183/2020; FEDER and National Funds through the Programa Operacional Regional ALENTEJO 2020 (ALT20-03-0246- FEDER-000064) – QualFastNut – Utilização da espectroscopia NIR para a análise rápida da qualidade em frutos secos