Analysis of Intact Glycosidic Aroma Precursors in Grapes by High-Performance Liquid Chromatography with a Diode Array Detector

© 2021 The authors. This document is made available under the CC-BY 4.0 license http://creativecommons.org/licenses/by /4.0/ This document is the published version of a published work that appeared in final form in Foods.Nowadays, the techniques for the analysis of glycosidic precursors in grapes involve changes in the glycoside structure or it is necessary the use of very expensive analytical techniques. In this study, we describe for the first time an approach to analyse intact glycosidic aroma precursors in grapes by high-performance liquid chromatography with a diode array detector (HPLC-DAD), a simple and cheap analytical technique that could be used in wineries. Briefly, the skin of Muscat of Alexandria grapes was extracted using a microwave and purified using solid-phase extraction combining Oasis MCX and LiChrolut EN cartridges. In total, 20 compounds were selected by HPLC-DAD at 195 nm and taking as a reference the spectrum of pheny

Evaluación de los sarmientos de poda para ser usados como una nueva fuente de aditivos enológicos

La problemática generada por la gran cantidad de sarmientos que anualmente son quemados o abandonados en los viñedos, y la necesidad de buscarles una nueva salida, ha sido abordada en los cinco artículos que componen esta Tesis Doctoral, mediante el estudio de su composición química y su uso como aditivos enológicos. La fracción minoritaria de sarmientos de la variedad Airén y Cencibel, constituida por compuestos fenólicos y aromáticos, incrementa durante el almacenamiento después de la poda, alcanzando su máximo a los 6 meses. Entre los compuestos fenólicos estudiados cabe destacar el importante aumento del trans-resveratrol, especialmente en la variedad Airén, conocido por su efecto positivo en la salud. Entre los compuestos aromáticos destaca la vainillina por su importancia en el sector enológico, cuyo incremento es especialmente significativo en Cencibel. El estudio de su fracción tánica, reveló por primera vez, que los taninos de los sarmientos son proantocianidinas, constituidas principalmente por procianidinas, con un grado de polimerización próximo a 3 y un porcentaje de galoilación cercano a 10 en Airén y a 9 en Cencibel. Además, se ha demostrado que cuando los sarmientos son sometidos a un proceso de tostado a 180ºC durante 45 minutos, se modifica notablemente su composición química, y tiene lugar un aumento significativo de compuestos volátiles de interés enológico como por ejemplo vainillina y guaiacol, y un ligero descenso del trans-resveratrol. El proceso de tostado también eliminó todos los residuos de los plaguicidas usados habitualmente en viticultura, si bien el propio almacenamiento disminuyó su contenido hasta valores inferiores a sus LMRs en uvas. Por todo ello, la composición química de los sarmientos de poda tras 6 meses de almacenamiento, y una vez tostados, permite que puedan ser propuestos como nuevos aditivos enológicos. Para ello, un estudio previo realizado en vinos modelo nos permitió fijar las características de los sarmientos (tostado o sin tostar), formato, dosis y tiempo de maceración adecuados para conseguir una mayor transferencia de los compuestos de interés. Los resultados revelaron que, indistintamente de la variedad, la mayor liberación de compuestos tiene lugar cuando los sarmientos son tostados y añadidos en una dosis de 12 g/L. Sin embargo, los de la variedad Airén trasfieren mayor cantidad de compuestos cuando se aportan en formato granulado, mientras con los sarmientos de Cencibel lo hacen cuando se utiliza el formato chip, siendo necesario menos tiempo de maceración en Airén que en Cencibel. Finalmente, y para poder proponer los sarmientos como aditivos enológicos desde un punto de vista objetivo y real, los sarmientos de ambas variedades, Airén y Cencibel, se adicionaron en los dos formatos propuestos, a los vinos de su misma variedad en diferentes momentos de la vinificación. En comparación con el vino control, los sarmientos contribuyen al vino con importantes concentraciones de vainillina en los vinos Cencibel, cuando estos se adicionaron en formato granulado después de la fermentación maloláctica, y una elevada transferencia de trans-resveratrol en los vinos Airén cuando se utilizó dicho formato, indistintamente del momento de adición. Además, la permanencia en botella durante 6 meses influyó positivamente en el perfil sensorial de estos vinos. Así, los vinos tintos mejor calificados fueron los que estuvieron en contacto con el formato granulado después de la fermentación maloláctica y con el formato chip en la etapa de maceración. En el caso de los vinos blancos, el vino mejor valorado fue el que estuvo en contacto con el formato chip adicionado después de la fermentación alcohólica. Estos resultados, por tanto, nos permiten proponer una nueva forma de aprovechamiento de los sarmientos como aditivos para el vino, los cuales constituyen el mayor residuo agrícola generado en las zonas vitícolas, como es Castilla-La Mancha. Es por tanto posible intervenir en el perfil fenólico y aromático de los vinos utilizando sus propios recursos e incrementar su posible efecto beneficioso en la salud del consumidor. Consecuentemente, en este trabajo de Tesis Doctoral, se demuestra que los sarmientos de poda, preparados y utilizados como se describe, pueden ser usados como valiosos aditivos enológicos, lo cual contribuye a un nuevo concepto de “Vitivinicultura Circular”

Relation between Rind Pigmentation and Internal Quality of Blood Orange ‘Sanguinelli’: Physicochemical and Sensory Studies

This study evaluated the relation between rind colour and the internal physicochemical and sensory qualities of ‘Sanguinelli’ blood oranges, one of the main blood orange cultivars grown in the Mediterranean region. To this end, 400 fruits were harvested in three different orchards and classified according to rind pigmentation intensity (slight, medium, intense, very intense). All fruits were individually evaluated by determining rind and pulp colour, total soluble solids, acidity, maturity index, juice yield, firmness, and size. Moreover, 71 consumers performed a triangle test to evaluate if fruit sensory properties depended on rind pigmentation. Our results revealed (for the first time) that pulp pigmentation and total soluble solid (TSS) content strongly depend on rind colouration. Among the fruit from the same orchard, the redder the pigmented fruit was (externally) the deeper the red pulp, and the higher the TSS became. This pattern was corroborated in the three orchards under study. Other characteristics, such as acidity, juice yield, firmness, and fruit size, did not depend on external pigmentation. Sensory studies showed that the more coloured the fruit, the higher the accumulated sugar content; consumers perceive these fruits as being sweeter than slightly pigmented ones. This information can be very useful for the citrus industry as external colour may become a quality index for blood oranges, as well as for consumers to make purchase decisions

Evolution of Oleuropein and Other Bioactive Compounds in Arbequina Olive Leaves under Different Agronomic Conditions

Oleuropein and other phenolic compounds contained in olive leaves give it the potential to be transformed from residue to co-product in an oil mill. However, the moment of the agronomic cycle in which their potential transformation is higher is not known in detail. Therefore, for the first time, a monthly study of the evolution of such compounds throughout an agronomic cycle is made (November 2019 to October 2020). Arbequina olive leaves were collected from three plots and the interactive effects of agronomic conditions were investigated, such as crop management (conventional and ecological), plantation framework (intensive and super-intensive) and location under different climatic conditions. The results showed that the main compound throughout the cycle was oleuropein and the highest levels occurred around the pruning season (February/March). Crop management and location affected the content of verbascoside and hydroxytyrosol, while plantation framework only influenced the flavonoid content. All compounds were affected by relative humidity and differential temperature, although hydroxytyrosol showed the highest correlation with the maximum temperature. The absorbance measurements by ultraviolet-visible spectrophotometry showed trends parallel to the oleuropein concentration measured by high-performance liquid chromatography, which suggests that this method could be useful to easily study the evolution of oleuropein in the oil mill

Vine-Shoots as Enological Additives. A Study of Acute Toxicity and Cytotoxicity

Toasted vine-shoots have been recently proposed as enological additives that can be used to improve the sensorial profile of wines. However, the possible toxicity of this new winery practice has not been studied so far. The aim of this study was to evaluate the toxicity of Tempranillo, Cencibel, and Cabernet Sauvignon toasted vine-shoots when used in winemaking. First, vine-shoots were characterized in terms of minerals and phenolic and furan compounds, and then their acute toxicity and cytotoxicity were studied using Microtox® and the metabolic reduction of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays. High EC50 values were obtained when the Microtox® assay was applied to vine-shoot aqueous extracts, similar to the case of herbal infusions. When the MTT assay was used, a cell viability above 70% was observed in all the wines made with those vine-shoots, and an even greater viability was observed in the case of Cabernet Sauvignon. Therefore, it was concluded that those vine-shoots have no cytotoxic potential

Evolution of Oleuropein and Other Bioactive Compounds in Arbequina Olive Leaves under Different Agronomic Conditions

Oleuropein and other phenolic compounds contained in olive leaves give it the potential to be transformed from residue to co-product in an oil mill. However, the moment of the agronomic cycle in which their potential transformation is higher is not known in detail. Therefore, for the first time, a monthly study of the evolution of such compounds throughout an agronomic cycle is made (November 2019 to October 2020). Arbequina olive leaves were collected from three plots and the interactive effects of agronomic conditions were investigated, such as crop management (conventional and ecological), plantation framework (intensive and super-intensive) and location under different climatic conditions. The results showed that the main compound throughout the cycle was oleuropein and the highest levels occurred around the pruning season (February/March). Crop management and location affected the content of verbascoside and hydroxytyrosol, while plantation framework only influenced the flavonoid content. All compounds were affected by relative humidity and differential temperature, although hydroxytyrosol showed the highest correlation with the maximum temperature. The absorbance measurements by ultraviolet-visible spectrophotometry showed trends parallel to the oleuropein concentration measured by high-performance liquid chromatography, which suggests that this method could be useful to easily study the evolution of oleuropein in the oil mill

Oleuropein Degradation Kinetics in Olive Leaf and Its Aqueous Extracts

Although olives leaves are currently considered a waste material from oil mills, they have great potential to be transformed into by-products due to their high oleuropein content. Oleuropein is a glycoside precursor of hydroxytyrosol, which is the phenolic compound with the highest antioxidant capacity in nature and which is associated with multiple health benefits. For this reason, the demand for oleuropein is growing in the pharmaceutical, cosmetic and food sectors. The objective of this study is to determine the stability of oleuropein in olive leaves from oil mills in solid and aqueous forms under different conditions of temperature, relative humidity and lighting. The results indicate that the degradation of oleuropein conforms well to first-order kinetics. The rate constants at the temperatures tested in the aqueous extracts indicate activation energies from RTl to 80 °C and from 7 °C to 14 °C, as the degradation reactions were different in these ranges. Furthermore, olive leaf powder stored at any temperature with an RH ≥ 57% showed greater stability after six months, which is an encouraging result for the storage and transformation of this waste in oil mills

Preliminary Studies on Endotherapy Based Application of Ozonated Water to Bobal Grapevines: Effect on Wine Quality

The application of ozonated water in the vineyard is an increasingly popular tool for disease management, but the quality of grapes and resulting wines is likely to be affected. Endotherapy, or trunk injection, is a particularly useful method to apply phytosanitary products since many fungal pathogens colonize the grapevine woody tissues. Thus, the present study aimed to evaluate the effect on wine quality of the ozonated water applied to Bobal grapevines, one of the most cultivated red varieties in Spain, through endotherapy (E) or its combination with spraying (E + S). Endotherapy was carried out four times before harvest for both E and E + S treatments, and spraying was performed 2 days before and after each endotherapy application. Grapes were harvested, vinified, and the quality of the finished wines was evaluated through several enological parameters and the phenolic and volatile composition. Both treatments resulted in less alcoholic and more acidic wines. The E treatment, although it reduced the content of phenolic acids, stilbenes and flavanols, significantly increased anthocyanins, whereas E + S decreased the overall amount of phenolics, which had different implications for wine colour. In terms of aroma, both treatments, but E to a greater extent, reduced the content of glycosylated precursors and differentially affected free volatiles, both varietal and fermentative. Thus, the dose of ozonated water, frequency and/or method of application are determining factors in the effect of these treatments on wine quality and must be carefully considered by winegrowers to establish the optimum treatment conditions so as not to impair the quality of wines

Variability in the Agronomic Behavior of 12 White Grapevine Varieties Grown under Severe Water Stress Conditions in the La Mancha Wine Region

Viticulture around the world is currently affected by climate change, which is causing an increasing scarcity of water resources necessary for the maintenance of vineyards. Despite the drought hardiness of grapevine (Vitis vinifera L.), this threat seriously compromises its cultivation in the near future, particularly in wine-growing areas with a semi-arid climate. Identifying varieties capable of producing suitable yields and good-quality grapes under drought conditions is integral to ensuring the sustainability of the wine sector. This study focuses on vines from both minority and widely grown varieties, which were supplied only with the water intended to ensure their survival. The carbon and oxygen isotope ratios, yield, and quality parameters were evaluated on the vines and musts during the period of 2018–2020. The results revealed that not all varieties responded equally well to drought. Albillo Real, Coloraillo, Macabeo, and Verdejo adapted well to drought conditions, simultaneously maintaining high yields and must quality. By contrast, Pedro Ximénez can be considered poorly adapted. This variety was the one that produced the lowest yield and had low acidity levels in the must