Phenolic compounds and sensorial characterization of wines aged with alternative to barrel products made of Spanish oak wood (Quercus pyrenaica Willd.)

Comparative study on the use of seasoned or unseasoned casks made of wood from different origins for the ageing of Sherry vinegar

BACKGROUND

In the present study, the ageing process of Sherry vinegar in used (seasoned) or new casks made of chestnut, American oak, Spanish oak or French oak wood has been investigated, considering that no research has investigated whether this seasoning has a definite influence on the final composition of the aged beverage. The polyphenolic and volatile contents of the aged vinegars were determined and their sensory properties were evaluated. Different statistical tools were applied to the data collected.

RESULTS

With respect to polyphenolic contents, ageing time was the most influential factor, followed by the seasoned-cask factor. The type of wood was only significant for gallic acid, p-hydroxybenzoic acid, methylfurfural, ethyl gallate, ferulic acid, coniferyl aldehyde and sinapaldehyde. Principal component analysis according to polyphenols did not allow the samples to be differentiated, whereas cluster analysis revealed a slight grouping trend according to ageing time and seasoning of the wood. In relation to volatile compounds, variance analysis revealed that, again, ageing time and cask-seasoning were the most significant factors, with the samples clustering according to these two parameters. Following the sensory study, a clear difference between seasoned and new cask vinegars could be established as a result of the high scores in olfactory quality obtained for those vinegars aged in new casks. This was probably because of an excess of the descriptor 'ethyl acetate' exhibited by seasoned-cask Sherry vinegars.

CONCLUSION

The previous seasoning of the casks together with the ageing time conditioned the composition of the vinegars aged in casks of different botanical origin, which translated into differences at a sensory level. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

The Application of Wood Species in Enology: Chemical Wood Composition and Effect on Wine Quality

Aging wine is a usual practice in winemaking, as the wine quality improves due to the compounds extracted from wood barrels or chips, cubes, blocks, or staves used. The wood species used are traditionally oak, namely from Quercus petraea, Q. alba, or Q. robur species. In the last years, the increasing request for oak wood has caused a significant increase in environmental and production costs. Therefore, heartwood from several alternative species has been considered a potential wood source for winemaking and aging. Thus, the main purpose of this review is the application of these alternative wood species on wine production and to discuss the advantages and disadvantages of its use compared with the traditional wood species, namely oak wood. In addition, a brief chemical characterization of several wood species with possible application in enology is also discussed in this review.

Accelerating Aging of White and Red Wines by the Application of Hydrostatic High Pressure and Maceration with Holm Oak (Quercus ilex) Chips. Influence on Physicochemical and Sensory Characteristics

BACKGROUND

The use of holm oak (Quercus ilex) chips as a potential alternative wood and the application of hydrostatic high pressure (HHP) as an alternative technique to accelerate the release to the wine of wood-related compounds within a short processing time were evaluated.

METHODS

Five treatments were investigated: (i) bottling without any treatment (B); (ii) and (iii) bottling after maceration (5 g/L) of holm oak chips with HHP treatments (400 MPa, 5 and 30 min) (HHP5, HHP30); (iv) bottling after maceration during 45 days with chips (M), and; (v) maceration in tanks without chips (T). The effects of treatments on general parameters, polyphenols, color, and sensorial characteristics of red and white wines were investigated over 180 days.

RESULTS

HHP5, HHP30, and M increased the polyphenols content, thus modified the chromatic characteristics regarding B and M treatments of white wines, also the tasters differentiated HHP5, HHP30, and M from B and T. However, these effects were not observed in red wines. Thus, the effect of the wood depends on the type of wine in which it is used.

CONCLUSIONS

This research contributes to better knowledge about these chips as a new alternative wood species and the use of HHP as a useful technology to accelerate the aging of wines.

Electrochemical Approaches for Rapid Characterization of Oxidizable Compounds in Different Oak Alternatives

Oak alternatives (OAs) such as chips, granulates or staves, are becoming increasingly used in the wine industry. Although they are mostly considered for their contribution to wine aroma, they are also a source of phenolic compounds to be released in the wine, in particular ellagitannins contributing to wine mouthfeel and antioxidant characteristics. In the present study, we explore the potential for a rapid analytical method based on linear sweep voltammetry (LSV) combined with disposable sensors to provide a rapid measure of the oxidizable compounds present in different OAs, as well as their characterization. Strong correlations were found between the tannin content of different OAs and the total current measures during LSV analysis, allowing a rapid quantification of the oxidizable compounds present, mostly ellagitannin. Application of derivatization to raw voltammograms allowed extraction of a number of features that can be used for classification purposes, in particular with respect to OAs types (chips or staves) and degree of toasting.

Application of Ultraviolet-Visible Absorption Spectroscopy with Machine Learning Techniques for the Classification of Cretan Wines

The present study was aimed at the identification, differentiation and characterization of red and white Cretan wines, which are described with Protected Geographical Indication (PGI), using ultraviolet–visible absorption spectroscopy. Specifically, the grape variety, the wine aging process and the role of barrel/container type were investigated. The combination of spectroscopic results with machine learning-based modelling demonstrated the use of absorption spectroscopy as a facile and low-cost technique in wine analysis. In this study, a clear discrimination among grape varieties was revealed. Moreover, a grouping of samples according to aging period and container type of maturation was accomplished, for the first time.

Wine Aging Technology: Fundamental Role of Wood Barrels

The aging of wines is a process used to preserve wine but also to enhance its properties. It is a process of great interest, mainly because of the additional properties it adds to wines and because of its economic implications. Historically, barrels have been employed for centuries for preserving and aging wine due to their resistance and relative impermeability. In general terms, the wine aging process can be divided into two phases: oxidative and reductive aging. Oxidative aging traditionally takes place in barrels while reductive phase occurs in the bottle. During both processes, oxygen plays a fundamental role as well as other factors, for instance: temperature, light, bottle position, microbial growth or storage time. Likewise, during the aging process, a series of chemical reactions take place influencing the composition and organoleptic profile of wine. At this point, oxidative aging in barrels is a fundamental step. Barrels are directly involved in the produced changes on wine's composition due to the transference of oxygen and phenolic and aromatic compounds from wood to wine. This way, barrels act as an active vessel capable of releasing compounds that affect and improve wine's characteristics. Regarding, the importance of barrels during aging process, some attention must be given to the species most used in cooperage. These species are conventionally oak species, either French or American. However, other non-conventional species are currently being studied as possible wood sources for the production of wines, such as chestnut robinia or other oak species. In the last decades, new approaches have been developed for barrel aging to find new alternatives more suitable, affordable and feasible to sanitize the process, such as other materials different from wood or the use of wood chips, which is regulated since 2006 by the EU. However, even though some of them have shown promising data, barrels are currently the most used technology for the oxidative stage of table wines aging.

Effect of the type of wood used for ageing on the volatile composition of Pedro Ximénez sweet wine

BACKGROUND

The present study investigated the volatile composition of a Pedro Ximénez sweet wine that had been aged in barrels made of different types of wood (Spanish oak, French oak, American oak and chestnut) and subjected to different degrees of toasting (medium toasting and intense toasting). The analyses were carried out using stir bar sorptive extraction gas chromatography-mass spectrometry after validation of the matrix in this case.

RESULTS

Good values of linearity, precision, limits of detection and limits of quantification were obtained for the 36 compounds studied, six of which were identified for the first time in Pedro Ximénez (propyl acetate, cis-3-hexenyl acetate, benzyl acetate, guaiacol, trans-whiskeylactone and 4-ethylguaiacol). The volatile composition of the samples varied as the ageing process progressed, and higher volatile concentrations were obtained in samples aged in barrels that had been intensely toasted compared to in those with medium toasting. A multivariate statistical study allowed the samples to be correctly classified according to ageing time, wood toasting and the type of wood used for ageing.

CONCLUSION

The organoleptic analysis performed on the Pedro Ximénez sweet wine samples resulted in differences between the wines aged in the different types of wood during the early weeks of ageing, and scarce differences towards the end of the study period. At the end of the process, all of the wines were better valued and wines aged in medium toasted barrels were the best rated by the panel of judges for all four woods under investigation. This fact could indicate the suitability of alternative woods for the ageing of Pedro Ximénez sweet wines. © 2020 Society of Chemical Industry.

Suitability of alternative wood types other than American oak wood for the ageing of Sherry vinegar

The present study has consisted on the monitoring of Sherry vinegar during a whole year ageing in American oak, French oak, Spanish oak and chestnut barrels in order to determine the suitability of alternative wood types other than American oak for the ageing of this type of vinegar. Thirty-two volatile compounds were quantified, CIELab parameters were determined and sensory analyses were carried out during the whole process. The multivariate analysis of the data revealed that the samples that had been aged in Spanish oak barrels were getting more similar to those aged in French oak as the ageing process was progressing. Furthermore, the samples that had been aged in chestnut presented some volatile compounds significantly different from American oak. Finally, although French oak wood transferred the best organoleptic characteristics to Sherry vinegar, Spanish oak and chestnut seemed to be satisfactory alternatives for the ageing process.

Effect of size, seasoning and toasting level of Quercus pyrenaica Willd. wood on wine phenolic composition during maturation process with micro-oxygenation

Seasoning and toasting treatments carried out in cooperage influence the chemical composition of the oak, and these treatments affect different oak species in different ways. For this reason, numerous studies have focused on the evaluation of both the oak wood materials and the resulting aged wines in order to optimize the different cooperage processes. Seasoning involves immobilizing the wood for long periods of time, leading to an increase in the price of the final product. When using alternative products instead of barrels, in addition to the seasoning and toasting of the wood, the size of the wood pieces is a determining factor in the characteristics of the final wine. Therefore, the objective of this work was to evaluate the polyphenolic composition of the same red wine aged with different alternative products and a small amount of oxygen for 120 days. Specifically, the effect of 2 types of seasoning and 3 types of toasting of chips and staves made from the wood of Q. pyrenaica Willd. was studied. The results showed that the size of the alternative product was the factor that determines the phenolic composition of the wines over the entire ageing process, independent of the seasoning or toasting method carried out on the wood.

Winemaking with vine-shoots. Modulating the composition of wines by using their own resources

Vine-shoots from two important Vitis vinifera, Airén and Cencibel, have been prepared in two different formats (chip and granule) and added (12 g/L) in their own wines in different winemaking steps. Results have shown significant differences depending in all conditions tested, and wine chemical composition was modulated while in contact with vine-shoots. Compounds such as trans-resveratrol, increased its concentration up to 4 mg/L in Airén white wines. In Cencibel red wines, vanillin was found in a concentration four times above its odor threshold and independently of the vine-shoot variety, format and moment of addition, compounds such as (-)-epicatechin and (+)-catechin increased the concentration with respect to the control wine. When vine-shoots were added after fermentation, β-ionol appeared for first time in all wines. In case of guaiacol, the higher increment was observed for Airén wines. Therefore, it is possible to elaborate distinctive wines using their own resources.

Prediction Models to Control Aging Time in Red Wine

A combination of physical-chemical analysis has been used to monitor the aging of red wines from D.O. Toro (Spain). The changes in the chemical composition of wines that occur over the aging time can be used to distinguish between wine samples collected after one, four, seven and ten months of aging. Different computational models were used to develop a good authenticity tool to certify wines. In this research, different models have been developed: Artificial Neural Network models (ANNs), Support Vector Machine (SVM) and Random Forest (RF) models. The results obtained for the ANN model developed with sigmoidal function in the output neuron and the RF model permit us to determine the aging time, with an average absolute percentage deviation below 1%, so it can be concluded that these two models have demonstrated their capacity to predict the age of wine.

Different Woods in Cooperage for Oenology: A Review

Contact of wine with wood during fermentation and ageing produces significant changes in its chemical composition and organoleptic properties, modifying its final quality. Wines acquire complex aromas from the wood, improve their colour stability, flavour, and clarification, and extend their storage period. New trends in the use of barrels, replaced after a few years of use, have led to an increased demand for oak wood in cooperage. In addition, the fact that the wine market is becoming increasingly saturated and more competitive means that oenologists are increasingly interested in tasting different types of wood to obtain wines that differ from those already on the market. This growing demand and the search for new opportunities to give wines a special personality has led to the use of woods within the Quercus genus that are different from those used traditionally (Quercus alba, Quercus petraea, and Quercus robur) and even woods of different genera. Thus, species of the genus Quercus, such as Quercus pyrenaica Willd., Quercus faginea Lam., Quercus humboldtti Bonpl., Quercus oocarpa Liebm., Quercus frainetto Ten, and other genera, such as Robinia pseudoacacia L. (false acacia), Castanea sativa Mill. (chestnut), Prunus avium L. and Prunus cereaus L. (cherry), Fraxinus excelsior L. (European ash), Fraxinus americana L. (American ash), Morus nigra L, and Morus alba L. have been the subject of several studies as possible sources of wood apt for cooperage. The chemical characterization of these woods is essential in order to be able to adapt the cooperage treatment and, thus, obtain wood with oenological qualities suitable for the treatment of wines. This review aims to summarize the different species that have been studied as possible new sources of wood for oenology, defining the extractable composition of each one and their use in wine.

Oxygen Consumption by Red Wines under Different Micro-Oxygenation Strategies and Q. Pyrenaica Chips. Effects on Color and Phenolic Characteristics

The use of alternative oak products (AOP) for wine aging is a common practice in which micro-oxygenation (MOX) is a key factor to obtain a final wine that is more stable over time and with similar characteristics as barrel-aged wines. Therefore, the oxygen dosage added must be that which the wine is able to consume to develop correctly. Oxygen consumption by red wine determines its properties, so it is essential that micro-oxygenation be managed properly. This paper shows the results from the study of the influence on red wine of two different MOX strategies: floating oxygen dosage (with dissolved oxygen setpoint of 50 µg/L) and fixed oxygen dosage (3 mL/L·month). The results indicated that the wines consumed all the oxygen provided: those from fixed MOX received between 3 and 3.5 times more oxygen than the floating MOX strategy, the oxygen contribution from the air entrapped in the wood being more significant in the latter. Wines aged with wood and MOX showed the same color and phenolic evolution as those aged in barrels, demonstrating the importance of MOX management. Despite the differences in the oxygen consumed, it was not possible to differentiate wines from the different MOX strategies at the end of the aging period in contact with wood.

Volatile composition and sensory characteristics of Carménère wines macerating with Colombian (Quercus humboldtii) oak chips compared to wines macerated with American (Q. alba) and European (Q. petraea) oak chips

Different oak species or origins have been studied to find an alternative to traditional ones and Quercus humboldtii from Colombia is a candidate. Some studies analyse the composition of this oak, but no work has been found to study its use for wine treatment. The aim was to evaluate volatile composition of toasted Q. humboldtii oak chips and the wines treated with these chips. To evaluate its oenological potential Q. alba and Q. petraea have been included in this trial. The wines were subjected to a sensory analysis. Results indicated that oak chips and wines macerated for 90 days with toasted Colombian chips exhibited higher 5-methylfurfural, guaiacol, trans-isoeugenol and syringol concentrations than others, while the furfural and cis-β-methyl-γ-octalactone content was lower. Sensory analysis showed that the wines treated with Colombian oak presented more notes of smoked and less of coconut. Therefore, this oak could probably be considered suitable for ageing.

Toasted vine-shoot chips as enological additive

Different ways of vine-shoots revalorization have been proposed, but not in wine yet, as for example in the same way as oak chips are being used. In this work, vine-shoot samples were submitted to a thermogravimetric analysis to establish the temperature range for its lignin structure decomposition, resulting between 160 and 180 °C. Then, vine-shoot chips from Airén and Cencibel cultivars, with a particle size around 2.5-3.5 cm, were submitted to six toasting conditions: 160 °C and 180 °C for 45, 60 and 75 min. Their volatile composition was very similar to oak chips, being vanillin the most important compound. Moreover, such vine-shoots have an interesting content of prodelphinidins that together with the stilbenes may contribute to wine antioxidant activity. The toasting conditions at 180 °C/45 min were the most suitable one for releasing the mentioned valuable compounds in order to propose vine-shoots as new enological additive similar to oak chips.

Oak wine barrel as an active vessel: A critical review of past and current knowledge

We review the role of the oak barrel as an active vessel for wine maturation. We present a historical background to highlight that previously established aspects of processes occurring with wine inside the oak barrel are still without confirmation. We argue that recently published new findings on the topic are determining factors in defining the manner in which the oak barrel works with wine. Several studies have been published reviewing how the wine barrel functions as an active vessel that releases chemical compounds into the wine, improving its physical, chemical, and sensory properties. Nevertheless, there are hardly any studies that describe how a wine barrel functions as an active vessel. The present review details the main factors affecting the gas exchange capacity of the barrel, such as the pressure drop generated within the barrel, the formation of a headspace, the effect of wood anatomy, the different oxygen entry routes, the role of wood moisture content and soluble ellagitannins, and the effect of barrel toasting on cooperage. Finally, a hypothesis is proposed regarding the function of the barrel as an active vessel, which determines the manner in which it interacts with the wine that it contains during aging.

Oxygen consumption by oak chips in a model wine solution; Influence of the botanical origin, toast level and ellagitannin content

The botanical origin, toast level and ellagitannin content of oak chips in a model wine solution have been studied in terms of their influence on oxygen consumption. French oak chips released significantly higher amounts of ellagitannins than American oak chips at any toast level. The release of ellagitannins by oak chips decreased as the toast level increased in the French oak but this trend was not so clear in American oak. Oxygen consumption rate was clearly related to the level of released ellagitannins. Therefore, oak chips should be chosen for their potential to release ellagitannins release should be considered, not only because they can have a direct impact on the flavor and body of the wine, but also because they can protect against oxidation.

Analytical phenolic composition and sensory assessment of selected rare Greek cultivars after extended bottle ageing

BACKGROUND

The Hellenic vineyard embraces a large number of native cultivars, which are mostly unexploited for their ageing potential. Therefore, it was thought that analyzing some quality parameters of 14 red wines produced by rare native varieties would be of great importance in obtaining a general picture of their potential for commercial use. Various analytical methods were applied to the selected wines, at bottling and after 8 years of ageing, in an attempt to provide reliable answers to this issue. In addition, it was of interest to investigate the alteration of the phenolic content and color parameters of the wines after extended bottle storage and to evaluate the overall changes with respect to their sensory properties.

RESULTS

Most of the oligomeric phenolic compounds identified in the wines studied diminished after 8 years of bottle storage, while significant correlations were obtained between wine chemical composition and sensory data.

CONCLUSIONS

After 8 years of bottle storage some of the unexploited varieties (Vitis vinifera) were found to be worthy of further study and use for the production of quality wines. Wines with the best sensory characteristics were those made by Limniona, Mavrotragano, Bakouri, Thrapsa and Mavrothiriko, in accordance (more or less) with the results of chemical analyses.

A review of polyphenolics in oak woods

Polyphenolics, which are ubiquitous in plants, currently are among the most studied phytochemicals because of their perceptible chemical properties and antioxidant activity. Oak barrels and their alternatives, which are widely used in winemaking nowadays, contribute polyphenolics to wines and are thought to play crucial roles in the development of wines during aging. This study summarizes the detailed information of polyphenolics in oak woods and their products by examining their structures and discussing their chemical reactions during wine aging. This paper evaluates the most recent developments in polyphenolic chemistry by summarizing their extraction, separation, and their identification by the use of chromatographic and spectral techniques. In addition, this paper also introduces polyphenol bioactive ingredients in other plant foods.