Chemical and sensory evaluation of wine matured in oak barrel: effect of oak species involved and toasting process

Metabolomics of Red Wines Aged Traditionally, with Chips or Staves

Traditionally and alternatively aged wines' odour activity values (OAVs) are investigated to differentiate and highlight the differences between the selected methods. An analysis of the volatile aroma compounds of wines derived from ageing in barrels, oak chips, and staves was performed using stir bar sorptive extraction chromatography-mass spectroscopy (SBSE-GC-MS). The results showed that alcohols, esters, and oak compounds were the main contributors to aroma, and their OAVs were higher in the stave samples after 3 months than in the samples from the other two systems of ageing. Furthermore, wines aged with staves have stronger fruity, spiced, and woody aromas, while samples aged in barrels present more chemistry-driven, floral, caramelly, and creamy aromas. The staves-medium plus toast (SMPT at 3 months > 225) and chips-medium plus toast (CMPT at 3 months > 170) showed the highest levels of aromatic series, suggesting that alternative systems provided more powerful aromas than traditional systems, such as barrels-medium plus toast (BMPT at 3 months > 150). A principal component analysis (PCA), orthogonal partial least squares (OPLS) analysis, and cluster analysis allowed for a clear differentiation to be made between red wines according to ageing systems and ageing times. The odour activity values fingerprint in winemaking is a feasible approach to characterise and distinguish wines. Moreover, OAVs provide important information on the effects of production methods on wine quality and aroma profile.

Factors in Modulating the Potential Aromas of Oak Whisky Barrels: Origin, Toasting, and Charring

In this study, the effects of origin (Chinese, France, and America), intensity of toasting, and degree of charring on the volatiles of oak whisky barrels were comprehensively investigated via liquid-liquid extraction-gas chromatography-mass spectrometry (LLE-GC-MS) combined with multivariate statistical analysis. Results of principal component analysis (PCA) showed that the main oak-derived volatiles in oak were more influenced by origin and toasting than by charring. French oak had a higher content of volatile compounds than the other two origins, and this difference decreased with toasting and charring. The process of toasting and charring was important for the release of volatile compounds from oak. The content of most oak-derived volatiles increased with deeper toasting intensity, and the degree of charring promoted or inhibited the release of oak-derived volatiles. The volatile components in oak blocks were affected by the two-factor interaction of toasting and charring. Continuing the process of the charring of oak at a certain level of toasting may have an enhancing or diminishing effect on the content of different volatile compounds, depending on the circumstances.

Mass spectrometry in the study of wood compounds released in the barrel-aged wine and spirits

Aging of wines and spirits in wooden barrels is an industrial process used to stabilize the color, to improve the limpidity and to enrich the sensorial characteristics of the products. In red wines, the oxygen that permeates through the wood staves promotes the oxidization of polyphenols and the formation of new pigments with consequent stabilization of the wine color. Barrel aging of spirits, such as brandy, whisky, rum, and grappa is finalized to enrich their aroma and improve their sensorial characteristics by the contribute of the compounds released by the wood. Oak is the wood type mostly used in making barrels; however, an increasing interest in the use of chestnut, cherry, acacia, and in less extent, ash and mulberry, has been observed in the recent years. Gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry are the main techniques used to characterize respectively the volatile and polar metabolites released by the wood barrels in the products. In this article are reported the recent advancements in this field.

A comparative study of the effect of bacteria and yeasts communities on inoculated and spontaneously fermented apple cider

Understanding bacteria and yeasts communities can reduce unpredictable changes of apple cider. In this study, apple juice inoculated with Saccharomyces cerevisiae WET 136 and fermented spontaneously were compared, the relationships of bacteria, yeasts, organic acids, and volatiles were analyzed. Results showed that microbial diversity affected the fermentation, organic acids and volatiles in apple ciders. In the first four spontaneous fermentation days, LAB (lactic acid bacteria) multiplied and reached 7.89 lg CFU/mL, and then triggered malolactic fermentation (MLF), leading to malic acid decreased by 3880.52 mg/L and lactic acid increased by 4787.55 mg/L. The citric, succinic and fumaric acids content was 2171.14, 701.51 and 8.06 mg/L lower than that in inoculated cider, respectively. Although the yeasts multiplied during spontaneous fermentation, it did not reach 7.50 lg CFU/mL until the 5th day, which led to a long lag period, as well as later and lower production of acetaldehyde and higher alcohols. The inoculated yeast inhibited LAB, acetic acid bacteria, Rahnella, and non-Saccharomyces. Yeasts were the key to produce citric acid, acetaldehyde and 3-methyl-1-butanol in apple cider; while bacteria were closely related to the formation of lactic acid, acetic acid and ethyl acetate. It suggested that low higher alcohols and acetaldehyde can be realized by selecting yeasts, and Leuconostoc pseudomesenteroides can work as candidate to reduce L-malic and citric acids in apple cider.

Contribution of Starmerella bacillaris and Oak Chips to Trebbiano d'Abruzzo Wine Volatile and Sensory Diversity

In this study, six fermentation trials were carried out: co-inoculation and sequential inoculation of Saccharomyces cerevisiae and Starmerella bacillaris in the presence and absence of oak chips. Moreover, Starm. bacillaris strain was attached to the oak chips and co-inoculated or sequentially inoculated with S. cerevisiae. Wines fermented with Starm. bacillaris adhered to oak chips showed a higher concentration of glycerol (more than 6 g/L) than the others (about 5 g/L). These wines also showed a higher content of polyphenols (more than 300 g/L) than the others (about 200 g/L). The addition of oak chips induced an increase of yellow color (b* value of about 3). Oak-treated wines were characterized by a higher concentration of higher alcohols, esters and terpenes. Aldehydes, phenols and lactones were detected only in these wines, independently from the inoculation strategy. Significant differences (p < 0.05) were also observed in the sensory profiles. The fruity, toasty, astringency, and vanilla sensations were perceived as more intense in wines treated with oak chips. The white flower descriptor showed a higher score in wines fermented without chips. Oak surface-adhered Starm. bacillaris cells could be a good strategy to improve the volatile and sensory profile of Trebbiano d'Abruzzo wines.

An efficient methodology for modeling to predict wine aroma expression based on quantitative data of volatile compounds: A case study of oak barrel-aged red wines

Correlating aroma expression with volatile compounds has long been an ambition in researches of flavor chemistry. To propose a reliable methodology to depict wine aroma, 76 oak barrel-aged dry red wines were investigated through the combination of machine learning algorithm and multivariate analysis. Aromatic characteristic was evaluated by quantitative descriptive analysis (QDA), while non- or oak derived volatiles were detected by HS-SPME-GC-MS and targeted SPE-GC-QqQ-MS/MS, respectively. Results showed that variable importance for projection values (VIPs) from partial least-squares regression (PLSR) and mean decrease accuracy (MDA) from random forest were efficient parameters for feature selection. The correlating accuracy of the optimal PLSR model to predict intensities of different aroma characteristics through selected volatile compounds could achieve 0.754 to 0.943, representing potential application to manage wine aroma by chemical assay in winemaking. From the perspective of mathematical modeling in the real wine matrix, the network analysis between aroma characteristics and key volatile compounds indicated that the expression of oak aroma was not only directly contributed by volatiles derived from oak wood, but also influenced by ethyl esters, including ethyl acetate, ethyl butanoate, ethyl hexanoate, ethyl decanoate, and ethyl nonanoate.

Developing novel oenological tannins from 44 plants sources by assessing astringency and color in model wine

BACKGROUND

Oenological tannins are commercial natural products extracted from different botanical sources, which were widely reported as prominent contributors to wine quality. Research on wine quality affected by tannins extracts promoted the development of new oenological products with low cost and high accessibility. In the present study, the structure and concentration of tannin in polyphenol extracts, as well as their correlation with astringency and the color of model wine, was investigated by UV spectrophotometer, HPLC, fluorescence quenching, sodium dodecylsulfate-polyacrylamide gel electrophoresis, colorimeter and sensory evaluation.

RESULTS

Resource extracts from 16 of 44 plants were screened as wine oenological tannins, according to the total polyphenol and total flavanol, as well as the intensity of astringency and bitterness. Polyphenols extracted from grape seeds and green tea were more effective in increasing the wine astringency compared to other plant tannins.

CONCLUSION

Total flavanol content and tannin activity showed a strong correlation with wine astringency. Condensed tannins with mean degree of polymerization also exhibited strong color stability, and the concentrations of (-)-epigallocatechin were associated with the a* value, a negative qualitative factor for wine color. The present study provides new clues regarding the development of low-cost and highly accessible sources of polyphenol extracts and lays a theoretical foundation for the development of the oenological product. © 2022 Society of Chemical Industry.

Ellagitannin evolution of aged Cognac eaux-de-vie; Impact of barrel toasting

The contribution of C-glucosidic ellagitannin-derived compounds to eaux-de-vie quality has been recently demonstrated. However, there is a gap in our knowledge of the content, composition, and evolution of these compounds in this specific matrix. The objective of this study was therefore to carry out an analysis of the kinetics of these compounds, and to study how they are impacted by barrel toasting. For this purpose, barrels representing eight different to asting levels were used to age the same eau-de-vie during the first 18 months. Ellagitannin quantification was carried out by HPLC-QQQ. The results showed that C-glucosidic ellagitannins were extracted during the first 3 months of aging and then decreased, whereas ellagitannin-derived spirit compound concentrations increased throughout aging. In addition, barrel toasting had such an impact on ellagitannin content that barrels were differentiated according to their levels.

Impact of Barrel Toasting on Ellagitannin Composition of Aged Cognac Eaux-de-Vie

It is well established that C-glucosidic ellagitannins contribute to wine quality, and new forms of ellagitannins have been found recently in cognac eaux-de-vie. The contribution of some ellagitannin-derived spirit compounds to eaux-de-vie taste has been demonstrated recently. However, there is a gap in our knowledge of the content, composition, and evolution of C-glucosidic ellagitannins in this matrix. Indeed, the quantification of these compounds and their evolutionary compounds have never before been researched in cognac eaux-de-vie. Thus, the aim of this study was not only to quantify these compounds, but also to study their kinetics and to observe how they are impacted by barrel toasting. For this purpose, barrels representing eight different toasting levels were used to age the same eau-de-vie during the first 18 months. Ellagitannin quantification was carried out by HPLC-Triple quadrupole. The results showed that the evolutionary trend of the eight ellagitannins is the same for all eight types of barrel toasting. The maximum concentrations of C-glucosidic ellagitannins were found after 3 months of aging (up to 23 mg/L) before decreasing to 18 months (9.7 mg/L), whereas ellagitannin-derived spirit compound concentrations increased throughout aging (up to 130.9 mg/L). In addition, barrel toasting had such an impact on ellagitannin content that barrels could be differentiated according to their levels. Eaux-de-vie in barrels with high toasting were lower in ellagitannins concentrations.

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.

Alternative Woods in Oenology: Volatile Compounds Characterisation of Woods with Respect to Traditional Oak and Effect on Aroma in Wine, a Review

The interest of winemakers to find new woods that can give their wines a special personality and the need for cooperage wood have led to the use of other woods than traditional oak. The aroma of wines is undoubtedly one of the quality factors most valued by consumers. Volatile compounds from wood are transferred to wines during ageing. The type and quantity of aromas in wood depend on several factors, with the species, origin and cooperage treatments, particularly toasting, being very important. The transfer of volatile compounds to the wine depends not only on the wood but also on the wine itself and the type of ageing. This review therefore aims to recapitulate the volatile composition of alternative oenological woods at different cooperage stages and to compare them with traditional woods. It also summarises studies on the effect of wine aromas during ageing both in barrels and with fragments of alternative woods. In summary, it is observed that both woods and wines aged with alternative species of the Quercus genus present the same volatile compounds as traditional ones, but differ quantitatively; however, non-Quercus woods also differ qualitatively.

Effect of bentonite and calcium chloride on apple wine

BACKGROUND

Apple wine is a popular alcoholic beverage for its nutrition and fresh taste. However, the methanol existing in apple wine restricts its quality. Unfortunately, there are no methods to reduce the methanol content in fruit wine. To this end, bentonite (B), calcium chloride (CC) and their combination (B&CC) were added into apple juice in this study. The treated juice (0) and supernatant obtained by standing the juice at 25 °C for 24 h were fermented at 25 °C and 10 °C, respectively.

RESULTS

Bentonite was an excellent methanol interrupter, a pectin retainer and a wine quality defender both at 25 and 10 °C. The lowest methanol content of 1.41 mg L^-1 and higher pectin content of 84.74 mg L^-1 were reached in the finished wine by B0 at 10 °C. Calcium chloride decreased pectin content, elevated methanol content and changed the profile of individual organic acids. In fact, the wine by B&CC0 at 25 °C showed dramatic changes in individual organic acids. The content of l-malic acid and succinic acid was only 2.22% and 6.29% of the control, respectively, while the lactic acid content was 17.72 times that of the control.

CONCLUSIONS

It is suggested that B0 and fermented at 10 °C was the most effective way to decrease methanol content, retain pectin content and defend wine quality. © 2021 Society of Chemical Industry.

Impact of High-Power Ultrasound for Barrel Regeneration on the Extraction of Wood Volatile and Non-Volatile Compounds

High-power ultrasound (HPU) is an innovative cleaning method used in wineries for oak barrel sanitation and regeneration. The process is associated with hot water (HPUhw) to ensure microbial stabilization and has been proved to be highly effective in recent years. This study thus examines the impact of different cleaning treatments on the subsequent extraction of wood compounds in wine and their impact on organoleptic properties. Red wines aging in barrels treated (HPUhw and steam) in different years (1, 2, and 3 years) were examined during the first 12 months for chemical exchange from wood to wine. Specific analyses were realized on ellagitannins, the physicochemical composition, and oak wood volatile compounds. Only a small increase in some wood volatile compounds occurred in the case of HPUhw, including furfural, 5-methylfurfural, trans-whisky lactone, vanillin, and syringaldehyde. The sensory analysis carried out by a panel of experts showed that the impact on the organoleptic properties of wines is similar with both processes (HPUhw and steam). However, since HPUhw treatment requires lower energy for the same efficiency, it could be an interesting alternative to steam treatment, given the promising prior microbial results.

Influence of pre-fermentative addition of aqueous solution tannins extracted from oak wood (Quercus petraea) on the composition of Grillo wines

In this research, the chemical characterization of fixed and volatile compounds of two different tannins in aqueous solution (Pratiko® L-Harvest and L-Fruit) extracted from oak wood, has been studied. The influence of the above tannins, at different concentrations, on the alcoholic fermentation kinetics and on the composition and sensorial characteristics of a white wine were then evaluated. The wines added tannins in aqueous solution compared to control wines showed significant differences in fixed compounds (colloids, polyphenols and ellagitannins) and volatile compounds (phenolic aldehydes, volatile phenols, furanic and piranic compounds). The differences of aqueous solution tannins extracted from oak wood were partly due to the drying/maturing and roasting methods used in barrel production. Alcoholic fermentation was partially facilitated by the addition of tannins in aqueous solution. The wines obtained showed a higher content of ethyl esters of medium-chain fatty acids (from 22 to 31%) and, in some cases, higher acetate alcohols (from 15 to 28%), relevant to the olfactory sensations provided to the wines. The tannins added to the must before fermentation also made it possible to obtain an additional supply of polyphenols (from 25 to 85%) able to induce more complex sensory profiles in the wines, with increased persistent taste notes.

Influence of Non-Saccharomyces on Wine Chemistry: A Focus on Aroma-Related Compounds

Wine fermentation processes are driven by complex microbial systems, which comprise eukaryotic and prokaryotic microorganisms that participate in several biochemical interactions with the must and wine chemicals and modulate the organoleptic properties of wine. Among these, yeasts play a fundamental role, since they carry out the alcoholic fermentation (AF), converting sugars to ethanol and CO₂ together with a wide range of volatile organic compounds. The contribution of Saccharomyces cerevisiae, the reference organism associated with AF, has been extensively studied. However, in the last decade, selected non-Saccharomyces strains received considerable commercial and oenological interest due to their specific pro-technological aptitudes and the positive influence on sensory quality. This review aims to highlight the inter-specific variability within the heterogeneous class of non-Saccharomyces in terms of synthesis and release of volatile organic compounds during controlled AF in wine. In particular, we reported findings on the presence of model non-Saccharomyces organisms, including Torulaspora delbrueckii, Hanseniaspora spp,Lachancea thermotolerans, Metschnikowia pulcherrima, Pichia spp. and Candida zemplinina, in combination with S. cerevisiae. The evidence is discussed from both basic and applicative scientific perspective. In particular, the oenological significance in different kind of wines has been underlined.

Polyphenolic Characterization of Nebbiolo Red Wines and Their Interaction with Salivary Proteins

The present study correlates the polyphenolic composition of two different Nebbiolo red wines from the 2015 vintage (M and P), with the salivary proteins’ precipitation process. The work centered on the polyphenolic characterization of Nebbiolo wines and their interaction with different families of salivary proteins. Overall, both wines were found to be very reactive with human saliva which was supposed to contribute to their astringent character. The comparison of both wines showed that the M wine presented higher values of total phenolics, total proanthocyanidins, and tannin specific activity. Moreover, this wine showed a higher interaction with salivary proteins. Altogether, the chemical characterization and reactivity toward human saliva could contribute to the wine astringency.

Changes in volatile compounds of grape pomace distillate (Italian grappa) during one-year ageing in oak and cherry barrels

The Italian grape pomace distillate grappa is often refined by ageing in wooden barrels. Chemical changes of the volatile profile of two samples produced from a Cabernet Sauvignon/Merlot blend and Prosecco pomace both at two ethanol contents (55% and 68%) were studied during one-year ageing in cherry and oak barriques. Grappa variety, ethanol content and barrel type strongly affected the volatiles profile of the distillates. Oak-aged grappa contained 10-fold the wood volatiles of the cherry-aged one, but the latter had higher levels of syringaldehyde, coniferaldehyde, and 3,4,5-trimethoxyphenol; 55% ethanol extracted higher levels of wood compounds and ethoxy-compounds were higher in the 68%-ethanol distillates. Prosecco grappa extracted higher wood compounds and showed no significant changes in the levels of fruity/floral esters and terpenols. Findings of this study can be also useful in the development of new ageing processes of distillates for which cherry barrels are still not used (e.g., brandy and whisky).

New C-Glycosidic Ellagitannins Formed upon Oak Wood Toasting; Identification and Sensory Evaluation

In the courses of studies on ellagitannin changes during oak wood toasting, two C-glycosidic ellagitannins were isolated from the french oak wood for the first time. These two compounds exhibited [M-H]- ion peak at m/z 1055.0631 (compound A) and at m/z 1011.0756 (compound B). A compound is named Castacrenin E and is produced by Castacrenin D oxidation. Castacrenin D is a vescalagin with an additional aromating ring to the C-1 through a C-C bond. These compounds are not only found under laboratory conditions but also in commercial oak wood representing different toasting methods and sizes. Their levels are conditioned by oak wood dimensions and toasting degree. The wood pieces with the smallest size present almost two times more compounds A and B. Moreover, the compound B is the only compound to be present in medium toasting temperatures of the smallest wood pieces. Both of them can influence either astringency sensation or bitterness taste.

Validation of a mass spectrometry method to identify and quantify ellagitannins in oak wood and cognac during aging in oak barrels

Ellagitannins are the main extractible phenolic compounds in oak wood; the monomers vescalagin and castalagin, lyxose/xylose-bearing monomers grandinin and roburin E, dimers roburins A and D and lyxose/xylose-bearing dimers roburins B and C are the principal ones. These compounds are responsible for the high durability of wood and may contribute to the organoleptic quality of wines and spirits (color, astringency, bitterness). Despite their importance, their presence and forms in distilled spirits are not well known. The aim of this work was therefore to develop and validate a method to identify and quantify oak wood ellagitannins in Cognac using high liquid chromatography-triple quadrupole (LC-QQQ) analysis. The method was validated using vescalagin as the standard and by studying sensitivity, linearity in working range, intraday repeatability, and intraday precision in order to quantify individual ellagitannins in this complex matrix.

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.

Use of Oak and Cherry Wood Chips during Alcoholic Fermentation and the Maturation Process of Rosé Wines: Impact on Phenolic Composition and Sensory Profile

There is a lack of knowledge about the use of different wood species on rosé wine production. Thus, this work focused on the impact of the addition of wood chips from oak and cherry trees during the alcoholic fermentation and maturation process on rosé wine characteristics. Therefore, phenolic composition and sensory characteristics were monitored during the rosé wines' production. The use of wood chips during alcoholic fermentation induced a significant increase of phenolic content in rosé musts. During rosé wine maturation, the wood chip contact induced significantly higher values of colored anthocyanins, color intensity, and polymeric pigments, and significantly lower values of color hue in the corresponding rosé wines. In terms of sensory profile, a tendency for lower scores of "overall appreciation" were attributed to control rosé wine, while significantly higher scores for "color intensity" descriptor were attributed to all rosé wines matured in contact with wood chips. For the majority of phenolic parameters and individual phenolic compounds quantified, a clear and specific influence of the use of oak and cherry wood chips was not detected, except for (+)-catechin, where the rosé wines produced in contact with cherry chips showed the highest values. This study provides relevant information for winemakers about the impact of the use of wood chips on rosé wine quality.

Interaction between Ellagitannins and Salivary Proline-Rich Proteins

The first contact of tannins with the human body occurs in the mouth, where some of these tannins are known to interact with salivary proteins, in particular with proline-rich proteins (PRPs). These interactions are important at a sensory level, especially for astringency development, but could also affect the biological activities of the tannins. This study gathers information on the relative affinity of the interaction, complex stoichiometry, and tannin molecular epitopes of binding for the interactions between the families of PRPs (bPRPs, gPRPs, and aPRPs) and three representative ellagitannins (castalagin, vescalagin, and punicalagin). These interactions were studied by saturation-tranfer difference NMR and microcalorimetry. The effect of the PRP-ellagitannin interaction on their antioxidant ability was also assessed by ferric reduction antioxidant power (FRAP) assays. The results support a significant interaction between the studied tannins and PRPs with binding affinities in the micromolar range. Punicalagin was always the ellagitannin with higher affinity. aPRPs were the salivary PRPs with higher affinity. Moreover, it was observed that when ellagitannins are present in low concentrations (5-50 μM), as occurs in food, the antioxidant ability of these tannins when complexed with salivary PRPs could be significantly impaired.

Acacia, cherry and oak wood chips used for a short aging period of rosé wines: effects on general phenolic parameters, volatile composition and sensory profile

BACKGROUND

There is a restricted knowledge about the potential impact of the use of different wood chip species on the rosé wine aging process. Thus, the aim of this work was to evaluate the general phenolic parameters, aroma composition and sensory profile of rosé wines during a short maturation (20 aging days) in contact with wood chips from oak, acacia and cherry. In addition, the different wood chips were added to a rosé wine without a previous clarification process (unfined wine) and to a rosé wine submitted to a clarification process (fined wine).

RESULTS

For the brief maturation time considered, the use of different wood chips induced a tendency for an increase of phenolic content, in particular for unfined rosé wine aged in contact with acacia chips. For volatile composition, the differentiation was clearer for aldehyde compounds group. Regarding sensorial overall appreciation the panel test preferred the unfined rosé wine aged in contact with acacia wood chips.

CONCLUSIONS

The results show that, in general, the use of different wood chip species (acacia, cherry and oak) for a brief maturation time of rosé wines could play an important role in rosé wine characteristics, in particular in their phenolic composition. © 2019 Society of Chemical Industry.

Study of High Power Ultrasound for Oak Wood Barrel Regeneration: Impact on Wood Properties and Sanitation Effect

This study aims to investigate the ability of high power ultrasound (HPU) to ensure oak barrel sterilization and wood structure preservation. Optimization was performed in terms of temperature and time and the impact of the HPU process on the porous material was also characterized. In this research, several wood characteristics were considered, such as the specific surface area, hydrophobicity, oxygen desorption and spoilage microorganisms after treatment. The study showed that the microbial stabilization could be obtained with HPU 60 °C/6 min. The results obtained show that microorganisms are impacted up to a depth of 9 mm, with a Brettanomyces bruxellensis population < 1 log CFU/g. The operating parameters used during the HPU treatment can also impact on wood exchange surface and oxygen desorption kinetics indicating that tartrate is removed. Indeed, the total oxygen desorption rate was recovered after HPU treatment, close to a new oak barrel, and thus may indicate that there is no impact on the ultrastructure (vessel, pore size or rays). Finally, wood wettability can also be impacted, depending on the temperature and the duration of exposure.

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.

Liberation of recalcitrant cell wall sugars from oak barrels into bourbon whiskey during aging

Oak barrels have been used by humans for thousands of years to store and transport valuable materials. Early settlers of the United States in Kentucky began charring the interior of new white oak barrels prior to aging distillate to create the distinctively flavored spirit we know as bourbon whiskey. Despite the unique flavor and cultural significance of “America’s Spirit”, little is known about the wood-distillate interaction that shapes bourbon whiskey. Here, we employed an inverse method to measure the loss of specific wood polysaccharides in the oak cask during aging for up to ten years. We found that the structural cell wall wood biopolymer, cellulose, was partially decrystallized by the charring process. This pyrolytic fracturing and subsequent exposure to the distillate was accompanied by a steady loss of sugars from the cellulose and hemicellulose fractions of the oak cask. Distinct layers of structural degradation and product release from within the barrel stave are formed over time as the distillate expands into and contracts from the barrel staves. This complex, wood-sugar release process is likely associated with the time-dependent generation of the unique palate of bourbon whiskey.

A Multi-Omics Analysis Pipeline for the Metabolic Pathway Reconstruction in the Orphan Species Quercus ilex

Holm oak (Quercus ilex) is the most important and representative species of the Mediterranean forest and of the Spanish agrosilvo-pastoral "dehesa" ecosystem. Despite its environmental and economic interest, Holm oak is an orphan species whose biology is very little known, especially at the molecular level. In order to increase the knowledge on the chemical composition and metabolism of this tree species, the employment of a holistic and multi-omics approach, in the Systems Biology direction would be necessary. However, for orphan and recalcitrant plant species, specific analytical and bioinformatics tools have to be developed in order to obtain adequate quality and data-density before to coping with the study of its biology. By using a plant sample consisting of a pool generated by mixing equal amounts of homogenized tissue from acorn embryo, leaves, and roots, protocols for transcriptome (NGS-Illumina), proteome (shotgun LC-MS/MS), and metabolome (GC-MS) studies have been optimized. These analyses resulted in the identification of around 62629 transcripts, 2380 protein species, and 62 metabolites. Data are compared with those reported for model plant species, whose genome has been sequenced and is well annotated, including Arabidopsis, japonica rice, poplar, and eucalyptus. RNA and protein sequencing favored each other, increasing the number and confidence of the proteins identified and correcting erroneous RNA sequences. The integration of the large amount of data reported using bioinformatics tools allows the Holm oak metabolic network to be partially reconstructed: from the 127 metabolic pathways reported in KEGG pathway database, 123 metabolic pathways can be visualized when using the described methodology. They included: carbohydrate and energy metabolism, amino acid metabolism, lipid metabolism, nucleotide metabolism, and biosynthesis of secondary metabolites. The TCA cycle was the pathway most represented with 5 out of 10 metabolites, 6 out of 8 protein enzymes, and 8 out of 8 enzyme transcripts. On the other hand, gaps, missed pathways, included metabolism of terpenoids and polyketides and lipid metabolism. The multi-omics resource generated in this work will set the basis for ongoing and future studies, bringing the Holm oak closer to model species, to obtain a better understanding of the molecular mechanisms underlying phenotypes of interest (productive, tolerant to environmental cues, nutraceutical value) and to select elite genotypes to be used in restoration and reforestation programs, especially in a future climate change scenario.

Effect of oak wood barrel capacity and utilization time on phenolic and sensorial profile evolution of an Encruzado white wine

BACKGROUND

Several studies have reported the influence of diverse winemaking technologies in white wine characteristics. However, the impact of the use of different oak wood barrel capacities and utilization time on the evolution of white wine phenolic content and sensorial characteristics are not usually considered. Thus the aim of this work was to evaluate the effect of oak wood barrel capacity and utilization time on the evolution of phenolic compounds, browning potential index and sensorial profile of an Encruzado white wine.

RESULTS

For the 180 aging days considered, the use of new oak wood barrels induced a greater increase in global phenolic composition, including several individual compounds, such as gallic and ellagic acid, independently of the barrel capacity. Tendency for a lesser increase of the browning potential index values was detected for white wines aged in new oak wood barrels. The sensorial profile evolution, showed significant differences only for the aroma descriptors, namely for 'wood aroma' and 'aroma intensity', white wine aged in 225 L new oak wood barrels being the highest scored.

CONCLUSION

The results show that, in general, the use of different capacities and utilization time of oak wood barrels used for white wine aging could play an important role in white wine quality. © 2017 Society of Chemical Industry.

The impact of different barrel sanitation approaches on the spoilage microflora and phenols composition of wine

Careful control of spoilage microflora inside wine containers is a key issue during winemaking. To date, attention has been paid to the development of an effective protocol for the eradication of spoilage agents, especially Brettanomyces, from barrels. Few studies have taken into account the modifications caused by sanitation treatments in wine and wood barrels. In the present study the effects of two sanitation treatments (ozone and sodium hydroxide) on barrel spoilage microflora and the composition of the wine stored inside them were evaluated. The phenols of wine (38 compounds) were characterised using a UHPLC-MS during the first 3 months of wine ageing, to see possible alterations in composition due to the chemical exchange from wood to wine in presence of sanitising agents. With the same scope, a panel of 13 judges carried out sensorial analysis of wines. The results showed that the tested treatments had little effect on the organoleptic characteristics of wines, but underline the different performance of the sanitation treatments in terms of eradicating microorganisms.