Model aging and oxidation effects on varietal, fermentative, and sulfur compounds in a dry botrytized red wine

Investigating the factors driving concentrations of volatile thiols and their precursors in white wines: The impact of Botrytis cinerea and grape variety

3-Sulfanylhexan-1-ol (3SH) and 3-sulfanylhexyl acetate (3SHA) are highly odiferous impact odorants in wines, imparting tropical aromas. Despite having a good understanding of how vintage, grape variety, region of production, and Botrytis cinerea infection affect the concentration of these volatile thiols, the influence of these factors on the concentrations of thiol precursors has not been comprehensively studied. Therefore, the concentrations of 3SH and 3SHA, and five precursors to 3SH, were quantitated for 40 commercial white wines, to explore how vintage, variety, region, and Botrytis cinerea infection, influence both thiol and precursor concentrations. The most impactful factors on wine thiol concentration were Botrytis and variety, although these factors influenced the thiols differently. 3SHA concentrations were also modulated, although less strongly, by vintage and region. However, only Botrytis and variety influenced precursor types and concentrations. Ultimately, variety was the most impactful factor in thiol and thiol precursor concentrations in the wines studied herein.

Characterizing the composition of volatile compounds in different types of Chinese bacon using GC-MS, E-nose, and GC-IMS

Chinese bacon is highly esteemed by consumers worldwide due to its unique aroma. The composition of volatile organic compounds (VOCs) varies significantly among different types of Chinese bacon. This study analyzed the VOCs of Chinese bacon from Sichuan, Hunan, Guangxi, and Shaanxi provinces using gas chromatography-mass spectrometry (GC-MS), an electronic nose (E-nose), and gas chromatography-ion mobility spectrometry (GC-IMS). The results demonstrate that the combination of GC-MS and GC-IMS effectively distinguishes Chinese bacon from different regions. Notably, Guangxi bacon lacks a smoky aroma, which sets it apart from the other types. However, it contains many esters that play a crucial role in its flavor profile. In contrast, phenols, including guaiacol, which is typical in smoked bacon, were present in the bacon from Sichuan, Hunan, and Shaanxi but were absent in Guangxi bacon. Furthermore, Hunan bacon exhibited a higher aldehyde content than Sichuan bacon. 2-methyl-propanol and 3-methyl-butanol were identified as characteristic flavor compounds of Zhenba bacon. This study provides a theoretical foundation for understanding and identifying the flavor profiles of Chinese bacon. Using various analytical techniques to investigate the flavor compounds is essential for effectively distinguishing bacon from different regions.

Dimethyl Sulfide (DMS) in Amarone Wines: Influence of Aging, Withering, Grape Variety, and Geographical Origin

Occurrence of dimethyl sulfide (DMS), a potent aroma compound accumulating during aging, was investigated in commercial and experimental Amarone wines. In commercial Amarone, DMS was observed in concentrations ranging from 2.9 to 64.3 μg/L. Model aging studies on experimental wines indicated that DMS in Amarone is strongly associated with aging and that wines from different vineyards can vary significantly in their ability to accumulate DMS during aging. The capacity of certain vineyards to give wines with higher DMS-forming potential was consistent across three consecutive vintages, representing a true terroir factor to be expressed with aging. Wine content of primary amino acids (PAN), a commonly analyzed enological parameter of grape must, was shown to be positively correlated with DMS accumulation during aging. Grape withering also increased DMS-forming potential mostly due to increased PAN resulting from concentration due to water loss. Increased pH due to withering also contributed to a higher DMS content of withered wines, but to a lower extent. In certain vineyard sites, an influence of vintage conditions on DMS-forming potential was also observed.

Dosing oxygen from the early stages of white winemaking: Effect on oxidation-reduction potential, browning stability, volatile composition, and sensory properties

This study investigated the effect of controlled oxygen addition during alcoholic fermentation (4 mg/L, at 2nd, 4th, 6th, 10th, 14th, 16th, 20th day) and aging on lees (2 mg/L, every 15 days for 3 months) in a stainless-steel tank for white wine production from a nearly neutral grape. Under less reductive conditions (Ox), alcoholic fermentation was completed in 27 days, whereas one extra week was required under more reductive conditions (no-Ox). The greatest amount of dissolved oxygen in Ox wine triggered the increase of redox potential (EH) starting from the end of alcoholic fermentation and throughout aging (169 and 150 mV in Ox and no-Ox wine, respectively), also improving the wine resistance to browning. Oxygen addition from the early stages of winemaking significantly modulated volatile composition and sensory attributes, which may contribute to the diversification of wine style.

New Insights into the Origin of Volatile Sulfur Compounds during Wine Fermentation and Their Evolution during Aging

Volatile sulfur compounds (VSCs) are associated with unpleasant reductive aromas and are responsible for an important reduction in wine quality, causing major economic losses. Understanding the origin of these compounds in wine remains a challenge, as their formation and further evolution during winemaking can involve both chemical and biological reactions. Comparing the VSCs profile (i) of fermenting synthetic grape juices supplemented with a selected VSC (eight compounds tested) and incubated in presence or absence of yeast, and (ii) during storage of wines under an accelerated aging procedure, allowed us to elucidate the chemical and metabolic connections between VSCs during fermentation and aging. Yeast metabolism, through the Ehrlich pathway and acetylation reactions, makes an important contribution to the formation of compounds such as methionol, 3-methylthiopropionate, 3-methylthiopropylacetate, 3-mercaptopropanol, 2-mercaptoethanol and thioesters. By contrast, chemical reactions are responsible for interconversions between thiols and disulfides, the formation of thiols from thioesters or, more surprisingly, the formation of ethylthiopropanol from methionol during fermentation. During aging, variations in heavy VSC concentrations, such as an increase in 3-methylthiopropylacetate and a decrease in ethyl-3-methylthiopropionate formation, were evidenced. Overall, this study highlights that it is essential to consider both yeast metabolism and the high chemical reactivity of VSCs to understand their formation and evolution during winemaking.

Sensorial and Volatile Analysis of Wines Made from Partially Dehydrated Grapes: An Ontario Case Study

Winemaking in cool climate viticultural areas can pose challenges due to difficulties in achieving optimal ripeness from climatic conditions that tend to vary vintage-to-vintage. To stabilize quality, the use of partially dehydrated grapes has been indicated as beneficial to the production of high-quality wine (“appassimento” style) despite climatic variation. Postharvest wine grape dehydration is a complex process that involves the concentration or formation of sugars, aromas, and flavours. One of the quality challenges facing appassimento style winemaking is elevated levels of undesirable oxidation compounds. The aim of this study was to characterize wines made from a local yeast isolate, Saccharomyces uvarum CN1, which demonstrates limited osmotolerance and may have application to this wine style, as it is a known lower producer of such compounds. Wines made with CN1 were compared to wines made with the accepted commercial standard, S. cerevisiae, EC1118. Fermentations (n = 24) were established at three target starting sugar concentrations from dehydrated Cabernet franc grapes (24.5, 26.0, and 27.5°Brix) and a control (21.5°Brix) and were assessed for volatile organic compound (VOC) composition via gas chromatography-mass spectrometry (GC-MS). Wines also underwent quantitative descriptive analysis to identify and quantify sensory attributes by a trained panel (n = 11). Results show that the wines fermented with the yeast isolate contain significant differences in the concentrations of VOCs in the wines. Sensorially, the wines differed in intensity for a number of attributes, including red fruit aroma, black fruit flavour, and length of finish both within Brix treatments and amongst yeast strains. The most important differentiating factor amongst these wines was the combination of yeast strain at the highest starting sugar concentration (27.5°Brix). These findings may assist winemakers by informing the yeast strain choice for optimizing appassimento style wine quality in cool climates.

Impact of Different Stoppers on the Composition of Red and Rosé Lagrein, Schiava (Vernatsch) and Merlot Wines Stored in Bottle

Different technical cork stoppers (blend of natural cork microgranules, one-piece natural cork, agglomerated natural cork, technical cork 1+1) were compared to evaluate the effects on the phenolic, volatile profiles and dissolved oxygen in three red (Merlot, Lagrein red, St. Magdalener) and one rosé (Lagrein rosé) wines, which were stored in bottles for 12 months. Gallic acid, caffeic acid, p-coumaric acid, trans-resveratrol, glutahionyl caftaric acid and protocatechuic acid did not vary remarkably during the first three months, whereas at six months a net increase was reported, followed by a clear decrease at 12 months. The same trend was observed in Lagrein rosé, but only for gallic acid. The total anthocyanins content decreased during the storage period in the four wines. Isopentyl acetate, 1-hexanol, ethyl hexanoate, 2-phenylethyl alcohol, diethyl succinate, ethyl octanoate and ethyl decanoate were the main volatile compounds. The sum of alcohols decreased in all four of the wines. The esters decreased in Merlot; however, they increased in Lagrein rosé, Lagrein red and St. Magdalener during the storage. Univariate and multivariate statistics and a sensory discriminant triangle test displayed similar influences of the different stoppers on the phenolic and volatile compounds during the whole storage duration. The changes detected in the phenolic and volatile concentrations were presumably due to the non-oxygen-mediated reactions occurring during 12 months of storage in bottle.

Norisoprenoids, Sesquiterpenes and Terpenoids Content of Valpolicella Wines During Aging: Investigating Aroma Potential in Relationship to Evolution of Tobacco and Balsamic Aroma in Aged Wine

During wine aging, tobacco and balsamic aroma notes appear. In this paper, volatile compounds directly or potentially related to those aromas have been investigated in Corvina and Corvinone wines during aging. Corvina and Corvinone are two northern-Italy autochthonous red grape varieties, used to produce Valpolicella Classico and Amarone wines, both characterized by tobacco and balsamic aroma notes. Wines were analyzed shortly after bottling or following model aging at 60°C for 48, 72, and 168 h. Volatile compounds were analyzed by HS-SPME-GC-MS. Results showed that compounds related to tobacco aroma [β-damascenone, 3-oxo-α-ionol, (E)-1-(2,3,6-Trimethylphenyl)-buta-1,3-diene (TPB), and megastigmatrienones] increased in relationship to storage time with different patterns. β-Damascenone and 3-oxo-α-ionol rapidly increased to reach a plateau in the first 48–72 h of model aging. Instead, TPB and megastigmatrienones concentration showed a linear correlation with aging time. During model aging, several cyclic terpenes tended to increase. Among them 1,8-cineole and 1,4-cineole, previously reported to contribute to red wine eucalyptus notes increased proportionally to storage time, and this behavior was clearly associated with reactions involving α-terpineol, limonene, and terpinolene, as confirmed by studies with model wine solutions. Among other relevant volatile compounds, sesquiterpenes appear to contribute potentially balsamic and spicy aroma notes. In this study, linear sesquiterpenes (nerolidol, farnesol) underwent acid hydrolysis during long wine aging, while cyclic sesquiterpenes seemed to increase with time. The chemical pathways associated with evolution of some of the compounds investigated have been studied in model wine.

Evolution of Volatile Sulfur Compounds during Wine Fermentation

Volatile sulfur compounds (VSCs) play a significant role in the aroma of foods and beverages. With very low sensory thresholds and strong unpleasant aromas, most VSCs are considered to have a negative impact on wine quality. In this study, headspace solid phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME/GC-MS) was used to analyze the time course of the biosynthesis of 12 VSCs formed during wine fermentation. Two different strains of Saccharomyces cerevisiae, the laboratory strain BY4743 and a commercial strain, F15, were assessed using two media: synthetic grape media and Sauvignon Blanc juice. Seven VSCs were detected above background, with three rising above their sensory thresholds. The data revealed remarkable differences in the timing and evolution of production during fermentation, with a transient spike in methanethiol production early during anaerobic growth. Heavier VSCs such as benzothiazole and S-ethyl thioacetate were produced at a steady rate throughout grape juice fermentation, whereas others, such as diethyl sulfide, appear toward the very end of the winemaking process. The results also demonstrate significant differences between yeast strains and fermentation media.

The use of active PET to package rosé wine: Changes of aromatic profile by chemical evolution and by transfers

Active Polyethylene Terephthalate (PET) bottles containing 1 or 3% of oxygen scavenger (named 1osPET and 3osPET) were used to pack rosé wine. Changes in the aromatic profiles were monitored during 12months and compared to those of a wine packed in glass bottles. Wine in 1osPET bottles was differentiated from wine in glass or 3osPET bottles by ten aging markers such as cis-dioxane, ethyl pyruvate or furfural. Only trans-1,3-dioxolane allowed to discriminate wine in glass and in 3osPET bottles. Methionol, an oxygen sensitive aroma compound, was preserved in glass and 3osPET bottles but was slightly degraded (15%) in 1osPET bottles. Chemical reactions were the main cause of the aroma compound degradation. Indeed, the total amount of compounds sorbed only reached 160μg considering the bottles and the joint of cap after 12months of storage. The use of PET with 3% of oxygen scavenger is adapted to pack wine for at least 12months.

Key changes in wine aroma active compounds during bottle storage of Spanish red wines under different oxygen levels

Samples from 16 Spanish red wines have been stored for 6 months at 25 °C under different levels of oxygen (0-56 mg/L). Amino acids, metals, and phenolic compounds were analyzed and related to the production or depletion of key oxidation- and reduction-related aroma compounds. Oxidation brings about sensory-relevant increases in Strecker aldehydes, 1-octen-3-one, and vanillin. Formation of Strecker aldehydes correlates to the wine content on the corresponding amino acid precursor, Zn, and caffeic acid ethyl ester and negatively to some flavonols and anthocyanin derivatives. Formation of most carbonyls correlates to wine-combined SO2, suggesting that part of the increments are the result of the release of aldehydes forming bisulfite combinations once SO2 is oxidized. Methanethiol (MeSH) and dimethylsulfide (DMS), but not H2S levels, increase during storage. MeSH increments correlate to methionine levels and proanthocyanidins and negatively to resveratrol and aluminum. H2S, MeSH, and DMS levels all decreased with oxidation, and for the latter two, there are important effects of Mn and pH, respectively.

Volatile profile of Madeira wines submitted to traditional accelerated ageing

The evolution of monovarietal fortified Madeira wines forced-aged by traditional thermal processing (estufagem) were studied in terms of volatiles. SPE extracts were analysed by GC-MS before and after heating at 45 °C for 3 months (standard) and at 70 °C for 1 month (overheating). One hundred and ninety volatile compounds were identified, 53 of which were only encountered in baked wines. Most chemical families increased after standard heating, especially furans and esters, up to 61 and 3-fold, respectively. On the contrary, alcohols, acetates and fatty acids decreased after heating. Varietal aromas, such as Malvasia's monoterpenic alcohols were not detected after baking. The accelerated ageing favoured the development of some volatiles previously reported as typical aromas of finest Madeira wines, particularly phenylacetaldeyde, β-damascenone and 5-ethoxymethylfurfural. Additionally, ethyl butyrate, ethyl 2-methylbutyrate, ethyl caproate, ethyl isovalerate, guaiacol, 5-hydroxymethylfurfural and γ-decalactone were also found as potential contributors to the global aroma of baked wines.

Effect of packaging material on enological parameters and volatile compounds of dry white wine

The enological parameters and volatile compounds of white wine packaged in dark coloured glass and two commercial bag-in-box (BIB) pouches (low density polyethylene - LDPE and ethylene vinyl acetate - EVA lined) were determined for a period of 6 months at 20 °C. Parameters monitored included: titratable acidity, volatile acidity, pH, total SO2, free SO2, colour, volatile compounds and sensory attributes. The BIB packaging materials affected the titratable acidity, total and free SO2 and colour of wine. A substantial portion of the wine aroma compounds was adsorbed by the plastic materials or lost to the environment through leakage of the valve fitment. Between the two plastics, the LDPE lined pouch showed a considerably higher aroma sorption as compared to EVA. Wine packaged in glass retained the largest portion of its aroma compounds. Sensory evaluation showed that white wine packaged in both plastics was of acceptable quality for 3 months vs. at least 6 months for that in glass bottles.

Oxygen contribution to wine aroma evolution during bottle aging

Wine aroma undergoes major changes during bottle aging, which are deeply influenced by the degree of oxygen exposure in the bottle. This review discusses the involvement of oxygen in the main chemical transformations occurring in wine aroma composition during bottle aging, with particular emphasis on the formation of oxidative aroma compounds and formation/degradation of sulfur-containing volatile compounds. The implications for wine sensory properties are discussed, as well as some practical aspects of oxygen management during bottle aging, including the role of closure oxygen permeability.

Oxygen consumption and development of volatile sulfur compounds during bottle aging of two Shiraz wines. Influence of pre- and postbottling controlled oxygen exposure

The evolution of different volatile sulfur compounds (VSCs) during bottle maturation of two Shiraz wines submitted to controlled oxygen exposure prior to bottling (through micro-oxygenation, MOX) and postbottling (through the closure) was investigated. H(2)S, methyl mercaptan (MeSH), and dimethyl sulfide (DMS) were found to increase during aging. Lower postbottling oxygen exposure, as obtained by different degrees of oxygen ingress through the closure, resulted in increased H(2)S and methyl mercaptan. In one wine MOX increased the concentration of H(2)S and methyl mercaptan during maturation. Dimethyl disulfide and DMS were not affected by any form of oxygen exposure. Overall, postbottling oxygen had a stronger influence than MOX on the evolution of VSCs. Data suggest that dimethyl disulfide was not a precursor to methyl mercaptan during bottle maturation. For the two wines studied, a consumption of oxygen of 5 mg/L over 12 months was the most effective oxygen exposure regimen to decrease accumulation of MeSH and H(2)S during bottle aging.

Amarone: a modern wine coming from an ancient production technology

Amarone wine is a renowned dry red wine produced in Valpolicella (Verona, Northern Italy). It is made from local grapes varieties (Corvina, Rondinella, and Molinara) that are slowly dried under natural conditions during the fall into winter. After the postharvest drying, carried out for several weeks in dedicated lofts called fruttaio, the grapes are vinified: crushed, given prefermentative cold maceration, undergo alcoholic fermentation on the skins, malolactic fermentation, and finally maturation. The partially dried grapes are traditionally crushed during the second half of January to February. Because cellar conditions are unfavorable for either alcohol or malolactic fermentation, selected microbial cultures (yeasts and malolactic bacteria) are often necessary to correctly manage fermentation. The progress of both fermentation processes needs constant surveillance. During maturation conducted in vessels or wooden containers (tonneau in durmast oak), clarification and stabilization lead to improvements in quality. Product specifications require that Amarone not be bottled before the wine has been aged for 2years (Anonymous (2010). Disciplinare di produzione dei vini a denominazione di Origine Controllata e Garantita "Amarone della Valpolicella". Gazzetta Ufficiale della Repubblica Italiana. Serie generale n. 84. April 12). Amarone achieved its DOCG (Controlled and Guaranteed Denomination) status in 2010.