Measuring Thiols in Single Cultivar South African Red Wines Using 4,4-Dithiodipyridine (DTDP) Derivatization and Ultraperformance Convergence Chromatography-Tandem Mass Spectrometry

Roles of sulfur-containing compounds in fermented beverages with 2-furfurylthiol as a case example

Aroma is a critical component of the flavor and quality of beverages. Among the volatile chemicals responsible for fragrance perception, sulfur compounds are unique odorants due to their extremely low odor threshold. Although trace amounts of sulfur compounds can enhance the flavor profile of beverages, they can lead to off-odors. Sulfur compounds can be formed via Maillard reaction and microbial metabolism, imparting coffee aroma and altering the flavor of beverages. In order to increase the understanding of sulfur compounds in the field of food flavor, 2-furfurylthiol (FFT) was chosen as a representative to discuss the current status of their generation, sensory impact, enrichment, analytical methods, formation mechanisms, aroma deterioration, and aroma regulation. FFT is comprehensively reviewed, and the main beverages of interest are typically baijiu, beer, wine, and coffee. Challenges and recommendations for FFT are also discussed, including analytical methods and mechanisms of formation, interactions between FFT and other compounds, and the development of specific materials to extend the duration of aroma after release.

Organosulfur in food samples: Recent updates on sampling, pretreatment and determination technologies

Organosulfur compounds (OSCs), mainly found in garlic, are the main biologically active substances for their pharmacological effects, including lowering of blood pressure and cholesterol, anti-cancer effect, liver protection, and anti-inflammatory. Efficient and sensitive pretreatment and determination methods of OSCs in different food matrices are of great significance. This review provides a comprehensive summary about the pretreatment and determination methods for OSCs in different food samples since 2010. Commonly used pretreatment methods, such as liquid-liquid extraction, microwave-assisted extraction, pressurized liquid extraction, liquid-liquid microextraction, solid phase extraction, dispersive solid phase extraction, solid-phase microextraction, and so on, have been summarized and overviewed in this paper. In particular, we discussed and compared various analysis methods including high performance liquid chromatography coupled with different detectors, gas chromatography-based methods, and few other methods. Finally, we tried to highlight the applicability, advantages and disadvantages of different pretreatment and analysis methods, and identified future prospects in this field.

Derivatization Strategies in Flavor Analysis: An Overview over the Wine and Beer Scenario

Wine and beer are the most appreciated and consumed beverages in the world. This success is mainly due to their characteristic taste, smell, and aroma, which can delight consumer’s palates. These olfactory characteristics are produced from specific classes of volatile compounds called “volatile odor-active compounds” linked to different factors such as age and production. Given the vast market of drinking beverages, the characterization of these odor compounds is increasingly important. However, the chemical complexity of these beverages has led the scientific community to develop several analytical techniques for extracting and quantifying these molecules. Even though the recent “green-oriented” trend is directed towards direct preparation-free procedures, for some class of analytes a conventional step like derivatization is unavoidable. This review is a snapshot of the most used derivatization strategies developed in the last 15 years for VOAs’ determination in wine and beer, the most consumed fermented beverages worldwide and among the most complex ones. A comprehensive overview is provided for every method, whereas pros and cons are critically analyzed and discussed. Emphasis was given to miniaturized methods which are more consistent with the principles of “green analytical chemistry”.

Characterization of volatile thiols in Chinese liquor (Baijiu) by ultraperformance liquid chromatography-mass spectrometry and ultraperformance liquid chromatography-quadrupole-time-of-flight mass spectrometry

Volatile thiols give a unique flavor to foods and they have been extensively studied due to their effects on sensory properties. The analytical assay of volatile thiols in food is hindered by the complexity of the matrix, and by both their high reactivity and their typically low concentrations. A new ultraperformance liquid chromatography (UPLC) strategy has been developed for the identification and quantification of volatile thiols in Chinese liquor (Baijiu). 4,4’-Dithiodipyridine reacted rapidly with eight known thiols to form derivatives, which provided a diagnostic fragment ion (m/z 143.5) for tandem mass spectrometry (MS/MS). To screen for new thiols, Baijiu samples were analyzed by means of UPLC–MS/MS screening for compounds exhibiting the diagnostic fragment ion (m/z X→143.5). New peaks with precursor ions of m/z 244, 200 and 214 were detected. Using UPLC with quadrupole-time-of-flight mass spectrometry (UPLC–Q-TOF–MS) and authentic standards, ethyl 2-mercaptoacetate, 1-butanethiol, and 1-pentanethiol were identified in Baijiu for the first time. Commercial Baijiu samples were analyzed with the new method and the distribution of 11 thiols was revealed in different Baijiu aroma-types. The aroma contribution of these thiols was evaluated by their odoractivity values (OAVs), with the result that 7 of 11 volatile thiols had OAVs > 1. In particular, methanethiol, 2-furfurylthiol, and 2-methyl-3-furanthiol had relatively high OAVs, indicating that they contribute significantly to the aroma profile of Baijiu.

Unraveling the Mystery of 3-Sulfanylhexan-1-ol: The Evolution of Methodology for the Analysis of Precursors to 3-Sulfanylhexan-1-ol in Wine

Volatile polyfunctional thiol compounds, particularly 3-sulfanylhexan-1-ol (3SH) and 3-sulfanylhexyl acetate (3SHA), are key odorants contributing to the aroma profile of many wine styles, generally imparting tropical grapefruit and passionfruit aromas. 3SH and 3SHA are present in negligible concentrations in the grape berry, juice, and must, suggesting that they are released from non-volatile precursors present in the grape. The exploration of the nature and biogenesis of these precursors to 3SH and 3SHA has proven important for the elucidation of polyfunctional thiol biogenesis during alcoholic fermentation. The development and validation of appropriate analytical techniques for the analysis of 3SH precursors in enological matrices have been extensive, and this review explores the analysis and discovery of these precursor compounds. The development of analytical methods to analyze 3SH precursors, from the selection of the analytical instrument, sample preparation, and methods for standardization, will first be discussed, before highlighting how these techniques have been used in the elucidation of the biogenesis of 3SH and 3SHA in grape wines. Lastly, the future of thiol precursor analysis will be considered, with the development of new methods that greatly reduce the sample preparation time and enable multiple precursors, and the thiols themselves, to be quantitated using a single method.

Biotransformation of Hops-Derived Compounds in Beer – A Review

Besides providing bitterness to beer, hops also impart a whole range of aromas, such as herbal, spice, floral, citrus, fruity and pine to this beverage. Although hops are usually added in relatively small amounts, they have a significant impact on the sensory characteristics of the product. Raw hop aroma significantly differs from the aroma resulting from its addition to the beer. The final aroma of the beer arises from substances in the malt, hops, other additives, and yeast metabolism. The biochemical transformation of hop compounds by yeast has become more and more popular in recent years. Knowledge of this process may allow more precise control over the final sensory characteristics of the beverage. The article describes the chemical composition of hops and discusses the influence of the hopping regime on the concentration of volatile compounds in the finished product. Moreover, the article describes the biotransformation of hop-derived compounds by traditionally used Saccharomyces cerevisiae yeast, as well as less commonly used non-Saccharomyces yeast. The paper outlines the current state of knowledge on biotransformation of hop-derived hydrocarbons, terpenoids, esters, sulfur compounds and glycosidically bound aroma precursors.

Impact of accentuated cut edges (ACE) technique on volatile and sensory profiles of Shiraz wines

Varietal thiols are important wine aroma compounds that are generally less abundant in red wines. Accentuated cut edges (ACE), known for accelerating phenolic extraction, was applied to Shiraz winemaking and compared with conventional crushing (NOACE) to examine the effects on varietal thiol precursor extraction and thiol formation. Water addition to grape must and skin contact time (SCT) during fermentation were also assessed. Although there was no difference for precursors in the must, ACE significantly decreased 3-S-glutathionylhexan-1-ol concentration during fermentation. 3-Sulfanylhexan-1-ol and ethyl esters were significantly influenced by crushing method and/or SCT, with NOACE or shorter SCT yielding higher concentrations. Acetates, higher alcohols, fatty acids, and isoprenoids differed according to the interaction of crushing method and SCT, with ACE and shorter SCT significantly enhancing all groups except acetates. Volatiles in Sauvignon blanc and Pinot noir wines produced at commercial scale with ACE were briefly evaluated, suggesting an impact of grape variety.

New Precursors to 3-Sulfanylhexan-1-ol? Investigating the Keto-Enol Tautomerism of 3-S-Glutathionylhexanal

The volatile thiol compound 3-sulfanylhexan-1-ol (3SH) is a key impact odorant of white wines such as Sauvignon Blanc. 3SH is produced during fermentation by metabolism of non-volatile precursors such as 3-S-gluthathionylhexanal (glut-3SH-al). The biogenesis of 3SH is not fully understood, and the role of glut-3SH-al in this pathway is yet to be elucidated. The aldehyde functional group of glut-3SH-al is known to make this compound more reactive than other precursors to 3SH, and we are reporting for the first time that glut-3SH-al can exist in both keto and enol forms in aqueous solutions. At wine typical pH (~3.5), glut-3SH-al exists predominantly as the enol form. The dominance of the enol form over the keto form has implications in terms of potential consumption/conversion of glut-3SH-al by previously unidentified pathways. Therefore, this work will aid in the further elucidation of the role of glut-3SH-al towards 3SH formation in wine, with significant implications for the study and analysis of analogous compounds.

Characterization of benzenemethanethiol in sesame-flavour baijiu by high-performance liquid chromatography-mass spectrometry and sensory science

Chinese sesame-flavour baijiu (CSB) is one of aroma types discovered after the founding of China. Sulfur-containing compounds have low content in CSB but play an important role. This study developed a quantitative method by derivatization reaction combined LC-MS/MS for the determination of benzenemethanethiol (BM), which has a roasted aroma in CSB. Under the optimized conditions, the LOD and LOQ of BM were 11.73 ng L^-1 and 39.09 ng L^-1, respectively. The recovery yield of the derivatization product ranged from 82.12% to 93.99%. The content of BM in 4 CSBs were 150.22-860.40 ng L^-1. To confirm the contribution of BM to the overall aroma of CSB, aroma recombination experiments and omission experiments were carried out. Compared with that of the simulated baijiu sample without BM, the roasted aroma of the simulated baijiu sample containing BM was enhanced. Omission experiments showed that BM made important contributions to the overall aroma of CSB.

The Flavor Chemistry of Fortified Wines-A Comprehensive Approach

For centuries, wine has had a fundamental role in the culture and habits of different civilizations. Amongst numerous wine types that involve specific winemaking processes, fortified wines possess an added value and are greatly honored worldwide. This review comprises the description of the most important characteristics of the main worldwide fortified wines-Madeira, Port, Sherry, Muscat, and Vermouth-structured in three parts. The first part briefly describes the chemistry of wine flavor, the origin of typical aroma (primary, secondary and tertiary), and the influencing parameters during the winemaking process. The second part describes some specificities of worldwide fortified wine, highlighting the volatile composition with particular emphasis on aroma compounds. The third part reports the volatile composition of the most important fortified wines, including the principal characteristics, vinification process, the evolution of volatile organic compounds (VOCs) during the aging processes, and the most important odor descriptors. Given the worldwide popularity and the economic relevance of fortified wines, much research should be done to better understand accurately the reactions and mechanisms that occur in different stages of winemaking, mainly during the oxidative and thermal aging.

Exploring the Typicality, Sensory Space, and Chemical Composition of Swedish Solaris Wines

The Swedish wine industry has exponentially grown in the last decade. However, Swedish wines remain largely unknown internationally. In this study, the typicality and sensory space of a set of twelve wines, including five Swedish Solaris wines, was evaluated blind by Swedish wine experts. The aim of the work was to evaluate whether the Swedish wine experts have a common concept of what a typical Solaris wines should smell and taste like or not and, also, to bring out more information about the sensory space and chemical composition of Solaris wines. The results showed a lack of agreement among the wine experts regarding the typicality of Solaris wines. This, together with the results from the sensory evaluation, could suggest the possibility of different wine styles for Solaris wines. From a chemical perspective, the global volatile profile showed a larger variability between individual wines than between Solaris and non-Solaris. However, 4MMP, ethyl propionate, ethyl 2-Methyl propanoate, and diethyl succinate were significantly higher in Solaris wines. Concerning non-volatile compounds, the results showed a significant discrimination between Solaris and non-Solaris wines, the former being characterized by higher ethanol %, Mg, succinic acid, tartaric acid, and sucrose levels.

Comparison of an Offline SPE-GC-MS and Online HS-SPME-GC-MS Method for the Analysis of Volatile Terpenoids in Wine

The aroma profile is an important marker for wine quality. Various classes of compounds are responsible for the aroma of wine, and one such class is terpenoids. In the context of this work, a validated gas chromatography-mass spectrometry (GC-MS) method for the quantitation of terpenoids in red and white wine using headspace solid-phase microextraction (HS-SPME) and solid-phase extraction (SPE) was established. Calibrations were performed in the respective base wine using both sample preparation methods. The linearity, precision and accuracy evaluated for the respective matrices were excellent for both sample preparations. However, the HS-SPME approach was more sensitive and more accurate. For both sample preparations, the quantification limits were lower than the odor thresholds in wine. The terpenoid concentrations (µg/L) were evaluated for 13 white wines using both sample preparation methods. Importantly, the online HS-SPME approach was more sensitive than the offline SPE method. The major terpenoids identified in the white wines evaluated were linalool (0.2-63 µg/L), geraniol (nd-66 µg/L) and α-terpineol (nd-85 µg/L).

Analysis of Potent Odour-Active Volatile Thiols in Foods and Beverages with a Focus on Wine

Certain volatile thiols are some of the most potent odour-active molecules that are found in nature. Thiols play significant roles in the aroma qualities of a range of foods and beverages, including wine, with extremely low odour detection thresholds (nanogram per litre range). A fundamental understanding of their formation, fate, and impact essentially depends on the development of suitable analytical methods. The analysis of volatile thiols in foods and beverages is a challenging task when considering (1) the complexity of food and beverage matrices and (2) that thiols are highly reactive, low molecular-weight volatiles that are generally present at trace to ultra-trace concentrations. For the past three decades, the analytical evaluation of volatile thiols has been intensively performed in various foods and beverages, and many novel techniques related to derivatisation, isolation, separation, and detection have been developed, particularly by wine researchers. This review aims to provide an up-to-date overview of the major analytical methodologies that are proposed for potent volatile thiol analysis in wine, foods, and other beverages. The analytical challenges for thiol analysis in foods and beverages are outlined, and the main analytical methods and recent advances in methodology are summarised and evaluated for their strengths and limitations. The key analytical aspects reviewed include derivatisation and sample preparation techniques, chromatographic separation, mass spectrometric detection, matrix effects, and quantitative analysis. In addition, future perspectives on volatile thiol research are also suggested.

A multivariate approach to evaluating the chemical and sensorial evolution of South African Sauvignon Blanc and Chenin Blanc wines under different bottle storage conditions

Volatile compound composition contributes to the aroma profile of wine and is susceptible to change due to oxidation which may occur during storage and transportation, especially at high temperatures. Changes in sensory attributes may also occur, altering the sensory profile of wine. Classical univariate analysis only looks at the deviations for one factor at a time and may overlook the overall effect of treatments. In this study, changes in South African Sauvignon Blanc and Chenin Blanc wine sensory profile, volatile and antioxidant-related parameters resulting from storage under different temperatures (room temperature, 15 °C and 25 °C) and durations (0, 3 and 9 months) were investigated using a multivariate approach. Bottled, unwooded wines of both cultivars from six wineries were used. As expected, the chemical evolution of the wines was characterised by increases in absorbance at 420 nm (browning), colour density and hue with prolonged storage at high temperatures. To be able to compare the evolution of the sample sets regardless of the initial (T0/control) wine profile and composition, multivariate regression analysis in the form of regression vector (RV) coefficients were used to assess the correlations in the sensory and chemical changes relative to the control in each set. Using Pivot©Profile for the first time in this type of stability assessment and applying a new algorithm for data handling in addition to the classical one, this study showed that prolonged exposure to higher temperatures resulted in the change from fruity to toasted aroma attributes.