Simulation of Pilsner-type beer aroma using 76 odor-active compounds

Quantitative determination of vanillin and its detection threshold in sake

Vanillin is naturally occurring in various food products, including alcoholic beverages; however, its contribution to the aroma of sake is unclear. In this study, an HPLC-MS/MS quantification method was developed and validated by linearity, precision, and recovery, and it was applied to 115 bottles of highly diversified sake. Furthermore, the odor detection threshold of vanillin in sake was determined. Notably, the established method exhibited great linearity (5-1500 μg/L), with a R2 >0.99, and the limit of detection and limit of quantification were 1.7 and 5.5 μg/L, respectively. The spiked recoveries of vanillin ranged from 96.2% to 97.8%, with relative standard deviation ˂ 6.22%. Results revealed trace amounts to 29.9 μg/L of vanillin in the premium young sake, below the detection threshold (78.9 μg/L), whereas aged sake (43 bottles, 3-56 years aging) exhibited varied concentrations from trace amounts to 1727.5 μg/L of vanillin, notably peaking in a 20-year oak barrel-aged sake. The concentration of vanillin in most of the ambient-temperature-aged sake exceeded the detection threshold after 11-15 years of aging. The proposed method facilitates accurate vanillin quantification in sake, crucial for evaluating its flavor impact. Moreover, the discoveries provide a theoretical basis for the sensory exploration of sake aromas and equip the brewing industry with insights for modulating vanillin synthesis during sake aging.

Characterization of Key Odor-Active Compounds in Draft Beers for the Chinese Market Using Molecular Sensory Science Approaches

Beer is a popular alcoholic beverage worldwide. However, limited research has been conducted on identifying key odor-active components in lager-type draft beers for the Chinese market. Therefore, this study aims to elucidate the odor characteristics of the four most popular draft beer brands through a sensory evaluation and an electronic nose. Subsequently, the four draft beers were analyzed through solid-phase microextraction and liquid-liquid extraction using a two-dimensional comprehensive gas chromatography-olfactometry-mass spectrometry analysis (GC×GC-O-MS). Fifty-five volatile odor compounds were detected through GC×GC-O-MS. Through an Aroma Extract Dilution Analysis, 22 key odor-active compounds with flavor dilution factors ≥ 16 were identified, with 11 compounds having odor activity values > one. An electronic nose analysis revealed significant disparities in the odor characteristics of the four samples, enabling their distinct identification. These findings help us to better understand the flavor characteristics of draft beer and the stylistic differences between different brands of products and provide a theoretical basis for objectively evaluating the quality differences between different brands of draft beer.

Development of the gas chromatography/mass spectrometry-based aroma designer capable of modifying volatile chemical compositions in complex odors

Many volatile organic compounds (VOCs) are used to produce various commercial products with aromas mimicking natural products. The VOCs responsible for aromas have been identified from many natural products. The current major strategy is to analyze chemical compositions and aroma qualities of individual VOCs using gas chromatography/mass spectrometry (GC/MS) and GC-olfactometry. However, such analyses cannot determine whether candidate VOCs contribute to the characteristic aroma in mixtures of many VOCs. In this study, we developed a GC/MS-based VOC collection/omission system that can modify the VOC compositions of samples easily and rapidly. The system is composed of GC/MS with a switching unit that can change gas flow routes between MS and a VOC collection device. We first applied this system to prepare gas samples for omission tests, and the aroma qualities of VOC mixtures with and without some VOCs were evaluated by panelists. If aroma qualities were different between the 2 samples, the omitted VOCs were likely key odorants. By collecting VOCs in a gas bag attached to the collection device and transferring some VOCs to MS, specific VOCs could be omitted easily from the VOC mixture. The system could prepare omission samples without chemical identification, preparation of each VOC, and laborious techniques for mixing VOCs, thus overcoming the limitations of previous methods of sample preparation. Finally, the system was used to prepare artificial aromas by replacing VOC compositions between different samples for screening of key odorants. In conclusion, the system developed here can improve aroma research by identifying key odorants from natural products.

Unraveling the source-water fishy odor occurrence during low-temperature periods: Odorants identification, typical algae species and odor-producing potential

In this study, odor characteristics and phytoplankton composition were systematically investigated in two winter periods in a reservoir with fishy odor in north China. Ten potential fishy odor-producing algae were isolated and odorant-producing potentials were evaluated. Olfactometry profile and odorant composition of water samples were analyzed using GC-Olfactometry combined with GC × GC-TOFMS. The results showed that 2,4-heptadienal and hexanal were major fishy odor contributors. The abundance of Uroglena sp., Synura sp. and Peridinium sp. was negatively correlated with total dissolved organic carbon, ammonia nitrogen, and nitrate, illustrating nutrient level might be major drivers for the succession of fishy odor-producing algae. Dinobryon sp. and Uroglena sp. made the greatest contribution to fishy odor, followed by Peridinium sp., Synura sp., and Ochromonas sp. Fishy odor in 2016 winter and the early of 2017 winter was mainly caused by Dinobryon sp., while Uroglena sp. contributes mostly in March in 2017 winter. This study demonstrates the main odorants and algae causing fishy odor in reservoir, which will provide a scientific basis for the management of seasonal fishy odor problems in water source.

From Natural Behavior to Drug Screening: Invertebrates as Models to Study Mechanisms Associated with Alcohol Use Disorders

Humans consume ethanol-containing beverages, which may cause an uncontrollable or difficult-to-control intake of ethanol-containing liquids and may result in alcohol use disorders. How the transition at the molecular level from "normal" ethanol-associated behaviors to addictive behaviors occurs is still unknown. One problem is that the components contributing to normal ethanol intake and their underlying molecular adaptations, especially in neurons that regulate behavior, are not clear. The fruit fly Drosophila melanogaster and the earthworm Caenorhabditis elegans show behavioral similarities to humans such as signs of intoxication, tolerance, and withdrawal. Underlying the phenotypic similarities, invertebrates and vertebrates share mechanistic similarities. For example in Drosophila melanogaster, the dopaminergic neurotransmitter system regulates the positive reinforcing properties of ethanol and in Caenorhabditis elegans, serotonergic neurons regulate feeding behavior. Since these mechanisms are fundamental molecular mechanisms and are highly conserved, invertebrates are good models for uncovering the basic principles of neuronal adaptation underlying the behavioral response to ethanol. This review will focus on the following aspects that might shed light on the mechanisms underlying normal ethanol-associated behaviors. First, the current status of what is required at the behavioral and cellular level to respond to naturally occurring levels of ethanol is summarized. Low levels of ethanol delay the development and activate compensatory mechanisms that in turn might be beneficial for some aspects of the animal's physiology. Repeated exposure to ethanol however might change brain structures involved in mediating learning and memory processes. The smell of ethanol is already a key component in the environment that is able to elicit behavioral changes and molecular programs. Minimal networks have been identified that regulate normal ethanol consumption. Other environmental factors that influence ethanol-induced behaviors include the diet, dietary supplements, and the microbiome. Second, the molecular mechanisms underlying neuronal adaptation to the cellular stressor ethanol are discussed. Components of the heat shock and oxidative stress pathways regulate adaptive responses to low levels of ethanol and in turn change behavior. The adaptive potential of the brain cells is challenged when the organism encounters additional cellular stressors caused by aging, endosymbionts or environmental toxins or excessive ethanol intake. Finally, to underline the conserved nature of these mechanisms between invertebrates and higher organisms, recent approaches to identify drug targets for ethanol-induced behaviors are provided. Already approved drugs regulate ethanol-induced behaviors and they do so in part by interfering with cellular stress pathways. In addition, invertebrates have been used to identify new compounds targeting molecules involved in the regulation in ethanol withdrawal-like symptoms. This review primarily highlights the advances of the last 5 years concerning Drosophila melanogaster, but also provides intriguing examples of Caenorhabditis elegans and Apis mellifera in support.

Alcohol-free and low-alcohol beers: Aroma chemistry and sensory characteristics

Alcohol-free beers have gained popularity in the last few decades because they provide a healthier alternative to alcoholic beers and can be more widely consumed. Consumers are becoming more aware of the benefits of reducing their alcohol consumption, and this has increased the sales of nonalcoholic alternatives. However, there are still many challenges for the brewing industry to produce an alcohol-free beer that resembles the pleasant fruity flavor and overall sensory experience of regular beers. The aim of this review is to give a comprehensive overview of alcohol-free beer focusing on aroma chemistry. The formation of the most important aroma compounds, such as Strecker aldehydes, higher alcohols, and esters, is reviewed, aiming to outline the gaps in current knowledge. The role of ethanol as a direct and indirect flavor-active compound is examined separately. In parallel, the influence of the most common methods to reduce alcohol content, such as physical (dealcoholization) or biological, on the organoleptic characteristics and consumer perception of the final product, is discussed.

Presence of Disulfide-Bonded Thiols in Malt and Hops as the Precursors of Thiols in Beer

Disulfide-bonded thiols in malt and hops were first identified as possible precursors of thiols in beer. The presence of disulfide-bonded 3-mercaptohexan-1-ol (3MH) was confirmed in malt and hops by observing an 8.9-9.9 times increase in the 3MH concentration in hopped water and unhopped wort after the reduction using tris(2-carboxyethyl)phosphine (TCEP), a reducing agent specific for disulfide bonds. The presence of disulfide-bonded 4-mercapto-4-methylpentan-2-one (4MMP) was confirmed in hops by observing 2.1 and 5.1 times increase in the 4MMP concentration after reduction in hopped water. Proteins, peptides, and amino acids having sulfhydryl groups or other thiol substances were assumed to form disulfide bonds with polyfunctional thiols in malt and hops. The release of thiols by the reduction of disulfide-bonded thiols during fermentation was first identified. A 65-82% of disulfide-bonded 3MH were reduced during fermentation, and as a result, concentrations of 3MH in hopped water and unhopped wort increased by 9.5-14.2 times during fermentation.

Production of Hydroxy Fatty Acids, Precursors of γ-Hexalactone, Contributes to the Characteristic Sweet Aroma of Beef

Aroma is an essential factor for meat quality. The meat of Japanese Black cattle exhibits fine marbling and a rich and sweet aroma with a characteristic lactone composition. The mechanism of lactone formation associated with beef aroma has not been elucidated. In this study, we examined the precursors of γ-hexalactone, an indicator of the sweet aroma of beef and identified the mechanism underlying γ-hexalactone production. A low-temperature vacuum system was used to prepare beef tallow from Japanese Black cattle and Holstein cattle. The odor components were identified using headspace–gas chromatography. The analysis revealed that γ-hexalactone, γ-dodecalactone, δ-tetradecalactone, and δ-hexadecalactone were present as sweet aroma components of beef tallow prepared from marbling and muscle. Since we previously reported that γ-hexalactone formation correlates with linoleic acid content in beef, we analyzed ten oxidized fatty acids derived from linoleic acid by liquid chromatography–triple quadrupole mass spectrometry and detected two hydroxy-octadecadienoic acids (9S-HODE and 13S-HODE) in beef tallow. Significant differences in arachidonic acid 15-lipoxygenase and cyclooxygenase protein expression levels among subcutaneous fat, intramuscular fat, and muscle tissue were observed. Our results suggest that the combination of linoleic acid and the expression of lipid oxidase derived from beef muscle and intramuscular fat produce hydroxy fatty acids that result in a sweet aroma.

Exploring the Lipids Involved in the Formation of Characteristic Lactones in Japanese Black Cattle

The meat from Japanese Black cattle (Japanese Wagyu) is finely marbled and exhibits a rich and sweet aroma known as Wagyu beef aroma. To clarify the key metabolites involved in the aroma, we analyzed the correlation between lactone and lipid composition in Japanese Black cattle. Using gas chromatography-olfactometry, we identified 39 characteristic odorants of the intermuscular fat. Seven characteristic lactones considered to be involved in Wagyu beef aroma were quantified and compared in the marbled area and intermuscular fat using a stable isotope dilution assay. Among them, γ-hexalactone was the only lactone whose level was significantly higher in the marbled area. To explore the lipid species involved in lactone formation, we analyzed samples with different aroma characteristics. Liquid chromatography-mass spectrometry revealed eight lipid classes and showed significant differences in triacylglycerides (TAGs). To determine the molecular species of TAGs, we performed high-performance liquid chromatography analysis and identified 14 TAG species. However, these analyses showed that seven lactones had a low correlation with the TAGs. However, γ-hexalactone showed a positive correlation with linoleic acid. This study suggests that lipid composition affects the characteristic lactone profile involved in the Wagyu beef aroma.

Exploring the Characteristic Aroma of Beef from Japanese Black Cattle (Japanese Wagyu) via Sensory Evaluation and Gas Chromatography-Olfactometry

Beef from Japanese Black cattle (Japanese Wagyu) is renowned for its flavor characteristics. To clarify the key metabolites contributing to this rich and sweet aroma of beef, an omics analysis combined with GC-olfactometry (GC-O) and metabolomics analysis with gas chromatography-mass spectrometry (GC-MS) were applied. GC-O analysis identified 39 odor-active odorants from the volatile fraction of boiled beef distilled by solvent-assisted flavor evaporation. Eight odorants predicted to contribute to Wagyu beef aroma were compared between Japanese Black cattle and Holstein cattle using a stable isotope dilution assay with GC-tandem quadrupole mass spectrometry. By correlating the sensory evaluation values of retronasal aroma, γ-hexalactone, γ-d2ecalactone, and γ-undecalactone showed a high correlation with the Wagyu beef aroma. Metabolomics data revealed a high correlation between the amounts of odorants and multiple metabolites, such as glutamine, decanoic acid, lactic acid, and phosphoric acid. These results provide useful information for assessing the aroma and quality of beef.

Elucidating the Odor-Active Aroma Compounds in Alcohol-Free Beer and Their Contribution to the Worty Flavor

Alcohol-free beers (AFBs) brewed by cold-contact fermentation exhibit a flavor reminiscent of wort which affects consumer acceptability. The aims of this study were to identify the odor-active compounds in AFB and elucidate the contribution of these to the overall aroma and worty character of the beer. Using a sensomics approach, 27 odor-active aroma compounds were identified and quantitated using gas chromatography-mass spectrometry. The most odor-active compound was methional (boiled potato-like aroma), followed by 3-methylbutanal (cocoa-like), (E)-β-damascenone (apple, jam-like), 5-ethyl-3-hydroxy-4-methyl-2(5H)-furanone (curry, spicy-like), and phenylacetaldehyde (floral, honey-like). The important contribution of these flavor compounds to the worty and honey aroma of AFB was determined by sensory assessment of the recombinate in a beer-like matrix with omission tests. The role of 5-ethyl-3-hydroxy-4-methyl-2(5H)-furanone in AFB aroma was reported for the first time. The outcomes from this study are of relevance for the brewing industry to design strategies for the reduction of the wortiness of AFB.

Development of Head Space Sorptive Extraction Method for the Determination of Volatile Compounds in Beer and Comparison with Stir Bar Sorptive Extraction

A headspace sorptive extraction method coupled with gas chromatography–mass spectrometry (HSSE–GC–MS) was developed for the determination of 37 volatile compounds in beer. After optimization of the extraction conditions, the best conditions for the analysis were stirring at 1000 rpm for 180 min, using an 8-mL sample with 25% NaCl. The analytical method provided excellent linearity values (R² > 0.99) for the calibration of all the compounds studied, with the detection and quantification limits obtained being low enough for the determination of the compounds in the beers studied. When studying the repeatability of the method, it proved to be quite accurate, since RSD% values lower than 20% were obtained for all the compounds. On the other hand, the recovery study was successfully concluded, resulting in acceptable values for most of the compounds (80–120%). The optimised method was successfully applied to real beer samples of different types (ale, lager, stout and wheat). Finally, an analytical comparison of the optimised HSSE method, with a previously developed and validated stir bar sorptive extraction (SBSE) method was performed, obtaining similar concentration values by both methods for most compounds.

Physicochemical and sensory profile of Beauregard sweet potato beer

Beer has been one of the most consumed alcoholic beverages worldwide. However, the incorporation of adjuncts in the beer can add new organoleptic and functional characteristics to the beverage. For this, Beauregard sweet potato shows high potential due to being a rich source of starch and many bioactive compounds. The aim of this study was to develop the best process condition to produce a Sweet potato beer with enhanced nutritional and antioxidant properties and good sensory characteristics. Beer samples showed increased antioxidant activity especially due to β-carotene and their total phenolic content. The phytochemical profile of sweet potato biocompounds demonstrated a direct effect of this adjunct on sensory and functional characteristics of the finished beer. In conclusion, it was found that Beauregard sweet potato is a promising adjunct for beer brewing with nutraceutical properties due to its rich composition of bioactive compounds.

Black rice addition prompted the beer quality by the extrusion as pretreatment

Flavor compounds, including total polyphenols, amino acids, and protein, in beer with extruded black rice as adjunct were detected and analyzed. Beer brewing technique has been intensively investigated in the past century. The chase of beer quality, including the color, flavor, foam, nutrition, and functionality, attracted considerable attention. Hence, headspace solid-phase microextraction in combination with a gas chromatography coupled to mass spectrometry (HS-SPME-GC-MS) was used to analyze flavor compounds qualitatively and quantitatively. A total of one organic acid, one aromatic, ten alcohols and 23 esters were present in extruded black rice adjunct beer. Protein components and molecular weight were analyzed, and the results were consistent with those of traditional beer in terms of content of foam-stabilizing protein. The contents of essential amino acid which is an important nutritive index were higher than those in traditional rice adjunct beer, especially valine (70.9 mg/L) and threonine (42.8 mg/L). The representative ingredients of extruded black rice adjunct beer were polyphenols, nerolidol, geraniol, and geranylgeraniol which affected the functionality and antioxidant ability.

A Bottom-Up Approach for Data Mining in Bioaromatization of Beers Using Flow-Modulated Comprehensive Two-Dimensional Gas Chromatography/Mass Spectrometry

In this study, we report the combination of comprehensive two-dimensional gas chromatography (GC×GC) with multivariate pattern recognition through template matching for the assignment of the contribution of Brazilian Ale 02 yeast strain to the aroma profile of beer compared with the traditional Nottingham yeast. Volatile organic compounds (VOC) from two beer samples, which were fermented with these yeast strains were sampled using headspace solid-phase microextraction (HS-SPME). The aroma profiles from both beer samples were obtained using GC×GC coupled to a fast scanning quadrupole mass spectrometer. Data processing performed through multiway principal components analysis succeeded in separating both beer samples based on yeast strain. The execution of a simple and reliable procedure succeeded and identified 46 compounds as relevant for sample classification. Furthermore, the bottom-up approach spotted compounds found exclusively in the beer sample fermented with the Brazilian yeast, highlighting the bioaromatization properties introduced to the aroma profile by this yeast strain.

Orthonasal and retronasal detection thresholds of 26 aroma compounds in a model alcohol-free beer: Effect of threshold calculation method

Detection thresholds are used routinely to determine the odour-active compounds in foods. The composition of a food matrix, such as hydrophobicity or solids content, has an impact on the release of flavour compounds, and thus on thresholds. In the case of beer, thresholds determined in alcoholic beer may not be the same for alcohol-free beer (AFB). Therefore, the aim of this study was to determine detection thresholds for aroma compounds typically found in beer, within a model AFB. The model was designed to match the sugar concentration and pH of an AFB brewed by a cold contact process. Thresholds were measured using a 3-AFC procedure and calculated using either Best Estimate Threshold (BET) method or by logistic regression. Moreover, an algorithm for the removal of false positives was applied to adjust the assessors' raw responses. Retronasal thresholds were generally lower than orthonasal. Those calculated by BET were significantly higher (p < 0.05) than those from logistic regression, and removal of false positives also produced significantly higher thresholds than those from raw data. The use of logistic regression has the advantage of providing the mathematical model describing the behaviour of the group. The results from this study can be used to better understand the role of flavour compounds in AFB and the effect of the calculation method to prevent under- or overestimated results.