Chemosensory characteristics of regional Vidal icewines from China and Canada

Characterization of Odorants Causing the Hawthorn Aroma in Cabernet Sauvignon Wine by Gas Chromatography-Olfactometry, Quantitation, Aroma Recombination, Omission, and Addition Studies

This study aimed to identify the specific odorants contributing to the distinctive hawthorn aroma present in wines, expanding upon previous research on the aroma characteristics of Cabernet Sauvignon wine. By utilization of high-performance liquid chromatography and gas chromatography-olfactory-mass spectrometry, 14 odorants showed a positive correlation with hawthorn aroma characteristics. Among these, ethyl isovalerate, ethyl butanoate, myrcene, and α-terpineol demonstrated the highest correlation coefficients. Further sensory experiments involving recombination, omission, and addition tests confirmed that ester compounds and terpenes were the predominant contributors to the hawthorn aroma in wine. Specifically, ethyl isovalerate, myrcene, and α-terpineol were found to significantly enhance the hawthorn aroma (p < 0.05), while higher concentrations of aldehydes and ketones were observed to diminish the intensity of hawthorn aroma.

Icewine fingerprint involved in latitude under climate change

Aroma plays a crucial role in determining icewine quality and influencing the profit of growers, but the influence of climate change on icewine sustainable production and the diversity of aroma volatiles in icewine among different regions are unknown. Here, we employed aroma volatiles of 8 Vidal icewines from 2 typical premium production regions (Liaoning in China and Ontario in Canada) and an emerging low-latitude mountainous area (Yunnan in China) to project future diversity and sustainability. We found that Ontario and Yunnan's icewines were characterized with intense apricot or peach and tropical fruit aromas, which was consistent with the excellent grade icewine around the world based on 225 icewine aroma datasets from 5 countries. Icewine from Liaoning was abundant with honey flavor. Moreover, projections suggested a northward trend of 3.5° N and 6° N in Ontario during near future (2021-2050) and far future (2070-2099) periods, respectively. However, Liaoning province might have more challenges for premium icewine production under the worst climate warming scenario. Notably, the lower latitude and higher altitude region, Yunnan province, would sustainable provide special premium icewine with a northward expansion of icewine production region to 28.5° N under climate change. The findings provide theoretical support in relieving climate change challenges to premium icewine availability and stability.

Characterization of Potent Odorants Causing an Oily Odor in Rice-Made Baijiu by Comparative Aroma Extract Dilution Analysis, Quantitative Measurements, and Aroma Addition and Omission Studies

The presence of an oily odor in rice-made Baijiu is a unique characteristic that has not been thoroughly studied. This study qualitatively and quantitatively identified important aroma-active compounds in samples with typical and atypical oily odors using aroma extract dilution analysis (AEDA). By comparing the differences between flavor dilution (FD) and odor activity values (OAVs), nine compounds showing significant differences were selected. By combining normal-phase silica gel column and sensory analysis, these nine potential oily odor compounds were isolated from the typical oily odor sample. Addition and omission experiments confirmed that hexanal, trans-2-heptenal, trans,trans-2,4-nonadienal, (2E)-2-decenal, trans,trans-2,4-decadienal, and γ-nonanolide are key contributors to the oily odor.

Decoding the aroma characteristics of icewine by partial least-squares regression, aroma reconstitution, and omission studies

The appeal of icewine is attributable to its distinct aroma characteristics, such as 'honey', 'caramel', and 'dried fruit', but little is known about the chemical basis of these aroma attributes. A set of icewines with different aroma intensities were selected by a panel of wine experts. Detailed volatile compound analyses and sensory descriptive analyses were performed on the selected icewines. Using partial least-squares regression, several lactones, esters, terpenes, furanones, and β-damascenone were positively correlated with 'honey', 'caramel', and 'dried fruit' aromas. Aroma reconstitution studies confirmed that terpenes could significantly enhance the 'honey' aroma, but weaken the 'caramel' aroma, while lactones and furanones could significantly enhance the 'caramel' and 'dried fruit' aromas. In addition, this study demonstrated that terpenes, lactones, and furanones interacted synergistically with each other to cause the sensory perception of the characteristic aromas of icewine.

Comparison of Aroma Compounds and Sensory Characteristics between Two Different Types of Rice-Based Baijiu

Rice-based Baijiu has gained popularity in the Chinese market. Qingya-flavored Baijiu, a variant of Xiaoqu-fermented Baijiu, employs rice as its primary raw material, with an improved production process compared to traditional rice-flavored Baijiu. We comprehensively characterized and compared the aroma profiles of these two rice-based Baijiu types using static sensory experiments (QDA, quantitative descriptive analysis) and dynamic sensory experiments (TDS, temporal dominance of sensations). Qingya-flavored Baijiu exhibited pronounced plant, oily, and roasted aromas, while traditional rice-flavored Baijiu displayed more prominent fruity, floral, and sour notes. Utilizing GC-O-MS (gas chromatography-olfactometry-mass spectrometry) and multi-method quantification, we qualitatively and quantitatively analyzed 61 key aroma compounds, identifying 22 compounds with significant aroma contributions based on odor activity values (OAVs). Statistical analyses, combining sensory and chemical results, were conducted to predict important aroma compounds responsible for the aroma differences between the two Baijiu types. Aroma Recombination and Omission experiments showed that seven compounds play key roles in the aroma of Qingya-flavored Baijiu, including (2E,4E)-Deca-2,4-dienal, linalool, apricolin, ethyl acetate, ethyl isobutyrate, ethyl caprylate, and ethyl isovalerate.

Molecular descriptors of icewine odorants: A first insight into their relationship with metabolism and olfactory perception

To investigate the differences in physicochemical parameters of compounds that are metabolized from different precursors and contribute to the aroma perception of icewine, odor-active compounds in icewine were identified by gas chromatography-olfactometry (GC-O) analysis combined with comprehensive two-dimensional GC and time-of-flight mass spectrometry (GC  ×  GC-TOFMS) analysis, and the molecular descriptors of these odor-active compounds were calculated by computational chemistry software. The distribution pattern of these odorants classified by their precursors and their olfactory perception was visualized on the basis of their molecular descriptor differences. The results showed that the odorants sourced from different precursors could be clearly separated from each other based on their molecular descriptors, which belonged to blocks such as constitution indices and 2D matrix-based descriptors. The results also showed that honey and cooked potatoe descriptions or peach and smoke descriptions have quite different molecular descriptors. This study should contribute to future research that relates to computational chemistry-based aroma perception and prediction in fermented beverages. PRACTICAL APPLICATION: The results obtained from this study may be useful for the construction of a classification system of various odor-active compounds in a given product and may provide a molecular solution for the determination of different perceptual dimensions of an odor mixture.

Chemosensory Characteristics of Brandies from Chinese Core Production Area and First Insights into Their Differences from Cognac

This work aimed to compare the aroma characteristics of representative brandies with different grades from Yantai (one of the Chinese core production areas) and Cognac and to establish relationships between sensory descriptors and chemical composition. Descriptive analysis was performed with a trained panel to obtain the sensory profiles. Forty-three aroma-active compounds were quantified by four different methodologies. A prediction model on the basis of partial least squares analysis was performed to identify candidate compounds that were unique to a certain group of brandies. The result showed that brandies from Yantai could be distinguished from Cognac brandies on the basis of spicy, dried fruit, floral, and fruity-like aromas, which were associated with an aromatic balance between concentrations of a set of compounds such as 5-methylfurfural, γ-nonalactone, and γ-dodecalactone. Meanwhile, brandy with different grades could be distinguished on the basis of compounds derived mostly during the aging process.

Beyond the Bottle: Exploring Health-Promoting Compounds in Wine and Wine-Related Products-Extraction, Detection, Quantification, Aroma Properties, and Terroir Effects

Health-promoting compounds in wine and wine-related products are important due to their potential benefits to human health. Through an extensive literature review, this study explores the presence of these compounds in wine and wine-related products, examining their relationship with terroir and their impact on the aromatic and flavor properties that are perceived orally: sunlight exposure, rainfall patterns, and soil composition impact grapevines' synthesis and accumulation of health-promoting compounds. Enzymes, pH, and the oral microbiome are crucial in sensory evaluation and perception of health promotion. Moreover, their analysis of health-promoting compounds in wine and wine-related products relies on considerations such as the specific target compound, selectivity, sensitivity, and the complexity of the matrix.

Impact of Candida railenensis during fermentation on the aromatic profile of Vidal blanc icewine

Mixed culture fermentation with non-Saccharomyces yeasts and Saccharomyces cerevisiae as multi-starters has more advantages than spontaneous fermentation, and wine products with distinctive and pleasant aromas can fulfill the diverse demands of consumers. This study was carried out to illuminate the effect of sequential inoculation of indigenous Candida railenensis and S. cerevisiae on alcoholic fermentation behavior and chemical and aromatic characteristics of Vidal blanc icewine. During the mixed culture fermentation, C. railenensis was present in the initial and middle stages but was absent after 14 days. The results of basic chemical parameters showed that the glycerol content in the mixed culture-fermented icewine was higher than that of the pure fermented icewine, but the acetic acid content was the opposite. In terms of volatile aroma compounds, C. railenensis in the mixed culture fermentation reduced some metabolites such as lower alcohols, 1-hexanol, 3-methylthiopropanol, and their unpleasant notes and increased the production of some desired volatile aroma compounds such as benzaldehyde, β-damascenone, 2-furanmethanol, and 5-methyl furfural associated with rose, honey, nut, and caramel characteristics. Furthermore, C. railenensis also changed the sensory performance of icewine by participating in the fermentation of S. cerevisiae. These findings suggest that C. railenensis with positive enological properties has the ability to be used in icewine production, which has never been reported before.

Identification, quantitation and organoleptic contributions of furan compounds in brandy

Furan compounds actively contribute to the characteristics of brandy. Herein, we have attempted to identify and quantify the furan compounds present in brandy using three different extraction methods combined with comprehensive two-dimensional gas chromatography and time-of-flight mass spectrometry. Threshold determination and omission experiments were carried out to verify their organoleptic contribution. Liquid-liquid extraction using dichloromethane was found to be the optimal extraction method. A total of 21 furan compounds were identified, in which 5 were detected in brandy for the first time. Our quantitative results showed a positive correlation between the furan compound content and the aging time. Among them, ethyl 5-oxotetrahydro-2-furancarboxylate exhibited a very high odor activity value (1.64 < OAV < 179.53) and smoky aroma. Omission tests showed that the three furan compounds with an OAV > 1 made a significant difference to brandy. These findings bring a new perspective to the sensory and chemical characteristics of brandy.

Investigation on fresh bamboo replacing rice husks for brewing light-aroma Baijiu

Husks are the main source of bran and furfural flavor in traditional Chinese light-aroma Baijiu, but they negatively affect its smell and taste. Here, bran husks were replaced with fresh bamboo to brew light-aroma Baijiu. Flavor components in Jiupei and Baijiu were detected through headspace solid-phase microextraction with gas chromatography-mass spectrometry, and physicochemical properties were assessed; flavor results were obtained from correlation, principal component, and cluster analyses. Starch and reducing sugar content in Jiupei negatively correlated with moisture, alcohol content, and acidity. Fresh bamboo reduced furfural from bran husks in Jiupei by 88.5% and increased alcohol distillation by 51%; it also improved starch efficiency (5%). Surprisingly, isovanillin was found to be present in Baijiu. Total Baijiu yield (57% ± 2.01%) was attained when crushed bamboo size was 1.5 cm × 0.3 cm × 0.3 cm. This study supports the use of fresh bamboo (an eco-friendly alternative for husks) in brewing light-aroma Baijiu. PRACTICAL APPLICATION: The use of fresh bamboo as a replacement for rice husks in brewing light-aroma Baijiu was investigated. It attenuated the chaff taste in light-aroma Baijiu and increased the liquor yield. Surprisingly, isovanillin was also present in the base Baijiu, and it added to the fragrance. This study not only supports the use of bamboo as an auxiliary material for brewing light-aroma Baijiu but also provides a reference for brewing light-aroma Baijiu with alternative auxiliary materials.

Saturated Linear Aliphatic γ- and δ-Lactones in Wine: A Review

Saturated linear aliphatic lactones are widespread aroma compounds in wine, linked to stone fruit, dried red fruit, and coconut descriptors. Despite their ubiquity, bioproduction pathways associated with these compounds in wine are unclear, but higher concentrations have been linked to many common vitivinicultural practices, including grape variety, microbiological influence, oak- and bottle-aging, and wine styles such as late harvest, noble rot, and icewine. Development of analytical techniques has enabled increasingly accurate quantification of lactones in wine, shedding more light on their potential origins. This review provides an in-depth summary of the research into linear aliphatic lactones over the past 50 years and provides direction for possible future research to elucidate the biogenesis of these compounds and better estimate their impact on wine aroma.

Effect of Bentonite Addition to Pedro Ximénez White Grape Musts before Their Fermentation with Selected Yeasts on the Major Volatile Compounds and Polyols of Wines and Tentative Relationships with the Sensorial Evaluation

In this work, we study the effect of bentonite addition to the grape must before alcoholic fermentation on the chemical composition and sensorial profile of the obtained wines. Fermentations were carried out with two Saccharomyces cerevisiae commercial active dry yeasts treated or not with bentonite and were compared with a control wine obtained by spontaneous fermentation (using the grape must microbiota). Several significant effects on the chemical and sensorial attributes were established by statistical treatments. The selection by multiple variable analysis of seven volatile molecules (ethyl acetate; methanol; 1-propanol; isobutanol; 2-methyl-1-butanol; 3-metyl-1-butanol and 2-phenylethanol) provided several footprints that provide an easy visualization of bentonite effects on wine volatile compounds. A Principal Component Analysis carried out with all the compounds quantified by Gas-Chromatography revealed that the first two Principal Components explain 60.15 and 25.91%, respectively, of the total variance and established five groups that match with the five wines analyzed. Lastly, predictive models at p ≤ 0.05 level for the attributes sight, smell and taste were obtained by Partial Least Squared regression analysis of selected chemical variables.

Analysis of Volatile Aroma Compounds and Sensory Characteristics Contributing to Regional Style of Red Wines from Hexi Corridor Based on Sixteen Grape Varieties/Clones

Hexi Corridor is an excellent region for high-quality wines in China, but the characteristic and style of red wine from this region is unclear. To elucidate the regional style of red wines from Hexi Corridor, the aroma properties of red wines made from 16 different varieties/clones of grapes were comprehensively analyzed using HS-SPME-GC-MS, sensory evaluation, odor activity value method, and partial least squares regression analyses. We identified 52 aroma compounds and found that floral and black berry provided a good reference for shaping red wine style and selecting related varieties in Hexi Corridor region. Ethyl caproate, (Z)-3-hexen-1-ol, ethyl 9-decenoate, and hexyl alcohol, which were the characteristic aroma substances of Hexi Corridor red wines, had positive effects on the floral aroma of Merlot, Cabernet Sauvignon, Pinot Noir, and Malbec wines. Hexyl alcohol and (Z)-3-hexen-1-ol also contributed to the black berry and spice aromas, while isobutyl acetate opposed the expression of these aromas of Malbec and Cabernet Franc wines. These results showed that the sensory characteristics of floral and black berry are of vital significance in shaping the red wine style of Hexi Corridor, among which ethyl caproate, (Z)-3-hexen-1-ol, ethyl 9-decenoate, and hexyl alcohol are important contributors.

Impact of Torulaspora delbrueckii During Fermentation on Aromatic Profile of Vidal Blanc Icewine

Non-Saccharomyces yeasts usually have a positive effect on improving the diversity of wine aroma and increasing the differentiation of wine products. Among these non-Saccharomyces yeast species, Torulaspora delbrueckii is often studied and used in winemaking in recent years, but its application in icewine has not been reported yet. In this study, indigenous T. delbrueckii strains (TD1 and TD2) and Saccharomyces cerevisiae strains (commercial yeast SC1 and indigenous icewine yeast SC2) were sequentially inoculated for icewine fermentations; meanwhile, pure S. cerevisiae (SC1 and SC2) fermentations were used as the control; TD1, TD2, and SC2 strains used were screened from spontaneous fermentations of Vidal blanc icewine. The aim was to investigate the effect of T. delbrueckii on the aroma complexity of icewine, which is of great significance to the application of T. delbrueckii in icewine production. The results showed that T. delbrueckii was completely replaced by S. cerevisiae at the middle and later fermentative stages in mixed culture fermentations. Compared with the icewine fermented with pure S. cerevisiae, mixed culture fermented icewines contained lower acetic acid and ethanol, and higher glycerol. The inoculation of T. delbrueckii greatly impacted the levels of several important volatile compounds, and more 2-phenylethyl alcohol, isoamyl acetate, linalool, D-limonene, p-cymene and cineole were produced, and the fruity, flowery, and sweet characteristic was intensified. Moreover, the relevance of strain-specificity within T. delbrueckii to aroma compound differences was shown. To our knowledge, this study is the first to investigate the application of T. delbrueckii in Vidal blanc icewine fermentation, and volatile aroma compounds in the icewine fermented by T. delbrueckii and S. cerevisiae.

Relationships between Shanghai Five Different Home-Brewed Wines Sensory Properties and Their Volatile Composition Assessed by GC-MS

In order to determine the key aroma components of home-brewed wines made from different local grapes in Shanghai. In the work, the identification and quantification of 63 aroma compounds of five home-brewed wines characterized by gas chromatography-mass spectrometry (GC-MS) combined with Headspace Solid-Phase Microextraction (HS-SPME). To study the possible correlation between the sensory attributions and 22 aroma compounds in Odor Activity Value (OAV) > 1 for five home-brewed wines, the Partial Least Squares Regression (PLSR) was a multivariate data analysis performed. Furthermore, to investigate the percentage of contribution of a particular aroma compound to its overall flavor, the relative odor contribution (ROC) and odor activity value of volatiles in home-brewed wines were conducted and performed. According to the comprehensive results, Summer Black Seedless grape (SBSG) and Black Beet grape (BBG) were the most appropriate varieties to be brewed wines for people in Shanghai or around it.

Comparison of the Fermentation Activities and Volatile Flavor Profiles of Chinese Rice Wine Fermented Using an Artificial Starter, a Traditional JIUYAO and a Commercial Starter

In this study, an artificial starter culture was prepared using the core microbial species of JIUYAO to produce Chinese rice wine (CRW). The fermentation activity and flavor profiles of CRW samples fermented with traditional JIUYAO, a commercial starter culture, and our artificial starter culture were compared. The optimal protectant combination for lyophilization of the artificial starter was established as 15.09% skim milk, 4.45% polyethylene glycol, 1.96% sodium glutamate, and 11.81% maltodextrin. A comparative analysis revealed that the ethanol content of the three CRW samples was similar. The total acid content of the CRW sample fermented with the artificial starter (7.10 g/L) was close to that of the sample fermented with JIUYAO (7.35 g/L), but higher than that of the sample fermented with the commercial starter (5.40 g/L). An electronic nose analysis revealed that the olfactory fingerprints of the CRW samples fermented with JIUYAO and the artificial starter resembled each other. For both above mentioned samples, the flavor profiles determined by gas chromatography–mass spectrometry indicated some differences in the variety and content of the aroma compounds, but the key odorants (odor activity values ≥1), such as isoamyl acetate, ethyl acetate, phenyl alcohol, and isoamyl alcohol, were similar.

Chemical and Sensory Characterization of Vidal Icewines Fermented with Different Yeast Strains

The aim of this study is to comprehensively investigate the aroma composition and sensory attributes of Vidal icewine fermented with four yeast strains (ST, K1, EC1118, and R2). A total of 485 kinds of volatile components were identified by comprehensive two-dimensional gas chromatography-time of flight mass spectrometry, among which 347 kinds of volatile compounds were the same in four kinds of sample. The heat map was conducted with 156 volatile compounds, which have aroma contributions, and the analysis results identified the characteristics of the aroma composition of icewine fermented with different yeasts. Quantitative descriptive analysis was performed with a trained panel to obtain the sensory profiles. The aroma attributes of honey and nut of the icewine fermented by R2 were much higher than others. Partial least squares discriminant analysis further provided 40 compounds that were mainly responsible for the differences of the aroma characteristics of the icewines fermented by four yeasts. This study provides more data on the current status of Vidal icewines by main commercial yeasts.

Aroma of Icewine: A Review on How Environmental, Viticultural, and Oenological Factors Affect the Aroma of Icewine

The aroma of a wine is mostly driven by not only the factors in the vineyard, such as the grape variety and harvest time, but also the fermentation process. Icewine is a unique, intensely sweet wine made from late harvested grapes that have frozen naturally on the vine. Different from normal table wines, the grapes used in icewine naturally undergo a dehydration process and freeze-thaw cycles, and the must for icewine making has to be pressed from frozen grapes. This pressing process leaves water behind as ice crystals and allows the grape juice to be concentrated with more sugars, acids, and other dissolved solids, resulting in a slower than normal fermentation. These special procedures can lead to a unique aroma characteristic of icewine. This review delves into recent advances in chemical compounds related to icewine aroma characteristics and addresses how changes in these aroma characteristics and composition are influenced by environmental, viticultural, and oenological factors in the vineyard and winery. Deficiencies in previous studies and future trends related to the flavor science of icewine were also briefly addressed.

Effects of Simultaneous Co-Fermentation of Five Indigenous Non-Saccharomyces Strains with S. cerevisiae on Vidal Icewine Aroma Quality

In this study, Vidal grape must was fermented using commercial Saccharomyces cerevisiae F33 in pure culture as a control and in mixed culture with five indigenous non-Saccharomyces yeast strains (Hanseniaspora uvarum QTX22, Saccharomycopsis crataegensis YC30, Pichia kluyveri HSP14, Metschnikowia pulcherrima YC12, and Rhodosporidiobolus lusitaniae QTX15) through simultaneous fermentation in a 1:1 ratio. Simultaneous fermentation inhibited the growth of S. cerevisiae F33 and delayed the time to reach the maximum biomass. Compared with pure fermentation, the contents of polyphenols, acetic esters, ethyl esters, other esters, and terpenes were increased by R. lusitaniae QTX15, S. crataegensis YC30, and P. kluyveri HSP14 through simultaneous fermentation. S. crataegensis YC30 produced the highest total aroma activity and the most abundant aroma substances of all the wine samples. The odor activity values of 1 C13-norisoprenoid, 3 terpenes, 6 acetic esters, and 10 ethyl esters improved significantly, and three lactones (δ-decalactone, γ-nonalactone, and γ-decalactone) related to coconut and creamy flavor were only found in this wine. Moreover, this sample showed obvious “floral” and “fruity” note odor due to having the highest amount of ethyl ester aromatic substances and cinnamene, linalool, citronellol, β-damascenone, isoamyl ethanoate, benzylcarbinyl acetate, isobutyl acetate, etc. We suggest that simultaneous fermentation of S. crataegensis YC30 with S. cerevisiae might represent a novel strategy for the future production of Vidal icewine.

Identification, quantitation and sensorial contribution of lactones in brandies between China and France

Lactones are important flavor compounds in lots of foodstuffs. They also play an important role in brandy, but have not been studied at large. In this study, solid-phase extraction (SPE) and stir bar sorptive extraction (SBSE) combined with comprehensive two-dimensional gas chromatography and time-of-flight mass spectrometry (GC × GC-TOFMS) were applied to identify and quantify lactones in brandies between China and France. Totally 17 lactones were identified, four of which were detected only in SBSE. Among them, γ-valerolactone, γ-heptalactone, δ-octalactone, γ-undecanolactone and δ-dodecalactone were detected in brandy for the first time. The results of partial least squares-discriminant analysis (PLS-DA) revealed that lactones distinguished regional characteristics among different brandies. The omission test showed that four lactones (OAV > 1) had direct impact on the aroma of brandy, and other seven lactones at sub-threshold (0.1 < OAV < 1) provided peach and apricot aroma characteristics through synergistic effects.

Influence of Harvest Date and Grape Variety on Sensory Attributes and Aroma Compounds in Experimental Icewines of Ukraine

Icewine is a sweet dessert wine whose sensory and chemical attributes are caused by technology peculiarities including the special climatic conditions and acceptable grape varieties. This study aimed to evaluate the sensory characteristics and aromatic compounds in experimental icewines produced from the grape varieties Rkatsiteli, Telti kuruk, Marselan, and Moldova that had been picked in the Odessa region at temperatures of at least minus 7 °C during the 2015 (H1) and 2016 (H2) harvests. Sensory attributes were determined by trained experts, and descriptors for icewines were chosen by consensus. A total of 33 aromatic compounds including 12 that exceeded the threshold were identified using chromatographic analysis. Rkatsiteli icewine obtained from H1 was characterized by the highest concentration of geraniol, 1-octanol, and 2-phenyl acetate, influencing the pronounced citrus and sweet fruit aromas in sensory profiles. The highest concentrations of ethyl hexanoate and ethyl octanoate associated with aromas of dried fruits were detected in Moldova and Marselan icewines made from H2. No 1-hexanol and benzyl alcohol were found in Rkatsiteli and Telti kuruk icewines. Only Moldova and Marselan icewines had γ-nonalactone and benzaldehyde, respectively. Sensory parameters and the quantity of aromatic compounds of Ukrainian experimental icewines depended on harvest date and grape varieties.

Drinking tastes of Chinese rice wine under different heating temperatures analyzed by gas chromatography-mass spectrometry and tribology tests

Drinking tastes and lubrication properties of Chinese rice wine (CRW) under different heating temperatures were studied by tribology tests, gas chromatography-mass spectrometry (GC-MS) and sensory evaluations. CRW's drinking tastes were evaluated by taste panelists. Flavor compounds were detected by GC-MS. Lubrication properties of CRW were measured by tribometer. Drinking tastes changed under different heating temperatures and were the best at 60°C assessed by panelists. Four key compounds, furfural, benzaldehyde, butanedioic acid diethyl ester, and phenylethyl alcohol, were determined by GC-MS affecting drinking tastes of CRW. Their variation trends were consistent with the changes of CRW's tastes. The variation of CRW's lubrication properties had a positive correlation with that of CRW's taste, especially astringency. The lowest friction coefficient implied the best lubrication performance and taste at 60°C. Therefore, it was possible to rapidly evaluate drinking tastes of CRW using tribology technology based on the results. Reasons for temperatures influencing CRW's lubrication properties and drinking tastes were also analyzed in this study.

Characterization of the key aroma compounds in Yunnan goat milk cake using a sensory-directed flavor analysis

To identify the key aroma compounds in Yunnan goat milk cake, seven varieties of milk cake samples were subjected to sensory analysis and gas chromatography-mass spectrometry (GC-MS), gas chromatography-olfactometry (GC-O), aroma recombination, omission, and addition tests. The GC-MS results revealed 53 compounds with aroma characteristics in all the samples. A further comparison of odor activity values and aroma intensities (AI) revealed 25 of these compounds as the initial key aroma compounds. The contributions of these key aroma compounds to the sensory attributes were determined using a partial least squares regression. Of these compounds, 2-heptanone and 2-nonanone were closely related to the "milky" and "cheesy" attributes and were highly abundant in the samples from Kunming. Fatty acids, including butanoic acid, hexanoic acid, octanoic acid, and decanoic acid, were the most abundant compounds detected in the milk cakes. These fatty acids were closely related to the "rancid" and "animalic (goat)" attributes and were largely detected in the samples from Dali Dengchuan and Dali Xiaguan. Sensory-directed aroma recombination, omission, and addition tests further validated the important contributions of ethyl butyrate, benzaldehyde, 3-methyl-1-butanol, 2-heptanone, hexanoic acid, and octanoic acid to the overall sensory properties. Moreover, ethyl butyrate, benzaldehyde, and 2-heptanone, when added, had evident inhibitory or masking effects on the AI of "sour," "rancid," and "animalic (goat)" attributes. PRACTICAL APPLICATION: Goat milk cake is a popular acid-curd cheese in Yunnan, China, however, our limited knowledge to its key aroma compounds restricts its development and industrial production. In this study, a sensory-directed flavor analysis was used to characterized the key aroma compounds of Yunnan goat milk cake, which will help to enhance our understanding on the flavor profile of Yunnan goat milk cake and provide a reference for optimizing the flavor feature and organoleptic quality of this fresh goat cheese.

Unraveling the chemosensory characteristics of strong-aroma type Baijiu from different regions using comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry and descriptive sensory analysis

Comprehensive 2D gas chromatography-time-of-flight mass spectrometry was combined with descriptive sensory analysis to elucidate the specificity of strong-aroma type Baijiu (Chinese liquor) from different regions, based on regionally distinct flavor characterized by chemical and sensory profiles. Numerous potential aroma compounds (262) were identified, among which 58 aroma compounds were significantly different between the samples from Sichuan and Jianghuai regions. Relationships between these potential aroma compounds and sensory attributes were investigated by partial least squares regression and network analysis. The compounds that dominantly contributed to the important sensory attributes were identified. The high pyrazines, furanoids, and carbonyls amounts contributed to the high intensities of the cellar, toasted, and grain aroma profiles of the Sichuan region samples, while the high ester and alcohol levels contributed to the fruity and floral aroma profiles of the Jianghuai region samples. This approach may have practical application in flavor characterization of other alcoholic beverages.

Effects of Tetragenococcus halophilus and Candida versatilis on the production of aroma-active and umami-taste compounds during soy sauce fermentation

BACKGROUND

Soy sauce is a well-known condiment worldwide. However, the high salt content in soy sauce contributes to the high intake of sodium salt, which usually results in high blood pressure. High salt soy sauce usually has the better quality (aroma and taste) than low salt. Tetragenococcus halophilus and Candida versatilis are important starters for soy sauce fermentation. It is of urgent need to explore what the effect of these two strains on the aroma- and taste-attributes of soy sauce to achieve high quality fermentation with low salt.

RESULTS

In this study, aroma-active and taste compounds in soy sauce were reviewed and listed. Then, soy sauce fermentation inoculated with different combinations of T. halophilus (at different inoculated time) and C. versatilis were completed. Aroma-active and taste compounds in different samples were quantified. Multivariate analysis was used to analyze these data. The aroma-active compounds which were highly related to the inoculation of T. halophilus and C. versatilis were found. Meanwhile, the addition time of T. halophilus could also be highly related to the production of aroma-active compounds. More importantly, T. halophilus was highly correlated with the production of umami-taste compounds in soy sauce, including aspartic acid, glutamic acid, alanine and N -succinyl-glutamic acid.

CONCLUSION

These results will provide a better understanding of the effects of T. halophilus and C. versatilis on the formation of significant aroma-active and umami-taste constituents in soy sauce. Furthermore, it will be helpful to realize fermentative control of soy sauce with high quality at low salt. © 2020 Society of Chemical Industry.

Characterization of tolerance and multi-enzyme activities in non-Saccharomyces yeasts isolated from Vidal blanc icewine fermentation

This work aim to study the tolerance and aroma-related enzymes activities of the non-Saccharomyces yeasts in Vidal blanc icewine from the Huanren region of China. The strains were identified by sequencing internal transcribed spacer (ITS) region and the 26S rDNA D1/D2 domain genes and all representative non-Saccharomyces yeasts were belonged to genera Metschnikowia, Hanseniaspora, Torulaspora, Candida, and Debaryomyces. A total of 28 strains were carried out for tolerance experiments and results suggested that most of them could tolerate 500 g/L glucose, 4% ethanol, 20 g/L tartaric acid, and 350 mg/L SO₂ . Finally, a total of 17 strains with better tolerance were carried out for the β-glucosidase, β-xylosidase, and pectinase activities experiments. The results showed that Candida railenensis HC08 and the strains of Hanseniaspora genus have satisfactory multi-enzyme activities, which can be used to design mixed fermentation to produce characteristic icewine. PRACTICAL APPLICATIONS: Non-Saccharomyces yeasts produces a series of hydrolytic enzymes that are thought to have a significant contribution to the aroma complexity of wines, however, are poorly explored in icewine. In this work, most of the non-Saccharomyces yeasts screened from Chinese icewine can adapt well to the high-sugar and high-acid environment of icewine, and can secrete hydrolase. The application of these strains in mixed fermentation could provide a prospect for the production of characteristic icewine.

Diversity and Dynamics of Yeasts During Vidal Blanc Icewine Fermentation: A Strategy of the Combination of Culture-Dependent and High-Throughput Sequencing Approaches

In this study, attention has been focused on the ecology of yeasts during the spontaneous and inoculated fermentation processes of Vidal blanc icewine in northeast China, which is very important for screening autochthonous yeast strains, understanding the roles of these strains, and managing fermentation. The strategies were to conduct spontaneous and inoculated laboratory-scale fermentation processes simultaneously and to analyze the samples taken at different fermentation stages by culture-dependent and -independent methods. Three hundred and thirty-eight yeast strains were isolated and twelve genera were identified by sequencing. During the spontaneous fermentation process, non-Saccharomyces yeasts were predominant in the initial and middle stages, whereas Saccharomyces dominated in the later stages; Candida was preponderant in the whole process, and its abundance in the final stages was only lower than Saccharomyces. The inoculated fermentation was characterized by a predominance of Saccharomyces throughout the fermentation process; non-Saccharomyces yeasts were observed in the early stage. The internal transcribed spacer (ITS) 2 region gene was firstly used to analyze the yeast diversity in the samples during the icewine fermentation processes by high-throughput sequencing (HTS), and a more complex mycobiota was revealed. Moreover, the dynamics of other major fungi (mainly Davidiella and Alternaria) during icewine fermentation processes were also revealed, which have never been reported in icewine before.

Chemical and Sensory Characterization of Cabernet Sauvignon Wines from the Chinese Loess Plateau Region

In this study, the aroma profiles of Cabernet Sauvignon wines from a new grape growing region, Loess Plateau, China, were established by gas chromatography–olfactometry, gas chromatography–mass spectrometry and sensory analysis. The sensory profiles of wines form five different young vineyards in the Loess Plateau region were obtained by descriptive analysis. Blackcurrant (p < 0.01), pear and dried plum (p < 0.05), mushroom, smoked and green pepper (p < 0.1) had significant differences on the five vineyards. A total of 76 odor-active aroma compounds were identified in the wines, and 45 volatile compounds were selected as those having the greatest impact on the aroma components and these were quantitated by five different methods. In addition, the correlation model of the Loess Plateau region’s sensory characteristics and aroma compounds was established by partial least squares regression (PLSR) to determine the influence of various aroma active substances on aroma attributes.

Characterization of key aroma compounds in Chinese rice wine using gas chromatography-mass spectrometry and gas chromatography-olfactometry

To determine the key aroma compounds in Chinese rice wine (CRW), four types of CRW (YH, JF, SN, and XX) were analyzed by gas chromatography-mass spectrometry (GC-MS), gas chromatography-olfactometry (GC-O), and sensory evaluation. The contributions of the key aroma compounds to the flavor characteristics were determined by partial least squares regression. Sixty-one aroma compounds were detected. Twenty-five components were identified as odor-active compounds. On the basis of their odor active values, 18 odor-active compounds were determined as key aroma compounds. Ethyl isovalerate, ethyl butyrate, ethyl acetate, ethyl hexanoate, and phenylethyl alcohol were key aroma compounds in all four types of wine. The unique key aroma compounds of JF wine were isovaleraldehyde and isoamyl acetate; those of XX wine were 1-butanol, benzaldehyde, ethyl benzoate, ethyl phenylacetate, 2-octanone, and furfural; that of YH wine was ethyl 2-methylbutyrate; and those of SN wine were 1-butanol, 1-hexanol, 2-butenoic acid ethyl ester, and 3-methyl-1-butanol.

Characterization and differentiation of key odor-active compounds of 'Beibinghong' icewine and dry wine by gas chromatography-olfactometry and aroma reconstitution

Freezing-thawing events contribute to the unique aroma profile of icewines. Differences in key odor-active volatile compounds between 'Beibinghong' (Vitis amurensis × V. vinifera) icewines and dry wines were investigated by gas chromatography-olfactometry and gas chromatography-mass spectrometry. Acceptable agreement between the olfactometric and quantitative results was obtained. 'Beibinghong' icewine was characterized by high concentrations of volatile phenols, lactones, (E)-β-damascenone, and phenylacetaldehyde, which were associated with on-vine freezing-thawing events in grape. Low concentrations of higher alcohol acetates and ethyl esters of fatty acids were attributed to hyperosmotic stress during fermentation. The overall aroma of icewine could be mimicked by reconstitution containing 44 identified volatiles. Partial least squares regression analysis demonstrated that the concentrations of these volatile compounds determined the distinct sensory profiles of icewines, which have higher intensities of honey/sweet, smoky, caramel, dried fruit, apricot/peach, and floral aromas, and lower intensities of fresh fruity and herbaceous notes in comparison with dry wines.

Use of Indigenous Hanseniaspora vineae and Metschnikowia pulcherrima Co-fermentation With Saccharomyces cerevisiae to Improve the Aroma Diversity of Vidal Blanc Icewine

Using novel non-Saccharomyces strains is regarded as an effective way to improve the aroma diversity of wines to meet the expectations of consumers. The non-Saccharomyces Hanseniaspora vineae and Metschnikowia pulcherrima have good aromatic properties useful for the production of table wine. However, no detailed information is available on their performances in icewine fermentation. In this study, simultaneous and sequential fermentation trials of indigenous M. pulcherrima CVE-MP20 or H. vineae CVE-HV11 with S. cerevisiae (SC45) were performed in 50-L fermenters of Vidal icewine, respectively. The results showed that SC45 cofermented with different non-Saccharomyces strains could generate a distinct aroma quality of icewine compared with four S. cerevisiae strain monocultures as evidenced by principal component analysis (PCA). Mixed fermentation of MP20/SC45 produced higher contents of acetate esters and β-damascenone with lower C₆ alcohols relative to SC45 monoculture. Interestingly, HV11/SC45 generated the highest amounts of C₆ alcohols [(Z)-3-hexen-1-ol and (E)-3-hexen-1-ol], higher alcohols (isobutanol, isopentanol, and 2-phenylethanol), acetate esters (2-phenethyl acetate and isoamyl acetate), cis-rose oxide, β-damascenone, and phenylacetaldehyde. Compared with simultaneous inoculation, sequential inoculation could achieve higher aroma diversity and produce higher intensity of fruity, flowery, and sweet attributes of icewine as assessed by calculating the odor activity values (OAVs). Our results verified the desired enological characteristics of H. vineae strain in icewine fermentation and also demonstrated that using indigenous non-Saccharomyces and Saccharomyces strains is a feasible way to improve aroma diversity of icewine products, which could provide an alternative way to meet the requirement of wine consumers for diversified aromatic quality.

Insight into the Chemical Diversity of Late/Ice Harvest Gewürztraminer Wine

Late harvest (LHW) and ice harvest (IHW) Gewürztraminer wine samples from Croatia (Ilok) were investigated. Their technological parameters, chromaticity coordinates, total phenols content, and antioxidant capacity were determined. 5-(Hydroxymethyl)furfural, xanthine, and trans-caftaric acid were analyzed in the samples by high performance liquid chromatography (HPLC-DAD). Headspace solid-phase microextraction (HS-SPME) followed by gas chromatography and mass spectrometry (GC/MS) analysis revealed isoamyl alcohol as predominant compound (21.25 - 60.30%). Diethyl succinate, 2-phenylethanol, and benzaldehyde were also abundant. Ethyl octanoate (1.48 - 5.70%) and ethyl caprate (0.48 - 4.83%) decreased significantly in LHW, being the lowest in IHW. Two solvents were applied for the samples extraction (solvent A - pentane/diethyl ether 1:2 (v/v) and solvent B - dichloromethane), and the extracts were analyzed by GC/MS. Ethyl hydrogen succinate (solvent A: 27.30 - 52.04%; solvent B: 28.04 - 46.69%) and diethyl succinate (solvent A: 5.21 - 18.2%; solvent B: 2.66 - 7.72%) were predominant in IHW and LHW. Aromatic alcohols were also found: 2-phenylethanol (solvent A: 7.07 - 21.09%; solvent B: 5.50 - 11.82%), 4-hydroxybenzyl alcohol (solvent A: 1.45 - 6.68%; solvent B: 2.47 - 12.16%) and benzyl alcohol (solvent A: 0.10 - 0.77%). The obtained results complement a previous study on IHW (Gewürztraminer) from Croatia providing new features and indicating great chemical diversity among the samples.