Olfactory Impact of Higher Alcohols on Red Wine Fruity Ester Aroma Expression in Model Solution

Metagenomics reveals the differences in flavor quality of rice wines with Hongqu and Maiqu as the fermentation starters

Chinese rice wine (CRW) is an alcoholic beverage made mainly from rice or grain through saccharification and fermentation with Jiuqu (starter). Jiuqu makes an important contribution to the formation of the flavor characteristics of rice wine. Hongqu and Maiqu are two kinds of Jiuqu commonly used in CRW brewing. This study compared the microbial community, biogenic amines (BAs), and volatile flavor components (VFCs) of two types of rice wine brewed with Hongqu and Maiqu as fermentation agents. The results showed that the amino acid content of rice wine fermented with Maiqu (MQW) was significantly lower than that of rice wine fermented with Hongqu (HQW). On the contrary, the majority of BAs in MQW were significantly higher than those in HQW, except for putrescine. Multivariate statistical analysis indicated that most of the VFCs detected were enriched in HQW, while ethyl 3-phenylpropanoate and citronellol were enriched in MQW. The results of metagenomic analysis showed that Weissiella, Enterobacter, Leuconostoc, Kosakonia, Saccharomyces, Aspergilus and Monascus were identified as the predominant microbial genera in HQW brewing process, while Saccharopolyspora, Lactococcus, Enterobacter, Leuconostoc, Kosakonia, Pediococcus, Pantoea, Saccharomyces, Aspergillus, Lichtheimia and Nakaseomyces were the predominant microbial genera in MQW brewing. In addition, some VFCs and BAs were strongly correlated with dominant microbial genera in HQW and MQW brewing. Bioinformatics analysis showed that the abundance of genes involved in BAs synthesis in MQW brewing was much higher than that in HQW brewing, while the abundances of genes related to metabolic pathway of characteristic VFCs in HQW brewing were obviously higher than those in MQW, which explained the differences in flavor quality between HQW and MQW from the perspective of microbial genes. Collectively, these findings provide scientific evidence for elucidating the contribution of different microbial genera to the formation of flavor quality of CRW, and is helpful for screening beneficial microbes to enhance flavor quality and drinking comfort of CRW.

Technological affinity index for interaction between lactic acid bacteria and Saccharomyces cerevisiae strains to modulate the fruity and floreal aroma of Catarratto wines

Microbial interactions during the fermentation process influence the sensory characteristics of wines. Alongside alcoholic fermentation, malolactic fermentation also plays a crucial role in determining the aromatic traits of wines. The time (t), rate (m) and volatile organic compounds (VOCs) of malolactic fermentation are linked to the interaction between yeasts and lactic acid bacteria. The study investigated the interactions between Lactiplantibacillus plantarum or Oenococcus oeni with Saccharomyces cerevisiae by using the Technological Affinity Index (TAIndex). The co-inoculation of L. plantarum/S. cerevisiae resulted in a higher TAIndex than the co-inoculation of O. oeni/S. cerevisiae conditions. A low TAIndex led to increased aromaticity of the wines. The time and rate of malolactic fermentation have a strong impact on the synthesis of VOCs with a high olfactory impact. Therefore, knowledge of the TAIndex could play a decisive role in improving winemaking planning to produce wines with higher fruit and floral perceptions.

Composition of Higher Alcohols in Different Alcoholic Beverages and Their Metabolic Dynamics in Bama Pigs

The unique flavour contribution of higher alcohols in alcoholic beverages has received growing attention; however, there is a dearth of information on their in vivo metabolic kinetics. In this study, the composition and content of higher alcohols in different alcoholic beverages from Chinese Baijiu and Lujiu were studied via in vivo analysis using Bama pigs to elucidate the mechanisms for intoxication of alcohol in vitro and in drinkers. Direct injection combined with gas chromatography-mass spectrometry (GC-MS) were used to accurately quantify a total of 14 higher alcohols in five alcoholic beverages. Based on the external standard method, a total content of 289.37-938.33 mg/L was detected, mainly 1-butanol, 3-methyl-1-butanol, 1-hexanol, 2-methyl-1-propanol and 2-butanol. Then, headspace solid-phase microextraction (HS-SPME) and solid-phase extraction (SPE) combined with GC-MS analysis strategy, respectively, were adopted to continuously monitor the changes in the concentrations of ethanol and 11 higher alcohols in the blood within 24 h after gavage of different alcoholic beverages, and the key pharmacokinetic parameters were analysed. The peak concentration (Cmax) and area under curve (AUC) of blood higher alcohols were significantly lower than those of ethanol (p < 0.05), accompanied by a later peak time (Tmax) and a larger apparent clearance rate (CL_F), and there were certain differences between the same higher alcohols in different alcoholic beverages and between different higher alcohols in the same alcoholic beverage. This work provides valuable insights into the metabolism of alcoholic beverages.

Flavoromic analysis of wines using gas chromatography, mass spectrometry and sensory techniques

Various sensory perceptions drive the quality and typicality of wines, with the volatile profile playing a fundamental role in the characteristics of odor, aroma and consequently flavor, which combines the smell (odor and aroma), taste, and trigeminal sensations. Efforts have been made in both the field of instrumental and sensory analysis to understand the relationship of volatile compounds with sensory attributes in omics approaches. Gas chromatography (monodimensional and two-dimensional (heartcutting and comprehensive)) associated with mass spectrometry (GC/MS, GC-GC/MS and GCxGC/MS) and chemometric tools have contributed to foodomics analyses, specifically those linked to metabolomics/volatilomics. These tools, along with the elucidation of sensory properties (sensomics), lead to advanced results in the field of flavoromics. They also help to define the best practices in both vineyard management and winemaking that enable the production of high-quality wines. The objective of this review is to report the challenges of determining the volatile profile of wines, pointing out the ways that can be followed in successful identification and quantification of volatile compounds. The state of the art of sensory evaluation methods is also addressed, providing information that helps in choosing the most appropriate sensory method to be conducted with chromatographic analysis to achieve more in-depth results in the field of flavoromics.

Olfactory dysfunction decreased local field potential in the reward system and increased EtOH consumption in mice

The relationship between olfactory dysfunction and alcohol intake is unobvious. Chronic alcohol intake results in reduced olfactory acuity and olfactory discrimination and addiction in humans. However, alcohol is a beverage with distinctive odors, which usually works as a cue to induce addictive memories and craving behavior. Whether olfactory impairment increase or decrease alcohol consumption remains an important but unclear issue. In this study, we measured ethanol (EtOH) consumption in the two-bottle choice EtOH drinking test, two bottle choice EtOH/sucrose drinking test and the drinking in the dark (DID) test during the olfactory loss. We also recorded local field potentials (LFPs) from the brain reward system, the ventral tegmental area (VTA), nucleus accumbens (NAc), and piriform cortex (Pir) one and four weeks after the induction of olfactory epithelium lesions using zinc sulfate (ZnSO4) in mice. The results showed that the EtOH consumption and preference were increased during the period of olfactory dysfunction. 1 week after the olfactory injury, LFP powers in the reward system at low- and high-gamma bands decreased significantly, coherence between the Pir and the reward system was also decrease. 4 weeks after the ZnSO4 treatment, LFP powers were reversed, but the coherence between VTA and NAc was decreased, indicating lasting effects post-recovery. This study demonstrates that olfactory dysfunction increased EtOH consumption in mice, which was accompanied by decreased LFP power and coherence in the reward system, which suggest that olfactory deficits changed activities in the reward system and could alter reward-seeking behaviors, which provide insights into the neurobiology of alcohol addiction.

Olfactory perception complexity induced by key odorants perceptual interactions of alcoholic beverages: Wine as a focus case example

The odorants in alcoholic beverages are frequently experienced as complex mixtures, and there is a complex array of influence factors and interactions involved during consumption that deeply increase its olfactory perception complexity, especially the complexity induced by perceptual interactions between different odorants. In this review, the effect of olfactory perceptual interactions and other factors related to the complexity of olfactory perception of alcoholic beverages are discussed. The classification, influencing factors, and mechanisms of olfactory perceptual interactions are outlined. Recent research progress as well as the methodologies applied in these studies on perceptual interactions between odorants observed in representative alcoholic beverages, especially wine, are briefly summarized. In the future, unified theory or systematic research methodology need to be established, since up to now, the rules of perceptual interaction between multiple odorants, which is critical to the alcoholic beverage industry to improve the flavor of their products, are still not revealed.

Studying how dry extract can affect the aroma release and perception in different red wine styles

BACKGROUND

Four red wine matrices representing different red wine styles with the same VOCs (volatile organic compounds), were obtained by enriching a bleed wine with increasing amounts of deodorized dry extract obtained from the pressed wine of the same vinification. The release of VOCs was determined by solid phase micro-extraction-gas chromatography-mass spectrometry (SPME-GC-MS), in conditions mimicking those applied during sensory assessments.

RESULTS

Results show that even though the perception of the overall odor intensity was not significantly influenced by the matrix, this latter modulated the odor profiles: at rising wine dry extract, fruity, floral odors decreased, while dehydrated fruit, woody-toasty, vegetal-earthy notes increased. These changes cannot be fully explained by the observed significant influence of the matrix on the release of VOCs or by their correlations with the considered matrix components (ethanol, residual sugars, phenolics, pH), but findings suggest that perceptual interactions are involved.

CONCLUSION

This study could be useful in pressing and blending management for wine aroma quality also considering wine compositional trends under the current climate change context. © 2024 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

A Comparative Study of Microbial Communities, Biogenic Amines, and Volatile Profiles in the Brewing Process of Rice Wines with Hongqu and Xiaoqu as Fermentation Starters

Rice wine is primarily crafted from grains through saccharification and liquification with the help of Qu. Qu plays an important role in the formation of the flavor quality of rice wine. Hongqu and Xiaoqu represent two prevalent varieties of Qu that are typically utilized in the brewing process of rice wine and play a crucial role in its production. In this study, GC, GC-MS, HPLC, and metagenomic sequencing techniques were used to contrast the microbial flora, biogenic amines, and aroma characteristics developed during the fermentation of rice wines, with Hongqu and Xiaoqu being used as initiating agents for the brewing process. The results show that the content of higher alcohols (including n-propanol, isobutanol, 3-methyl-1-butanol, and phenethyl alcohol) in rice wine brewed with Xiaoqu (XQW) was significantly higher than that in rice wine brewed with Hongqu (HQW). Contrarily, the concentration of biogenic amines in HQW surpassed that of XQW by a notable margin, but tyramine was significantly enriched in XQW and not detected in HQW. In addition, a multivariate statistical analysis revealed distinct disparities in the constitution of volatile components between HQW and XQW. Hexanoic acid, ethyl acetate, isoamyl acetate, ethyl caproate, ethyl decanoate, 2-methoxy-4-vinylphenol, etc., were identified as the characteristic aroma-active compounds in HQW and XQW. A microbiome analysis based on metagenomic sequencing showed that HQW and XQW had different dominant microorganisms in the brewing process. Burkholderia, Klebsiella, Leuconostoc, Monascus, and Aspergillus were identified as the primary microbial genera in the HQW fermentation period, while Pediococcus, Enterobacter, Rhizopus, Ascoidea, and Wickerhamomyces were the main microbial genera in the XQW brewing process. A bioinformatics analysis revealed that the concentrations of microbial genes involved in biogenic amines and esters biosynthesis were significantly higher in HQW than those in XQW, while the content of genes relevant to glycolysis, higher alcohol biosynthesis, and fatty acid metabolism was significantly higher in XQW than in HQW, which are the possible reasons for the difference in flavor quality between the two kinds of rice wine from the perspective of microbial functional genes.

Exploration of carbonyl compounds in red-fleshed kiwifruit wine and perceptual interactions among non-volatile organic acids

Carbonyl compounds are vital constituents that contribute to the flavor profile of alcoholic beverages. We examined 3-nitrophenylhydrazine as a derivatizing reagent for the measurement of 34 carbonyl compounds using UPLC-MS/MS. Adding formic acid and sodium acetate to the mobile phase significantly enhanced the detection limit of carbonyl compounds. The technique exhibited a notable extraction efficiency, yielding recovery percentages ranging from 83.6% to 117.1%, coupled with exceptional sensitivity, as evidenced by detection limits spanning from 0.07 μg/L to 4.80 μg/L. The relative standard deviation was <6.9%, indicating the precision and reliability of the analytical methodology. The method was verified by analyzing carbonyl compounds from red-fleshed kiwifruit wine. Furthermore, sensory assessment revealed that the amalgamation of tartaric acid, malic acid, and citric acid contributes to sour taste perception at sub-threshold concentrations through an additive interaction with supra-threshold non-volatile organic acids such as lactic acid and acetic acid.

Investigation of the interaction between lactones and ketones in a Cheddar cheese matrix using Feller's additive model, σ-τ plots, U-models, and aroma addition experiments

The objective of this study was to examine the sensory interactions between lactones and ketones in a Cheddar simulation matrix through perceptual interaction analysis. The olfactory thresholds of 6 key lactones had values ranging from 8.32 to 58.88 μg/kg, whereas those of the 4 key ketones ranged from 6.61 to 660.69 μg/kg. Both Feller's additive model and σ-τ plots demonstrated complex interactions in 24 binary mixtures composed of the 6 lactones and 4 ketones, including synergy, addition, and masking effects. Specifically, we found that 6 binary mixtures exhibited aroma synergistic effects using both methods. Moreover, the σ-τ plot showed a synergistic effect of aroma in 3 ternary mixtures. The U-model further confirmed the synergistic effects of the 6 groups of binary systems and 3 groups of ternary systems on aroma at actual cheese concentrations. In an aroma addition experiment, the combination of δ-octalactone and diacetyl in binary mixtures had the most pronounced effect on enhancing milk flavor. In ternary mixtures, 2 combinations, namely δ-octalactone/δ-dodecalactone/diacetyl and γ-dodecalactone/δ-dodecalactone/acetoin, significantly enhanced the milky and sweet aroma properties of cheese, while also enhancing the overall acceptability of the cheese aroma.

Creating alternative seafood flavour from non-animal ingredients: A review of key flavour molecules relevant to seafood

This review summarises current knowledge of the molecular basis for flavour profiles of popular seafood types (crustacean (crab, lobster, prawn, etc.), mollusc (oyster, squid, etc.), oily fish (salmon, sardine, etc.) and white fish (barramundi, turbot, etc.)), and provides a foundation for formulating improved plant-based seafood alternative (PBSA) flavours. Key odour-active volatile molecules were identified from a systematic review of published olfactometry studies and taste-active compounds and macronutrient profiles of different seafood species and commercial PBSAs from nutrition databases were compared. Ingredients commonly used in commercial BPSAs and new potential sources of flavouring agents are evaluated. While significant challenges in replicating seafood flavour and texture remain, this review provides some insights into how plant-based ingredients could be applied to improve the acceptability of PBSAs.

Sequential Fermentation in Red Wine cv. Babić Production: The Influence of Torulaspora delbrueckii and Lachancea thermotolerans Yeasts on the Aromatic and Sensory Profile

This research aimed to analyze the impact of two different non-Saccharomyces yeast species on the aromatic profile of red wines made from the cv. Babić (Vitis vinifera L.) red grape variety. The grapes were obtained from two positions in the Middle and South of Dalmatia. This study compared a control treatment with the Saccharomyces cerevisiae (Sc) strain as a type of sequential inoculation treatment with Lachancea thermotolerans (Lt x Sc) and Torulaspora delbrueckii (Td x Sc). The focus was on the basic wine parameters and volatile aromatic compound concentrations determined using the SPME-Arrow-GC/MS method. The results revealed significant differences in cis-linalool oxide, geraniol, neric acid, and nerol, which contribute to the sensory profile with floral and rose-like aromas; some ethyl esters, such as ethyl furoate, ethyl hexanoate, ethyl lactate, ethyl 2-hydroxy-3-methylbutanoate, ethyl 3-hydroxy butanoate, diethyl glutarate, and diethyl succinate, contribute to the aromatic profile with fruity, buttery, overripe, or aging aromas. A sensory evaluation of wines confirmed that Td x Sc treatments exhibited particularly positive aromatic properties together with a more intense fullness, harmony, aftertaste, and overall impression.

Decoding Polysaccharides from Two Pichia Yeasts and Their Molecular Interaction with Wine Fruity Esters

This study extensively characterized yeast polysaccharides (YPs) from Pichia fermentans (PF) and Pichia kluyveri (PK), with a specific focus on their structural attributes and their interaction with wine fruity esters in a model wine system. By finely tuning enzymatic reactions based on temperature, pH, and enzyme dosage, an optimal YP yield of 77.37% was achieved, with a specific mass ratio of cellulase, pectinase, and protease set at 3:5:2. There were four YP fractions (YPPF-W, YPPF-N, YPPK-W, and YPPK-N) isolated from the two yeasts. YPPF-N and YPPK-N were identified as glucans based on monosaccharide analysis and Fourier-transform infrared spectroscopy analysis. "Specific degradation-methylation-nuclear magnetic" elucidated YPPF-W's backbone structure as 1,3-linked α-l-Man and 1,6-linked α-d-Glc residues, while YPPK-W displayed a backbone structure of 1,3-linked α-Man residues, indicative of a mannoprotein nature. Isothermal titration calorimetry revealed spontaneous interactions between YPPK-W/YPPF-W and fruity esters across temperatures (25-45 °C), with the strongest interaction observed at 30 °C. However, distinct esters exhibited varying interactions with YPPK-W and YPPF-W, attributed to differences in molecular weights and hydrophobic characteristics. While shedding light on these intricate interactions, further experimental data is essential for a comprehensive understanding of yeast polysaccharides' or mannoproteins' impact on fruity esters. This research significantly contributes to advancing our knowledge of yeast polysaccharides' role in shaping the nuanced sensory attributes of wine.

Effect of ultrasonic treatment during fermentation on the quality of fortified sweet wine

The present study aimed to investigate the potential of ultrasonic treatment during fermentation for enhancing the quality of fortified wines with varying time and power settings. Chemical analysis and sensory evaluation were conducted to assess the impact of ultrasonic treatment on wine quality. Results showed that ultrasonic treatment could increase total anthocyanin and total phenol content, reduce anthocyanin degradation rate, and improve color stability. Moreover, ethyl carbamate content was lower in the ultrasonic group after aging compared to non-ultrasonic group. A combination of 200 W for 20 min resulted in higher sensory scores and more coordinated taste, while a combination of 400 W for 40 min produced higher levels of volatile compounds (21860.12 μg/L) leading to a richer and more elegant aroma. Therefore, ultrasound can be used as a potential technology to improve the quality of wine.

Evaluation of perceptual interactions between key aldehydes in Kung Pao Chicken

Aldehydes are the strongest and most abundant aromatic compounds in Kung Pao Chicken. However, the perceptual interactions between these aldehydes are not fully understood. Therefore, the flavor contribution of nine key aldehydes was estimated by determining thresholds. Except for benzaldehyde, the thresholds of all aldehydes measured in tasteless chicken matrices (TM) were significantly larger than their comparable values in water. Based on these results, the perceptual interactions of nine aldehydes were evaluated using S-curves and σ-τ plots. The interactions indicated that 31 of their 36 binary mixtures exhibited additive effects, three had masking effects, while two had synergistic effects. Recombination experiments showed that the addition of aldehydes lowered the odor threshold of aldehyde reconstitution (AR), thereby enhancing the aroma intensity of AR. These findings contribute to a better understanding of Kung Pao Chicken's aroma and can be used to improve its aroma quality.

THI3 contributes to isoamyl alcohol biosynthesis through thiamine diphosphate homeostasis

Isoamyl alcohol is a precursor of isoamyl acetate, an aromatic compound that imparts the ginjo aroma to sake. The isoamyl alcohol biosynthesis pathway in yeasts involves the genes PDC1, PDC5, PDC6, ARO10, and THI3 encoding enzymes that decarboxylate α-ketoisocaproic acid to isovaleraldehyde. Among these genes, THI3 is the main gene involved in isoamyl alcohol biosynthesis. Decreased production of isoamyl alcohol has been reported in yeast strains with disrupted THI3 (Δthi3). However, it has also been reported that high THI3 expression did not enhance decarboxylase activity. Therefore, the involvement of THI3 in isoamyl alcohol biosynthesis remains unclear. In this study, we investigated the role of THI3 in isoamyl alcohol biosynthesis. While reproducing previous reports of reduced isoamyl alcohol production by the Δthi3 strain, we observed that the decrease in isoamyl alcohol production occurred only at low yeast nitrogen base concentrations in the medium. Upon investigating individual yeast nitrogen base components, we found that the isoamyl alcohol production by the Δthi3 strain reduced when thiamine concentrations in the medium were low. Under low-thiamine conditions, both thiamine and thiamine diphosphate (TPP) levels decreased in Δthi3 cells. We also found that the decarboxylase activity of cell-free extracts of the Δthi3 strain cultured in a low-thiamine medium was lower than that of the wild-type strain, but was restored to the level of the wild-type strain when TPP was added. These results indicate that the loss of THI3 lowers the supply of TPP, a cofactor for decarboxylases, resulting in decreased isoamyl alcohol production.

Exploring the effects of mixture composition factors and perceptual interactions on the perception of icewine odor: An olfactometer-based study

The perception of food odor, derived from complex mixtures of odorants, remains poorly understood. This study investigated how key odorants of icewine influence odor mixture perception and mixture-induced perceptual interactions. A multichannel olfactometer was used to deliver 90 mixtures to 36 trained participants who used a Rate-All-That-Apply method to rate the odor samples. Results showed that adding odorants to a mixture affected both the characteristic odor of the individual component and other odor characteristics, revealing specific perceptual interactions. Combining up to six odorants with icewine odor influenced a maximum of two odor characteristics in the mixture, regardless of the specific combination. Interestingly, adding odorants had a stronger impact on the overall mixture odor profile than omitting them, particularly when manipulating fewer than three odorants. These findings emphasize the complexity of odor mixture perception and provide new insights into the influence of key odorants on the aroma of wine.

Synergy Effect between Fruity Esters and Potential Odorants on the Aroma of Hutai-8 Rose Wine Revealed by Threshold, S-Curve, and σ-τ Plot Methods

To analyze the contribution of fruity esters on wine aroma perception, the interaction levels between 12 esters and key odorants of Hutai-8 rose wine were investigated using threshold, S-curve, and σ-τ plot methods, and the aroma enhancement performance of esters was verified by using addition experiments. Results indicated that esters enhance the sweet, floral, and fruity traits of citronellol, β-damascenone, and nerolidol, especially at subthreshold levels. Meanwhile, esters increased the floral and fruity characteristics of key fermentative odorants mainly by additive effects, with acetate esters possessing a better synergy ability. In contrast, the synergy levels between binary esters were less influenced by the concentration but more by the compound structure and aroma. Additionally, moderately subjoining the type and content of esters in wine proved that their synergy effects improved the sweet trait and decreased the sour fruit trait. This finding characterized that the contribution of esters to the wine aroma was obtained by the combined synergy of odorants at a suitable concentration.

Variation of wine preference amongst consumers is influenced by the composition of salivary proteins

The preferences of consumers for different flavours and aromas in wine are varied and may be explained by inherent factors such as cultural background, wine education and personal taste of the wine consumer. Wine flavour, as perceived in the mouth, includes aroma compounds released through the retronasal pathway, which are shaped by interactions with saliva. Saliva and wine interactions could provide an explanation as to why wine tasters express different preferences for wine. To test this hypothesis, 13 Western and 13 Chinese experienced wine tasters were recruited. Sensory evaluation was performed in formal surroundings to acquire free description-based and perceived sensory intensity data using the Pivot® Profile and continuous scale assessment, respectively. Participants' saliva samples were collected before the sensory evaluation and spiked into a wine sample to investigate the impact on the wine's volatile release using comprehensive two-dimensional gas chromatography-mass spectrometry (GC × GC-MS). Saliva samples were subjected to enzyme activity assays and protein composition profiling by Tandem Mass Tag (TMT) quantitative proteomics. The wine tasters showed differences in wine flavour perception, which was supported by the difference in wine volatile release resulting from the addition of saliva. The two groups of participants did not have significant differences in total salivary protein concentrations or the amounts of esterase and α-amylase. However, statistically significant variations in the concentrations of specific proteins (proline-rich proteins (PRPs) and lipocalin-1 (LCN-1); p < 0.01) were found between the two groups. Significant correlations between perceived intensities of wine attributes and concentrations of PRPs and LCN-1 were observed. These results indicate that the composition of proteins in saliva is a factor that influences wine perception and preference. Our results provide a biochemical basis for understanding preference for food based on interactions between aroma compounds and salivary proteins and could be used to suggest foods or beverages to particular cultural groups.

Development of a New Method for the Quantitative Analysis of Aroma Compounds Potentially Related to the Fruity Aroma of Red Wines

To determine the concentrations of aroma compounds involved in the fruity aroma of red wines, an analytical method was developed and optimized using liquid-liquid extraction and gas chromatography coupled to mass spectrometry (GC/MS). The aim was to reduce sample preparation and analysis time, with a single sample preparation and a single injection being needed to quantify 43 compounds. 19 esters, 13 monoterpenes, 5 C13-norisoprenoids, and 6 C6-aldehyde and alcohol compounds were quantified in 14 red wines made from different grape varieties grown in the Mediterranean basin. Samples were selected based on typical varietal aroma by a panel of experts, who produced 7 olfactory descriptors linked to desirable or non-desirable wine aromas. The instrumental analysis showed variations in concentrations of the quantified compounds among the wines. The wines described using positive fruity descriptors had higher mean total concentrations of esters, C6-alcohols, monoterpenes, and C13-norisoprenoids. Some non-ester compounds were positively correlated with the fruity descriptors. Sensory profile results obtained by a panel of 16 trained judges revealed that the addition of non-ester compounds (including 2 cyclic esters) to a red wine initially described as having cooked fruit aromas had a positive contribution to some fresh fruity notes. This study opens up new avenues for research on the potential involvement of non-ester compounds in the fruity expression of red wines.

The Impact of Fermentation Temperature and Cap Management on Selected Volatile Compounds and Temporal Sensory Characteristics of Grenache Wines from the Central Coast of California

Grenache wines from the Central Coast of California were subjected to different alcoholic fermentation temperature regimes (Cold, Cold/Hot, Hot) and cap management protocols, namely, punch down (PD), or no punch down (No PD), to determine the effect of these practices on the color, aroma, and the retronasal and mouthfeel sensory characteristics of the resulting wines. Descriptive analysis (n = 8, line scale rating 0-15) results indicated that the combination of a hot fermentation temperature and no punch downs led to a significantly higher intensity in perceived color saturation (7.89) and purple hue (8.62). A two-way analysis of variance (ANOVA) showed that cap management was significantly more impactful on the perception of orthonasal aromas than fermentation temperature. The reduction aroma was significantly higher in No PD wines (5.02) compared to PD wines (3.50), while rose and hot aromas had significantly higher intensity perception for PD wines (5.18, 6.80) than for No PD wines (6.80, 6.14). Conversely, analysis of selected volatile compounds indicated that fermentation temperature was more impactful than cap management regime. Cold/Hot wines had higher concentrations of important esters such as ethyl hexanoate (650 µg/L) and isoamyl acetate (992 µg/L). Cold wines had a higher concentration of β-damascenone (0.719 µg/L). TCATA evaluation (n = 8) indicated that Cold/Hot PD wines had a significantly higher citation proportion of fruit flavor (1.0) and velvet astringency perception (0.80) without significant reduction flavors. Finally, the present study represents a contribution with the main volatile compounds (e.g., β-damascenone and esters in the Cold and Cold/Hot fermented wines, respectively; hexanol in PD wines, which may be potentially responsible for a hot mouthfeel), and sensory characteristics (red fruit, tropical fruit, white pepper, and rose) of Grenache wines grown in the Mediterranean climate of the Central Coast of California.

Effect of Sequential Fermentation with Lachancea thermotolerans/S. cerevisiae on Aromatic and Flavonoid Profiles of Plavac Mali Wine

In this study, the effects of sequential fermentation of Lachancea thermotolerans/S. cerevisiae on the production of Plavac Mali wines were investigated in comparison with the commonly used inoculation of the commercial Saccharomyces cerevisiae strain and spontaneous fermentation. A total of 113 aroma compounds and 35 polyphenolic compounds were analyzed. Sequential inoculation resulted in a decrease in alcohol content and pH (up to 0.3% v/v and 0.12 units, respectively) and an increase in total acidity (0.6 g/L, expressed as tartaric acid). The wines produced by spontaneous fermentation exhibited the greatest diversity of volatile compounds and the highest concentration of C13 norisoprenoids, lactones, and other compounds. These wines exhibited maximum hydroxycinnamic acids, prodelphinidin monomer units, epigallocatechin, B1, B3, and B4 dimers, and total flavan-3-ols. Sequential inoculation decreased the content of the aromas and polyphenols in the wines. The practical significance of this procedure lies in the selective effect on aroma compounds, the decrease in green aromas, undetectable volatile phenols, and the decrease in bitter and astringent compounds such as gallic acid, flavan-3-ol monomers (catechin and epicatechin), and dimers (B1, B2, B3, and B4). This work demonstrates the potential of sequential and spontaneous fermentation to improve the aromatic characteristics and overall quality of Plavac Mali wines.

Sensory relevance of seven aroma compounds involved in unintended but potentially fraudulent aromatization of wine due to aroma carryover

Bottling regular wines following aromatized wines on the same filling lines bears the risk of unintentional aroma carryover, which has led to accusations of illegal aromatization. Obeying guidelines of good manufacturing practice, aroma carryover with no sensory relevance shall be considered as a technical unavoidable transfer having no legal consequences. To detect sensory relevance, odor activity values greater than one are proposed. Odor detection thresholds (OTs) were determined in water, model wine, and white wine for three lactones, α-ionone, ethyl 2-methylbutanoate, trans-cinnamaldehyde, and eugenol. Using different matrices OTs varied by factors of 2 for α-ionone and up to 23000 for ethyl 2-methylbutanoate. For α-ionone, being most prone for carryover, the three times higher OT of consumers did not trigger any preference for the aromatized wines, but rejection at 300 µg/L. Assessing α-ionone spiked wines by descriptive analysis, significant changes in sensory attributes only occurred at concentrations 10 times above OT.

Impact of the Closure Oxygen Transfer Rate on Volatile Compound Composition and Oxidation Aroma Intensity of Merlot and Cabernet Sauvignon Blend: A 10 Year Study

This study evaluated the impact of closure type on unoaked 100 %-Merlot, oak-aged 70%-Merlot/30%-Cabernet Sauvignon, and 30%-Merlot/70%-Cabernet Sauvignon during a 10 year period. Closures were microagglomerate corks, screw caps, and synthetics with the known oxygen transfer rate (OTR), ranging from 0.1 to 4.6 mg/y, including natural corks. Oxidation intensity perception, dissolved oxygen, sulfite, and 3-methyl-2,4-nonanedione (MND) were monitored on a regular basis. After 10 years of aging, additional aroma impact markers were evaluated (3-sulfanylhexan-1-ol, H₂S, DMS, methional, and phenylacetaldehyde). Low OTR levels (≤0.3 mg/y) delayed the oxidation of red wines in this long-term experiment. In addition, our results led us to hypothesize that the MND concentration in young wines might be linked with their ability to produce it during bottle aging that is with their aging potential. Finally, we found that the kinetic accumulation of MND in wines was first strongly impacted by its intrinsic composition and thereafter by the OTR_T0 of the stopper.

Characterization of a putative tropinone reductase from Tarenaya hassleriana with a broad substrate specificity

A novel short-chain alcohol dehydrogenase from Tarenaya hassleriana labeled as putative tropinone reductase was heterologously expressed in Escherichia coli. Purified recombinant protein had molecular weight of approximately 30 kDa on 12% sodium dodecyl sulfate-polyacrylamide gel electrophoresis. T. hassleriana tropinone reductase-like enzyme (ThTRL) had not detected oxidative activity. The optimum pH for enzyme activity of ThTRL was weakly acidic (pH 5.0). 50°C was the optimum temperature for ThTRL. The highest catalytic efficiency and substrate affinity for recombinant ThTRL were observed with (+)-camphorquinone (k_cat /K_m  = 814.3 s^-1  mM^-1 , K_m  = 44.25 μM). ThTRL exhibited a broad substrate specificity and reduced various carbonyl compounds, including small lipophilic aldehydes and ketones, terpene ketones, and their structural analogs.

Effects of Purified β-Glucosidases from Issatchenkia terricola, Pichia kudriavzevii, Metschnikowia pulcherrima on the Flavor Complexity and Typicality of Wines

The aim of this study was to investigate the effects of purified β-glucosidases from Issatchenkia terricola SLY-4, Pichia kudriavzevii F2-24, and Metschnikowia pulcherrima HX-13 (named as SLY-4E, F2-24E, and HX-13E, respectively) on the flavor complexity and typicality of wines. Cabernet Sauvignon wines were fermented by Saccharomycescerevisiae with the addition of SLY-4E, F2-24E, and HX-13E; the fermentation process and characteristics of wines were analyzed. The addition of SLY-4E, F2-24E, and HX-13E into must improved the contents of terpenes, higher alcohols, and esters, and decreased the contents of C6 compounds and fatty acids, which enhanced the fruity, floral, and taste aspects, reducing the unpleasant green of wines with no significant difference in their appearance. β-glucosidases from different yeast species produced different aroma compound profiles which presented different flavor and quality. F2-24EW had the best effect on flavor and quality of wine followed by SLY-4EW and HX-13EW. These research results can provide references for the use of β-glucosidases from non-Saccharomyces yeasts to improve the flavor complexity, typicality, and quality of wines.

Pilot-Scale Vinification of Cabernet Sauvignon Using Combined Lactiplantibacillus plantarum and Saccharomyces cerevisiae to Achieve Wine Acidification

Insufficient acidity in grape berries from warm climate regions has been exacerbated due to global warming, thereby becoming a major concern for winemaking. The wine lactic acid bacterium Lactiplantibacillus plantarum has potential to ameliorate wine acidity by producing lactic acid from hexose metabolism, but its impact on wine compositions and sensory outcomes is not well studied. Here, we evaluated acidification and fermentation performance of indigenous L. plantarum in two inoculation regimes (i.e., reverse inoculation and co-inoculation) by conducting pilot-scale vinification using Cabernet Sauvignon with low acidity. Important parameters of the bio-acidified wines, including fermentation kinetics, basic oenological parameters, volatile and sensory profile were compared to those in wines produced by single Saccharomyces cerevisiae with/without chemical acidification. Total titratable acidity in L. plantarum wines were either comparable or significantly higher compared to the chemical acidification control. Chemical profiling reviewed remarkable differences in certain organic acids and major volatile compounds, especially an up to a five-fold, six-fold, and nine-fold increase in lactic acid, ethyl lactate and isoamyl lactate, respectively. Changes in chemical compositions of the bio-acidified wines resulted in differentiated sensory perception compared to the control wines. Except having higher scores for “wine acidity”, the flavour profile of the bio-acidified wines was shifted towards “jammy fruit” and “butter” aromas. Together, these findings highlighted the applicability of using L. plantarum to induce biological acidification along with modulation of wine flavour.

Adaptive Laboratory Evolution of Yeasts for Aroma Compound Production

Aroma compounds are important in the food and beverage industry, as they contribute to the quality of fermented products. Yeasts produce several aroma compounds during fermentation. In recent decades, production of many aroma compounds by yeasts obtained through adaptive laboratory evolution has become prevalent, due to consumer demand for yeast strains in the industry. This review presents general aspects of yeast, aroma production and adaptive laboratory evolution and focuses on the recent advances of yeast strains obtained by adaptive laboratory evolution to enhance the production of aroma compounds.

Microbial succession and exploration of higher alcohols-producing core bacteria in northern Huangjiu fermentation

Higher alcohols (HAs) are abundant compounds that provide important flavors in Huangjiu, but they also cause hangover. Previous studies have shown the production of HAs to be related to yeast, but the correlations between HAs and other microorganisms are rarely reported. In this study, we detected changes in levels of HAs and microbial dynamics during the Huangjiu fermentation process. Relationships were characterized using Pearson’s correlation coefficient. The functional core HA-producing bacteria were selected by bidirectional orthogonal partial least squares (O2PLS). The result showed that 2-methyl-1-propanol, phenethyl alcohol and 3-methyl-1-butanol were the principle HAs present at high levels. Lactococcus and Saccharomyces were predominant at the genus level of bacteria and fungi, respectively. A total of 684 correlations between HAs and microorganisms were established. Five genera were screened as functional core HA-producing bacteria. Our findings might provide some new inspiration for controlling the content of HAs, enhancing international prestige and market expansion of Huangjiu.

Impact of Lachancea thermotolerans on Chemical Composition and Sensory Profiles of Viognier Wines

Viognier is a warm climate grape variety prone to loss of acidity and accumulation of excessive sugars. The yeast Lachancea thermotolerans can improve the stability and balance of such wines due to the partial conversion of sugars to lactic acid during alcoholic fermentation. This study compared the performance of five L. thermotolerans strains in co-inoculations and sequential inoculations with Saccharomyces cerevisiae in high sugar/pH Viognier fermentations. The results highlighted the dichotomy between the non-acidified and the bio-acidified L. thermotolerans treatments, with either comparable or up to 0.5 units lower pH relative to the S. cerevisiae control. Significant differences were detected in a range of flavour-active yeast volatile metabolites. The perceived acidity mirrored the modulations in wine pH/TA, as confirmed via “Rate-All-That-Apply” sensory analysis. Despite major variations in the volatile composition and acidity alike, the varietal aromatic expression (i.e., stone fruit aroma/flavour) remained conserved between the treatments.

Assessing the contribution of odor-active compounds in icewine considering odor mixture-induced interactions through gas chromatography-olfactometry and Olfactoscan

The sensory impact of odor-active compounds on icewine aroma could be influenced by perceptual interactions with other odor-active compounds. The aim of this study was to establish an approach to evaluate the contribution of odor-active compounds found in icewine considering mixture-induced perceptual interactions. By comparing the impact of key odorants detected in icewine following a gas chromatography-olfactometry approach with an Olfactoscan-based methodology using a background odor of icewine, 69 odor zones were detected, and their related compounds were further identified. The results revealed that icewine background odor could exert odor masking or enhancement on key odorants when they are considered in the complex wine aroma buffer. Several compounds can induce qualitative changes in the overall wine aroma. This study underlined the efficiency of Olfactoscan-like approaches to screen for the real impact of key odorants and to pinpoint specific compounds that could be highly influential once embedded in the aroma buffer.

Impact of Different Oak Chips’ Aging on the Volatile Compounds and Sensory Characteristics of Vitis amurensis Wines

In this work, different oak chips were used to age Vitis amurensis wine, and the effects on sensory properties were observed. Twenty-one different oak chips were added to a one-year-old wine made by a traditional technique. The wine was aged for 6 months before analysis by CIELab for color parameters, GC–MS for volatile compounds, and electronic tongue and a tasting panel for sensory properties. The results showed that the addition of any tested oak chip could significantly strengthen the wine’s red color. Among 61 volatile compounds, alcohols presented the highest concentrations (873 to 1401 mg/L), followed by esters (568 to 1039 mg/L) and organic acids (157 to 435 mg/L), while aldehydes and volatile phenols occurred at low concentrations. Different oak species with different toasting levels could affect, to varying degrees, the concentrations of esters, alcohols, and volatile phenols, but to a lesser extent those of aldehydes. Sensory analysis by a tasting panel indicated that non- and moderately roasted oak chips gave the wines higher scores than those with heavy toasting levels. The major mouthfeel descriptors determined by electronic tongue were in good agreement with those from the tasting panel.

Insight into the Aroma Profile and Sensory Characteristics of ‘Prokupac’ Red Wine Aromatised with Medicinal Herbs

Autochthones grape variety of ‘Prokupac’ (Vitis vinifera L.) is being increasingly cultivated in the Republic of Serbia and is one of the predominant varieties in the vineyards of southern Serbia. ‘Prokupac’ grapes are used to produce red wine with specific and distinctive varietal aromatic characteristics. Medicinal herbs can be effectively combined in alcoholic beverages. The aim of this study was to evaluate the effect of medicinal herbs on the aroma profile and sensory characteristics of ‘Prokupac’ red wine. The analysis of the aromatic composition was conducted on ‘Prokupac’ wine (control) and ‘Prokupac’ wine aromatised with selected medicinal herbs: anise (Pimpinella anisum L.), cinnamon (Cinnamomum verum J. Presl.), wormwood (Artemisia absinthium L.) and licorice (Glycyrrhiza glabra L.). The analysis of volatile aromatic compounds in the wines, performed by the gas chromatography-mass spectrometry (GC/MS) method, identified 48 compounds that were classified in the following groups: alcohols, aldehydes, ketones, acids, ethyl esters and terpenes. Sensory analysis of wines was performed including visual, olfactory, gustatory and gustatory-olfactory perceptions. Terpenes were not identified in the ‘Prokupac’ control wine, while the highest content of all identified aromatic compounds was found in wines aromatised with anise, wormwood and cinnamon. The results indicated that selected medicinal herbs affected the composition and content of volatile aromatic compounds, as well as the sensory characteristics of analyzed wines. The unique aroma profile and pleasant taste of the wine aromatised with cinnamon contributed to its differentiation from other wines, and classification as very good wine.

Use of Non-Saccharomyces Yeast Co-Fermentation with Saccharomyces cerevisiae to Improve the Polyphenol and Volatile Aroma Compound Contents in Nanfeng Tangerine Wines

This study attempted to improve the polyphenol and volatile aroma compound contents in Nanfeng tangerine wines using non-Saccharomyces yeast and Saccharomyces cerevisiae. The effects of fermentation with pure cultures of Candida ethanolica, Hanseniaspora guilliermondii and Hanseniaspora thailandica, as well as in sequential and mixed inoculations (1:1 or 1:100 ratio) with S. cerevisiae in Nanfeng tangerine wines were evaluated. C. ethanolica was found to produce the most polyphenols (138.78 mg/L) during pure fermentation, while H. guilliermondii produced the most volatile aroma compounds (442.34 mg/L). The polyphenol content produced during sequential fermentation with S. cerevisiae and H. guilliermondii (140.24 mg/L) or C. ethanolica (140.21 mg/L) was significantly higher than other co-fermentations. Meanwhile, the volatile aroma compounds were found to be more abundant in S. cerevisiae/H. guilliermondii mixed fermentation (1:1 ratio) (588.35 mg/L) or S. cerevisiae/H. guilliermondii sequential fermentation (549.31 mg/L). Thus, S. cerevisiae/H. guilliermondii sequential fermentation could considerably boost the polyphenol and volatile aroma component contents in Nanfeng tangerine wines. The findings of this study can be used to drive strategies to increase the polyphenol content and sensory quality of tangerine wines and provide a reference for selecting the co-fermentation styles for non-Saccharomyces yeast and S. cerevisiae in fruit wine fermentation.

Characterization of Six Lactones in Cheddar Cheese and Their Sensory Interactions Studied by Odor Activity Values and Feller's Additive Model

To evaluate the perceptual interactions among important lactone compounds in cheddar cheese, a molecular-level flavoromic approach, in combination with perceptual interaction analysis, was applied. Six aroma-active lactones with flavor dilution factors ranging from 4 to 128 were identified in three cheddar samples by gas chromatography-olfactometry-mass spectrometry. Odor thresholds of these six aroma-active lactones were determined with values from 7.16 to 30.03 μg/kg using a deodorized cheddar matrix. The odor activity value approach demonstrated complicated interactions among the 15 binary mixtures of six important lactones, including additive, synergistic, or masking effects. Based on partial differential odor intensities, each lactone with similar degrees of perceptual interactions in binary mixtures tends to present synergistic or masking effects. Owing to the difference in the chemical structure and mixture composition, δ-dodecalactone and γ-dodecalactone caused promotive and inhibitory effects on the expression of lactone fruity aroma, respectively.

Comparison of Ultrasound Type and Working Parameters on the Reduction of Four Higher Alcohols and the Main Phenolic Compounds

In this paper, studies were conducted by a series of single-factor experiments to investigate the effects of ultrasound types and working parameters on the higher alcohols (HA), phenolic compounds, and color properties of red wine, so as to highlight the importance of the comprehensive consideration on its application. The results indicate that ultrasound devices and working parameters do have some definite influences on the HA of wine; moreover, the ultrasound bath (SB-500DTY) is better than the SCIENTZ-950E and the KQ-300VDE. With the SB-500DTY employed to further investigate its effects on phenols and color properties other than on HA, unexpectedly, some variations of color parameters are opposite to the results ever obtained from other ultrasound conditions. In summary, all these results suggest that both the ultrasound type and parameters should be fully considered or neutralized so as to have a comprehensive evaluation about its application, instead of some contradictory results.

Mitigating Grapevine Red Blotch Virus Impact on Final Wine Composition

Grapevine red blotch virus (GRBV), the causative agent of red blotch disease, causes significant decreases in sugar and anthocyanin accumulation in grapes, suggesting a delay in ripening events. Two mitigation strategies were investigated to alleviate the impact of GRBV on wine composition. Wines were made from Cabernet Sauvignon (CS) (Vitis vinifera) grapevines, grafted onto 110R and 420A rootstocks, in 2016 and 2017. A delayed harvest and chaptalization of diseased grapes were employed to decrease chemical and sensory impacts on wines caused by GRBV. Extending the ripening of the diseased fruit produced wines that were overall higher in aroma compounds such as esters and terpenes and alcohol-related (hot and alcohol) sensory attributes compared to wines made from diseased fruit harvested at the same time as healthy fruit. In 2016 only, a longer hangtime of GRBV infected fruit resulted in wines with increased anthocyanin concentrations compared to wines made from GRBV diseased fruit that was harvested at the same time as healthy fruit. Chaptalization of the diseased grapes in 2017 produced wines chemically more similar to wines made from healthy fruit. However, this was not supported by sensory analysis, potentially due to high alcohol content masking aroma characteristics.

Toward a Better Understanding of Perceptive Interactions between Volatile and Nonvolatile Compounds: The Case of Proanthocyanidic Tannins and Red Wine Fruity Esters-Methodological, Sensory, and Physicochemical Approaches

The impact of commercial proanthocyanidic tannins on fruity pool of esters, representing the fruitiness of Bordeaux red wines, was assessed in model solutions. It was shown that the presence of tannins in the matrix significantly attenuated perception of fruity notes (p = 0.013). Physicochemical analysis demonstrated that the presence of proanthocyanidic tannins in dilute alcohol solution resulted in a decrease in ester partition coefficients and thus in a decrease in ester contents in the headspace (p < 0.05). This fact highlighted the changes that may occur in wines at a pre-sensory level, prior to sensory evaluation. Finally, a new sensory tool was developed, consisting in an ISO glass containing two compartments separated by a glass wall, providing a way to compare perceived odors according to whether or not the components of the odor mixtures were actually mixed in solution (p < 0.001). This new tool was used to demonstrate the impact and the only implication of pre-sensory level in the consequences of physical mixture between proanthocyanidic tannins and esters on their odor perception.

Volatile and Non-Volatile Characterization of White and Rosé Wines from Different Spanish Protected Designations of Origin

The quality of wines has often been associated with their geographical area of production, as well as the grape variety used in their elaboration. Many research studies have been carried out to characterize and differentiate between red wines labeled with Protected Designation of Origin (PDO) from different geographical areas, but very few have been carried out on white and rosé wines. The objective of this work was to characterize white and rosé PDO wines from different geographical areas of Spain very close to each other elaborated with different grape varieties and select the variables that most contribute to their differentiation. Analysis of variance (ANOVA) and principal component analysis (PCA) were used as statistical methods. The ethanol content was the nonvolatile variable that most contributed to differentiating between some of the white and rosé wines according to their PDO. The white wines from RD (Ribera del Duero) and BI (Bierzo) were characterized by a high terpenic content (floral notes) while the wines from RU (Rueda), TO (Toro) and CI (Cigales)by a high content of ethyl esters and alcohol acetates (fruity aromas). The rosé wines elaborated with the Mencía grape variety from BI were characterized by their highest polysaccharidic content, which could have a positive sensory effect on the mouthfeel. The rosé wines from CI were characterized by their volatile profile complexity, having the highest content of volatile compounds from the oak wood, terpenes and C6 alcohols which provide pleasant woody, floral and herbaceous aromas. On the contrary, the RD wines were richest in alcohol acetates responsible for fruity aromas.

Biosyntheses of geranic acid and citronellic acid from monoterpene alcohols by Saccharomyces cerevisiae

Geraniol is one of the important aromatic ingredients in alcoholic beverages. Bioconversions of geraniol to other terpenoids and genes involved in the oxidation of geraniol were investigated. Geranic acid and citronellic acid were detected in yeast culture, where geraniol or nerol was added. Addition of citral, a mixture of geranial and neral, resulted in the production of geranic acid and citronellic acid, whereas the addition of citral or citronellal resulted in the production of citronellic acid, suggesting that citronellic acid might be produced through the conversion of citral to citronellal followed by the oxidation of citronellal. Consumption of geraniol and production of geranic acid, citronellic acid, and citronellol were affected in adh1Δ, adh3Δ, adh4Δ, and sfa1Δ yeast strains, which possess single deletion of a gene encoding alcohol dehydrogenase. This is the first report of the bioconversion of monoterpene alcohols, geraniol and nerol, to geranic acid and citronellic acid in yeast culture.

Determination and comparison of flavor (retronasal) threshold values of 19 flavor compounds in Baijiu

Nineteen compounds, including ten esters, six acids, and three alcohols, were characterized and considered as significant tastants and aromas in Baijiu (Chinese Liquor). The flavor (retronasal) threshold values (FTVs) of these 19 compounds were determined by the 10 samples test method in hydroalcoholic solutions (46% v/v in ethanol). The FTVs of the compounds were calculated based on the best estimate threshold method. All the FTVs determined by the professional Chinese Baijiu tasters were lower than those by the nonprofessional tasters. For instance, the detection (2.31 mg/kg) and recognition (11.74 mg/kg) values of ethyl hexanoate determined by the nonprofessional group were higher than the respectively corresponding values 0.44 and 3.80 mg/kg determined by the professional group. All of the odor activity values (OAVs) of ethyl valerate (OAV: 1176.00 to 2321.17), ethyl octanoate (OAV: 6841.20 to 7851.60), and 1-butanol (OAV: 26.78 to 39.72) in Gujinggong Baijiu were more than 10-fold larger than their dose-over-threshold values (DoTs), for which the DoTs of ethyl valerate, ethyl octanoate, and 1-butanol were 92.84 to 183.25, 180.03 to 206.62, 1.18 to 1.75, respectively. On the contrary, the OAVs of ethyl heptanoate (OAV: 3.60 to 5.70) and isoamyl alcohol (OAV: 1.18 to 1.57) were lower than their corresponding DoTs at 152.62 to 241.63 and 12.26 to 16.41. The results demonstrated that it is necessary to consider and compare their DoTs and OAVs simultaneously on evaluating the contribution of flavor compounds in Baijiu. PRACTICAL APPLICATION: Sensory evaluation of threshold values of various flavor compounds could be significantly affected by their existing matrix. Most of the published results of the flavor threshold value of compounds were determined from the matrix such as beer, whiskey, red wine, rather than Chinese Baijiu. The results of this work not only could provide valuable information for flavor studies of Chinese Baijiu but also give useful information for the Baijiu industry to quality control.

Volatile-Based Prediction of Sauvignon Blanc Quality Gradings with Static Headspace-Gas Chromatography-Ion Mobility Spectrometry (SHS-GC-IMS) and Interpretable Machine Learning Techniques

The analytical scope of static headspace-gas chromatography-ion mobility spectrometry (SHS-GC-IMS) was applied to wine aroma analysis for the first time. The method parameters were first fine-tuned to achieve optimal analytical results, before the method stability was demonstrated, in terms of repeatability and reproducibility. Succinct qualitative identification of compounds was also realized, with the identification of several volatiles that have seldom been described previously in Sauvignon Blanc wine, such as methyl acetate, ethyl formate, and amyl acetate. Using the SHS-GC-IMS data in an untargeted approach, computer modeling of large datasets was applied to link aroma chemistry via prediction models to wine sensory quality gradings. Six machine learning models were compared, and artificial neural network (ANN) returned the most promising performance with a prediction accuracy of 95.4%. Despite its inherent complexity, the ANN model offered intriguing insights on the influential volatiles that correlated well with higher and lower sensory gradings. These findings could, in the future, guide winemakers in establishing wine quality, particularly during blending operations prior to bottling.

Concentrate Apple Juice Industry: Aroma and Pomace Valuation as Food Ingredients

Apple concentrate juice industry generates a flavored coproduct (apple aroma) recovered in the evaporation process, which is poorly valuated due to the lack of chemical characterization and standardization. In this study, industry apple aroma was characterized, allowing for the identification of 37 compounds, the majority esters (20), alcohols (7), and aldehydes (4). The storage temperature did not affect its volatile composition. Five key compounds were selected and monitored for 10 months of storage, and also compared with other three productions of another season allowing for observation of the same Aroma Index. Apple pomace was also used to produce a hydrodistillate. Contrary to the apple aroma, apple pomace hydrodistillate was unpleasant, reflected in a different volatile composition. Although no additional aroma fraction could be obtained from this wet byproduct, when dried, apple pomace presented 15 volatile compounds with toasted, caramel, sweet, and green notes. The infusions prepared with the dried apple pomace exhibited 25 volatile compounds with a very pleasant (fruity, apple-like, citrus, and spicy notes) and intense aroma. The addition of sugar changed the volatile profile, providing a less intense flavor, with almond, caramel, and sweet notes. These results show that apple aroma and pomace are high-quality flavoring agents with high potential of valuation as food ingredients.

Chemical, Physical, and Sensory Effects of the Use of Bentonite at Different Stages of the Production of Traditional Sparkling Wines

The addition of bentonite to wine to eliminate unstable haze-forming proteins and as a riddling adjuvant in the remuage is not selective, and other important molecules are lost in this process. The moment of the addition of bentonite is a key factor. Volatile profile (SPME-GC-MS), foam characteristics (Mosalux method), and sensory analyses were performed to study the effect of the distribution of the dosage of bentonite for stabilization of the wine among the addition on the base wine before the tirage (50%, 75%, and 100% bentonite dosage) and during the tirage (addition of the remaining dosage for each case). Results showed that the addition of 50% of the bentonite to the base wine (before the tirage) resulted in sparkling wines with the lowest quantity of volatile compounds, mainly esters and norisoprenoids. No significant differences were found among the sparkling wines after 9 months of aging in relation to foam properties measured by Mosalux, although higher foamability and crown’s persistence were perceived in the sparkling wines with the addition of 75% and 100% of the bentonite dosage in sensory trials. The results of this study suggested that the amount of bentonite added as a fining agent in the tirage had greater effects than during the addition of this agent in the base wine.

Evaluation of the Perceptual Interactions Between Higher Alcohols and Off-Odor Acids in Laimao Baijiu by σ-τ Plot and Partition Coefficient

The volatile compounds in three Laimao baijius ("Chuanchenglan, CCL", "Hongyu, HY", and "Zhencang, ZC") were comprehensively analyzed by gas chromatography-olfactometry and gas chromatography-mass spectrometry. The results demonstrated that 44, 42, and 42 compounds with flavor dilution factors ≥ 16 and odor activity values ≥ 1 were, respectively, identified as important odorants. Additionally, the perceptual interactions of 6 higher alcohols and 3 off-odor acids were evaluated by σ-τ plot, and the partition coefficient was calculated to explain the release of odorants in the matrix. The interactions indicated that adding a high concentration of 1-propanol or 2-phenylethanol to the matrix could mask the sweaty note of 3-methylbutyric acid. The partition coefficients explained that high concentrations of 1-propanol and 2-phenylethanol were able to significantly inhibit the release of 3-methylbutyric acid when the phase ratio was relatively large, and the effect of 1-propanol on it was higher than that of 2-phenylethanol.