Key Odorants Research Articles

A strategy to maintain the organoleptic quality of flavor-β-cyclodextrin inclusion complexes: Characteristics aroma reconstruction of Osmanthus absolute

The proportion of odorants has a key effect on the odor/flavor profile of perfumes or food products. However, direct encapsulation changes the odorant release characteristics, resulting in corresponding variations in their organoleptic qualities. In this study, nine key odorants (KOs) of Osmanthus absolute (OA) were identified for the aroma reconstruction of OA. Inclusion complexes of β-cyclodextrin (β-CD) with KOs (KO-β-CDs) were obtained via co-precipitation, the loading of KOs in β-CD was varied from 34.86 to 108.88 mg/g. Based on the aroma release behavior analyses, main aroma characteristics of OA were reconstructed from the KO-β-CDs via replication of the headspace KO distributions of OA. Aroma profile evaluation validated the effectiveness of aroma reconstruction. Besides, the release characteristics of directly encapsulated OA (OA-β-CD) and OA were found to significantly differ. For example, linalool oxide furanoid contributed greater than 20% of the total KOs in the headspace of OA, contributed only 8.89% in the headspace of the OA-β-CD. Further, the aroma intensity of the five main descriptors was reduced to different degrees. The KO-β-CDs mixture resembles the odor profile of OA to a greater degree than OA-β-CD. Our methodology provides a route to maintain the organoleptic quality of flavors in β-CD inclusion complexes.

Glucosinolates or erucic acid, which one contributes more to volatile flavor of fragrant rapeseed oil?

This study aims to investigate the effect of three rapeseed varieties with different erucic acid (EA) and glucosinolates (GLSs) content, and different degumming methods on the volatile flavor profiles of fragrant rapeseed oil (FRO). A total of 171 volatile compounds were identified by headspace solid-phase microextraction combine with gas chromatography-mass spectrometry (HS-SPME/GC–MS), and 87 compounds were identified as key odorants owing to their relative odor activity values (ROAV) ≥ 1. Methyl furfuryl disulfide was identified in rapeseed oil for the first time, with highest ROAVs (up to 26805.46). The volatile flavor profile of rapeseed oil was affected by GLSs content to a certain extent rather than EA content. Rapeseed varieties with low-EA and high-GLSs are suitable to produce FRO. Silicon dioxide adsorbing was an effective alternative method to water degumming in FRO. This work provided a new idea for selection of raw materials and degumming methods in FRO production.

Characterization of the key odorants and investigation of the effects of drying methods on the aroma, taste, color and volatile profiles of the fruit of Clausena anisum-olens (Blanco) Merr.

With a distinctive aroma, Shanhuangpi (SHP), the fruit of the plant Clausena anisum-olens (Blanco) Merr., has been newly developed as a commercial fruit resource. The fresh fruit deteriorates rapidly due to its high respiration and metabolism. Therefore, an effective drying process is urgently needed for its preservation. The influence of two commonly used drying methods for plant materials, i.e., vacuum freeze-drying (VFD) and hot air drying (HAD) was evaluated on the aroma, taste, color, and volatile profiles of this fruit. The results indicated that the VFD process well retained the color and volatile composition of the fresh fruit but produced extra graininess and sticky mouthfeel. Alternatively, the HAD process offered a shorter drying time, kept a more palatable sour/sweet ratio, but created a darker brown color and shrinking texture of the fruit. The volatile components were enriched by the micro-chamber/thermal extractor (μ-CTE) and 38 compounds were identified with gas chromatography-mass spectrometry. Sixteen odor-active compounds (detection frequency ≥4) were detected by gas chromatography–olfactometry. Results obtained in this study can be served as a reference for the evaluation and further development of SHP.

Mushroom-Mediated Reductive Bioconversion of Aldehyde-Rich Essential Oils for Aroma Alteration: A Rose-like Floral Bioflavor from Citronella Oil.

The bioflavors are of high demand in food and beverage industries. The current study identified reductive processes mediated by mushroom species to alter the aroma of aldehyde-rich essential oils in the submerged culture. Neofomitella polyzonata, a polypore mushroom, reduced citronellal and citral in the citronella oil into corresponding alcohols that altered the oil aroma, creating a new bioflavor. The screening with 43 aldehydes showed its broad substrate scope within aromatic and linear aldehydes, yet influenced by the electronic and steric factors. Under an optimized condition, it efficiently converted up to 1.5 g/L citrusy and sharp citronella oil into a terpene alcohol-rich (citronellol and geraniol) floral, sweet, fresh, and rosy oily product within 12 h. The preparative-scale fermentation in the shake flask followed by distillation, an organic solvent-free downstream process, furnished the product in 87.2% w/w yield. Detailed sensory analyses and volatile chemo-profiling established the uniqueness in the product aroma and identified citronellol and geraniol as the key odorants. The chemometric analysis found best compositional similarity of this product with Damask or Turkish rose oils. The preference test for the water flavored with the fermented product (0.001-0.005% v/v) indicated its potential as a rosy bioflavor for the beverages.

Characterization of key odor-active compounds in high quality high-salt liquid-state soy sauce

Solid-phase microextraction and liquid–liquid extraction with gas chromatography– olfactometry–mass spectrometry (GC–O–MS) were used to analyze four award-winning high-salt liquid-state soy sauces (HLS). In this study, 110 volatile odor compounds were detected using GC–O–MS. Twenty key odor-active compounds with a flavor dilution factor ≥ 1024 were identified through aroma extract dilution analysis(AEDA), of which 11 compounds had odor activity values > 1; these were methional, 4-hydroxy-2,5-dimethyl-3(2H)-furanone (HDMF), guaiacol, 4-hydroxy-2(or 5)-methyl-5(or 2)-ethyl-3(2 H)-furanone (HEMF), 1-hydroxy-2-propanone, 3-hydroxy-4,5-dimethyl-2(5H)-furanone, 2-ethyl-6-methylpyrazine, 3-methyl-1-butanol, 2,6-dimethylpyrazine, ethyl benzoate, and 4-ethylguaiacol. Sensory evaluation showed that roasted, cooked potato-like, seasoning-like, and smoky odors were the main odor characteristics in the award-winning HLS. Electronic nose analysis indicated that the odor characteristics of the four samples were significantly different and could be distinguished from each other. This study helps to understand and explore the odor characteristics and key odor components of the award-winning HLS.

Characterization of odors and volatile organic compounds changes to recycled high-density polyethylene through mechanical recycling

The application of post-consumer recycled (PCR) plastics is gaining growing attention, yet, the residual odor of recycled plastics hinders its application. In current study, electronic nose (E-nose), headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS), and headspace-gas chromatography-mass spectrometry (HS-GC–MS) combined with multiple chemometrics methods were analyzed to obtain different information of VOCs in rHDPE. In the meantime, the potential influence of the re-granulation process on VOCs was investigated. Relative odor activity values (ROAV) was applied to distinguish characteristic odors description of HDPE pellets in different manufacturers. Results showed that the established fingerprinting of VOCs based on HS-GC-IMS could provide an effective means for rapidly identifying rHDPE plastics. The more substantial amounts of VOCs in rHDPE flakes and pellets are terpenes and aliphatic hydrocarbons. Although the re-granulation process effectively removed most of the VOCs remaining in the washing process, acids, aromatic hydrocarbons, and terpenes were potentially residual in the rHDPE pellets. It was also revealed that terpenes and acids were the volatile odor compounds in most rHDPE pellets. Both d-limonene and octanal are the main key compounds of rHDPE pellets because of their maximum contribution to the overall odor, and together with other key odor compounds with similar odor, form the characteristic odor of citrus, sweet, and floral.

Malodorous volatile organic compounds (MVOCs) formation after dewatering of wastewater sludge: Correlation with the extracellular polymeric substances (EPS) and microbial communities

Malodorous volatile organic compounds (MVOCs) are often the key odorants in determining sludge odor character and odor impact. However, the emission characterization and generation mechanisms of MVOCs from various dewatered sludge have not been sufficiently understood partly due to the diverse and complex composition and low concentration of odorants. In this study, waste activated sludge (WAS) was collected to examine the variation of MVOC emission from sludge after different dewatering treatment in lab-scale trials. The MVOCs were measured using the electronic nose (eNose), headspace gas chromatography-coupled ion mobility spectrometry (HS-GC-IMS), and headspace solid-phase microextraction gas chromatography–mass spectrometry (HS-SPME-GC–MS). The results showed that centrifugation treatment promoted the generation of various odorous volatiles. The identified key odorants included dimethyl sulfide (DMS), dimethyl disulfide (DMDS), dimethyl trisulfide (DMTS), geosmin, and p-cresol according to their odor activity values (OAVs). The effects of the enhanced dewatering on volatile production were greater than thickening, however, the key odorants of dewatered sludge using gravity thickening varied more greatly than sludges from centrifuge thickening. The distribution of extracellular polymeric substances (EPS) and variation of microbial community showed correlations with the production of key odorants. Tryptophan-like substances in the inner layer of EPS (LB-EPS and TB-EPS) were better correlated with the key odorants. The bound EPS released by centrifugation may play the role of precursor for odorous microbial volatiles. According to the predicted functions of differential microbial genera, Desulfobulbus (Desulfobacterota), Gordonia (Actinobacteriota), and Hyphomicrobium (Proteobacteria) were associated with the production of DMS, DMDS, and DMTS, while Gordonia and Hyphomicrobium were related to p-cresol production.

Metabolomics investigation on the volatile and non-volatile composition in enzymatic hydrolysates of Pacific oyster (Crassostrea gigas)

To investigate the differences of volatile and non-volatile metabolites between oyster enzymatic hydrolysates and boiling concentrates, molecular sensory analysis and untargeted metabolomics were employed. “Grassy,” “fruity,” “oily/fatty,” “fishy,” and “metallic” were identified as sensory attributes used to evaluate different processed oyster homogenates. Sixty-nine and 42 volatiles were identified by gas chromatography–ion mobility spectrometry and gas chromatography–mass spectrometry, respectively. Pentanal, 1-penten-3-ol, hexanal, (E)-2-pentenal, heptanal, (E)-2-hexenal, 4-octanone, (E)-4-heptenal, 3-octanone, octanal, nonanal, 1-octen-3-ol, benzaldehyde, (E)-2-nonenal, and (E, Z)-2,6-nonadienal were detected as the key odorants (OAV > 1) after enzymatic hydrolysis. Hexanal, (E)-4-heptenal, and (E)-2-pentenal were significantly associated with off-odor, and 177 differential metabolites were classified. Aspartate, glutamine, alanine, and arginine were the key precursors affecting the flavor profile. Linking sensory descriptors to volatile and nonvolatile components of different processed oyster homogenates will provide information for the process and quality improvement of oyster products.

Insights into the key quality components in Se-Enriched green tea and their relationship with Selenium

Selenium-enriched green tea (Se-GT) is of increasing interest because of its health benefits, but its quality components obtained limited research. In this study, Enshi Se-enriched green tea (ESST, high-Se green tea), Pingli Se-enriched green tea (PLST, low-Se green tea), and Ziyang green tea (ZYGT, common green tea) were subjected to sensory evaluation, chemical analysis, and aroma profiling. Chemical profiles in Se-GT were consistent with the taste attributes of the sensory analysis. 9 volatiles were identified as key odorants of Se-GT based on multivariate analysis. Correlations between Se and quality components were further assessed and highly Se-related compounds contents in these three tea samples were compared. The results showed that most amino acids and non-gallated catechins were highly negatively correlated with Se, while gallated catechins exhibited strong positive correlation with Se. And there were strong and significant associations between the key aroma compounds and Se. Moreover, 11 differential markers were found between Se-GTs and common green tea, including catechin, serine, glycine, threonine, l-theanine, alanine, valine, isoleucine, leucine, histidine, and lysine. These findings provide great potential for quality evaluation of Se-GT.

Characterization of stale odor in green tea formed during storage: Unraveling improvements arising from reprocessing by baking

Changes in key odorants and aroma profiles of three types of green tea during storage and after baking treatment were determined using headspace solid-phase microextraction–gas chromatography–mass spectrometry/olfactometry, odor activity value (OAV) and orthogonal partial least-squares discriminant analysis. As the stale odor developed during storage, the content of aldehydes decreased, whereas the contents of ketones and heterocycles (furans, pyrroles, etc.) increased. Key odorants, including (E,E)-2,4-heptadienal, α-terpineol, (E,E)-2,4-nonadienal and (E,E)-2,4-decadienal, appeared to be mainly responsible for the stale odor. After baking treatment, the stale odor was significantly improved, the contents of aldehydes and heterocycles were significantly increased and the content of alcohols was significantly decreased. Of these, 2-pentylfuran, hexanal, nonanal and limonene, which increased after baking, contribute the green, fruity and roasted aromas of green tea, because of their high OAVs, aroma intensities and variable importance in projection values. This study has improved understanding of the chemical changes resulting in stale odor development in green tea during storage and improvements arising from baking treatment, as well as providing a theoretical basis for the improvement of storage conditions and green tea flavor.

Identification of key odor compounds in the burnt smell of upper tobacco leaves through the molecular sensory science technique

Identification of key odor compounds in the burnt smell of upper tobacco leaves through the molecular sensory science technique

Identification of the key off-flavor odorants for undesirable spoiled odor in thermally sterilized fermented soymilk

Spoiled odors are a problem in thermally sterilized fermented soymilk. This study aims to clarify production conditions and key odorants of spoiled odors. The sensory evaluation showed that thermal sterilization caused a decrease in the sensory intensity of yogurt and fruity odors while significantly increasing undesirable aromas including beany, acidic, cooked-beans and spoiled odors. The spoiled odors increased with increasing acidity and heating temperatures. The strongest spoiled odor was observed in fermented soymilk at titratable acidity of 5.4 g/kg, sterilized at 90 °C. Apart from common volatiles that were inherent in soymilk and generated from lactic fermentation, 2-methyltetrahydrothiophen-3-one was found for the first time in soybean foods and was found to cause the spoiled odor. 44 volatiles found in thermally sterilized fermented soymilk were jointly formed its flavor wheel. This study provides important theoretical support for solving the problem of spoiled odor restricting the popularization of plant-based fermented soymilk.

The critical roles of α-amylase and amyloglucosidase in improving the quality of black waxy corn beverages: Special attentions to the color and flavor

To preserve the nutrients while maximizing the value of black waxy corn, beverage is the most promising manufacturing product. However, the poor stability and bland flavor profile are significant issues limiting its popularization. This study, firstly profiled the anthocyanidins of black waxy corn and the effects of α-amylase and amyloglucosidase treatments on the anthocyanidin levels, color properties, and flavor qualities were systematically studied. A total of 5 anthocyanidins and 11 anthocyanins were identified. The concentration of cyanidin, petunidin, peonidin, pelargonidin, and malvidin in liquefied liquids (YHY) and saccharified liquids (THY) were significantly increased by 55.46% and 56.62% after α-amylase and amyloglucosidase treatments. The enzymatic hydrolysis was found to enrich the volatile profile. The relative odor activity value and multivariate statistical analyses further suggested isoamyl acetate, benzaldehyde, 2-nonenal, 2,4-decadienal, dodecanal, 2-buten-1-one, 3-buten-2-one, and dimethyl trisulfide as key odorants to discriminate black waxy corn beverages produced by α-amylase or amyloglucosidase.

Insights into the Key Odorants in Large-Leaf Yellow Tea (Camellia sinensis) by Application of the Sensomics Approach

Large-leaf yellow tea (LYT) is a yellow tea product with a specific aroma characteristic and is enjoyed with increasing enthusiasm in China. However, its key odorants are still unknown. In this study, 46 odorants in the headspace and vacuum-distillate of the tea infusion were identified via aroma extract dilution analysis. Sixteen compounds were newly found in LYT infusion. They were present in the highest flavor dilution factors together with 2-ethyl-3,5-dimethylpyrazine. All odorants were quantitated to evaluate their own odor activity values (OAVs). High OAVs were found for 2-methylbutanal (malty, 210), (E,E)-2,4-heptandienal (fatty/flowery, 170), 2-methylpropanal (malty, 120) and 2,3-diethyl-5-methylpyrazine (earthy/roasty, 110). An aroma recombinate consisting of 17 odorants (all OAVs ≥ 1) in an odorless nonvolatile LYT matrix mimicked the overall aroma of the original infusion, verifying the successful characterization of key aroma components in a LYT beverage. The knowledge of key odorants obtained showed potential for simplifying industrial flavor optimization of the LYT product.

GC-MS-Olfactometric Characterization of Volatile and Key Odorants in Moringa (Moringa oleifera) and Kinkeliba (Combretum micranthum G. Don) Herbal Tea Infusions Prepared from Cold and Hot Brewing

Herbal teas are a popular global drink and are widely used in many traditional medicines. Key odorants are one of the main parameters to elucidate the final herbal tea’s overall quality and consumer acceptance. In the present study, for the first time, the brewing effect on volatile, key odorants, total phenolic contents, and antioxidant potential of Moringa (Moringa oleifera) and Kinkeliba (Combretum micranthum G. Don) herbal teas was comprehensively investigated. Two different infusions were studied and labeled as 25 °C/24 h (room temperature) and 98 °C/10 min (hot temperature). A total of 45 and 44 aroma compounds were detected in Moringa cold and hot teas, respectively, whereas 39 volatiles were determined in both infusion techniques for Kinkeliba herbal teas. The total amount of volatile compounds in both cold-infused herbal teas was higher than those in the hot-infused ones. Based on GC-MS-Olfactometry results, 19 and 21 key odorants in total were found in Moringa and Kinkeliba teas, respectively. The principal key odorants in Moringa teas with the highest flavor dilution (FD) factors were (E)-2-hexen-1-ol (herbal/fresh aroma), 3-hexanol (green/grassy), 2-phenyl ethanol (floral/rose), while in Kinkeliba teas they were 2-hexanol (herbal/green) and 3-penten-2-ol (green/fresh). The total phenolic content and antioxidant potential in Moringa and Kinkeliba teas increased using hot infusion. Principal component analysis showed that each tea infusion was clearly discriminated in terms of its volatile profiles. Our findings demonstrated that the brewing procedures had a significant impact on the key odorants of Moringa and Kinkeliba infusions.

A Targeted and an Untargeted Metabolomics Approach to the Volatile Aroma Profile of Young 'Maraština' Wines.

This study investigated the detailed volatile aroma profile of young white wines of Maraština, Vitis Vinifera L., produced by spontaneous fermentation. The wines were produced from 10 vineyards located in two Dalmatian subregions (Northern Dalmatia and Central and Southern Dalmatia). Volatile compounds from the wine samples were isolated by solid-phase extraction (SPE) and analyzed by an untargeted approach using two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC×GC/TOF-MS) and a targeted approach by gas chromatography-tandem mass spectrometry (GC-MS/MS). A comprehensive two-dimensional GC×GC analysis detailed the total volatile metabolites in the wines due to its excellent separation ability. More than 900 compounds were detected after untargeted profiling; 188 of them were identified or tentatively identified. A total of 56 volatile compounds were identified and quantified using GC-MS/MS analysis. The predominant classes in Maraština wines were acids, esters, and alcohols. The key odorants with odor activity values higher than one were β-damascenone, ethyl caprylate, ethyl isovalerate, ethyl 2-methylbutyrate, ethyl caproate, isopentyl acetate, ethyl butyrate, and phenylacetaldehyde. The metabolomics approach can provide a large amount of information and can help to anticipate variation in wines or change winemaking procedures.

Characterization of Key Odorants in Chardonnay Seeds.

Chardonnay marc, a co-product of the winemaking industry, is a combination of skins, seeds, and stems remaining after the juice is pressed from the grapes. This co-product amounts to over half a million tons per year. Recently, Chardonnay marc has been emerging as a healthy and flavorful food ingredient. The aroma contribution of the seeds to the overall aroma of Chardonnay marc remains unknown. In the present study, 43 odorants were identified in Chardonnay seeds employing aroma extract dilution analysis (AEDA) performed on a distillate prepared by solvent extraction and solvent-assisted flavor evaporation (SAFE) distillation. Of those, 6 odorants with a flavor dilution (FD) factor ≥64 were quantitated using stable isotope dilution assays (SIDAs). The odorants included (2E,4E)-deca-2,4-dienal (fatty, OAV 8028), 3-methylnonane-2,4-dione (hay, OAV 4772), (2E,4E)-nona-2,4-dienal (fatty, OAV 1750), hexanal (green, OAV 1481), linalool (floral, citrus, OAV 28), and 2-phenylethanol (floral, rose, OAV 2). An aroma simulation model was prepared based on the quantitative data, and its aroma was a close match to the Chardonnay seed powder. Omission studies applied to the aroma simulation model showed that hexanal and 3-methylnonane-2,4-dione were the key odorants driving the aroma profile. This research established a foundation for future studies aimed at optimizing the flavor of Chardonnay marc powder.

Changes in Key Aroma Compounds and Esterase Activity of Monascus-Fermented Cheese across a 30-Day Ripening Period.

Monascus-fermented cheese (MC) is a new type of mold-ripened cheese that combines a traditional Chinese fermentation fungus, Monascus purpureus M1, with Western cheese fermentation techniques. In this study, the compositions of the volatile aroma compounds in MC were analyzed during a 30-day ripening period using SPME-Arrow and GC-O-MS. The activity of esterase in MC, which is a key enzyme catalyzing esterification reaction, was determined and compared with the control group (CC). Next, sensory analysis was conducted via quantitative descriptive analysis followed by Pearson correlation analysis between esterase activity and the key flavor compounds. A total of 76 compounds were detected. Thirty-three of these compounds could be smelled at the sniffing port and were identified as the key aroma compounds. The esterase activity in MC was found to be 1.24~1.33 times that of the CC. Moreover, the key odor features of ripened MC were alcohol and fruity flavors, considerably deviating from the sour and cheesy features found for the ripened CC. Furthermore, correlation analysis showed that esterase activity was strongly correlated (|r|> 0.75, p < 0.05) with various acids such as pentanoic and nonanoic acids and several aromatic esters, namely, octanoic acid ethyl ester and decanoic acid ethyl ester, revealing the key role that esterases play in developing the typical aroma of ripened MC.

GC–MS-Olfactometric characterization of key odorants in rainbow trout by the application of aroma extract dilution analysis: Understanding locational and seasonal effects

The effect of seasonal and regional differences of rainbow trout on its aroma and aroma-active profile was investigated. Solvent–assisted flavor evaporation (SAFE) procedure was employed for the aroma extraction while Gas Chromatography–Mass Spectrometry–Olfactometry (GC–MS–O) and aroma extract dilution analysis (AEDA) were utilized to assess the aroma-active substances. The olfactometric analysis indicated seasonal and regional differences in the aroma-active compounds contributing to the characteristic odours of the trout samples and the compounds were more intense in autumn and winter. The strongest aroma-actives were hexanal (green), acetoin (buttery, green), limonene (citrus), 2-hexanol (green, pungent) and 1-octen-3-ol (oily, mushroom). The findings of this study can provide useful information for the selection of rainbow trout based on the seasons and locations in terms of marketing and consumer preference.

Effect of non-core microbes on the key odorants of paocai

Paocai is a widely consumed plant-based fermented food. We studied the effects of microbial community succession and non-core microbes on the key odorants of naturally fermented paocai. Microbiome and molecular sensory science were used to analyze potential relationships between microbial diversity and key flavor compounds. High-throughput analysis pointed out that paocai had a high level of biodiversity, with core microbes mainly represented by Weissella, Lactococcus, and Lactiplantibacillus and non-core microbes mainly represented by Acinetobacter, Raoultella, Enterobacteriales, Debaryomyces, Kazachstania, and Candida species. Ethyl acetate (OAV = 156.84), 1-hexanal (OAV = 76.18) and 1-nonanal (OAV = 57.90) were the key odorants, producing flavors described as etherial, fruity, green, and aldehydic. A total of 57 bacterial strains and 36 fungal strains were isolated and identified from paocai. A Spearman correlation analysis and in vitro simulation system comprehensively analyzed to the correlation of the microbial community and key flavors metabolism characteristics. Bacteria in non-core microbes are not conducive to the quality and safety of paocai, while yeast have the characteristics of “low quantity and great influence” on the key odorants of paocai. These findings will help elucidating the role of non-core microbial community plays in spoilage as well as flavor formation of paocai.