Flavor Chemistry Research Articles

Roasted sesame oil: A review on production technology, flavor chemistry, and other related issues

AbstractSesame oil (SO) produced through roasting technology offers pleasant flavor, often named roasted sesame oil (RSO) in the market. During the RSO production process, roasting is an essential technology in determining the flavor of RSO, which directly influences the consumer acceptance. Therefore, the present work systematically offers current knowledge on flavors and related issues of RSO, which will focus on production technologies (i.e., roasting technology, extraction technology, subsequent processing technology), flavor characteristics and flavor compounds, formation pathways of major flavor compounds (i.e., Maillard reaction pathway, oil oxidation pathway, thermal degradation pathway), and effects of roasting on the nutrition and safety. In addition, the present work provides an outlook for the future development of RSO industry, including the establishment of a grading system for the evaluation of RSO flavors, high‐value utilization of by‐products from RSO processing, and how to improve production efficiency of RSO. This work could provide a better understanding of RSO roasting process and promising information for better production of aromatic, nutritious and safe RSO by controlling/innovating the roasting process.

Comparative Investigation of Aroma-Active Volatiles in ("Ruixue", "Liangzhi", "Crystal Fuji," and "Guifei") Apples by Application of Gas Chromatography-Mass Spectrometry-Olfactometry (GC-MS-O) and Two-Dimensional Gas Chromatography-Quadrupole Mass Spectrometry (GC × GC-qMS) Coupled with Sensory Molecular Science.

Aroma dramatically impacts the overall flavor profiles and consumer acceptance; therefore, it is necessary to conduct a comprehensive analysis of the aroma characteristics of apples. In this study, the aroma differences among four popular apple varieties ("Ruixue", "Liangzhi", "Crystal Fuji," and "Guifei") were compared using two extraction methods (headspace-solid phase microextraction, and solvent-assisted flavor evaporation) coupled with gas chromatography-mass spectrometry-olfactometry (GC-MS-O) and two-dimensional gas chromatography-quadrupole mass spectrometry (GC × GC-qMS). A total of 82 odorants were identified via GC-MS-O, and 143 volatiles were identified by GC× GC-qMS. Among them, 41 key aroma-active compounds (butanal, ethyl acetate, 3-methylbutanal, methyl butanoate, 2-methylpropyl acetate, ethyl 2-methylbutanoate, ethyl 3-methylbutanoate, butyl acetate, hexanal, 2-methylbutyl acetate, 1-butanol, 2-methylpropyl butanoate, 3-methylbutyl acetate, (E)-2-hexenal, butyl butanoate, butyl 2-methylbutanoate, hexyl acetate, hexyl butanoate, hexyl, 2-methylbutanoate, 1-octen-3-ol, 3-methylthiopropanol, 1,3-octanediol, linalyl acetate, and so on) with high odor activity values (OAVs) and AI value (odor activity values ≥1 or aroma intensity ≥3) were identified. Partial least-squares-discriminant analysis showed that Ruixue exhibited a high "fruity" note, Guifei and Crystal Fuji had the greatest "wood," "floral," and "sweet" notes, while Liangzhi presented a significant "green" note. This study provided flavor chemistry support for the apple quality control and production.

Special Edition Dedicated to the 13th Wartburg Symposium on Flavor Chemistry & Biology

Special Edition Dedicated to the 13th Wartburg Symposium on Flavor Chemistry & Biology

PungentDB: Bridging traditional Chinese medicine of medicine food homology and modern food flavor chemistry

Merging traditional Chinese medicine's (TCM) principles of medicine-food homology with modern flavor chemistry, this research unveils PungentDB (http://www.pungentdb.org.cn/home), a database documenting 205 unique pungent flavor compounds from 231 TCMs. It provides detailed insights into their chemical attributes, biological targets (including IC50/EC50 values), and molecular structures (2D/3D), enriched with visualizations of target organ distribution and protein structures, exploring the pungent flavor space with the help of a feature-rich visual interface. This collection, derived from over 3249 sources and highlighting 9129 targets, delves into the compounds' unique pungent flavors—taste, aroma, and thermal sensations—and their interaction with taste and olfactory receptors. PungentDB bridges ancient wisdom and culinary innovation, offering a nuanced exploration of pungent flavors' role in enhancing food quality, safety, and sensory experiences. This initiative propels flavor chemistry forward, serving as a pivotal resource for food science advancement and the innovative application of pungent flavors.

Spatiotemporal analysis of microstructure, sensory attributes, and full-spectrum metabolomes reveals the relationship between bitterness and nootkatone in Alpinia oxyphylla miquel fruit peel and seeds

The Alpinia oxyphylla fruit (AOF) is a popular condiment and traditional Chinese medicine in Asia, known for its neuroprotective compound nootkatone. However, there has not been a comprehensive study of its flavor or the relationship between sensory and bioactive compounds. To address this issue, we examined AOF’s microstructure, flavor, and metabolomic profiles during fruit maturation. The key markers used to distinguish samples included fruit expansion, testa pigmentation, aril liquefaction, oil cell expansion, peel spiciness, aril sweetness, and seed bitterness. A full-spectrum metabolomic analysis, combining a nontargeted metabolomics approach for volatile compounds and a widely targeted metabolomics approach for nonvolatile compounds, identified 1,448 metabolites, including 1,410 differentially accumulated metabolites (DAMs). Notably, 31 DAMs, including nootkatone, were associated with spicy peel, sweet aril, and bitter seeds. Correlational analysis indicated that bitterness intensity is an easy-to-use biomarker for nootkatone content in seeds. KEGG enrichment analysis linked peel spiciness to phenylpropanoid and capsaicin biosynthesis, seed bitterness to terpenoid (especially nootkatone) biosynthesis, and aril sweetness to starch and sucrose metabolism. This investigation advances the understanding of AOF’s complex flavor chemistry and underlying bioactive principle, encapsulating the essence of the adage: “no bitterness, no intelligence” within the realm of phytochemistry.

Changes in water-soluble taste compounds of tilapia (Oreochromis niloticus) fillets subjected to different thawing methods during long-term frozen storage.

The taste of fish is highly dependent on the composition of free amino acids (FAAs) and nucleotides. The present study aimed to investigate the effect of long-term frozen storage periods (-18 °C, up to 6 months) and thawing methods [water thawing (WT, 25 °C), air thawing (AT, 25 °C), and chilled air thawing (CAT, 4 °C)] on the taste quality of tilapia (Oreochromis niloticus) fillets. The results showed that increase in bitter FAAs of CAT samples was 150.57% at 6 months of storage, which was lower than that of AT and WT. Glycine was the most abundant FAA and CAT maintained the highest sweet FAAs (249.90 mg/100 g). Additionally, the inosine monophosphate (IMP) of CAT samples were 1.18 and 1.09 times higher than that of WT and AT, respectively, at a frozen period of 6 months. In particular, the increase in equivalent umami concentration (EUC) values ranged from 24.25% to 103.16% in the three groups during the first 2 months. Data from principal component analysis (PCA) and orthogonal partial least-squares discrimination analysis (OPLS-DA) indicated that the taste quality was highly correlated with high levels of FAAs, hypoxanthine inosine (HxR) and hypoxanthine (Hx) as the storage time progressed. In general, CAT is beneficial in maintaining the taste quality of tilapia fillets during frozen storage, and frozen durations for 2 months enhances the umami flavor. This study provides useful information for the preservation of frozen aquatic products during the storage and thawing, and enrich the theoretical knowledge of the flavor chemistry of fish products. © 2024 Society of Chemical Industry.

Unveiling the mechanism of efficient β-phenylethyl alcohol conversion in wild-type Saccharomyces cerevisiae WY319 through multi-omics analysis.

β-Phenylethanol (2-PE), as an important flavor component in wine, is widely used in the fields of flavor chemistry and food health. 2-PE can be sustainably produced through Saccharomyces cerevisiae. Although significant progress has been made in obtaining high-yield strains, as well as improving the synthesis pathways of 2-PE, there still lies a gap between these two fields to unpin. In this study, the macroscopic metabolic characteristics of high-yield and low-yield 2-PE strains were systematically compared and analyzed. The results indicated that the production potential of the high-yield strain might be contributed to the enhancement of respiratory metabolism and the high tolerance to 2-PE. Furthermore, this hypothesis was confirmed through comparative genomics. Meanwhile, transcriptome analysis at key specific growth rates revealed that the collective upregulation of mitochondrial functional gene clusters plays a more prominent role in the production process of 2-PE. Finally, findings from untargeted metabolomics suggested that by enhancing respiratory metabolism and reducing the Crabtree effect, the accumulation of metabolites resisting high 2-PE stress was observed, such as intracellular amino acids and purines. Hence, this strategy provided a richer supply of precursors and cofactors, effectively promoting the synthesis of 2-PE. In short, this study provides a bridge for studying the metabolic mechanism of high-yield 2-PE strains with the subsequent targeted strengthening of relevant synthetic pathways. It also provides insights for the synthesis of nonalcoholic products in S. cerevisiae.

Microbial terroir: associations between soil microbiomes and the flavor chemistry of mustard (Brassica juncea).

Here, we characterized the independent role of soil microbiomes (bacterial and fungal communities) in determining the flavor chemistry of harvested mustard seed (Brassica juncea). Given the known impacts of soil microbial communities on various plant characteristics, we hypothesized that differences in rhizosphere microbiomes would result in differences in seed flavor chemistry (glucosinolate content). In a glasshouse study, we introduced distinct soil microbial communities to mustard plants growing in an otherwise consistent environment. At the end of the plant life cycle, we characterized the rhizosphere and root microbiomes and harvested produced mustard seeds for chemical characterization. Specifically, we measured the concentrations of glucosinolates, secondary metabolites known to create spicy and bitter flavors. We examined associations between rhizosphere microbial taxa or genes and seed flavor chemistry. We identified links between the rhizosphere microbial community composition and the concentration of the main glucosinolate, allyl, in seeds. We further identified specific rhizosphere taxa predictive of seed allyl concentration and identified bacterial functional genes, namely genes for sulfur metabolism, which could partly explain the observed associations. Together, this work offers insight into the potential influence of the belowground microbiome on the flavor of harvested crops.

Flavor Chemical Research on Different Bee Pollen Varieties Using Fast E-Nose and E-Tongue Technology.

Bee pollen, derived from various plant sources, is renowned for its nutritional and bioactive properties, aroma, and taste. This study examined the bee pollen with the highest yield in China obtained from four plant species, namely Brassica campestris (Bc), Nelumbo nucifera (Nn), Camellia japonica (Cj), and Fagopyrum esculentum (Fe), using fast e-nose and e-tongue technology to analyze their flavor chemistry. Results showed substantial differences in scent profiles among the varieties, with distinct odor compounds identified for each, including n-butanol, decanal, and ethanol, in Bc, Nn, and Cj, respectively. The primary odorants in Fe consist of E-2-hexen-1-ol and (Z)-3-hexen-1-ol. Additionally, e-tongue analysis revealed seven distinct tastes in bee pollen samples: AHS, PKS, CTS, NMS, CPS, ANS, and SCS, with variations in intensity across each taste. The study also found correlations between taste components and specific odor compounds, providing insights for enhancing product quality control in bee pollen processing.

Plant protein flavor chemistry fundamentals and techniques to mitigate undesirable flavors

AbstractMany plant protein ingredients have unpleasant flavor (e.g., green, beany, bitterness) characteristics. Isolation of the protein fraction will reduce the intensity of the undesirable flavors but in most cases the flavor issue is not eliminated. The objective of this review is to provide information about undesirable flavors associated with plant proteins and approaches to mitigate these flavors. The focus of the review will be on flavor associated with plant proteins from pulses, soybean, and oilseeds (e.g., hempseed, flaxseed). While other plant proteins exist, they will not be covered extensively in this limited review. The undesirable flavors are defined as volatile organic compounds (VOCs) and non‐volatile organic compounds (non‐VOCs). Example VOCs include aldehydes, ketones, and isobutyl pyrazines whereas saponins, bitter peptides, and phenolics are among the most common non‐VOCs. The raw material used as the source for the protein dictates the undesirable flavors remaining in the protein ingredient. The intensity of the binding of the VOCs and non‐VOCs to protein serves as the basis for the detection and difficulty in removing these compounds from the protein. A discussion about flavor binding and processing methods to mitigate unwanted flavors in protein ingredients will be provided. Methods presented will focus on extraction and thermal treatment. Although flavor masking is an approach to minimize undesirable, this topic will not be covered. Understanding the compounds responsible for the flavor issues and methods to minimize their impacts on sensory characteristic of protein ingredients can provide manufacturers with solutions to addressing flavor issues inherent to plant proteins.

Flavor Chemistry and Technology: The Challenges of Working with Flavors in the Food Industry

The term “flavor” refers to the overall sensory experience of a food or beverage, including olfaction (the perception of smell and aroma), gustation (the perception of taste), and trigeminal sensations, which combine the perception of texture, mouthfeel, temperature, and chemesthesis (i [...]

Insight into the effects of different ripeness levels on the quality and flavor chemistry of Noni fruit (Morinda citrifolia L.)

Different ripeness plays a key role in the final quality and flavor of Noni products, but the variations of quality and flavor during Noni ripening are still unclear. In this study, physicochemical analysis combined with electronic nose, electronic tongue and gas chromatography-mass spectrometry (GC–MS) were used to investigate the effect of different ripeness levels on Noni fruit quality and flavor chemistry. The results showed that the optimum stage of nutrient accumulation is 7–8 ripe (7M−8M), in which especially the higher contents were 144Mg/100 g vitamin C, 11.08 g/kg polyphenols, 15.32 g/kg flavonoids and 2420Mg/kg potassium. Octanoic acid and hexanoic acid with an unfriendly odor began to decrease significantly after 8 ripe (8M), the lowest contents were 256.76 and 231.26 ng/g at 9 ripe (9M). Sour, astringent and fresh tastes are the dominant tastes of Noni fruit. Therefore, the optimum harvesting time of Noni fruit is 8M.

Characterization of Volatile Organic Compounds in Five Celery (Apium graveolens L.) Cultivars with Different Petiole Colors by HS-SPME-GC-MS.

Celery (Apium graveolens L.) is an important vegetable crop cultivated worldwide for its medicinal properties and distinctive flavor. Volatile organic compound (VOC) analysis is a valuable tool for the identification and classification of species. Currently, less research has been conducted on aroma compounds in different celery varieties and colors. In this study, five different colored celery were quantitatively analyzed for VOCs using HS-SPME, GC-MS determination, and stoichiometry methods. The result revealed that γ-terpinene, d-limonene, 2-hexenal,-(E)-, and β-myrcene contributed primarily to the celery aroma. The composition of compounds in celery exhibited a correlation not only with the color of the variety, with green celery displaying a higher concentration compared with other varieties, but also with the specific organ, whereby the content and distribution of volatile compounds were primarily influenced by the leaf rather than the petiole. Seven key genes influencing terpenoid synthesis were screened to detect expression levels. Most of the genes exhibited higher expression in leaves than petioles. In addition, some genes, particularly AgDXS and AgIDI, have higher expression levels in celery than other genes, thereby influencing the regulation of terpenoid synthesis through the MEP and MVA pathways, such as hydrocarbon monoterpenes. This study identified the characteristics of flavor compounds and key aroma components in different colored celery varieties and explored key genes involved in the regulation of terpenoid synthesis, laying a theoretical foundation for understanding flavor chemistry and improving its quality.

Comparison analysis of full-spectrum metabolomics revealed on the variation of potential metabolites of unscented, Chloranthus spicatus scented, and Osmanthus fragrans (Thunb.) Lour. scented Congou black teas.

In recent years, scented black tea has attracted much attention due to its pleasant floral aroma and mellow flavor, but little research has been carried out on its flavor metabolic profile. In this study, the flavor metabolic profiles of unscented, Chloranthus spicatus scented, and Osmanthus fragrans (Thunb.) Lour. scented Congou black teas were investigated using full-spectrum metabolomics analysis method, the first time that the flavor profiles of scented black tea were characterized in detail. The results revealed that a total of 3,128 metabolites were detected in the three teas. Based on the criteria of variable importance in the project >1 and fold change ≥2 or ≤ 0.5, 761 non-volatile metabolites and 509 volatile metabolites were filtered as differential metabolites. Many differential non-volatile metabolites belonged to flavonoids, phenolic acids, and terpenoids. Floral, fruity and herbaceous volatile metabolites were significantly up-regulated in Chloranthus spicatus scented Congou black tea while sweet and fruity volatile metabolites were significantly down-regulated in Osmanthus fragrans (Thunb.) Lour. scented Congou black tea. The results contribute to a better understanding of the scenting techniques on the flavor quality of scented black teas and provide some information on the flavor chemistry theory of scented black teas.

Elucidating the flavour of cooked white asparagus by combining metabolomics and taste panel analysis

A typical feature of cooked white spears of Asparagus officinalis is their specific flavour. This has been the focus of several recent instrumental and panel studies. Few of these report on the comparison of raw and cooked materials which may lead to a deeper understanding of the flavour chemistry and compositional shifts occurring during food preparation. Here, solid-phase microextraction GC-MS and LC-MS analyses of raw and cooked spears were performed to profile asparagus metabolites. A taste panel evaluated flavour attributes of the same materials. Unsupervised and supervised statistical approaches were applied to investigate the profiles and link metabolomics and sensory results. Flavonoids, saponins and medium-chain volatile carbonyls were more abundant in the raw spears while sulphur-containing volatile compounds, oxidized fatty acids and phenolic acids were more abundant in the cooked spears. GC-Olfactometry-MS was also performed and revealed 35 odour-active volatile flavour compounds. We have proposed and discussed the key biochemical pathways and chemical transformations relevant to asparagus ‘flavour’.

Characterization of aroma compounds in Rosa roxburghii Tratt using solvent-assisted flavor evaporation headspace-solid phase microextraction coupled with gas chromatography-mass spectrometry and gas chromatography-olfactometry.

Rosa roxburghii Tratt (RRT) has become popular owing to its high vitamin C content. Volatiles are important factors that affect the quality of RRTs and their processed products. In this study, volatile compounds were extracted using headspace-solid phase microextraction (HS-SPME) and solvent-assisted flavor evaporation (SAFE); 143 volatile compounds were identified by gas chromatography-mass spectrometry (GC-MS), and RRT from different origins were well distinguished based on principal component analysis. 45 odor-active components were identified using gas chromatography-olfactometry (GC-O). Through quantitative descriptive analysis (QDA), there were prominent "grassy" and "tea-like" attributes in RRT. Partial least-squares regression (PLSR) revealed that Longli RRT was greatly related to "tea-like" and "woody" attributes. Among the volatiles identified, alcohols and esters were considered the dominant volatile compounds of RRT, 4-methoxy-2,5-dimethyl-3(2H)-furanone was the most prominent compound. This study enriches the flavor chemistry theory of RRT and provides a scientific basis for optimizing the aroma of RRT and its processed products.

Data-Driven Elucidation of Flavor Chemistry.

Flavor molecules are commonly used in the food industry to enhance product quality and consumer experiences but are associated with potential human health risks, highlighting the need for safer alternatives. To address these health-associated challenges and promote reasonable application, several databases for flavor molecules have been constructed. However, no existing studies have comprehensively summarized these data resources according to quality, focused fields, and potential gaps. Here, we systematically summarized 25 flavor molecule databases published within the last 20 years and revealed that data inaccessibility, untimely updates, and nonstandard flavor descriptions are the main limitations of current studies. We examined the development of computational approaches (e.g., machine learning and molecular simulation) for the identification of novel flavor molecules and discussed their major challenges regarding throughput, model interpretability, and the lack of gold-standard data sets for equitable model evaluation. Additionally, we discussed future strategies for the mining and designing of novel flavor molecules based on multi-omics and artificial intelligence to provide a new foundation for flavor science research.

Exploring the protein content and odor-active compounds of black soldier fly larvae for future food applications

Black soldier fly (Hermetia illucens L., BSF) larvae are a promising alternative for future sustainable nutrient sources both as feed and food. However, the scientific investigation of BSF larvae is still limited, especially on the flavor chemistry aspects of understanding consumer acceptance. This research examined the odor-active compounds and protein content of BSF larvae. Whole and partially defatted BSF larvae meals were compared to an anchovy fish meal. Gas chromatography/mass spectrometry and gas chromatography/olfactometry were employed to determine and identify the odor-active compounds of BSF larvae and observe the differences in volatile composition between fat-reduced samples. 95 volatile and more than 40 odor-active compounds were detected in the BSF larvae and anchovy fish meal. Overall BSF larvae meal odor profile was characterized by having more fishy, earthy, cheesy, and roasted notes. Trimethylamine, acetic acid, 3-methylbutanoic acid were considered by assessors as key off-flavor compounds contributing undesirable smell in BSF larvae meal. The defatting process slightly affected the overall odor profile; however, it did not change the volatile composition.

Analyzing the influence of withering degree on the dynamic changes in non-volatile metabolites and sensory quality of Longjing green tea by non-targeted metabolomics.

Withering is an important processing stage in green tea, which contributes to the tea flavor quality. The aim of this work was to comprehensively investigate the changes of chemical features and flavor attributes in Longjing green teas produced with five different withering degrees (moisture content of 75.05, 72.53, 70.07, 68.00, and 64.78%, w.b.). Combined with human sensory evaluation, electronic tongue and chromatic differences analysis, an assessment of the relationship between the withering degree and the sensory quality of Longjing tea was obtained. By using a non-targeted metabolomics approach, 69 significantly differential metabolites were screened. As the withering degree increased, most free amino acids and catechin dimers were increased, largely attributed to the hydrolysis of proteins and catechin oxidative polymerization, respectively. The contents of organic acids as well as phenolic acids and derivatives were reduced. Interestingly, flavone C-glycosides decreased overall while flavonol O-glycosides increased. The correlation analysis revealed that metabolites such as theasinensin F, theasinensin B, theaflavin, theaflavin-3,3'-gallate, theaflavin-3'-gallate, malic acid, succinic acid, quinic acid, theanine glucoside and galloylglucose had a greater influence on the taste and color of tea infusion (|r| > 0.6, p < 0.05). Overall, an appropriate withering degree at a moisture content of around 70% is more favorable to enhance the Longjing tea quality. These results may enhance the understanding of green tea flavor chemistry associated with withering and provide a theoretical basis for green tea processing.

A new strategy to strongly release sweet-enhancing volatiles from goji pomace using trivalent iron salts

Efforts to fully utilize pomace volatiles have been obstructed by the lack of high-performance technologies to release free and bound volatiles. This study first established that ferric chloride (FeCl3) could strongly release the sweet-enhancing volatiles (SVs) from goji pomace, thus increasing the main aroma compounds [MACs; odor activity value (OAV) > 1] from 9 to 27. The underlying mechanism included the special hydrolysis to glycosides by ferric ions acting as Brønsted and Lewis acids, and the oxidation of β-carotene and β-ionone by electrophilic ferrite. The sweet fragrance could be reconstituted and simulated by the 27 MACs. Subsequent extraction and concentration increased MACs on average by 2.28-fold, and the extracted essence could be used as a green and safe sweet-enhancing sugar substitute for specific consumers. These study findings laid a foundation for understanding the relationship between metal salts and flavor chemistry, further providing an opportunity for the full utilization of resources.