Flavor chemistry of lemon-lime carbonated beverages

Molecular-Sensory Decoding of the Citrus latifolia Aroma

A modified aroma extract dilution approach (AEDA), followed by the determination of flavor dilution (FD) factors, a quantitative analysis and calculation of the relative flavor activity (RFA) and odor activity values (OAVs) as well as recombination experiments were conducted to evaluate the odor- and taste-relevant components of cold-pressed Citrus latifolia peel oil. A 2-fold concentration by distillation and reanalysis, compared with the original oil, revealed relevant components. Partition of the odor-active substances into four reconstitution groups according to their respective FD factors, followed by a recombination, allowed for a better understanding of the contribution of each FD-factor group to the overall aroma. Especially α-pinene, limonene, γ-terpinene, and 7-methoxycoumarin contribute significantly to the distinct aroma profile of C. latifolia. Heptadecanal (CAS 629-90-3) was described for the first time as an odor-active substance in an enriched C. latifolia peel oil. Campherenyl acetate (CAS 18530-07-9) was identified in nature for the first time and described with a herbal, minty and citrus-like odor. The odor profile of the final recombinant mixture, containing 36 components, was similar to cold-pressed C. latifolia peel oil for most descriptors, whereas the taste profile was described as more aldehydic and citral-like.

Characterization of Odorants in a Commercial Culinary Sage (Salvia officinalis L.) and Several Cultivars

Culinary sage, Salvia officinalis L., is a popular spice plant commonly used throughout the world. In this study, 35 odorants were identified in dried sage via solvent-assisted flavor evaporation (SAFE) and aroma extract dilution analysis (AEDA), including 9 that were identified in sage for the first time. Fifteen odorants were quantitated by stable isotope dilution analysis (SIDA), and their odor activity values (OAVs) were determined. Odorants with high OAVs included (2E,6Z)-nona-2,6-dienal, 1,8-cineole, and β-myrcene. A formulated aroma simulation model closely matched the aroma profile of an aqueous infusion of dried sage. Enantiomeric proportions of selected odorants were determined by chiral gas chromatography. Furthermore, 6 different sage cultivars were grown in the greenhouse, dried under the same conditions, and analyzed. Sensory analysis determined that all cultivars were dominated by an herbaceous sensory attribute and had varying intensities of eucalyptus, mint, clove, pine, green, earthy, floral, and citrus notes. Cultivars with varying intensities of herbaceous, eucalyptus, pine, and green sensory notes correlated with the OAVs of α-thujone/β-thujone, 1,8-cineole, α-pinene, and (2E,6Z)-nona-2,6-dienal, respectively. This study identified the odorants driving the sensory profiles of different sage cultivars and serves as a foundation for future studies on the aroma chemistry of culinary sage.

Effects of Cooking Processes on Protein Nutritional Values and Volatile Flavor Substances of Silver Carp (Hypophthalmichthys molitrix)

Silver carp (Hypophthalmichthys molitrix) is normally cooked at a high temperature. In order to explore the effects of cooking methods on the protein nutritional values and volatile flavor substances of silver carp meat, the meat was fried, roasted and steamed, and its contents were determined in relation to moisture, protein, fat, ash, amino acids and volatile flavor substances. The results show that the moisture content of cooked silver carp can be ranked as follows: raw > steamed > roasted > fried. The protein content order of the four samples can be ranked: fried > roasted > raw > steamed. The ash and the fat contents of the four samples showed similar significant (p < 0.05) differences, in the order of fried > roasted > steamed > raw. The contents of all the amino acids in the fried meat were significantly (p < 0.05) higher than the contents in others, and the frying, roasting and steaming processes improved the umami taste (supported by the increased content of glutamate and aspartate) and the protein nutritional value (supported by the amino acid score, essential amino acid index and protein efficiency ratio) of the silver carp meat. A total of 51 compounds were detected in the fried, roasted and steamed meat. Frying and roasting reduced the fishy flavor of this meat. The odor activity value (OAV) indicated that methanethiol, 1-octen-3-ol and 2-heptanone were the key flavor chemicals in raw meat. Hexanal, propionaldehyde, octanal, nonanal, decanal, 1-octen-3-ol and 2-heptanone were key to the flavor of fried meat. Pentanal, decanal, methyl mercap-tan and 1-octen-3-ol contributed greatly to the overall flavor of the roasted meat. Nonanal, methylmercaptan and 1-octene-3-ol had strong effects on the flavor of the steamed silver carp meat.

Dynamic Changes in Flavor and Microbiota in Traditionally Fermented Bamboo Shoots (Chimonobambusa szechuanensis (Rendle) Keng f.)

Dissecting flavor formation and microbial succession during traditional fermentation help to promote standardized and large-scale production in the sour shoot industry. The principal objective of the present research is to elucidate the interplay between the physicochemical attributes, flavor, and microbial compositions of sour bamboo shoots in the process of fermentation. The findings obtained from the principal component analysis (PCA) indicated notable fluctuations in both the physicochemical parameters and flavor components throughout the 28 day fermentation process. At least 13 volatile compounds (OAV > 1) have been detected as characteristic aroma compounds in sour bamboo shoots. Among these, 2,4-dimethyl Benzaldehyde exhibits the highest OAV (129.73~668.84) and is likely the primary contributor to the sour odor of the bamboo shoots. The analysis of the microbial community in sour bamboo shoots revealed that the most abundant phyla were Firmicutes and Proteobacteria, while the most prevalent genera were Enterococcus, Lactococcus, and Serratia. The results of the correlation analysis revealed that Firmicutes exhibited a positive correlation with various chemical compounds, including 3,6-nonylidene-1-ol, 2,4-dimethyl benzaldehyde, silanediol, dimethyl-, nonanal, and 2,2,4-trimethyl-1,3-pentylenediol diisobutyrate. Similarly, Lactococcus was found to be positively correlated with several chemical compounds, such as dimethyl-silanediol, 1-heptanol, 3,6-nonylidene-1-ol, nonanal, 2,2,4-trimethyl-1,3-pentanediol diisobutyrate, dibutyl phthalate, and TA. This study provides a theoretical basis for the standardization of traditional natural fermented sour bamboo production technology, which will help to further improve the flavor and quality of sour bamboo.

Advances in the Biosynthesis of Terpenoids and Their Ecological Functions in Plant Resistance

Secondary metabolism plays an important role in the adaptation of plants to their environments, particularly by mediating bio-interactions and protecting plants from herbivores, insects, and pathogens. Terpenoids form the largest group of plant secondary metabolites, and their biosynthesis and regulation are extremely complicated. Terpenoids are key players in the interactions and defense reactions between plants, microorganisms, and animals. Terpene compounds are of great significance both to plants themselves and the ecological environment. On the one hand, while protecting plants themselves, they can also have an impact on the environment, thereby affecting the evolution of plant communities and even ecosystems. On the other hand, their economic value is gradually becoming clear in various aspects of human life; their potential is enormous, and they have broad application prospects. Therefore, research on terpenoids is crucial for plants, especially crops. This review paper is mainly focused on the following six aspects: plant terpenes (especially terpene volatiles and plant defense); their ecological functions; their biosynthesis and transport; related synthesis genes and their regulation; terpene homologues; and research and application prospects. We will provide readers with a systematic introduction to terpenoids covering the above aspects.

Effect of cooking modes on quality and flavor characteristic in Clitocybe squamulose chicken soup

The effects of cooking modes [cooking in stainless-steel pot (SS), ceramic pot (CP), and electrical ceramic stewpot (EC) with different stewing time] on chemical compositions, whiteness, 5'-nucleotides, fatty acids (FAs), sensory quality and flavor substances in chicken soup added Clitocybe squamulose (Pers.) Kumm (a natural edible fungus) were investigated. The results showed that CP chicken soup had higher soluble solid matter (5.83 g/100 mL), total sugar (2.38 mg/mL), crude protein (7.58 g/100 g), and 5'-nucleotides (325.53 mg/mL) than EC and SS chicken soups. 48 volatile flavor compounds, mainly aldehydes and alkanes, were found by gas chromatography-mass spectrometry (GC-MS), and the characteristic flavor substances were identified by Principal component analysis (PCA) and orthogonal partial least squares discrimination analysis (OPLS-DA). Hexanal, (E,E)-2,4-decadienal and 3-methyl-hexadecane were the most abundant differential volatile compounds in the CP chicken soup. Additionally, the results of sensory evaluation showed that the chicken soup cooked in CP had the higher values of aroma, taste, and overall acceptability. Our results indicate that CP mode might be the best option for cooking chicken soup. This study provides a new perspective in the improvement of the quality and flavor of chicken soup by using an appropriate cooking mode. Theoretical support for the use of various cooking modes is also discussed to improve the quality of chicken soup at home and in the industry.

Evaluation of Coriolis Micro Air Sampling to Detect Volatile and Semi-Volatile Organic Compounds

There are several analytical procedures available for the monitoring of volatile organic compounds (VOCs) in the air, which differ mainly on sampling procedures. The Coriolis micro air sampler is a tool normally designed for biological air sampling. In this paper, the Coriolis micro bio collector is used to evaluate its ability to sample organic contaminants sampling and detecting them when combined GC-MS. We also compare the use of the Coriolis micro with a standardized sampling method, which is the use of a lung box with a Nalophan^® bag. The results show that the Coriolis micro sampling method is suitable for the sampling of organic contaminants. Indeed, the Coriolis micro allows to sample and detect mainly semi-volatile molecules, while the lung box/Nalophan^® bags allow to sample more volatile molecules (highly volatile and volatile). These results were confirmed in the controlled air lab with a slight difference with the field. The simultaneous use of the both techniques allow to sample and detect a larger number of molecules with specific physicochemical properties to each sampling technique. In conclusion, the Coriolis micro can sample and detect volatile organic compounds present in air. We have shown that the development of alternative sampling methods and the use of non-target analysis are essential for a more comprehensive risk assessment. Moreover, the use of the Coriolis micro allows the detection of emergent molecules around the Thau lagoon.

Toxicity of Selected Monoterpenes and Essential Oils Rich in These Compounds

Monoterpenes make up the largest group of plant secondary metabolites. They can be found in numerous plants, among others, the Lamiaceae family. The compounds demonstrate antioxidative, antibacterial, sedative and anti-inflammatory activity, hence, they are often employed in medicine and pharmaceuticals. Additionally, their fragrant character is often made use of, notably in the food and cosmetic industries. Nevertheless, long-lasting studies have revealed their toxic properties. This fact has led to a detailed analysis of the compounds towards their side effects on the human organism. Although most are safe for human food and medical applications, there are monoterpene compounds that, in certain amounts or under particular circumstances (e.g., pregnancy), can cause serious disorders. The presented review characterises in vitro and in vivo, the toxic character of selected monoterpenes (α-terpinene, camphor, citral, limonene, pulegone, thujone), as well as that of their original plant sources and their essential oils. The selected monoterpenes reveal various toxic properties among which are embryotoxic, neurotoxic, allergenic and genotoxic. It is also known that the essential oils of popular plants can also reveal toxic characteristics that many people are unaware of.

An Integrative Volatile Terpenoid Profiling and Transcriptomics Analysis in Hoya cagayanensis, Hoya lacunosa and Hoya coriacea (Apocynaceae, Marsdenieae)

Hoya’s R.Br. attractive flower shapes and unique scents make it suitable to be exploited as a new source of tropical fragrance. Therefore, this study aims to elucidate the biosynthesis of secondary metabolites using phytochemical and transcriptomic approaches to understand the mechanisms of scents biosynthesis, especially terpenoid in Hoya. Three Hoya flower species were selected in this study: Hoya cagayanensis, Hoya lacunosa, and Hoya coriacea. The secondary metabolite profiles characterizing scents on flowers were performed using head space solid phase microextraction (HS-SPME). Gas chromatography-mass spectrometry (GC-MS) revealed 23 compounds from H. cagayanensis, 14 from H. lacunose, and 36 from H. coriacea. Volatiles from the three species had different fragrance profiles, with β-ocimene and methyl salicylate compounds dominating the odor in H. cagayanensis. The 1-octane-3-ol was found highest in H. lacunosa, and (Z)-acid butyric, 3-hexenyl ester was found highest in H. coriacea. Subsequent studies were conducted to identify the biosynthesis pathway of secondary metabolites responsible for the aroma profile released by Hoya flowers through transcriptome sequencing using the Illumina Hiseq 4000 platform. A total of 109,240 (75.84%) unigenes in H. cagayanensis, 42,479 (69.00%) in H. lacunosa and 72,610 (70.55%) in H. coriacea of the total unigenes were successfully annotated using public databases such as NCBI-Nr, KEGG, InterPro, and Gene Ontology (GO). In conclusion, this study successfully identified the complete outline of terpenoid biosynthesis pathways for the first time in Hoya. This discovery could lead to the exploitation of new knowledge in producing high-value compounds using the synthetic biology approach.

A novel strategy for discriminating different cultivation and screening odor and taste flavor compounds in Xinhui tangerine peel using E-nose, E-tongue, and chemometrics

A rapid strategy for discriminating Quanzhi (QZ) and Bozhi (BZ) of different cultivation of Xinhui tangerine peel was established by combining electronic nose, electronic tongue and chemometrics, which can be used as tool in the market to identify food fraud. 30 volatiles and 34 low molecular weight compounds of characteristic fingerprints of Xinhui tangerine peel of 108 samples were identified using GC-MS and UHPLC-Q-TOF-MS. Key compounds of BZ and QZ were screened and further compared by chemometrics. We discriminated odor and taste of BZ and QZ using electronic nose and electronic tongue, respectively. Our studies showed that β-myrcene, limonene, β-trans-Ocimene, γ-terpinene and terpinolene, etc, were screened the chief volatile flavor compounds by Spearman's rank correlation. Hydroxymethyl furfural, hesperitin, nobiletin and tangeretin, etc, were screened the key taste flavor compounds based gray relational analysis and partial least squares regression. Our study provides further insight for quality evaluation of Xinhui tangerine peel.

Performance of alternative drying techniques on hop (Humulus lupulus L.) aroma quality: An HS-SPME-GC-MS-O and chemometrics combined approach

Economically feasible and effective hop drying strategies are urgently needed to respond to the increasing number of microbrewers in US. In this study, hops were dried by dehydrator-drying (52 °C), oven-drying (52 °C) and freeze-drying (25 °C) until the final moisture content reached 8-10%. Headspace solid-phase microextraction-gas chromatography-mass spectrometry-olfactometry (HS-SPME-GC-MS-O) was employed to analyze the aroma profiles in all dried hops. Methyl octanoate, β-myrcene, trans-α-bergamotene, linalool and geraniol were perceived as high-intensity aromas in all samples. Generally, dehydrator-dried hops contained the highest contents of aroma compounds among all groups, showing an increase of 5-23% and 6-37% when compared to freeze- and oven-dried hops, respectively. Principal component and hierarchical cluster analyses also revealed aroma content differences from three drying methods. Dehydrator drying at 52 °C was therefore considered as an alternative and promising drying approach for smaller-scale hop processing, which can largely benefit regional producers and local craft breweries.

Biosynthesis, evolution and ecology of microbial terpenoids

Covering: through June 2021Terpenoids are the largest class of natural products recognised to date. While mostly known to humans as bioactive plant metabolites and part of essential oils, structurally diverse terpenoids are increasingly reported to be produced by microorganisms. For many of the compounds biological functions are yet unknown, but during the past years significant insights have been obtained for the role of terpenoids in microbial chemical ecology. Their functions include stress alleviation, maintenance of cell membrane integrity, photoprotection, attraction or repulsion of organisms, host growth promotion and defense. In this review we discuss the current knowledge of the biosynthesis and evolution of microbial terpenoids, and their ecological and biological roles in aquatic and terrestrial environments. Perspectives on their biotechnological applications, knowledge gaps and questions for future studies are discussed.

Comparative investigation on aroma profiles of five different mint (Mentha) species using a combined sensory, spectroscopic and chemometric study

Mint is a widely used aromatic plant, and the aroma varies among different species. The aroma of five mint species, Mentha citrata L. (MC), Mentha piperita L. (MPI), Mentha spicata L. (MSP), Mentha persicaria L. (MPE), and Mentha suaveolens L. (MSU), were comparatively studied on the sensorial and molecular level. Quantitative descriptive analysis revealed that MC presented a pronounced lemon-like note, MSU is dominated by citrus and floral aromas, MPI has a prominent minty flavor, MSP and MPE have a similar scent, both of which are flavored with a spearmint-like note. Forty-one odorants with odor activity values (OAVs) ≥1 were characterized. Principal component analysis and orthogonal partial least squares discrimination analysis based on OAVs indicated that α-citral, menthofuran, isomenthone, menthol, carvone, and linalool were potential odor-active markers for five mint species discrimination. This study herein will provide guidance for mint resources utilization and also aid mint breeding with better flavor.

Aroma characterization of regional Cascade and Chinook hops (Humulus lupulus L.)

Aroma compounds in Cascade and Chinook hops harvested from multiple Virginia locations were identified by gas chromatography-mass spectrometry-olfactometry (GC-MS-O) and aroma extract dilution analysis (AEDA). Selected aroma compounds were quantitated by combination of stable isotope dilution analysis (SIDA) and standard addition method (SAM). A total of 33 aroma-active compounds were detected in five samples with β-myrcene, methyl octanoate, geraniol and linalool being the predominant compounds based on their high flavor dilution (FD) factors and odor activity values (OAVs). L-Calamenene and germacrene B was the major characteristic component unique to Cascade and Chinook variety, respectively. Principal component analysis (PCA) showed distinctive aroma profiles for all samples except for Blacksburg and Petersburg Cascade. Hierarchical cluster analysis (HCA) reflected the higher contents of most aroma-active compounds in Meadowview Cascade and Chinook when compared to their counterparts. The significant variations suggested the potential influences of environmental factors and agronomic practices on hop aroma quality.

Catalytic Oxygenation-Mediated Extraction as a Facile and Green Way to Analyze Volatile Solutes

Sparging-based methods have long been used to liberate volatile organic compounds (VOCs) from liquid sample matrices prior to analysis. In these methods, a carrier gas is delivered from an external source. Here, we demonstrate "catalytic oxygenation-mediated extraction" (COME), which relies on biocatalytic production of oxygen occurring directly in the sample matrix. The newly formed oxygen (micro)bubbles extract the dissolved VOCs. The gaseous extract is immediately transferred to a separation or detection system for analysis. To start COME, dilute hydrogen peroxide is injected into the sample supplemented with catalase enzyme. The entire procedure is performed automatically-after pressing a "start" button, making a clapping sound, or triggering from a smartphone. The pump, valves, and detection system are controlled by a microcontroller board. For quality control and safety purposes, the reaction chamber is monitored by a camera linked to a single-board computer, which follows the enzymatic reaction progress by analyzing images of foam in real time. The data are instantly uploaded to the internet cloud for retrieval. The COME apparatus has been coupled on-line with the gas chromatography electron ionization mass spectrometry (MS) system, atmospheric pressure chemical ionization (APCI) MS system, and APCI ion-mobility spectrometry system. The three hyphenated variants have been tested in analyses of complex matrices (e.g., fruit-based drinks, whiskey, urine, and stored wastewater). In addition to the use of catalase, COME variants using crude potato pulp or manganese(IV) dioxide have been demonstrated. The technique is inexpensive, fast, reliable, and green: it uses low-toxicity chemicals and emits oxygen.

Authentication Using Volatile Composition: A Proof-of-Concept Study on the Volatile Profiles of Fourteen Queensland Ciders

Although relatively small, the Australian cider industry has experienced significant growth in recent years. One of the current challenges in the industry is the lack of research specific to Australian ciders. Establishing baseline volatile organic compound (VOC) profiles of Australian cider is paramount to developing a better understanding of the industry. This understanding may ultimately be utilized for both the categorization and authentication of existing ciders, and the targeted modification of cider volatiles for the development and improvement of cider quality. This study utilized gas chromatography, coupled with mass spectrometry, to identify key VOCs present in 14 ciders sourced from four different manufacturers in Queensland, Australia. A total of 40 VOCs were identified across the ciders, with significant variation depending on the flavor and manufacturer. Principal component analysis indicated that the ciders were well-separated based on the manufacturer, supporting the prospect of using the volatile composition to discriminate between cider manufacturers. Furthermore, hierarchical cluster analysis highlighted the commonalities and differences in cider composition between different manufacturers, which may be indicative of the varying ingredients and manufacturing processes used to create the ciders. Future studies profiling the volatile composition of larger numbers of Australian ciders are recommended to support the use of this analytical technique for authentication purposes. Likewise, exploration of the relationship between specific processes and VOCs is recommended to fortify an understanding of how to optimize cider production to improve consumer satisfaction.

Gas chromatography-mass spectrometry-based metabolomics analysis of metabolites in commercial and inoculated pickles

BACKGROUND

Starter cultures are nowadays more and more used to make inoculated pickles (IPs), but it remains unclear whether there are differences in flavors between IPs and naturally fermented pickles. In this study 16 commercial pickles (CPs) produced by spontaneous fermentation method were purchased from markets in Sichuan province and Chongqing. Ten strains of three lactic acid bacteria species - Lactobacillus plantarum, Leuconostoc mesenteroides and Pediococcus ethanolidurans - were selected as single starter cultures to produce IPs.

RESULTS

Differences in flavor components between the CPs and IPs were monitored using a combination of gas chromatography-mass spectrometry and multivariate statistical methods. Higher levels of nonvolatile substances such as glucose, fructose, tagatose, sucrose, lactic acid and mannitol were detected in most IPs than in the CPs. The values of flavor characteristics such as sweetness, umami and astringency, which were correlated positively with consumers' overall preferences for pickles, were higher in the IPs than in the CPs. Volatile compounds such as geranyl acetate, dimethyl trisulfide, eucalyptol and linalool were distinguished as the main compounds that contributed to the flavor characteristics of the CPs. In addition to dimethyl trisulfide, dimethyl disulfide was also an odor contributor to the IPs.

CONCLUSIONS

The CPs and IPs had different flavor characteristics, especially in the composition and content of volatile components, and the inoculation method reflected some fermentation advantages, which could reduce the bitterness and increase umami and lead to a higher score of sensory preference. This will be helpful for industrial production. © 2020 Society of Chemical Industry.

Evaluating the Chemical Components and Flavor Characteristics Responsible for Triggering the Perception of "Beer Flavor" in Non-Alcoholic Beer

Forty-two commercial non-alcoholic beer (NAB) brands were analyzed using sensory and chemical techniques to understand which analytes and/or flavors were most responsible for invoking the perception of "beer flavor" (for Northern Californian consumers). The aroma and taste profiles of the commercial NABs, a commercial soda, and a carbonated seltzer water (n = 44) were characterized using replicated descriptive and CATA analyses performed by a trained sensory panel (i.e., 11 panelists). A number of non-volatile and volatile techniques were then used to chemically deconstruct the products. Consumer analysis (i.e., 129 Northern Californian consumers) was also used to evaluate a selection of these NABs (i.e., 12) and how similar they thought the aroma, taste and mouthfeels of these products were to beer, soda, and water. The results show that certain constituents drive the aroma and taste profiles which are responsible for invoking beer perception for these North American consumers. Further, beer likeness might not be a driver of preference in this diverse beverage class for Northern Californian consumers. These are important insights for brewers planning to create products for similar markets and/or more broadly for companies interested in designing other functional/alternative food and beverage products.

Characterizing Volatile and Nonvolatile Factors Influencing Flavor and American Consumer Preference toward Nonalcoholic Beer

In this study, the chemical and sensory profiles of 42 different nonalcoholic beer (NAB) brands/styles already on the global market and produced through several different brewing techniques were evaluated. A trained panel (i.e., 11 panelists) performed standard-driven descriptive and check-all-that-apply analyses in triplicate to sensorially characterize the aroma and taste/mouthfeel profiles of 42 commercial NABs, a commercial soda, and a commercial seltzer water (n = 44). These beers were also chemically deconstructed using several different analytical techniques targeting volatile and nonvolatile compounds. Consumer analysis (n = 129) was then performed to evaluate the Northern Californian consumer hedonic liking of a selection (n = 12) of these NAB brands. These results provide direction to brewers and/or beverage producers on which techniques they should explore to develop desirable NAB offerings and suggest chemical targets that are indicators of specific flavor qualities and/or preference for American consumers.

Identification of Characterizing Aroma Components of Roasted Chicory "Coffee" Brews

The roasted and ground root of the chicory plant (Cichorium intybus), often referred to as chicory coffee, has served as a coffee surrogate for well over 2 centuries and is still in common use today. Volatile components of roasted chicory brews were identified by direct solvent extraction and solvent-assisted flavor evaporation (SAFE) combined with gas chromatography-olfactometry (GC-O), aroma extract dilution analysis (AEDA), and gas chromatography-mass spectrometry (GC-MS). A total of 46 compounds were quantitated by stable isotope dilution analysis (SIDA) and internal standard methods, and odor-activity values (OAVs) were calculated. On the basis of the combined results of AEDA and OAVs, rotundone was considered to be the most potent odorant in roasted chicory. On the basis of their high OAVs, additional predominant odorants included 3-hydroxy-4,5-dimethyl-2(5H)-furanone (sotolon), 2-methylpropanal, 3-methylbutanal, 2,3-dihydro-5-hydroxy-6-methyl-4H-pyran-4-one (dihydromaltol), 1-octen-3-one, 2-ethyl-3,5-dimethylpyrazine, 4-hydroxy-2,5-dimethyl-3(2H)-furanone (HDMF), and 3-hydroxy-2-methyl-4-pyrone (maltol). Rotundone, with its distinctive aromatic woody, peppery, and "chicory-like" note was also detected in five different commercial ground roasted chicory products. The compound is believed to an important, distinguishing, and characterizing odorant in roasted chicory aroma. Collectively, a group of caramel- and sweet-smelling odorants, including dihydromaltol, cyclotene, maltol, HDMF, and sotolon, are also thought to be important aroma contributors to roasted chicory aroma.

Comparison of Potent Odorants in Raw and Ripened Pu-Erh Tea Infusions Based on Odor Activity Value Calculation and Multivariate Analysis: Understanding the Role of Pile Fermentation

Infusions prepared from raw pu-erh tea (RAPT) and ripened pu-erh tea (RIPT) showed remarkable aroma differences. Predominant odorants in RAPT and RIPT infusions were identified and compared by the combined use of gas chromatography-olfactometry, aroma extract dilution analysis, odor activity values (OAVs), and multivariate analysis. A total of 35 and 19 odorants (OAV > 1) were detected in RIPT and RAPT, respectively. Odorants in RAPT and RIPT are significantly different in both odor properties and aroma compound intensities. Overall, RAPT contained a complex variety of chemical classes with diverse odors and moderate odor intensities, while RIPT is dominated by structurally and organoleptically similar compounds with high potency. Specifically, stale and musty smelling methoxybenzenes contributed the most to RIPT, while floral-, sweet-, and woody-smelling terpene alcohols, terpene ketones, and phenolic compounds were the predominant odorants in RAPT. Orthogonal partial least squares discriminant analysis revealed that linalool, α-ionone, 1,2,4-trimethoxybenzene, 1,2,3-trimethoxy-5-methylbenzene, 1,2,3,4-tetramethoxybenzene, and 1,2,3-trimethoxybenzene underwent remarkable changes during pile fermentation and could be used as potential odor-active markers for RIPT and RAPT discrimination. The comprehensive aroma characterization of pu-erh tea and determination of the effect of pile fermentation on odorant alteration herein will provide guidance for pu-erh tea flavor quality control and evaluation.

Streamlined approach for careful and exhaustive aroma characterization of aged distilled liquors

•

A careful and exhaustive streamlined method for aroma analysis of distilled liquors was developed.

•

Perceived aromas did not differ between SAFE distillates and original (neat) liquors.

•

Accurate quantitation was achieved for aroma compounds of high and intermediate volatility.

•

Less accurate results were obtained by the streamlined method for semi-volatile components.

Solvent-assisted flavor evaporation (SAFE) is considered to be the best overall method to produce a “clean” aroma extract to avoid the loss of labile aroma compounds or the formation of thermally generated artifacts during gas chromatographic (GC) analysis. However, SAFE is both time consuming and labor intensive, especially when applied repeatedly for quantitation by stable isotope dilution analysis (SIDA), which requires the addition of isotopes within specific mass ratio ranges relative to target analytes. The streamlined approach described herein allows for accurate quantitation of odor-active components in liquor products with a single SAFE operation. The quantitative results achieved by this method are nearly identical for most odor-active components, except for specific semi-volatile constituents not recovered well by SAFE (e.g., vanillin and syringaldehyde in oak-aged liquors). The streamlined approach provides a simple and convenient way to expedite the careful and exhaustive study of the flavor chemistry of aged liquors.

Terpenes and isoprenoids: a wealth of compounds for global use

Role of terpenes and isoprenoids has been pivotal in the survival and evolution of higher plants in various ecoregions. These products find application in the pharmaceutical, flavor fragrance, and biofuel industries. Fitness of plants in a wide range of environmental conditions entailed (i) evolution of secondary metabolic pathways enabling utilization of photosynthate for the synthesis of a variety of biomolecules, thereby facilitating diverse eco-interactive functions, and (ii) evolution of structural features for the sequestration of such compounds away from the mainstream primary metabolism to prevent autotoxicity. This review summarizes features and applications of terpene and isoprenoid compounds, comprising the largest class of secondary metabolites. Many of these terpene and isoprenoid biomolecules happen to be high-value bioproducts. They are essential components of all living organisms that are chemically highly variant. They are constituents of primary (quinones, chlorophylls, carotenoids, steroids) as well as secondary metabolism compounds with roles in signal transduction, reproduction, communication, climatic acclimation, defense mechanisms and more. They comprise single to several hundreds of repetitive five-carbon units of isopentenyl diphosphate (IPP) and its isomer dimethylallyl diphosphate (DMAPP). In plants, there are two pathways that lead to the synthesis of terpene and isoprenoid precursors, the cytosolic mevalonic acid (MVA) pathway and the plastidic methylerythritol phosphate (MEP) pathway. The diversity of terpenoids can be attributed to differential enzyme and substrate specificities and to secondary modifications acquired by terpene synthases. The biological role of secondary metabolites has been recognized as pivotal in the survival and evolution of higher plants. Terpenes and isoprenoids find application in pharmaceutical, nutraceutical, synthetic chemistry, flavor fragrance, and possibly biofuel industries.

Identification and Quantitation of Potent Odorants in Spearmint Oils

Potent odorants in Native spearmint, Scotch spearmint, and Macho mint oils were determined by the combined use of gas chromatography-olfactometry (GCO), gas chromatography-mass spectrometry (GC-MS), and aroma extract dilution analysis (AEDA). Of the 85 odorants detected, ( R)-(-)-carvone was the most potent odorant in all three spearmint oils. Additional predominant odorants in all spearmint oils included eugenol, ethyl ( S)-(+)-2-methylbutanoate, ( E)-β-damascenone, and (3 E,5 Z)-1,3,5-undecatriene. Forty-six compounds were quantitated using various methods, including 19 by gas chromatography with flame ionization detection (GC-FID), 20 by stable isotope dilution analysis (SIDA), and 14 by GCO dilution analysis. Concentrations were used to calculate the odor activity values (OAVs) for predominant odorants in the oils. Among the compounds quantitated, those with the highest OAVs were ( R)-(-)-carvone, 1,8-cineole, ( E, Z)-2,6-nonadienal, ( E)-β-damascenone, and (3 E,5 Z)-1,3,5-undecatriene.

Extended aroma extract dilution analysis profile of Shiikuwasha ( Citrus depressa Hayata) pulp essential oil

Shiikuwasha pulp is an important raw material for producing citrus essential oils. The volatile aroma composition of pulp essential oil was evaluated using gas chromatography (GC) methods, and its aroma profile was assessed using GC-olfactometry with an extended aroma extract dilution analysis (AEDA) technique in regard to alterations of odor strength and sensorial perception throughout serial dilution steps. The essential oil comprised a mixture of 55 aroma compounds, including monoterpene hydrocarbon, sesquiterpene hydrocarbon, alcohol, aldehyde, ester, and oxide compounds. The predominant compounds were limonene [57.36% (4462.80 mg/100 g of pulp)] and γ-terpinene [25.14% (1956.21 mg/100 g of pulp)]. However, linalool was identified as one of the key aroma components providing the highest flavor dilution factor in AEDA, whilst three sesquiterpene hydrocarbons (δ-elemene, germacrene B, and bicyclosesquiphellandrene) and two esters (heptyl acetate and decyl acetate) had superior relative flavor activities. The extended AEDA profile identified variations in assessed odor perceptions, intensity, and duration of aroma components over dilution, whereas the 12 most odor-active compounds showed comparable odor strengths.

Simultaneous determination of acrylamide and 4-hydroxy-2,5-dimethyl-3(2H)-furanone in baby food by liquid chromatography-tandem mass spectrometry

A liquid chromatography triple quadrupole mass spectrometry method was developed and validated for the simultaneous determination of acrylamide and 4-hydroxy-2,5-dimethyl-3(2H)-furanone (HDMF) in baby food. The sample preparation involves acetonitrile-based extraction combined with dispersive primary secondary amine (PSA) cleanup and cation-exchange solid-phase extraction (SPE), which promotes efficient removal of matrix interferences. Analytical selectivity and sensitivity were achieved for the quantification of acrylamide and HDMF in complex matrices such as fruit, cereal and milk-based baby foods; furthermore, adequate linearity (range 10-300μgkg^-1) in solvent and matrix-matched calibration curves, and appropriate recoveries (94-110%) and precision (RSD≤10%), under repeatability and within-laboratory reproducibility conditions, were also obtained. Expanded measurement uncertainty was estimated at the 20μgkg^-1 level (limit of quantification) on the basis of data obtained from in-house validation, with values of 25.5 and 16.5% for acrylamide and HDMF, respectively. The fitness for purpose of developed method was verified by analyzing 15 commercial baby foods available in the Brazilian market. Acrylamide was detected in one plum-based baby food (35μgkg^-1) while HDMF in 67% of the samples analyzed (levels between 25 and 262μgkg^-1).

Characterization of the key odorants of fennel essential oils of different regions using GC-MS and GC-O combined with partial least squares regression

The key odorants and the aroma profile of six fennel essential oils from different regions were investigated by using gas chromatography-olfactometry (GC-O), gas chromatography-mass spectrometry (GC-MS) and sensory evaluation. A total of 30 volatile compounds were determined by GC-O with aroma extract dilution analysis (AEDA) and the odor activity values (OAV) of them were calculated. Among these compounds, α-pinene, α-phellandrene, limonene, α-cubebene, β-caryophyllene, estragole, α-humulene, trans-anethole, δ-cadinene and p-anisaldehyde contributed greatly to the aroma of fennel essential oil due to their high flavor dilution (FD) factors and high OAVs. The aroma of fennel essential oils was described by 7 sensory terms as spicy, woody, grassy, floral, musty, sweet and green, and was correlated to the key odorants by partial least squares regression (PLSR). It was showed that spicy, woody, grassy, musty and green attributes were covaried well with aroma compounds. In addition, hierarchical cluster analysis (HCA) was used to find out the similarities among different samples and the result indicated that three main groups were identified.

Characterization of the differences in the aroma of cherry wines from different price segments using gas chromatography-mass spectrometry, odor activity values, sensory analysis, and aroma reconstitution

The aroma composition, aroma-active compounds, and sensory attributions of cherry wines from three different price segments were investigated. A total of 48 aroma compounds were identified and quantified using headspace solid-phase microextraction (HS-SPME)/gas chromatography-mass spectrometry (GC-MS), among which 23 aroma compounds were further screened out as important odorants based on their odor activity values (OAVs); then, the previously mentioned 23 volatiles were correlated to sensory attributes using partial least-squares regression (PLSR). The result indicates that the differently priced wines were associated with different compounds and aroma attributions. Finally, aroma reconstitution was performed by mixing odor-active aroma compounds (OAVs>1) on the basis of their measured concentrations in the original sample. The result indicated that the aroma profile of the reconstituted sample was similar to that of the original sample.

Changes in Volatile and Non-Volatile Flavor Chemicals of "Valencia" Orange Juice over the Harvest Seasons

Florida "Valencia" oranges have a wide harvest window, covering four months after first reaching the commercial maturity. However, the influence of harvest time on juice flavor chemicals is not well documented, with the exception of sugars and acids. Therefore, we investigated the major flavor chemicals, volatile (aroma), non-volatile (taste) and mouth feel attributes, in the two harvest seasons (March to June in 2007 and February to May in 2012). Bitter limonoid compounds, limonin and nomilin, decreased gradually. Out of a total of 94 volatiles, 32 increased, 47 peaked mid to late season, and 15 decreased. Juice insoluble solids and pectin content increased over the season; however, pectin methylesterase activity remained unchanged. Fruit harvested in the earlier months had lower flavor quality. Juice from later harvests had a higher sugar/acid ratio with less bitterness, while, many important aroma compounds occurred at the highest concentrations in the middle to late season, but occurred at lower concentrations at the end of the season. The results provide information to the orange juice processing industry for selection of optimal harvest time and for setting of precise blending strategy.

Characterization of typical potent odorants in cola-flavored carbonated beverages by aroma extract dilution analysis

The aroma-active compounds in typical cola-flavored carbonated beverages were characterized using gas chromatography-olfactometry and gas chromatography-mass spectrometry. The potent odorants in the top three U.S. brands of regular colas were identified by aroma extract dilution analysis (AEDA). Among the numerous odorants identified, eugenol (spicy, clovelike, sweet) and coumarin (sweet, herbaceous) were predominant in all colas. Other predominant odorants in at least one brand included guaiacol (smoky) and linalool (floral, sweet), while 1,8-cineole (minty, eucalyptus-like) was a moderately potent odorant in all colas. Determination of the enantiomeric compositions indicated that (R)-(-)-linalool (34.5%) was a more potent odorant than the (S)-(+)-enantiomer (65.6%) due to its much lower odor detection threshold. In addition, lemon-lime and cooling attributes determined by sensory descriptive analysis had the highest odor intensities among the eight sensory descriptors. The aroma profiles of the three colas were in good agreement with the potent odorants identified by AEDA.

Identification of character-impact odorants in a cola-flavored carbonated beverage by quantitative analysis and omission studies of aroma reconstitution models

Thirty aroma-active components of a cola-flavored carbonated beverage were quantitated by stable isotope dilution assays, and their odor activity values (OAVs) were calculated. The OAV results revealed that 1,8-cineole, (R)-(-)-linalool, and octanal made the greatest contribution to the overall aroma of the cola. A cola aroma reconstitution model was constructed by adding 20 high-purity standards to an aqueous sucrose-phosphoric acid solution. The results of headspace solid-phase microextraction and sensory analyses were used to adjust the model to better match authentic cola. The rebalanced model was used as a complete model for the omission study. Sensory results indicated that omission of a group consisting of methyleugenol, (E)-cinnamaldehyde, eugenol, and (Z)- and (E)-isoeugenols differed from the complete model, while omission of the individual components of this group did not differ from the complete model. These results indicate that a balance of numerous odorants is responsible for the characteristic aroma of cola-flavored carbonated beverages.