Understanding retention and metabolization of aroma compounds using an in vitro model of oral mucosa

New Method of Direct Sampling Gas Chromatography-Ion Mobility Spectrometry to Identify the Dynamic Retronasal Volatile Compounds in the Alcoholic Beverage and Their Release Behaviors: A Case Study on Huangjiu

Owing to extremely low concentrations and dynamic changes, it is difficult to detect and trace the retronasal volatile organic compounds (VOCs) generated during the consumption of alcoholic beverages. We developed a direct sampling gas chromatography-ion mobility spectrometry (GC-IMS) method to identify the dynamic VOCs after drinking Huangjiu-a fermented alcoholic beverages. The optimal procedure was obtained: take a sip of 10 mL Huangjiu, holding it in mouth for 10 s and then swallow, and the VOCs in one nasal expiration were collected with gas sampling bag and transferred directly to the injection port of GC-IMS. The repeatability was satisfactory (RSD < 5%). Twenty-two VOCs were detected in Huangjiu, with esters and alcohols being dominant, which were divided into five distinct release behavior groups. Their release was found significantly inhibited by saliva. Overall, this new method offers a technical approach to understanding and assessing the characteristics of retronasal aroma in alcoholic beverages.

Stimulation of Saliva Affects the Release of Aroma in Wine: A Study of Microbiota, Biochemistry, and Participant Origin

Saliva influences the release of aroma in the oral cavity. The composition of human saliva varies depending on stimulation and host's origin; however, the compositional differences of saliva and their influences on aroma release have not been fully evaluated. In this study, we recruited 30 healthy adults (15 Australians and 15 Chinese) and collected saliva samples at three stages: before, during, and after stimulation. Salivary samples were characterized by the flow rate, total protein concentration, esterase activity, microbiome composition by full-length 16S rRNA gene sequencing, and the ability to release aroma from wine by headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS). Differences in salivary composition and specific wine volatiles were found between Australian and Chinese participants and among the three stimulation stages. Significant correlations between the relative abundance of 3 bacterial species and 10 wine volatiles were observed. Our results confirm the influence of participant's geographic origin and stimulation on the salivary composition, highlighting the role of salivary components, especially salivary bacteria, on the release of aroma from wine.

Flavor Engineering: A comprehensive review of biological foundations, AI integration, industrial development, and socio-cultural dynamics

This state-of-the-art review comprehensively explores flavor development, spanning biological foundations, analytical methodologies, and the socio-cultural impact. It incorporates an industrial perspective and examines the role of artificial intelligence (AI) in flavor science. Initiating with the biological intricacies of flavor, the review delves into the interplay of taste, aroma, and texture rooted in sensory experiences. Advances in mathematical modeling and analytical techniques open avenues for interdisciplinary collaboration and technological innovation, addressing variations in flavor perception. The impact of flavor extends beyond gustatory experiences, influencing economics, society, nutrition, health, and technological innovation. This collective understanding deepens insight into the dynamic interplay between olfactory and flavor elements within cultural landscapes, emphasizing how sensory experiences are woven into human culture and heritage. The evolution of food flavor analysis, encompassing sensory analysis, instrumental analysis, a combination of both, and the integration of artificial intelligence techniques, signifies dynamic progression and, promising advancements in precision, efficiency, and innovation within the flavor industry. This comprehensive review involved analyzing key aspects within flavor engineering and related sectors. Articles and book chapters on these topics were collected using metadata analysis. The data for this analysis was extracted from major online databases, including Scopus, Web of Science, and ScienceDirect.

Peanut Pairing Baijiu: To Enhance Retronasal Aroma Intensity while Reducing Baijiu Aftertaste

Liquor-pairing food is a common dietary combination. Baijiu and peanuts are unquestionably a classic pairing in China. But no one has explained why. Its alteration in baijiu flavor was studied using multiple sensory evaluation, as well as nontargeted proton-transfer reaction mass spectrometry coupled with GC × GC-MS. Multiple statistical analyses were used to discover the changes in the retronasal aroma and its contribution to baijiu flavor. It showed that the consumption of peanuts enhances the burst intensity of ester aroma (0.814-1.00) and Jiao aroma (0.889-0.963) but decreases the aftertaste of baijiu (p < 0.05). Meanwhile, it increases the release intensity and advances the burst time of baijiu retronasal aroma (p < 0.05), suppressing its aftertaste through the retention effect of the food matrix, the changes in oral processing, and cross-modal interactions. Hydrophobicity, polarity, and chemical characteristics are key factors of the uneven impact of accompanying food to aroma compounds. Esters, especially ethyl caprylate (2103 ± 927 to 51.9 ± 4.05) is most impacted by peanuts and contributes most to baijiu flavor changes. Pyrazines from peanut enhance the Qu-aroma, grain aroma, and Chen aroma in baijiu flavor. Therefore, we revealed the chemical nature of baijiu-peanut combination and help to optimize baijiu consumption experience.

Microbial β C-S Lyases: Enzymes with Multifaceted Roles in Flavor Generation

β C-S lyases (β-CSLs; EC 4.4.1.8) are enzymes catalyzing the dissociation of β carbon-sulfur bonds of cysteine S-conjugates to produce odorant metabolites with a free thiol group. These enzymes are increasingly studied for their role in flavor generation in a variety of food products, whether these processes occur directly in plants, by microbial β-CSLs during fermentation, or in the mouth under the action of the oral microbiota. Microbial β-CSLs react with sulfur aroma precursors present in beverages, vegetables, fruits, or aromatic herbs like hop but also potentially with some precursors formed through Maillard reactions in cooked foods such as meat or coffee. β-CSLs from microorganisms like yeasts and lactic acid bacteria have been studied for their role in the release of polyfunctional thiols in wine and beer during fermentation. In addition, β-CSLs from microorganisms of the human oral cavity were shown to metabolize similar precursors and to produce aroma in the mouth with an impact on retro-olfaction. This review summarizes the current knowledge on β-CSLs involved in flavor generation with a focus on enzymes from microbial species present either in the fermentative processes or in the oral cavity. This paper highlights the importance of this enzyme family in the food continuum, from production to consumption, and offers new perspectives concerning the utilization of β-CSLs as a flavor enhancer.

Drivers of the In-Mouth Interaction between Lupin Protein Isolate and Selected Aroma Compounds: A Proton Transfer Reaction-Mass Spectrometry and Dynamic Time Intensity Analysis

Plant proteins often carry off-notes, necessitating customized aroma addition. In vitro studies revealed protein-aroma binding, limiting release during consumption. This study employs in vivo nose space proton transfer reaction-time-of-flight-mass spectrometry and dynamic sensory evaluation (time intensity) to explore in-mouth interactions. In a lupin protein-based aqueous system, a sensory evaluation of a trained "green" attribute was conducted simultaneously with aroma release of hexanal, nonanal, and 2-nonanone during consumption. Results demonstrated that enlarging aldehyde chains and relocating the keto group reduced maximum perceived intensity (Imax_R) by 71.92 and 72.25%. Protein addition decreased Imax_R by 30.91, 36.84, and 72.41%, indicating protein-aroma interactions. Sensory findings revealed a perceived intensity that was lower upon protein addition. Aroma lingering correlated with aroma compounds' volatility and hydrophobicity, with nonanal exhibiting the longest persistence. In vitro mucin addition increased aroma binding four to 12-fold. Combining PTR-ToF-MS and time intensity elucidated crucial food behavior, i.e., protein-aroma interactions, that are pivotal for food design.

Rattus norvegicus Glutathione Transferase Omega 1 Localization in Oral Tissues and Interactions with Food Phytochemicals

Glutathione transferases are xenobiotic-metabolizing enzymes with both glutathione-conjugation and ligandin roles. GSTs are present in chemosensory tissues and fluids of the nasal/oral cavities where they protect tissues from exogenous compounds, including food molecules. In the present study, we explored the presence of the omega-class glutathione transferase (GSTO1) in the rat oral cavity. Using immunohistochemistry, GSTO1 expression was found in taste bud cells of the tongue epithelium and buccal cells of the oral epithelium. Buccal and lingual extracts exhibited thiol-transferase activity (4.9 ± 0.1 and 1.8 ± 0.1 μM/s/mg, respectively). A slight reduction from 4.9 ± 0.1 to 4.2 ± 0.1 μM/s/mg (p < 0.05; Student's t test) was observed in the buccal extract with 100 μM GSTO1-IN-1, a specific inhibitor of GSTO1. RnGSTO1 exhibited the usual activities of omega GSTs, i.e., thiol-transferase (catalytic efficiency of 8.9 × 104 M-1·s-1), and phenacyl-glutathione reductase (catalytic efficiency of 8.9 × 105 M-1·s-1) activities, similar to human GSTO1. RnGSTO1 interacts with food phytochemicals, including bitter compounds such as luteolin (Ki = 3.3 ± 1.9 μM). Crystal structure analysis suggests that luteolin most probably binds to RnGSTO1 ligandin site. Our results suggest that GSTO1 could interact with food phytochemicals in the oral cavity.

The coming future: The role of the oral-microbiota-brain axis in aroma release and perception

The field of aroma release and perception during the oral process has been well studied. However, the traditional approaches have not fully explored the integration of oral biology, microbiology, and neurology to further understand aroma release and perception mechanisms. Herein, to address the existing challenges in this field, we introduce the oral-microbiota-brain axis (OMBA), an innovative framework that encapsulates the interactive relationships among saliva and the oral mucosa, the oral microbiota, and the brain in aroma release and perception. This review introduces the OMBA and highlights its role as a key interface facilitating the sensory experience of aroma. Based on a comprehensive literature survey, the specific roles of the oral mucosa, oral microbiota, saliva, and brain in the OMBA are discussed. This integrated approach reveals the importance of each component and the interconnected relationships within this axis in the overall process of aroma release and perception. Saliva and the oral mucosa play fundamental roles in aroma release and perception; the oral microbiota regulates aroma release and impacts olfactory perception; and the brain's intricate neural circuitry is central to the decoding and interpretation of aroma signals. The components of this axis are interdependent, and imbalances can disrupt aroma perception. The OMBA framework not only enhances our comprehension of aroma release and perception but also paves the way for innovative applications that could heighten sensory experiences.

Development of New Models of Oral Mucosa to Investigate the Impact of the Structure of Transmembrane Mucin-1 on the Mucosal Pellicle Formation and Its Physicochemical Properties

The mucosal pellicle (MP) is a biological film protecting the oral mucosa. It is composed of bounded salivary proteins and transmembrane mucin MUC1 expressed by oral epithelial cells. Previous research indicates that MUC1 expression enhances the binding of the main salivary protein forming the MP, MUC5B. This study investigated the influence of MUC1 structure on MP formation. A TR146 cell line, which does not express MUC1 natively, was stably transfected with genes coding for three MUC1 isoforms differing in the structure of the two main extracellular domains: the VNTR domain, exhibiting a variable number of tandem repeats, and the SEA domain, maintaining the two bound subunits of MUC1. Semi-quantification of MUC1 using dot blot chemiluminescence showed comparable expression levels in all transfected cell lines. Semi-quantification of MUC5B by immunostaining after incubation with saliva revealed that MUC1 expression significantly increased MUC5B adsorption. Neither the VNTR domain nor the SEA domain was influenced MUC5B anchoring, suggesting the key role of the MUC1 N-terminal domain. AFM-IR nanospectroscopy revealed discernible shifts indicative of changes in the chemical properties at the cell surface due to the expression of the MUC1 isoform. Furthermore, the observed chemical shifts suggest the involvement of hydrophobic effects in the interaction between MUC1 and salivary proteins.

Characterization of human oxidoreductases involved in aldehyde odorant metabolism

Oxidoreductases are major enzymes of xenobiotic metabolism. Consequently, they are essential in the chemoprotection of the human body. Many xenobiotic metabolism enzymes have been shown to be involved in chemosensory tissue protection. Among them, some were additionally shown to be involved in chemosensory perception, acting in signal termination as well as in the generation of metabolites that change the activation pattern of chemosensory receptors. Oxidoreductases, especially aldehyde dehydrogenases and aldo-keto reductases, are the first barrier against aldehyde compounds, which include numerous odorants. Using a mass spectrometry approach, we characterized the most highly expressed members of these families in the human nasal mucus sampled in the olfactory vicinity. Their expression was also demonstrated using immunohistochemistry in human epitheliums sampled in the olfactory vicinity. Recombinant enzymes corresponding to three highly expressed human oxidoreductases (ALDH1A1, ALDH3A1, AKR1B10) were used to demonstrate the high enzymatic activity of these enzymes toward aldehyde odorants. The structure‒function relationship set based on the enzymatic parameters characterization of a series of aldehyde odorant compounds was supported by the X-ray structure resolution of human ALDH3A1 in complex with octanal.

Role of Insect and Mammal Glutathione Transferases in Chemoperception

Glutathione transferases (GSTs) are ubiquitous key enzymes with different activities as transferases or isomerases. As key detoxifying enzymes, GSTs are expressed in the chemosensory organs. They fulfill an essential protective role because the chemosensory organs are located in the main entry paths of exogenous compounds within the body. In addition to this protective function, they modulate the perception process by metabolizing exogenous molecules, including tastants and odorants. Chemosensory detection involves the interaction of chemosensory molecules with receptors. GST contributes to signal termination by metabolizing these molecules. By reducing the concentration of chemosensory molecules before receptor binding, GST modulates receptor activation and, therefore, the perception of these molecules. The balance of chemoperception by GSTs has been shown in insects as well as in mammals, although their chemosensory systems are not evolutionarily connected. This review will provide knowledge supporting the involvement of GSTs in chemoperception, describing their localization in these systems as well as their enzymatic capacity toward odorants, sapid molecules, and pheromones in insects and mammals. Their different roles in chemosensory organs will be discussed in light of the evolutionary advantage of the coupling of the detoxification system and chemosensory system through GSTs.

Recent trends in aroma release and perception during food oral processing: A review

The dynamic and complex peculiarities of the oral environment present several challenges for controlling the aroma release during food consumption. They also pose higher requirements for designing food with better sensory quality. This requires a comprehensive understanding of the basic rules of aroma transmission and aroma perception during food oral processing and its behind mechanism. This review summarized the latest developments in aroma release from food to retronasal cavity, aroma release and delivery influencing factors, aroma perception mechanisms. The individual variance is the most important factor affecting aroma release and perception. Therefore, the intelligent chewing simulator is the key to establish a standard analytical method. The key odorants perceived from the retronasal cavity should be given more attention during food oral processing. Identification of the olfactory receptor activated by specific odorants and its binding mechanisms are still the bottleneck. Electrophysiology and image technology are the new noninvasive technologies in elucidating the brain signals among multisensory, which can fill the gap between aroma perception and other senses. Moreover, it is necessary to develop a new approach to integrate the relationship among aroma binding parameters, aroma concentration, aroma attributes and cross-modal reactions to make the aroma prediction model more accurate.

The role of capsaicin stimulation on the physicochemical properties of saliva and aroma release in model aqueous and oil systems

Capsaicin increases saliva production, but the impact of this additional saliva on the food matrix is unknown. This study aimed to explain the impact of capsaicin on saliva properties and in-vivo release of 14 aroma compounds in aqueous [aqu] and oil systems [oil]. To investigate the physicochemical effect from diverse properties of aroma compounds, one healthy subject participated in all the sessions to minimise large variations between individuals. Capsaicin enhanced saliva flow rate (by 172% [aqu] and 85% [oil]) and salivary protein concentration (by 142% [aqu] and 149% [oil]). Furthermore, capsaicin-in-oil stimulated saliva formed a more stable emulsion in the mouth (17% higher zeta-potential and 15% smaller particle size). In-nose release concentrations measured by APCI-MS for certain esters were reduced by capsaicin (e.g., isoamyl acetate was reduced by 65% [aqu] and 76% [oil]), which suggests that capsaicin may induce stronger oral interactions between specific aroma compounds and salivary proteins.

Metabolism of Cysteine Conjugates and Production of Flavor Sulfur Compounds by a Carbon-Sulfur Lyase from the Oral Anaerobe Fusobacterium nucleatum

Flavor perception is a key factor in the acceptance or rejection of food. Aroma precursors such as cysteine conjugates are present in various plant-based foods and are metabolized into odorant thiols in the oral cavity. To date, the involved enzymes are unknown, despite previous studies pointing out the likely involvement of carbon-sulfur lyases (C-S lyases) from the oral microbiota. In this study, we show that saliva metabolizes allyl-cysteine into odorant thiol metabolites, with evidence suggesting that microbial pyridoxal phosphate-dependent C-S lyases are involved in the enzymatic process. A phylogenetic analysis of PatB C-S lyase sequences in four oral subspecies of Fusobacterium nucleatum was carried out and led to the identification of several putative targets. FnaPatB1 from F. nucleatum subspecies animalis, a putative C-S lyase, was characterized and showed high activity with a range of cysteine conjugates. Enzymatic and X-ray crystallographic data showed that FnaPatB1 metabolizes cysteine derivatives within a unique active site environment that enables the formation of flavor sulfur compounds. Using an enzymatic screen with a library of pure compounds, we identified several inhibitors able to reduce the C-S lyase activity of FnaPatB1 in vitro, which paves the way for controlling the release of odorant sulfur compounds from their cysteine precursors in the oral cavity.

Hydrogen bonds and hydrophobicity with mucin and α-amylase induced honey aroma in Feng-flavor Baijiu during 16 years aging

Honey aroma is one of the most significant factors of Feng-flavor Baijiu, which is also an essential element to attract consumers. However, the evaluation and chemical basis of honey aroma is unclear. Palmitoleic acid, lagochilin, phomotenone and ethyl behenate were confirmed to be the strongest contributors to honey aroma by time-intensity analysis and UHPLC-Q-Orbitrap-MS. Predictive modeling was developed for processing honey aroma intensity responses in order to obtain significant Feng-flavor Baijiu rankings. In this study, the effects of ex-vivo saliva on Feng-flavor Baijiu were investigated for the first time. Mucin and α-amylase, as major proteins in ex-vivo saliva, were applied to simulate molecular docking of ethyl benzoate. Mucin and α-amylase modified the aroma release, which depended on hydrogen bonds and hydrophobic interactions, respectively. It is blazing a trail in the field in sensory experience of Feng-flavor Baijiu as well as contributes to our understanding of Feng-flavor Baijiu drinking process.

Odorant Metabolism in Humans

Odorants are relatively small molecules which are easily taken up and distributed in the human body. Despite their relevance in everyday life, however, only a limited amount of evidence about their metabolism, pathways, and bioactivities in the human body exists. With this Review, we aim to encourage future interdisciplinary research on the function and mechanisms of the biotransformation of odorants, involving different disciplines such as nutrition, medicine, biochemistry, chemistry, and sensory sciences. Starting with a general overview of the different ways of odorant uptake and enzymes involved in the metabolism of odorants, a more precise description of biotransformation processes and their function in the oral cavity, the nose, the lower respiratory tract (LRT), and the gastrointestinal tract (GIT) is given together with an overview of the different routes of odorant excretion. Finally, perspectives for future research are discussed.

Effects of oenological tannins on aroma release and perception of oxidized and non-oxidized red wine: A dynamic real-time in-vivo study coupling sensory evaluation and analytical chemistry

Addition of oenological tannins claims to have a positive impact on wine stability, protection from oxidation and likely sensory persistence. However, their role on red wine aroma during oxidation is controversial. The present study aims at investigating the effect of addition of oenological tannins on wine flavour (mainly aroma) before and after air exposure. Temporal Dominance of Sensations, a dynamic sensory evaluation, was coupled with a dynamic chemical measurement (nosespace analysis) using a Proton-Transfer-Reaction Mass-Spectrometer connected to the nasal cavity of 17 assessors. Results showed that the oxidation of a non-oaked Pinot Noir red wine decreases the fruity aroma dominance and increases the maderised and prune one. A contextual decrease of the fruity ethyl decanoate and increase of oxidative Strecker aldehydes are observed. Ellagitannins but not proanthocyanidins preserved perception of fruitiness and prevented increase of maderised notes. Moreover, ellagitannins increase the aroma persistence mainly in the non-oxidized wine.

Predicting Satiety from the Analysis of Human Saliva Using Mid-Infrared Spectroscopy Combined with Chemometrics

The aim of this study was to evaluate the ability of mid-infrared (MIR) spectroscopy combined with chemometrics to analyze unstimulated saliva as a method to predict satiety in healthy participants. This study also evaluated features in saliva that were related to individual perceptions of human–food interactions. The coefficient of determination (R²) and standard error in cross validation (SECV) for the prediction of satiety in all saliva samples were 0.62 and 225.7 satiety area under the curve (AUC), respectively. A correlation between saliva and satiety was found, however, the quantitative prediction of satiety using unstimulated saliva was not robust. Differences in the MIR spectra of saliva between low and high satiety groups, were observed in the following frequency ratios: 1542/2060 cm⁻¹ (total protein), 1637/3097 cm⁻¹ (α-amino acids), and 1637/616 (chlorides) cm⁻¹. In addition, good to excellent models were obtained for the prediction of satiety groups defined as low or high satiety participants (R² 0.92 and SECV 0.10), demonstrating that this method could be used to identify low or high satiety perception types and to select participants for appetite studies. Although quantitative PLS calibration models were not achieved, a qualitative model for the prediction of low and high satiety perception types was obtained using PLS-DA. Furthermore, this study showed that it might be possible to evaluate human/food interactions using MIR spectroscopy as a rapid and cost-effective tool.

Molecular mechanisms of aroma persistence: From noncovalent interactions between aroma compounds and the oral mucosa to metabolization of aroma compounds by saliva and oral cells

The present study aims to reveal the molecular mechanisms underlying aroma persistence, as it plays a major role in food appreciation and quality. A multidisciplinary approach including ex vivo experiments using a novel model of oral mucosa and saliva as well as in vivo dynamic instrumental and sensory experiments was applied. Ex vivo results showed a reduction in aroma release between 7 and 86% in the presence of the thin layer of salivary proteins covering the oral mucosa (mucosal pellicle). This reduction was explained by hydrophobic interactions involving the mucosal pellicle and by the ability of oral cells and saliva to metabolize specific aroma compounds. The in vivo evaluation of exhaled air and perception confirmed the ex vivo findings. In conclusion, this work reveals the need to consider physiological reactions occurring during food oral processing to better understand aroma persistence and open new avenues of research.

Oral enzymatic detoxification system: Insights obtained from proteome analysis to understand its potential impact on aroma metabolization

The oral cavity is an entry path into the body, enabling the intake of nutrients but also leading to the ingestion of harmful substances. Thus, saliva and oral tissues contain enzyme systems that enable the early neutralization of xenobiotics as soon as they enter the body. Based on recently published oral proteomic data from several research groups, this review identifies and compiles the primary detoxification enzymes (also known as xenobiotic-metabolizing enzymes) present in saliva and the oral epithelium. The functions and the metabolic activity of these enzymes are presented. Then, the activity of these enzymes in saliva, which is an extracellular fluid, is discussed with regard to the salivary parameters. The next part of the review presents research evidencing oral metabolization of aroma compounds and the putative involved enzymes. The last part discusses the potential role of these enzymatic reactions on the perception of aroma compounds in light of recent pieces of evidence of in vivo oral metabolization of aroma compounds affecting their release in mouth and their perception. Thus, this review highlights different enzymes appearing as relevant to explain aroma metabolism in the oral cavity. It also points out that further works are needed to unravel the effect of the oral enzymatic detoxification system on the perception of food flavor in the context of the consumption of complex food matrices, while considering the impact of food oral processing. Thus, it constitutes a basis to explore these biochemical mechanisms and their impact on flavor perception.

Impact of Oral Microbiota on Flavor Perception: From Food Processing to In-Mouth Metabolization

Flavor perception during food intake is one of the main drivers of food acceptability and consumption. Recent studies have pointed to the oral microbiota as an important factor modulating flavor perception. This review introduces general characteristics of the oral microbiota, factors potentially influencing its composition, as well as known relationships between oral microbiota and chemosensory perception. We also review diverse evidenced mechanisms enabling the modulation of chemosensory perception by the microbiota. They include modulation of the chemosensory receptors activation by microbial metabolites but also modification of receptors expression. Specific enzymatic reactions catalyzed by oral microorganisms generate fragrant molecules from aroma precursors in the mouth. Interestingly, these reactions also occur during the processing of fermented beverages, such as wine and beer. In this context, two groups of aroma precursors are presented and discussed, namely, glycoside conjugates and cysteine conjugates, which can generate aroma compounds both in fermented beverages and in the mouth. The two entailed families of enzymes, i.e., glycosidases and carbon-sulfur lyases, appear to be promising targets to understand the complexity of flavor perception in the mouth as well as potential biotechnological tools for flavor enhancement or production of specific flavor compounds.

Influence of Prebiotic Fructans on Retronasal Aroma from Elderly Individuals

This study investigates for the first time the role of fructans with prebiotic effects (oligofructose and inulin) on retronasal aroma among elderly individuals. The impact of oligofructose (20% w/w) on retronasal aroma release was investigated using proton transfer reaction-mass spectrometry (PTR-MS) after 73 elderly individuals consumed aqueous solutions aromatized with five aroma compounds (pentan-2-one, nonan-2-one, hexan-2,3-dione, octanal and linalool). The influence of oligofructose and inulin (10% w/w) on the perceived intensity (n = 26) of two aroma descriptors (butter and floral) was also studied together with the possibility of a dumping effect on aroma evaluation due to the sweetness provided by the fructans. The results showed that the presence of oligofructose produced a significant reduction in retronasal aroma release, which could be generally explained by the physicochemical properties of aroma compounds. The presence of prebiotic fructans did not significantly affect the perceived intensity of butter and floral notes, although a dumping effect for the butter descriptor in the presence of oligofructose was observed. To conclude, these findings suggest that although fructans can exert an impact on retronasal aroma, they can be used at precise concentrations to increase the prebiotic fibre content of food products without affecting the aroma profile of foods.

Recent trends in the chromatographic analysis of volatile flavor and fragrance compounds: Annual review 2020

The chromatographic analysis of volatile flavor and fragrance compounds is performed routinely in several industries and in many fields of scientific research. Typical applications include food-, environmental-, essential oil- and cosmetics analysis. Even though the analysis of flavors and fragrances have become increasingly standardized during the past decade, there are still a large variety of techniques that can be used for their extraction, chemical analysis, and sensory analysis. Moreover, there are certain less commonly used techniques that are now being used with increased frequency and that are showing the potential of being used as alternatives to the existing standard techniques. In this annual review, the techniques that were most commonly used in 2020 for the investigation of these volatile compounds are discussed. In addition, a number of emerging trends are discussed, notably the use of solvent assisted flavor evaporation (SAFE) for extraction, GC ion mobility spectrometry (IMS) for volatile compound analysis and electronic senses, that is, E-noses and E-tongues, for sensory analysis. Miscellaneous hyphenated techniques, advances in stationary phase chemistry and a number of interesting applications are also highlighted.

Oral Release Behavior of Wine Aroma Compounds by Using In-Mouth Headspace Sorptive Extraction (HSSE) Method

The oral release behavior of wine aroma compounds was determined by using an in-mouth headspace sorptive extraction (HSSE) procedure. For this, 32 volunteers rinsed their mouths with a red wine. Aroma release was monitored at three time points (immediately, 60 s, and 120 s) after wine expectoration. Twenty-two aroma compounds belonging to different chemical classes were identified in the mouth. Despite the large inter-individual differences, some interesting trends in oral release behavior were observed depending on the chemical family. In general, esters and linear alcohols showed rapid losses in the mouth over the three sampling times and therefore showed a low oral aroma persistence. On the contrary, terpenes, lactones, and C13 norisoprenoids showed lower variations in oral aroma release over time, thus showing a higher oral aroma persistence. Additionally, and despite their low polarity, furanic acids and guaiacol showed the highest oral aroma persistence. This work represents the first large study regarding in-mouth aroma release behavior after wine tasting, using real wines, and it confirmed that oral release behavior does not only depend on the physicochemical properties of aroma compounds but also on other features, such as the molecular structure and probably, on the characteristics and composition of the oral environment.

The Relationship Between Salivary Redox, Diet, and Food Flavor Perception

The mouth is the gateway for entrance of food and microorganisms into the organism. The oral cavity is bathed by saliva, which is thus the first fluid that food and microorganisms will face after their entrance. As a result, saliva plays different functions, including lubrication, predigestion, protection, detoxification, and even transport of taste compounds to chemoreceptors located in the taste buds. To ensure its function of protection, saliva contains reactive harmful compounds such as reactive oxygen species that are controlled and neutralized by the antioxidant activity of saliva. Several antioxidant molecules control the production of molecules such as reactive oxygen compounds, neutralize them and/or repair the damage they have caused. Therefore, a balance between reactive oxidant species and antioxidant compounds exists. At the same time, food can also contain antioxidant compounds, which can participate in the equilibrium of this balance. Numerous studies have investigated the effects of different food components on the antioxidant capacity of saliva that correspond to the ability of saliva to neutralize reactive oxygen species. Contradictory results have sometimes been obtained. Moreover, some antioxidant compounds are also cofactors of enzymatic reactions that affect flavor compounds. Recent studies have considered the salivary antioxidant capacity to explain the release of flavor compounds ex vivo or in vivo. This article aims to review the effect of food on the antioxidant capacity of saliva and the impact of salivary antioxidant capacity on flavor perception after a brief presentation of the different molecules involved.

Interactions between Polyphenols and Volatile Compounds in Wine: A Literature Review on Physicochemical and Sensory Insights

Wine polyphenols (PPhs) and volatile organic compounds (VOCs) are responsible for two of the main sensory characteristics in defining the complexity and quality of red wines: astringency and aroma. Wine VOCs’ volatility and solubility are strongly influenced by the matrix composition, including the interactions with PPhs. To date, these interactions have not been deeply studied, although the topic is of great interest in oenology. This article reviews the available knowledge on the main physicochemical and sensory effects of polyphenols on the release and perception of wine aromas in orthonasal and retronasal conditions. It describes the molecular insights and the phenomena that can modify VOCs behavior, according to the different chemical classes. It introduces the possible impact of saliva on aroma release and perception through the modulation of polyphenols–aroma compounds interactions. Limitations and possible gaps to overcome are presented together with updated approaches used to investigate those interactions and their effects, as well as future perspectives on the subject.

Aroma release during wine consumption: Factors and analytical approaches

During wine consumption, aroma compounds are released from the wine matrix and are transported to the olfactory receptor in vivo, leading to retronasal perception which can affect consumer acceptance. During this process, in addition to the influence of the wine matrix compositions, some physiological factors can significantly influence aroma release leading to altered concentrations of the aroma compounds that reach the receptors. Therefore, this review is focused on the impact of multiple factors, including the physiology and wine matrix, on the aroma released during wine tasting. Moreover, to reflect the pattern of volatiles that reach the olfactory receptors during wine consumption, some analytical approaches have been described for in vitro and in vivo conditions.

Sensorial Perception of Astringency: Oral Mechanisms and Current Analysis Methods

Understanding consumers' food choices and the psychological processes involved in their preferences is crucial to promote more mindful eating regulation and guide food design. Fortifying foods minimizing the oral dryness, rough, and puckering associated with many functional ingredients has been attracting interest in understanding oral astringency over the years. A variety of studies have explored the sensorial mechanisms and the food properties determining astringency perception. The present review provides a deeper understanding of astringency, a general view of the oral mechanisms involved, and the exciting variety of the latest methods used to direct and indirectly quantify and simulate the astringency perception and the specific mechanisms involved.