An increase in concentration of one of the tastants in a 'real food' hearing as tested at Hz (for detailed selection criteria, see Mojet et al. isolation, separation, concentration, purification, etc. A flavor material in high concentration usually can not be used directly in food. Its . The selection of the. The very pleasant flavor of elder flowers (Sambucus niger L.) was the focus of . the Concentrations of Selected Key Aroma Compounds of Dornfelder Red Wine.
and Concentration Selection Flavor
Following cell treatments, conditioned media were collected 24 h post-treatment of different concentrations of flavoring chemicals.
In U cells, flavoring chemical treatments with 2, 3-pentanedione, cinnamaldehyde, and o-vanillin significantly affected the cell viability compared to the untreated control group Figure 1. Other flavoring chemicals, acetoin, diacetyl, maltol, and coumarin did not affect the cell viability at the tested concentrations.
To assess any effects on viability by the solvents used with the flavoring chemicals, DMSO and ethanol treatments were also performed in which no considerable effects on cell viability were observed. Percent viability of U cells 24 h post-exposure to e-cigarette flavoring chemicals, i. The viability of the cells was assessed using the Cellometer In MM6 cells, the tested flavoring chemicals caused no significant cell death except in cinnamaldehyde treatment groups Figure 2.
Percent viability of Mono Mac 6 MM6 cells 24 h post-exposure to e-cigarette flavoring chemicals, i. In order to assess the cytotoxicity of the flavored e-liquids, we exposed U cells to 0. Typically, e-liquid base includes propylene glycol PG. Thus, PG was used as a control. PG showed no cytotoxicity. Tested e-liquids caused decreased cell viability at the higher dose for each e-liquid in general.
Percent viability of U cells 24 h post-exposure to e-liquid base propylene glycol and selected nicotine-free e-liquids, i. U monocytes were treated with e-liquids at two concentrations, 0. To measure the amount of exogenous ROS released by flavoring chemicals in e-liquids, the DCFH-DA dye was treated with the flavoring chemicals of interest, and the florescence was measured. For all the tested flavoring chemicals, acetoin, diacetyl, pentanedione, cinnamaldehyde, maltol, o-vanillin, and coumarin, the solvent controls DMSO and ethanol gave rise to extremely low H 2 O 2 equivalents.
Cell-free ROS in flavoring chemicals. Oxidized DCF fluorescence was measured using a fluorometer. A Cell-free ROS in flavored e-liquids with a new atomizer at each use with one puff per min. C Cell-free ROS in acute exposure of consecutively aerosolized flavors. Statistical significance was determined by student t -test. In order to quantify the ROS levels released with a used atomizer, the same atomizer was continuously used with selected e-liquids and PG was used in between to reduce the carryover of residual ROS from one e-liquid to the next during aerosolization.
The inflammatory response due to the exposure to flavoring chemicals was assessed by treating MM6 and U monocytic cells with flavoring chemicals and measuring the IL-8 concentrations in the conditioned media. In U cells, treatment with flavoring chemicals of interest was performed at least twice with various dose concentrations.
Representative treatment and its respective control data sets were chosen. Treatment with acetoin decreased IL-8 levels in a dose-dependent manner. U monocytes were treated with flavoring chemicals for 24 h. Student t -test for comparing two groups.
Diacetyl and coumarin treatments did not show an appreciable increase in IL-8 release in the treated groups in comparison to the untreated control group data not shown. Inflammatory response due to flavored e-liquid treatment was assessed by the measurement of IL-8 concentrations in conditioned media after 24 h of flavored e-liquid treatment.
These treatments were performed twice, and representative data sets were chosen with its corresponding control. U monocytes were treated with e-liquids at two doses, 0. E-cigarettes hold the popular misconception that they have relatively less or no harm to the consumer's health in contrast to conventional combustible tobacco due to lack of sufficient evidence to prove its harmful effects.
These uncertainties are primarily due to many unstandardized facets of ENDS such as e-liquid constituents and unstandardized e-cigarette devices.
Many studies have shown that the consumption of e-cigarettes potentially causes harm to pulmonary, cardiovascular, immune and nervous systems Qasim et al. The adverse health effects of nicotine have been well established; however, health effects related to e-cigarettes without nicotine are still emerging. These health effects are mainly due to constituents of e-liquid vapors Varlet et al. Studies have shown that e-liquid aerosols contain significant levels of toxic compounds, such as aldehydes and acrolein that are detrimental to e-cigarette users Sleiman et al.
The focus of this study was to investigate the oxidative stress and inflammatory effects of commonly used e-cigarette flavoring chemicals and flavored e-liquids without nicotine. We selected cell-free ROS levels and IL-8 levels as they are well established biomarkers for oxidative stress mediated inflammation and tissue damage Vlahopoulos et al. Exogenous ROS levels produced by flavoring chemicals and e-liquids were quantified in this study. Oxidative stress caused by these reactive species activates inflammatory genes, such as IL-8 chemokine.
IL-8 has a profound effect on neutrophil recruitment and activation. We have previously demonstrated that the exposure to e-cigarette flavoring chemicals induces a significant IL-8 response Lerner et al. The flavoring chemicals, acetoin, diacetyl, pentanedione, cinnamaldehyde, maltol, ortho-vanillin, and coumarin were tested in this study. According to Tierney et al. Among the flavoring chemicals tested, cinnamaldehyde showed the most toxicity to both the cell types. O-vanillin and pentanedione also showed significant cytotoxicity.
Treatment of cells with selected e-liquids from commonly marketed categories exhibited cytotoxicity. This is consistent with other in vitro studies in which other investigators have found significant cytotoxicity with menthol flavoring aerosol exposures on epithelial cell lines Leigh et al. Mixing equal proportions of e-liquids from 10 differently flavored e-liquids gave rise to the highest cytotoxicity.
This suggests that e-cigarette users who inhale a variety of flavored e-liquids at social events are perhaps prone to higher toxic effects than those who vape a single flavor of e-liquid. There was no distinct trend in ROS release with a new or used atomizer suggesting that continuous use of an atomizer does not enhance the ROS production. Mixing various flavors of e-liquids together produced comparable H 2 O 2 equivalents to aerosolizing the same e-liquid flavors consecutively.
This simulates a social situation where smokers exchange and vape several e-liquid flavors in a short period of time. This data suggest that acute exposure to a combination of e-liquid flavors is more harmful than the exposure to a single flavor. This response is consistent with the cell viability and IL-8 data where exposure to Mixed Flavors was more cytotoxic compared to individual flavors and caused significant inflammation. This is consistent with the human study conducted by Carnevale et al.
Pro-inflammatory cytokine, IL-8, is a neutrophil chemoattractant mediating the inflammatory process. IL-8 plays a crucial role in the pathogenesis of chronic inflammation and cancer Mukaida, In our study, we observed that diacetyl, pentanedione, o-vanillin, maltol, coumarin, and cinnamaldehyde induced significant levels of IL-8 secretion in MM6 and U monocytes. These findings are similar to other studies that showed an increased pro-inflammatory response in other cells, such as THP-1 monocytes and primary human airway epithelial cells Wu et al.
In contrast, with the acetoin treatment, we observed a dose-dependent reduction in IL-8 secretion. It may be due to immuno-suppressive effects, as there have been several studies with similar results, e. Many studies have shown that e-cigarette exposure can dampen immunity against bacteria, such as Streptococcus pneumonia, Staphylococcus aureus , and viruses, such as influenza A in mice Sussan et al. Our data suggest that the presence of ROS in flavored e-liquids could play an essential role in the oxidative stress-mediated inflammatory response.
Thus, IL-8 modulation in monocytes treated with flavored e-liquids and flavoring chemicals was observed. Recent studies have demonstrated that the most preferred e-liquid flavors are the sweet, fruity, creamy, and buttery flavors. These commonly consumed flavors are derived from flavoring chemicals tested in our study. The most prevalent class of compounds in e-liquids is aldehydes which include acetaldehyde and formaldehyde example: Most prevalent non-aldehydes include acetoin and diacetyl Klager et al.
The most prevalent alcoholic compound classes include alcohols, such as maltol and menthol Tierney et al. Other most common flavoring chemicals include acetoin, diacetyl, and 2'3'-pentanedione Allen et al.
Obliterative bronchiolitis bronchiolitis obliterans is a disease caused by exposure to butter flavoring chemicals diacetyl, 2, 3-pentanedione. Chronic inhalation of these chemicals causes airway epithelium injury ultimately resulting in the formation of pro-fibrotic lesions Morgan et al.
Chocolate flavoring chemical, 2. Mucus-hypersecretion can hinder the respiratory pathogen clearance and exacerbate respiratory function in pulmonary diseases, such as COPD and asthma Vareille et al. ROS present in flavoring chemicals and flavored e-liquids can also bind to biomolecules, such as DNA and cause adducts along with histone modifications Sundar et al. Inhaling these nanoparticles provides a route of exposure of toxic chemicals to the bloodstream Lee et al.
These nanoparticles included copper, tin, chromium and nickel that can pose detrimental health risks Williams et al. Findings in our study as well as from others imply that there is much to be scientifically investigated and the ENDS must be standardized.
E-liquid flavoring chemicals and other constituents must be tightly regulated to minimize the risk of lung disease especially among teens. There are several limitations to this study. Exposure of U monocytes directly to the e-liquid provided meaningful toxicological data.
However, it ideally would be preferable to expose the cells to e-liquid aerosols with lower concentrations to understand the cellular toxicity of flavored e-liquid aerosol.
As a future direction, we intend to perform in vitro and in vivo flavored e-liquid aerosol exposures and assess the inflammatory cytokine profile. We plan to quantify other inflammatory mediators induced by acute and chronic flavored e-liquid exposures in the future. In conclusion, cinnamaldehyde, vanillin, and pentanedione were the most toxic flavoring chemicals on monocytes.
Majority of the tested flavoring chemicals and the e-liquids caused the secretion of significantly elevated pro-inflammatory cytokine levels by monocytes. Mixing multiple flavors of e-liquids caused the greatest cytotoxicity implying the health risk of acute exposure to a variety of e-liquids as opposed to a single flavor. Some flavors and their key flavoring chemicals which impart flavors were more toxic than others. Based on flavoring chemical toxicity of the individual flavoring chemicals in e-liquids, flavors can be regulated.
Further, our data indicate that tighter regulations are necessary to reduce the risk of inhalation toxicity due to exposure to e-liquids without nicotine and flavoring chemicals. The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH or the Food and Drug Administration. Flavoring chemicals in E-Cigarettes: Flavored tobacco product use among US youth aged years, Molecular and cellular responses to oxidative stress and changes in oxidation-reduction imbalance in the intestine. PubMed Abstract Google Scholar.
Interleukin-8, a chemotactic and inflammatory cytokine. Comparison of electronic cigarette refill fluid cytotoxicity using embryonic and adult models. Respiratory morbidity in a coffee processing workplace with sentinel obliterative bronchiolitis cases. Flavorings in electronic cigarettes: Taste or aroma does not only affect the perceived flavour as an independent modality, but the combination of taste and aroma can also change both the intensity and quality of the perceived flavour as a result cross-modal association Wallace, Aroma-taste cross-modal association was supported by neural imaging studies.
Potentially, aroma and taste do not only affect appetite and food intake independently but also as a synergistic combination of both modalities. Warwick, Hall, Pappas, and Schiffman reported that the combination of vanilla aroma and aspartame in a meal decreased the subsequent hunger sensation, compared with a nutritionally same but unflavoured meal.
However, the effect of the combination of aroma and taste modalities, in comparison to the independent effect of aroma or taste modality, on appetite sensation and food intake has not been reported previously, as far as the authors are aware.
The objective of this study was, therefore, to investigate the impact of aroma and taste, independently and in combination, on appetite sensation and subsequent food intake. A flavoured drink model was constructed with different combinations of strawberry aroma and taste substances sucrose and citric acid. Appetite sensation was evaluated during and after consumption, and food intake at the next meal measured. Sucrose and citric acid may interact with some aroma at a physicochemical level, resulting in changes in the aroma delivery to the nasal cavity.
The study was a single-blind, randomised crossover experiment. Water without any taste or aroma substances was used as a control preload in parallel to the three sample drinks. This study was approved by the Medical Ethical Committee of the University of Nottingham ethics reference number: A recruitment email with the inclusion and exclusion criteria was sent to prospective participants. They were asked to participate voluntarily in the study by replying to the email.
Inclusion criteria were that participants were 19—40 years healthy non-smoking females, with a normal BMI within The study was explained to all participants who were given the opportunity to ask questions.
All participants signed written informed consent prior to participation. Participants were only informed that this study was about food and appetite. No further information was given to them to prevent response bias. The participants who were recruited had a mean BMI of A brief training on reporting appetite sensation using the Visual Analogue Scale VAS was given to the 26 selected participants, followed by an in-lab practice prior to the study sessions.
Each participant completed all the four sample drink conditions on 4 separate days during their luteal phases days 18—25 of a menstrual cycle over 2 to 3 menstrual cycles. Between any two session days, there was a time interval of at least 3 days.
They were also instructed to eat the same self-chosen dinner on the evening before each session day, between Participants were then required to fast until arriving in the laboratory the next morning. Water consumption was permitted while fasting. On each of the four test sessions, participants arrived at the laboratory at Participants were requested to remove heavy shoes or clothing, and their body weight and height were assessed.
Baseline appetite sensation was reported at Unlimited water was allowed during the pasta meal. No other food or drink consumption was permitted. Participants were required to stay quietly in a waiting room, when not required to undertake study-related activities.
Protocol for each study visit. The arrows indicate the start and the end of breakfast, sample drink or pasta meal. Strawberry aroma compounds included ethyl butyrate, ethyl 2-methyl butyrate, and ethyl hexanoate, which were diluted in propylene glycol.
While drinking, participants were instructed to keep their normal breathing rate, swallow at a comfortable frequency, and focus on the perception of the flavour. On the evening prior to the study, participants were free to choose a dinner within their regular diet, but they were requested to eat a comparable meal of equivalent energy value and type prior to each study visit.
The ad libitum pasta meal was made of penne pasta Sainsbury's Supermarkets Ltd. The penne pasta was cooked and mixed with the pasta sauce, olive oil and cheddar cheese on the evening before each study day, using a standard cooking procedure. The pasta meal had an energy density of 1. The question for each appetite sensation was: Participants were asked to score on the scales by placing a mark on the horizontal line, using the computerised data acquisition system FIZZ 2.
They were instructed to ask for another portion once the previous portion was finished if required. The pasta meal EI was calculated as the weight g of pasta consumed multiplied by the energy density of the pasta 1. After the completion of the appetite sensation and food intake measurement, 60 healthy female participants, including the previous 26 participants, from the University of Nottingham were recruited to complete two sensory tests to evaluate the flavour intensity and liking of the previous four sample drinks, on two separate days.
In addition, 5 of these participants completed an extra session to measure in-vivo aroma release of the sample drinks by APCI-MS. Participants were non-smoking females of normal weight BMI: Each participant's height and weight were measured. Any participants who had a BMI outside The study procedure was explained to all potential participants, who were given the opportunity to ask questions. They all signed written informed consent prior to participation.
The 60 female participants had a mean BMI of Sample pairs were presented in a balanced and randomised order between and within pairs.
Water and crackers were used to cleanse the palate between samples. The overall sensory liking of the four sample drinks was assessed using a 9-point hedonic scale Peryam, All 60 participants assessed the four sample drinks in a randomised and balanced order.
Five participants consumed both samples in triplicate. The sample drink presentation order was balanced and randomised. A p-value less than 0. VAS appetite ratings were measured in millimetres from the left end to the points where the participants scored.
Data from the remaining 25 participants were used for the final analysis of appetite sensation. If a significant main effect of sample drinks was obtained from ANOVA, post hoc tests with Bonferroni correction for pairwise multiple comparisons were done to determine which samples were significantly different.
The rank sum of each sample was calculated by adding the sum of times when a sample was selected as less intense to twice the sum of times when the sample was selected as more intense in the perceived overall flavour. Liking ratings were analysed using Friedman statistic test with post hoc Wilcoxon signed-rank test. The objective was only to compare the intensities of aroma delivered from S2 and S4. Therefore, aroma intensity measured as arbitrary units relative intensity ratio was sufficient to analyse differences.
The VAS appetite sensation for hunger Fig. Error bars represent standard errors. The interaction effect between the sample drink and time was not significant.
Sample drinks were arranged on a line scale of rank sums of the perceived overall flavour intensity which were calculated from the pairwise ranking test Fig. A higher rank sum indicates a more intense flavour perception. Their liking ratings for S1 water and S2 aroma were also not significantly different. This indicates that the addition of sucrose and citric acid did not significantly alter the delivery of strawberry aroma to the nasal cavity. The objective of this study was to investigate the effects of the independent aroma or taste and their combination, in a sample drink, on appetite sensation and subsequent food intake.
It is worth mentioning that sucrose was used in this study rather than non-nutritive sweeteners. The combination of sugar and citric acid taste had no noticeable effect on the self-reported appetite sensation and subsequent food intake. However, little is known about the effects of citric acid and its sourness on appetite sensation and food intake.
Further investigations can be done to understand the independent effect of citric acid and the interaction of sucrose and citric acid on hunger sensation and food intake.
Aroma stimuli alone in water S2 did not affect the self-reported appetite sensation at any time point over the study period and the subsequent pasta energy intake when compared with the water control S1. The retronasal aroma in drink S2 aroma was delivered in water without the presence of a noticeable taste stimuli. It may be that retronasal aroma only induces satiation when presented with a congruent taste. However, this was not the case in the current study.
This indicated that citric acid or sucrose did not affect the physical chemistry of the strawberry aroma release. Instead, the difference in the hunger sensation was more likely to result from the difference in flavour perception between the sample drinks. S4 taste and aroma was perceived as the most intense in the perceived overall flavour, and it also suppressed hunger sensation more than S1 water , S2 aroma and S3 taste over the sample drink consumption period and for a short time after the sample drink was consumed.
This suggests that adding the two modalities, aroma and taste, together to a drink reduced the hunger sensation to a greater extent than the independent aroma or taste, potentially via increasing the overall perceived flavour intensity of the drink. However, the observed greater hunger suppression effect of the combined aroma and taste than the independent aroma or taste, may not only be due to a quantitative increase in the flavour intensity but also due to a qualitative change in the flavour quality and complexity as a result of aroma-taste cross-modal perception.
This suggested that the cognitive process of aroma and taste association, rather than a physiochemical interaction between aroma and taste, might have contributed to the observed hunger suppression.
Increasing the complexity of retronasal aroma has been reported to enhance satiation. Participants felt more satiated when consuming a yoghurt with a multi-component strawberry aroma more complex , compared with the same yoghurt with a single-component strawberry aroma of the similar intensity.
Based on the current study, whether the hunger sensation was reduced as a result of a simple addition of aroma and taste intensities, or due to a change in the perceived flavour quality via cross-modal association is inconclusive. Future experiments could be carried out to further examine this hypothesis. For example, the perceived overall flavour intensity and the palatability of a drink containing a single modality aroma or taste could be kept the same as the flavour intensity of a drink containing both aroma and taste modalities, when comparing their effect on appetite sensation and food intake.
Alternatively the effect of an incongruent aroma-taste combination on appetite sensation could be studied in comparison to a congruent aroma-taste combination with the similar flavour intensity and palatability. Because the cross-modal association between aroma and taste depends on the congruency of aroma and taste, and non-congruent aroma and taste do not show the same perceptual association that affects the flavour quality.
The mechanism behind the finding that the addition of more flavour modalities reduced hunger sensation is unknown. It may be due to the combination of physiological and psychological mechanisms. Adding flavour modalities may reduce hunger sensation by influencing the hormonal signals for satiation or satiety.
In addition, in the current study, participants might be consciously aware of the distinctly different flavour characteristics between the sample drinks. It is likely that participants might have some cognitive belief or expectation about the satiating effect of the sample drinks, which contributed to the difference in appetite sensation, to some extent. Participants may have gradually learnt that food with more intense or complex flavour profile may be more nutritionally rich, and therefore, more satiating.
Further investigation is required to explain the mechanism behind the study finding and to investigate whether the effects that have been noted are sustained at a similar level over repeated exposure. However, this did not result in a significant reduction in the subsequent pasta meal intake. Taste or aroma stimuli presented alone in a drink preload neither influenced satiation nor satiety, as measured by the appetite sensation and subsequent pasta meal energy intake, compared with the water control.
The combination of aroma and taste in a drink induced greater satiation hunger suppression than the water control and the drink with the independent aroma or taste. A quantitative increase in the perceived flavour intensity and a qualitative enhancement of the perceived flavour quality as a result of cross-modal association may have contributed to the observed hunger suppression effect of the drink with both aroma and taste.
However, subsequent pasta meal energy intake did not differ between the drinks that varied with respect to the presence of aroma and taste stimuli. This study suggests that cross modal flavour enhancement without the addition of extra energy may facilitate the development of food or drinks that contribute to the reduction of hunger.
The University of Nottingham funded this work, and Mane Ltd. Derby provided the strawberry aroma. We are grateful to Deepa Agarwal and Awg Hj Tengah Hjh for help in running the sensory sessions and all participants for their contribution. National Center for Biotechnology Information , U.
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Understanding flavor perception is a complex .. Rapid analysis of selected beer . Droplet formation Skin formation H2O Flavor FIGURE Selective the flavor phase equilibrium include flavor concentration, diluent selection, partial molar. Clonal selection of flavor producing yeasts occurring in natural populations, has obvious concentration/sensory effect relationships cannot be readily drawn.