Temporal patterns in taste sensitivity

Individuals vary in their ability to taste, and some individuals are more sensitive to certain tastes than others. Taste sensitivity is a predictor of various factors, such as diet, eating behavior, appetite regulation, and overall health. Furthermore, taste sensitivity can fluctuate within an individual over short to long periods of time: for example, in daily (diurnal) cycles, monthly (menstrual) cycles (in females), and yearly (seasonal) cycles. Understanding these temporal patterns is important for understanding individual eating habits and food preferences, particularly in the context of personalized and precision nutrition. This review provides a summary of the literature on taste sensitivity patterns across 3 temporal dimensions: daily, monthly, and yearly. Good evidence for diurnal patterns has been observed for sweet taste and fat taste, although the evidence is limited to rodent studies for the latter. Obese populations showed limited variation to sweet and fat taste sensitivities over a day, with limited variation in sweet taste sensitivity being linked to insulin resistance. There were mixed observations of temporal variation in sensitivity to sour and umami tastes, and there were no patterns in sensitivity to bitter taste. Menstrual patterns in sweet taste sensitivity were consistent with patterns in food intake. Other taste modality investigations had mixed findings that had little agreement across studies. Hormonal changes in females influence taste sensitivity to some degree, although the overall patterns are unclear. Seasonal patterns have been less well studied, but there is weak evidence that sweet, salty, and bitter taste sensitivities change across seasons. Differences in seasonal taste patterns have been observed in subgroups susceptible to mental health disorders, requiring further investigation. Patterns of taste sensitivity are evident across multiple temporal dimensions, and more research is needed to determine the influence of these patterns on food intake. Dysregulation of these patterns may also be a marker of certain diseases or health conditions, warranting further investigation. Notably, the alimentary tastes (umami, fat, and carbohydrate) are underrepresented in this research area and require additional investigation.

Variability of oral/taste sensitivity to fat: An investigation of attribution from detection threshold methods with repeated measurements

Accumulating psychophysical evidence suggests substantial individual variability in oral/taste sensitivity to non-esterified, long-chain fatty acids (NEFA), which is commonly referred to as fat taste or oleogustus. Recent studies have sought to determine its associations with human factors such as body mass index (BMI) and food preferences, as it has been claimed that excessive fat consumption is related to several health conditions, including obesity. Yet, the findings are controversial. On the other hand, it has been noted that considerable variability also occurs based on the methodology used to measure the fatty acid taste. Specifically, learning effects have been observed over repeated measurements of the detection threshold of NEFA, yet there has been no methodology available to take into account these learning effects. Accordingly, in the present study, a novel methodology using a descending-block dual reminder A-Not A (DR A-Not A) method with a warm-up has been proposed to measure the NEFA detection threshold based on the signal detection theory and considering NEFA taste learning effects over repeated sessions. Homogeneous subjects (young adult Korean females within the normal BMI range, non-vegetarians) were randomized to either the novel descending-block DR A-Not A method or ascending triangle method that is commonly used for fat perception studies. Pure oleic acid emulsions were used as fat taste stimuli to be discriminated from pure mineral water. Each subject completed 14 repeated visits. For the ascending triangle method, 14 thresholds were determined using a stopping rule, while for the novel method, 7 thresholds were determined each per two consecutive days, using a criterion of a lower limit of 50% confidence interval of d' = 0.5, considering the practical aspects of taste studies in food sensory science. Based on the group median results of the last two visits, the variability of the detection thresholds was reduced using the novel descending-block DR A-Not A method due to better learning effects over repeated sessions. This shows the potential of the descending-block DR A-Not A threshold method for further studies on oral/taste sensitivity to fat.

Integrating Effects of Human Physiology, Psychology, and Individual Variations on Satiety–An Exploratory Study

Satiety can influence food intake, and as a consequence has the potential to affect weight and obesity. Human factors such as physiology and psychology are likely to be important in determining satiety. However, it is not well-understood how these factors (individual variations) alone or combined contribute to satiety feelings. In addition, there have been limited or no attempts to use a holistic approach to evaluate satiety. In this study, three plant-based foods were used as mid-morning snack for 52 participants to evaluate satiety response (during three consecutive days, one-day-one-food type). The foods were served ad libitum until participants felt comfortably full prior to satiety monitoring. The study explored diverse human factors (n = 30) that might contribute to satiety including those related to oral physiology, metabolic factors, body composition and psychology. It identified important variables for satiety as well as the interactions among them and the influences of age, gender, and low satiety phenotype (consistently lower reported fullness scores) on satiety. Overall, combinations of factors rather than individual ones contributed to self-reported satiety. Food factors (e.g., type, composition) had limited effects, but there were only three types used in the study. The combination of metabolic factors [respiratory quotient, age, and body energy usage type (e.g., carbohydrate or fat)], oral sensitivity & processing, personality traits (agreeableness, conscientiousness, and neuroticism), and eating behavior (e.g., emotional and external eating) were the most important for explaining individual satiety responses. Older participants had significantly higher reported satiety than younger participants, associated with significant differences in oral physiology, increased body fat, and mature psychological characters. Moreover, different satiety phenotypes had significant differences in relationships with body fat, oral physiology, personalities, food neophobia, and eating behaviors. The results of this study indicate that much greater insights into the factors determining satiety responses can be obtained by combining multiple food and human physiological and psychological characteristics. This study used more diverse measures of individual variation than previous studies of satiety and points the way toward a more holistic approach to understanding the (control of) perceptions of fullness at both individual and group levels.

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.

Olfactory Cues in Infant Feeds: Volatile Profiles of Different Milks Fed to Preterm Infants

Background: Smell is determined by odor-active volatile compounds that bind to specific olfactory receptors, allowing us to discriminate different smells. Olfactory stimulation may assist with digestion and metabolism of feeds in the neonate by activation of the cephalic phase response of digestion. Infants' physiological responses to the smell of different milks suggest they can distinguish between breastmilk and infant formula. We aimed to describe the profile of volatile compounds in preterm breastmilk and investigate how this differed from that of other preterm infant feeding options including pasteurized donor breastmilk, breastmilk with bovine milk-based fortifier, human milk-based products and various infant formulas. Methods: Forty-seven milk samples (13 different infant formulas and 34 human milk-based samples) were analyzed. Volatile compounds were extracted using Solid Phase Micro Extraction. Identification and relative quantification were carried out by Gas Chromatography with Mass Spectrometry. Principal Component Analysis (PCA) and one-way Analysis of Variance (ANOVA) with Tukey's HSD (parametric data) or Conover's post-hoc test (non-parametric data) were used as appropriate to explore differences in volatile profiles among milk types. Results: In total, 122 compounds were identified. Breastmilk containing bovine milk-based fortifier presented the highest number of compounds (109) and liquid formula the lowest (70). The profile of volatile compounds varied with 51 compounds significantly different (adjusted p < 0.001) among milk types. PCA explained 47% of variability. Compared to preterm breastmilk, the profile of volatile compounds in breastmilk with added bovine milk-based fortifier was marked by presence of fatty acids and their esters, ketones and aldehydes; infant formulas were characterized by alkyls, aldehydes and furans, and human milk-based products presented high concentrations of aromatic hydrocarbons, terpenoids and specific fatty acids. Conclusions: Sensory-active products of fatty acid oxidation are the major contributors to olfactory cues in infant feeds. Analysis of volatile compounds might be useful for monitoring quality of milk and detection of oxidation products and environmental contaminants. Further research is needed to determine whether these different volatile compounds have biological or physiological effects in nutrition of preterm infants.

Identification and Quantitation of Hydroxy Fatty Acids in Fermented Sausage Samples

The quality of fermented sausage is strongly influenced by its fatty acid (FA). However, the role of a defined starter culture in modifying sausage FA composition, and especially in the production of hydroxy FAs (HFAs), has not been determined. In this study, the FA compositions of sausages fermented with Latilactobacillus sakei, with L. sakei plus Staphylococcus carnosus, and with an aseptic control were characterized by liquid chromatography-mass spectrometry (MS)/MS and gas chromatography-MS. The sausages fermented with L. sakei, and with L. sakei plus S. carnosus, showed a reduced accumulation of poly and/or diunsaturated FAs and distinct composition of HFAs compared to the aseptic control. 2-HFAs were enriched via high-speed counter-current chromatography and identified uniquely in the L. sakei plus S. carnosus fermented sausage. Through lipid analyses, this study illustrated how the choice of a defined starter culture affected the observed FA metabolism in fermented sausages, facilitating the development of starter cultures or additives that impart desirable characteristics to sausage.

Taste Perception of Nutrients Found in Nutritional Supplements: A Review

Nutritional supplements are prescribed when one’s nutritional status is not conducive to good health. These foodstuffs constitute concentrated sources of nutrients such as vitamins, minerals, amino acids, and fatty acids. For nutritional supplements to be effective, patients must consume the amount that has been prescribed for the recommended period of time. Therefore, special attention must be given to the sensory attributes of these products. Indeed, the presence of active compounds can cause an off-taste or aftertaste. These negative sensations can lead to a reduction in the consumption of nutritional supplements and reduce the effectiveness of the treatment. In this manuscript, we provide an overview of the sensory characteristics and the sensing receptor mechanism of the main compounds present in oral nutritional supplements, such as amino acids, minerals, fatty acids, and vitamins. Part of this article is devoted to the development of new masking strategies and the corresponding potential influence at the industrial level.

Unstimulated saliva: Background noise in taste molecules

Saliva is a highly complex bodily fluid composed of many proteins, peptides, small organic molecules, and ions. Saliva is produced and secreted by the major and minor salivary glands to protect the mouth and to participate in digestion. Generally, a distinction is made between unstimulated saliva that is a result of autonomic stimulation and stimulated saliva that is produced during chewing and taste stimulation. The link between saliva and sensory perception can thus be regarded in two ways: the role of unstimulated saliva as a background taste and the mechanistic role of stimulated saliva during eating. Indeed, unstimulated saliva (and its components) is continuously bathing our oral cavity and as such stimulates our taste receptors, thus playing a role in taste sensitivity. However, the role of unstimulated salivary components in mediating taste has been studied only in very few substances. To explore this question, this review attempts to compare data from the literature on unstimulated salivary composition with those on taste sensitivity. The main conclusion centres around the concept that the gustatory self-adaptation phenomenon may be relevant for only a few salivary compounds. Further studies at the level of the salivary Von Ebner glands and salivary pellicle are necessary before arriving at definitive conclusions on this subject. PRACTICAL APPLICATION: Unstimulated saliva contains taste substances that can influence sensory perception through taste adaptation. However, large inter-individual variability exists in unstimulated salivary composition both qualitatively and quantitatively. These differences may explain the variability in taste perception and thus the food choices and behaviors of an individual. Thus, in the context of providing personalized food and nutrition to the consumer, variability of unstimulated saliva should be considered for specific formulation of food products.

How are macronutrient intake, BMI, ethnicity, age, and gender related to the composition of unstimulated saliva? A case study

This study investigated how macronutrient intake, BMI, ethnicity, age, and gender are related to the composition of unstimulated saliva. First, two groups of Caucasian, Dutch subjects varying in daily intake of carbohydrate, fat, and protein were selected. The daily intake of macronutrients differed by two- to threefold between the low (n = 14) and high (n = 16) macronutrient intake groups. The same subjects were divided into two groups based on BMI: normal weight (n = 14, 22.5 ± 2.0 kg/m² ) and overweight (n = 16, 28.1 ± 3.4 kg/m² ). Second, one group of Caucasian, Dutch (n = 15) and one group of Asian, Chinese (n = 15) subjects were selected. Unstimulated saliva was collected from all groups. Protein concentration, amylolytic activity, lipolytic activity, and saliva flow rate were determined. None of the salivary parameters varied according to macronutrient intake and BMI. An effect of ethnicity on protein concentration was observed (p < .01; η² = 0.142), with Asians having a 45% higher protein concentration in unstimulated saliva than Caucasians. Age had a significant effect on all salivary parameters. Protein concentration (p < .01; η² = 0.256), amylolytic activity (p < .01; η² = 0.234), and lipolytic activity (p < .05; η² = 0.207) increased with age, while saliva flow rate decreased (p < .01; η² = 0.262). Gender had a significant effect on saliva flow rate (p < .01; η² = 0.130), with male subjects having a 32% higher flow rate than females. Age was the factor that had the greatest impact on the characteristics of unstimulated saliva. As the modulation of saliva composition according to diet has been reported previously, the extent to which macronutrient intake can affect saliva composition needs to be further investigated. PRACTICAL APPLICATIONS: Saliva plays an important role in food oral processing. From the breakdown of food structures to the binding of flavor compounds and the formation of a swallowable bolus, saliva is essential for the perception and appreciation of foods. Identifying the factors that affect saliva composition is, therefore, necessary to understand the differences in eating behavior, food perception, and preference across different consumer groups. This article aims to highlight the importance of considering saliva variability when designing food products that meet the needs of specific consumer groups.

Oral sensations and secretions

Sensations experienced in the mouth influence food choices, both immediately and in the long term. Such sensations are themselves influenced by experience with flavors, the chemical environment of the mouth, genetics of receptors for flavors, and individual behavior in the chewing of food. Gustation, the sense of taste, yields information about nutrients, influences palatability, and feeds into the human body's preparation to receive those nutrients. Olfaction, the sense of smell, contributes enormously to defining and identifying food flavors (and is experienced even after placing food inside the mouth). Another vital component of food flavor is texture, which contributes to palatability, especially if a food's texture violates a person's expectations. Next, chemesthesis is the sense of chemically induced irritancy and temperature, for example spiciness and stinging. All of these sensations are potentially modified by saliva, the chemical and physical media of the mouth. As a person experiences the culmination of these oral sensations, modified through an individual's own unique saliva, the flavors in turn influence both what and how a person eats.

Extra virgin olive oil aroma release after interaction with human saliva from individuals with different body mass index

BACKGROUND

The interindividual variability observed in saliva characteristics raises the question of its relationship with variability in fat sensory perception, particularly in aroma compounds. In the present study, which aimed to measure aroma release from different individuals, eleven key aroma compounds of extra virgin olive oil (EVOO) were monitored and quantified in dynamic headspace after an in vitro interaction between EVOO and human saliva. Therefore, 60 individuals were studied from those who were normal weight (NW), overweight (OW) and obese (O).

RESULTS

OW and O demonstrate a higher release of C₆ compounds compared to NW. By contrast, NW have a higher release of C₅ compounds. Pentanal and hexanal also increased after saliva interaction in a refined olive oil that is free from volatiles. Among the saliva samples with a higher release in NW individuals, only pentanal was different. However, the low levels of these lipid oxidation end-products do not appear to be very important with respect to increasing odorous fat sensitivity.

CONCLUSION

The results obtained in the present study demonstrate the important role of saliva in the aroma release of EVOO, indicating that humans can perceive it differently in relation to their body mass index. © 2017 Society of Chemical Industry.

Obese Subjects With Specific Gustatory Papillae Microbiota and Salivary Cues Display an Impairment to Sense Lipids

Some obese subjects overeat lipid-rich foods. The origin of this eating behavior is unknown. We have here tested the hypothesis that these subjects could be characterized by an impaired fatty taste sensitivity linked to a change in the gustatory papillae microbial and salivary environment. The composition of microbiota and saliva surrounding the circumvallate papillae was analyzed in combination with the orosensory lipid detection threshold in normal weight (NW) and obese (O) adults. Microbial architecture was similar to what was known in feces, but with an increased frequency of Proteobacteria. No difference in the orosensory sensitivity to lipids and composition of oral microbiota and saliva was observed between NW and O subjects. By contrast, specific bacterial and salivary signatures were found in lipid non-tasters, irrespectively of BMI. A multivariate approach highlighted that the salivary flow, lysozyme activity, total antioxidant capacity and TM7 bacterial family discriminated between tasters and non-tasters. Subgroup analysis of obese tasters (OT) versus obese non-tasters (ONT) identified specific bacterial metabolic pathways (i.e. phosphotransferase and simple sugar transport systems) as being higher in ONT. Altogether with the identification of a set of significant salivary variables, our study suggests that an "obese tongue" phenotype is associated with decreased orosensory sensitivity to lipids in some obese subjects.

Main effects of human saliva on flavour perception and the potential contribution to food consumption

Whole saliva is a mixture composed by the secretions of the major and minor salivary glands and the crevicular fluid, bacteria, cells and food debris. Its properties (flow and composition) are highly intra- and inter-individually dependent and reflect the health status of individuals. Saliva plays a key role in the eating process and on the perception of flavour. Flavour corresponds to the combined effect of taste sensations, aromatics and chemical feeling factors evoked by food in the oral cavity. It is a key determinant of food consumption and intake. This review summarises the evidence about the role of saliva in flavour perception and its potential contribution to food intake. All in all, evidence on the relationships between salivary parameters and both food perception and feeding behaviour is presented. This review emphasises that new studies accounting for the effect of salivary constituents on flavour alterations due to diseases (i.e. cancer, obesity and diabetes) are lacking and are expected in the incoming years.

Differences in the Density of Fungiform Papillae and Composition of Saliva in Patients With Taste Disorders Compared to Healthy Controls

This study investigated the relation of the fungiform taste papillae density and saliva composition with the taste perception of patients suffering from diagnosed taste disorders. For this purpose, 81 patients and 40 healthy subjects were included. Taste was measured by means of regional and whole mouth chemosensory tests, and electrogustometry. Olfaction was assessed using the Sniffin Sticks. Fungiform papillae were quantified using the "Denver Papillae Protocol for Objective Analysis of Fungiform Papillae". In addition, salivary parameters [flow rate, total proteins, catalase, total anti-oxidative capacity (TAC), carbonic anhydrase VI (caVI), and pH] were determined and the Beck Depression Inventory was administered. Patients showed less taste papillae compared to healthy subjects. The number of papillae correlated with total taste strip score and salivary flow rate. Regarding salivary parameters, the flow rate, protein concentration, and TAC of patients were higher compared to controls. In addition, salivary flow rate, protease, caVI, and catalase values correlated with the summed taste strip score. Regarding various taste disorders, salty-dysgeusia patients showed the lowest taste test scores compared to those with bitter or metal-dysgeusia. Olfactory function of patients was significantly worse compared to healthy controls. This difference was most pronounced for ageusia patients. Compared to controls, patients also exhibited higher depressive symptoms. The density of fungiform papillae seemed to be positively associated with taste perception. Furthermore, patients exhibited changes in saliva composition (higher salivary flow rate, increased protein concentration, proteolysis, and TAC) compared to controls indicating that assessment of saliva may be critical for the diagnostic procedure in taste disorders.

Understanding fat, proteins and saliva impact on aroma release from flavoured ice creams

The release profile of fourteen aroma compounds was studied in ice cream samples varying in fat and protein, both in level and type. In vitro aroma release was monitored by solid phase micro-extraction gas chromatography using an innovative saliva reactor, which imitated human chewing under temperature control. The results showed that the effect of the fat type on aroma release was smaller than that of fat level. Ice creams with low fat level released more hydrophobic aroma compounds than ice creams with high fat level. At low fat level more aroma compounds were released from ice creams with lower protein content. At high fat level a small increase of aroma release was observed by the addition of saliva, which was explained by a salting out effect, due to the presence of proteins and salts in the saliva. These findings confirmed that the interactions between salivary proteins and aroma compounds occurring in aqueous solutions are not observed in emulsions.

Salivary Proteome Patterns Affecting Human Salt Taste Sensitivity

To investigate the role of perireceptor events in inter-individual variability in salt taste sensitivity, 31 volunteers were monitored in their detection functions for sodium chloride (NaCl) and classified into sensitive (0.6-1.7 mmol/L), medium-sensitive (1.8-6.9 mmol/L), and nonsensitive (7.0-11.2 mmol/L) subjects. Chemosensory intervention of NaCl-sensitive (S⁺) and nonsensitive (S^-) panellists with potassium chloride, ammonium chloride, and sodium gluconate showed the salt taste sensitivity to be specific for NaCl. As no significant differences were found between S⁺ and S^- subjects in salivary sodium and protein content, salivary proteome differences and their stimulus-induced dynamic changes were analyzed by tryptic digestion, iTRAQ labeling, and liquid chromatography-tandem mass spectrometry analysis. Differences in the salivary proteome between S⁺ and S^- subjects were found primarily in resting saliva and were largely independent of the dynamic alterations observed upon salt stimulation. Gene ontology enrichment analysis of key proteins, i.e., immunoglobulin heavy constant y1, myeloblastin, cathepsin G, and kallikrein, revealed significantly increased serine-type endopeptidase activity for the S⁺ group, while the S^- group exhibited augmented cysteine-type endopeptidase inhibitor activity by increased abundances in lipocalin-1 and cystatin-D, -S, and -SN, respectively. As proteases have been suggested to facilitate transepithelial sodium transport by cleaving the y-subunit of the epithelial sodium channel (ENaC) and protease inhibitors have been shown to reduce ENaC-mediated sodium transport, the differentially modulated proteolytic activity patterns observed in vivo for S⁺ and S^- subjects show evidence of them playing a crucial role in affecting human NaCl sensitivity.

Model cheese aroma perception is explained not only by in vivo aroma release but also by salivary composition and oral processing parameters

The aim of the present paper was to determine, from four model cheeses differing in fat content and firmness, the respective impacts ofin vivoaroma release, bolus rheology, chewing activity, mouth coating and salivary composition on dynamic aroma perception.

Salivary Composition Is Associated with Liking and Usual Nutrient Intake

Salivary flow and composition have an impact on flavor perception. However, very few studies have explored the relationship between saliva, individual liking and usual dietary intake. The aim of our study was to evaluate the association of salivary flow and composition with both a liking for fat, saltiness and sweetness and the usual nutrient intake in an adult French population. Liking for fat, saltiness, and sweetness were inferred from liking scores obtained during hedonic tests on 32 food products among 282 French adults participating in the Nutrinet-Santé Study. Before assessing liking, resting saliva was collected. Standard biochemical analyses were performed to assess specific component concentrations and enzymatic activities. Dietary data were collected using three web-based 24h records. Relationships between salivary flow and composition, sensory liking and nutrient intake were assessed using linear regression. Total antioxidant capacity was positively associated with simple carbohydrate intake (β = 31.3, 95% CI = 1.58; 60.99) and inversely related to complex carbohydrate consumption (β = -52.4, 95% CI = -87.51; -19.71). Amylolysis was positively associated with both total (β = 0.20, 95% CI = 0.01; 0.38) and simple carbohydrate intake (β = 0.21, 95% CI = 0.01; 0.39). Salivary flow was positively associated with liking for fat (β = 0.14, 95% CI = 0.03; 0.25). Proteolysis was positively associated with liking for saltiness and for fat (β = 0.31, 95% CI = 0.02; 0.59; β = 0.28, 95% CI = 0.01; 0.56, respectively). Amylolysis was inversely associated with liking for sweetness (β = -10.13, 95% CI = -19.51; -0.75). Carbonic anhydrase 6 was inversely associated with liking for saltiness (β = -46.77, 95% CI = -86.24; -7.30). Saliva does not substantially vary according to a usual diet, except for carbohydrate intake, whereas the specific association between salivary flow/composition and sensory liking suggests the influence of saliva characteristics in food acceptance.

Controversies in fat perception

Nutritional fat is one of the most controversial topics in nutritional research, particularly against the background of obesity. Studies investigating fat taste perception have revealed several associations with sensory, genetic, and personal factors (e.g. BMI). However, neuronal activation patterns, which are known to be highly sensitive to different tastes as well as to BMI differences, have not yet been included in the scheme of fat taste perception. We will therefore provide a comprehensive survey of the sensory, genetic, and personal factors associated with fat taste perception and highlight the benefits of applying neuroimaging research. We will also give a critical overview of studies investigating sensory fat perception and the challenges resulting from multifaceted methodological approaches. In conclusion, we will discuss a multifactorial approach to fat perception to gain a better understanding of the underlying mechanisms that cause varying fat sensitivity which could be responsible for overeating. Such knowledge might be beneficial in new treatment strategies for obesity and overweight.

Associations between orosensory perception of oleic acid, the common single nucleotide polymorphisms (rs1761667 and rs1527483) in the CD36 gene, and 6-n-propylthiouracil (PROP) tasting

Orosensory perception of dietary fat varies in individuals, thus influencing nutritional status. Several studies associated fat detection and preference with CD36 or 6-n-propylthiouracil (PROP) sensitivity. Other studies have not confirmed the latter association. We analyzed the relationship between orosensory perception of oleic acid, two CD36 variants, and PROP tasting. Thresholds of oleic acid perception were assessed in 64 subjects using a modification of the three-alternative forced-choice procedure. Subjects were classified for PROP taster status and genotyped for TAS2R38 and CD36 (SNPs: rs1761667 and rs1527483). Subjects homozygous for GG of the rs1761667 polymorphism showed higher sensitivity to oleic acid than AA subjects. The capability to detect oleic acid was directly associated with TAS2R38 or PROP responsiveness. PROP non-tasters had a lower papilla density than tasters, and those with genotype GG of the rs1761667 polymorphism had lower oleic acid thresholds than PROP non-tasters with genotype AA. In conclusion, results showed a direct association between orosensory perception of oleic acid and PROP tasting or rs1761667 polymorphism of CD36, which play a significant role in PROP non-tasters, given their low number of taste papillae. Characterization of individual capability to detect fatty acids may have important nutritional implications by explaining variations in human fat preferences.

Humans are more sensitive to the taste of linoleic and α-linolenic than oleic acid

Health concerns have led to recommendations to replace saturated fats with unsaturated fats. However, addition of unsaturated fatty acids may lead to changes in the way foods are perceived in the oral cavity. This study tested the taste sensitivity to and emulsion characteristics of oleic, linoleic, and α-linolenic acids. The hypothesis tested was that oral sensitivity to nonesterified fatty acids would increase with degree of unsaturation but that in vitro viscosities and particle sizes of these emulsions would not differ. Oral taste thresholds were obtained using the three-alternative, forced-choice, ascending method. Each participant was tested on each fat 7 times, for a total of 21 study visits, to account for learning effects. Viscosities were obtained for the blank solutions and all three emulsions. Results indicate lower oral thresholds to linoleic and α-linolenic than oleic acid. At higher shear rates, 5% oleic and linoleic acid were more viscous than other samples. More-dilute emulsions showed no significant differences in viscosity. Particle sizes of the emulsions increased very slightly with increasing unsaturation. Together, the emulsion characteristics and oral sensitivity data support a taste mechanism for nonesterified fatty acid detection.

Understanding the role of saliva in aroma release from wine by using static and dynamic headspace conditions

The aim of this work was to determine the role of saliva in wine aroma release by using static and dynamic headspace conditions. In the latter conditions, two different sampling points (t = 0 and t = 10 min) corresponding with oral (25.5 °C) and postoral phases (36 °C) were monitored. Both methodologies were applied to reconstituted dearomatized white and red wines with different nonvolatile wine matrix compositions and a synthetic wine (without matrix effect). All of the wines had the same ethanol concentration and were spiked with a mixture of 45 aroma compounds covering a wide range of physicochemical characteristics at typical wine concentrations. Two types of saliva (human and artificial) or control samples (water) were added to the wines. The adequacy of the two headspace methodologies for the purposes of the study (repeatability, linear ranges, determination coefficients, etc.) was previously determined. After application of different chemometric analysis (ANOVA, LSD, PCA), results showed a significant effect of saliva on aroma release dependent on saliva type (differences between artificial and human) and on wine matrix using static headspace conditions. Red wines were more affected than white and synthetic wines by saliva, specifically human saliva, which provoked a reduction in aroma release for most of the assayed aroma compounds independent of their chemical structure. The application of dynamic headspace conditions using a saliva bioreactor at the two different sampling points (t = 0 and t = 10 min) showed a lesser but significant effect of saliva than matrix composition and a high influence of temperature (oral and postoral phases) on aroma release.

Understanding aroma release from model cheeses by a statistical multiblock approach on oral processing

For human beings, the mouth is the first organ to perceive food and the different signalling events associated to food breakdown. These events are very complex and as such, their description necessitates combining different data sets. This study proposed an integrated approach to understand the relative contribution of main food oral processing events involved in aroma release during cheese consumption. In vivo aroma release was monitored on forty eight subjects who were asked to eat four different model cheeses varying in fat content and firmness and flavoured with ethyl propanoate and nonan-2-one. A multiblock partial least square regression was performed to explain aroma release from the different physiological data sets (masticatory behaviour, bolus rheology, saliva composition and flux, mouth coating and bolus moistening). This statistical approach was relevant to point out that aroma release was mostly explained by masticatory behaviour whatever the cheese and the aroma, with a specific influence of mean amplitude on aroma release after swallowing. Aroma release from the firmer cheeses was explained mainly by bolus rheology. The persistence of hydrophobic compounds in the breath was mainly explained by bolus spreadability, in close relation with bolus moistening. Resting saliva poorly contributed to the analysis whereas the composition of stimulated saliva was negatively correlated with aroma release and mostly for soft cheeses, when significant.