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Fresh strawberries (Fragaria x ananassa) are valued for their characteristic red color, juicy texture, distinct aroma, and sweet fruity flavor. In this study, genetic and environmentally induced variation is exploited to capture biochemically diverse strawberry fruit for metabolite profiling and consumer rating. Analyses identify fruit attributes influencing hedonics and sensory perception of strawberry fruit using a psychophysics approach. Sweetness intensity, flavor intensity, and texture liking are dependent on sugar concentrations, specific volatile compounds, and fruit firmness, respectively. Overall liking is most greatly influenced by sweetness and strawberry flavor intensity, which are undermined by environmental pressures that reduce sucrose and total volatile content. The volatile profiles among commercial strawberry varieties are complex and distinct, but a list of perceptually impactful compounds from the larger mixture is better defined. Particular esters, terpenes, and furans have the most significant fits to strawberry flavor intensity. In total, thirty-one volatile compounds are found to be significantly correlated to strawberry flavor intensity, only one of them negatively. Further analysis identifies individual volatile compounds that have an enhancing effect on perceived sweetness intensity of fruit independent of sugar content. These findings allow for consumer influence in the breeding of more desirable fruits and vegetables. Also, this approach garners insights into fruit metabolomics, flavor chemistry, and a paradigm for enhancing liking of natural or processed products.

Breeding for a subjective goal such as flavor is challenging, as many blueberry cultivars are grown worldwide, and identifying breeding targets relating to blueberry flavor biochemistry that have a high degree of genetic control and low environmental variability are priorities. A variety of biochemical compounds and physical characters induce the sensory responses of taste, olfaction, and somatosensation, all of which interact to create what is perceived flavor. The goal of this study was to identify the flavor compounds with a larger genetic versus environmental component regulating their expression over an array of cultivars, locations, and years. Over the course of three years, consumer panelists rated overall liking, texture, sweetness, sourness, and flavor intensity of 19 southern highbush blueberry (Vaccinium corymbosum hybrids) genotypes in 30 sensory panels. Significant positive correlations to overall liking of blueberry fruit (P<0.001) were found with sweetness (R2 = 0.70), texture (R2 = 0.68), and flavor (R2 = 0.63). Sourness had a significantly negative relationship with overall liking (R2 = 0.55). The relationship between flavor and texture liking was also linear (R2 = 0.73, P<0.0001) demonstrating interaction between olfaction and somatosensation. Partial least squares analysis was used to identify sugars, acids, and volatile compounds contributing to liking and sensory intensities, and revealed strong effects of fructose, pH, and several volatile compounds upon all sensory parameters measured. To assess the feasibility of breeding for flavor components, a three year study was conducted to compare genetic and environmental influences on flavor biochemistry. Panelists could discern genotypic variation in blueberry sensory components, and many of the compounds affecting consumer favor of blueberries, such as fructose, pH, β-caryophyllene oxide and 2-heptanone, were sufficiently genetically controlled that allocating resources for their breeding is worthwhile.

Psychophysical comparisons seem to show that obese individuals experience normal sweet and fat sensations, they like sweetness the same or less, but like fat more than the non-obese do. These psychophysical comparisons have been made using scales (visual analogue or category) that assume intensity labels (e.g. extremely) which denote the same absolute perceived intensity to all. In reality, the perceived intensities denoted by labels vary because they depend on experiences with the substances to be judged. This variation makes comparisons invalid. Valid comparisons can be made by asking the subjects to rate their sensory/hedonic experiences in contexts that are not related to the specific experiences of interest. Using this methodology, we present the evidence that the sensory and hedonic properties of sweet and fat vary with body mass index. The obese live in different orosensory and orohedonic worlds than do the non-obese; the obese experience reduced sweetness, which probably intensifies fat sensations, and the obese like both sweet and fat more than the non-obese do. Genetic variation as well as taste pathology contribute to these results. These psychophysical advances will impact experimental as well as clinical studies of obesity and other eating disorders.

Inadequate vegetable intake appears to increase colon cancer risk. Since genetic variation in taste influences vegetable preference, we tested associations between bitterness of 6-n-propylthiouracil (PROP), a measure of taste genetics, and number of colonic polyps, a measure of colon cancer risk, in 251 men who underwent screening lower endoscopy. Patients used the general Labeled Magnitude Scale to rate bitterness of 1.6 mg PROP delivered via filter paper. A subset of 86 patients reported weekly vegetable intakes, excluding salad or potatoes. PROP bitterness correlated significantly with polyp number, an effect separate from age-associated increases in polyp number. The PROP-polyp relationship was strongest in men over 66 years, and older men with polyps were most likely to be overweight or obese. In the subset reporting vegetable intake, men who tasted PROP as more bitter consumed fewer vegetables. These preliminary findings suggest that taste genetics may influence colon cancer risk, possibly through intake of vegetables.

Taste and oral sensations vary in humans. Some of this variation has a genetic basis, and two commonly measured phenotypes are the bitterness of propylthiouracil (PROP) and the number of fungiform papillae on the anterior tongue. While the genetic control of fungiform papilla is unclear, PROP bitterness associates with allelic variation in the taste receptor gene, TAS2R38 . The two common alleles are AVI and PAV (proline, alanine, valine, and isoleucine); AVI/AVI homozygotes taste PROP as less bitter than heterozygous or homozygous PAV carriers. In this laboratory-based study, we determined whether taste of a bitter probe (quinine) and vegetable intake varied by taste phenotypes and TAS2R38 genotype in healthy adults (mean age = 26 years). Vegetable intake was assessed via two validated, complementary methods: food records (Food Pyramid servings standardized to energy intake) and food frequency questionnaire (general intake question and composite vegetable groups). Quinine bitterness varied with phenotypes but not TAS2R38 ; quinine was more bitter to those who tasted PROP as more bitter or had more papillae. Nontasters by phenotype or genotype reported greater consumption of vegetables, regardless of type (i.e., the effect generalized to all vegetables and was not restricted to those typically thought of as being bitter). Furthermore, nontasters with more papillae reported greater vegetable consumption than nontasters with fewer papillae, suggesting that when bitterness does not predominate, more papillae enhance vegetable liking. These findings suggest that genetic variation in taste, measured by multiple phenotypes or TAS2R38 genotype, can explain differences in overall consumption of vegetables, and this was not restricted to vegetables that are predominantly bitter.

Objective To determine if individuals who taste 6- n-propylthiouracil (PROP), one marker of genetic variation in taste, as exceptionally bitter can also perceive sugars as sweeter, other bitters as more intense, and dietary fats as more creamy and/or viscous than do individuals who taste PROP as weakly bitter. This study examined the association between genetic variation in taste and acceptance for sweet, high-fat, and bitter foods and beverages. Design Genetic variation was measured by perceived bitterness of PROP. (influenced by genetic, hormonal, and pathologic factors) and density of fungi form papillae on the anterior portion of the tongue (influenced primarily by genetic factors). Four sweet, 3 fat, and 3 bitter groups were derived from principal components analyses of questionnaire items. Subjects Convenience sample of healthy adults (24 women, 22 men; mean age±standard deviation=21±6 years) who did not report high dietary restraint. Statistical analyses Pearson product moment correlations between genetic taste measures and food and beverage groups. Results The sample showed diversity in genetic taste measures: perceived bitterness of 0.0032 mol/L PROP ranged from “weak” to well above “very strong”; fungi form papillae densities ranged from 33 to 156 papillae per square centimeter. Distribution of perceived bitterness of PROP and fungi form papillae density differed in women and men. The association between genetic taste measures and acceptance of sweet and high-fat groups differed in women and men. In women, liking of sweet and high-fat food and beverage groups decreased with increasing perceived bitterness of PROP. In men, liking of these foods and beverages increased but with increasing papillae densities. Genetic taste measures were not associated with a dislike of bitter food and beverage groups. Applications The influence of genetic variation in taste on food intake depends on how perceptible sweet, fat, or bitter components are in foods and beverages, as well as the value of sensory factors vs other factors (eg, health, convenience) on personal dietary choices. Female supertasters of PROP bitterness may avoid high-fat or sweet foods because these oral sensations are too intense and thus less pleasant. Supertasters may taste more bitterness in vegetables but still enjoy eating them because of their healthfulness and because condiments (especially those that are salt based) can block bitterness. J Am Diet Assoc. 2000;100:647–655.

Amyotrophic lateral sclerosis (ALS) is a degenerative neurological disease that affects the motor systems in patients but also may affect some sensory systems. Some ALS patients report taste changes that may decrease their oral intake and nutritional status. This study examined whether focal taste damage occurs in ALS patients compared to age/gender-matched adult healthy controls. An abbreviated Spatial Taste Test was administered to the fungiform and circumvallate papillae. Compared to healthy controls, ALS patients exhibited significantly lower taste intensities across the four basic tastes and significantly lower taste intensities at both the fungiform and vallate papillae, but no significant difference in whole mouth taste intensities. Seven out of nine ALS patients with self reported altered taste had tongue fasciculations, involuntary movements within the tongue dorsum due to lower motor neuron impairment (a common sign of bulbar ALS). Additionally, for patients taking riluzole taste perception at the fungiform papillae appears to be further reduced relative to the vallate papillae. This study suggests ALS decreases taste at both the fungiform and vallate papillae. In addition, riluzole may further damage the chorda tympani. Further studies need to be conducted to examine the etiology for taste loss.

The search for biological attributes that contribute to the obesity epidemic in the United States that disproportionately affects racial and ethnic groups is of great public health importance. The understanding of taste perception, its influence on eating behavior, and its contribution to obesity and obesity-related disease has increased with research in taste physiology and genetics. Additionally, newer methods for psychophysical assessments of taste perception and preference allow for valid comparisons across groups. Emerging evidence of ethnic differences in sensory taste experiences provide the basis for future studies to explore the mechanisms by which taste may contribute to existing health disparities and differences in cardiometabolic risk.

Although the heteromeric combination of type 1 taste receptors 2 and 3 (T1r2 + T1r3) is well established as the major receptor for sugars and noncaloric sweeteners, there is also evidence of T1rindependent sweet taste in mice, particularly so for sugars. Before the molecular cloning of the T1rs, it had been proposed that sweet taste detection depended on (a) activation of sugar-gated cation channels and/or (b) sugar binding to G protein-coupled receptors to initiate second-messenger cascades. By either mechanism, sugars would elicit depolarization of sweet-responsive taste cells, which would transmit their signal to gustatory afferents. We examined the nature of \"Mr-independent sweet taste; our starting point was to determine if taste cells express glucose transporters (GLUTs) and metabolic sensors that serve as sugar sensors in other tissues. Using RT-PCR, quantitative PCR, in situ hybridization, and immunohistochemistry, we determined that several GLUTs (GLUT2, GLUT4, GLUT8, and GLUT9), a sodium-glucose cotransporter (SGLT1), and two components of the ATP-gated K⁺ (K ATP ) metabolic sensor [sulfonylurea receptor (SUR) 1 and potassium inwardly rectifying channel (Kir) 6.1] were expressed selectively in taste cells. Consistent with a role in sweet taste, GLUT4, SGLT1, and SUR1 were expressed preferentially in T1r3-positive taste cells. Electrophysiological recording determined that nearly 20% of the total outward current of mouse fungiform taste cells was composed of K ATP channels. Because the overwhelming majority of T1r3-expressing taste cells also express SUR1, and vice versa, it is likely that K ATP channels constitute a major portion of K⁺ channels in the T1 r3 subset of taste cells. Taste cell-expressed glucose sensors and K ATP may serve as mediators of the T1r-independent sweet taste of sugars.