Sour Taste Research Articles

Epitope tagging with genome editing in mice reveals that the proton channel OTOP1 is apically localized and not restricted to Type III "sour" taste receptor cells.

The gustatory system allows animals to assess the nutritive value and safety of foods prior to ingestion. The first step in gustation is the interaction of taste stimuli with one or more specific sensory receptors, that are generally believed to be present on the apical surface of the taste receptor cells. However, this assertion is rarely tested. We recently identified OTOP1 as a proton channel and showed that it is required for taste response to acids (sour) and ammonium. Here we examined the cellular and subcellular localization of OTOP1 by tagging the endogenous OTOP1 protein with an N-terminal HA epitope (HA-OTOP1). Using both male and female HA-OTOP1 mice and high-resolution imaging, we show that OTOP1 is strictly localized to the apical tips of taste cells throughout the tongue and oral cavity. Interestingly, immunoreactivity is observed in the actin-rich taste pore above the tight junctions defined by Zonula Occludens-1 (ZO-1) and also immediately below these junctions. Surprisingly, OTOP1 immunoreactivity is not restricted to Type III taste receptor cells (TRCs) that mediate sour taste but is also observed in glia-like Type I TRCs proposed to perform housekeeping functions, a result that is corroborated by scRNA-seq data. The apical localization of OTOP1 supports the contention that OTOP1 functions as a taste receptor and suggests that OTOP1 may be accessible to orally available compounds that could act as taste modifiers.Significance Statement It is generally accepted that humans and other vertebrates can detect five basic tastes, each mediated by a unique receptor. Recently the receptor for sour taste was identified as the proton channel OTOP1. Here we show that OTOP1 is expressed at the apical surface of taste receptors cells, consistent with a sensory function. Surprisingly, OTOP1 is not restricted to Type III taste cells that detect sour tastes but is also expressed by glia-like taste cells, where it may play a role in removing excess protons. These results provide insight and tools applicable to understanding the contribution of OTOP1 to cell physiology and pathology in other contexts where the channel is expressed such as in the vestibular system.

Changes of volatile flavored compounds during lactic acid fermentation in cereal-based products

Changes of volatile flavored compounds during lactic acid fermentation in cereal-based products

Association of oral health with nutritional status of the older adults: a cross-sectional study.

The potential association between oral health and nutritional status of the very old, has been poorly investigated. Thus, we carried out the cross-sectional study to evaluate the association of oral health with the nutritional status of the older adults. 210 participants aged over 75 years were included in the study. Nutritional status was assessed by the Short-form Mini-Nutritional Assessment (MNA-SF) and body composition measurement. Data were available for self-reported oral health (10-item Eating Assessment Tool (EAT-10) and Chewing Function Questionnaire (CFQ)) and specific experimental tests including salivary flow, tongue and lip pressure, occlusal force, water swallow test and taste test for the detection of oral functions. Spearman rank correlation was used to analyze the correlation between body composition and oral health. Logistic regression and restricted cubic spline models were applied to examine the association of oral health with malnutrition. The study reveals that poor oral health is related to the malnutrition. The tongue pressure and molar occlusal force were significantly associated with malnutrition in an L-shaped dose-response relationship after adjustment for potential confounding factors. The higher the tongue pressure and molar occlusal force, the lower the risk of malnutrition. Besides, the CFQ score, salty, sour, and bitter taste, are risk factors for malnutrition. The presence of malnutrition is significantly associated with poor oral health in older adults. Our study supposes that the design of food suitable for oral conditions of the older adults may be another feasible solution to the nutritional problems among them.

Effectively Enhancing the Physiological Activity and Sensory Quality of Whole Calamondin Puree via Yeast Fermentation.

To explore the feasibility of pure yeast fermentation in whole Calamondin puree (FWCP) for the utilization of the whole fruit, yeasts were isolated from naturally fermented Calamondin, and their fermentation characteristics were evaluated. The results indicated that all yeasts were able to ferment FWCP, reducing the sour taste by degrading citric acid, increasing the contents of nutrients (such as phenols and limonins) and volatile compounds, and enhancing the antioxidant activity and inhibition of α-glucosidase activity (p < 0.05). Among them, P. terricola QJJY1 and H. opuntiae QJJY14 exhibited stronger abilities to degrade organic acids, with P. terricola QJJY1 enhancing the antioxidant capacity by releasing phenolic compounds such as phloretin-3',5'-di-c-β-glucoside, vitexin-2″-O-rhamnoside, and isomargaritene. Moreover, H. opuntiae QJJY15 improved the contents of characteristic volatile compounds such as terpene hydrocarbons and higher alcohols. In total, 70 components were identified as differential metabolites based on their fold change in the metabolites, with 42 differential metabolites involved in 29 metabolic pathways across four strains. The main pathways related to phenol and flavor enrichment were flavonoid, flavone, and flavonol biosynthesis, monoterpenoid biosynthesis, and glyoxylate and dicarboxylate metabolism. Therefore, yeast fermentation is an effective method for utilizing whole Calamondin.

Possible Adverse Effects (AEs) of Semaglutide (Ozempic) Administration for the Latest Investigation

Semaglutide has been widely used in the treatment of type 2 diabetes (T2D) and obesity within medical and healthcare settings. Among its formulations, Ozempic has drawn attention for potential adverse effects (AEs). In a study involving 3,962 cases of obesity, the average data showed a weight reduction of 11.8%, a BMI decrease of 4.5 kg/m², and a reduction in waist circumference of 9.4 cm. One notable effect, termed “Ozempic tongue,” is characterized by altered taste sensitivity—such as sour, metallic, or bitter tastes—reported in approximately 6% of cases. These effects are not only considered AEs but are also linked to beneficial outcomes in weight reduction. Additionally, some users have reported changes in the appearance of the breasts, buttocks, and lips with Ozempic administration.

Red dragon fruit (Hylocereus polyrhzus) syrup: evaluation of parameters affecting the production process

Studies on the production of red dragon fruit syrup (Hylocereus polyrhzus) were carried out based on investigating the influence of concentration (0.1 - 0.4%) and hydrolysis time (15 - 45 mins) of pectinase enzyme on the process of pectinase hydrolyzed red dragon fruit juice. The recipe for red dragon fruit syrup with factors that change the concentration of citric acid (0.05 - 0.15%) and the concentration of Aspartame (0.1 - 0.5%) was investigated. At the same time, the concentration temperature was determined to achieve the quality syrup within the concentration temperature range (70 - 80℃). Research results showed that the 0.3% pectinase enzyme used for hydrolysis of fruit juice in 25 mins will yield a high juice recovery yield. Red dragon fruit juice (after hydrolysis) supplemented with 0.1% citric acid and 0.1% Aspartame at a concentrated temperature of 80℃ will produce a red dragon fruit syrup with a mildly sour taste, pungent taste and colour characteristic of red dragon fruit.

Combined Transcriptome and Metabolome Analyses Provide New Insights into the Changes in the Flesh Color of Anthocyanins in Strawberry (Fragaria × ananassa (Weston) Duchesne ex Rozier).

Strawberries are bright in color, sweet and sour in taste, and rich in nutrients and flavonoid compounds such as anthocyanins and proanthocyanidins. The synthesis and accumulation of anthocyanins are the decisive factors that make strawberries appear bright red. From the perspective of plant breeding, a change in flesh color is an important goal. In this study, two strawberry plants with different flesh colors were selected, and transcriptome and metabolome analyses were performed during the color change period (S1) and ripening period (S2). RNA-seq revealed a total of 13,341 differentially expressed genes (DEGs) between and within materials, which were clustered into 5 clusters. A total of 695 metabolites were detected via metabolome analysis, and 243 differentially regulated metabolites (DRMs) were identified. The anthocyanin biosynthesis, starch and sucrose metabolism and glycolysis/gluconeogenesis pathways were determined to be important regulatory pathways for changes in strawberry flesh color through a joint analysis of RNA-seq data and the metabolome. The leucoanthocyanidin reductase (LAR) and chalcone synthase (CHS) gene is a key gene related to anthocyanins, cinnamic acid, and phenylalanine. In addition, through joint RNA-seq and metabolome analyses combined with weighted gene co-expression network analysis (WGCNA), we identified 9 candidate genes related to strawberry flesh color. Our research findings have laid the groundwork for a more comprehensive understanding of the molecular mechanisms governing the color transformation in strawberry flesh. Additionally, we have identified novel genetic resources that can be instrumental in advancing research related to strawberry color change.

Fermentation of soymilk with Lactobacillus acidophilus enhances the functional attributes and health-promoting properties

Fermented soymilk is a traditional oriental food beverage that has various health benefits due to its bioactive compounds. However, the fermentation process and the probiotic strains used can affect the quality and functionality of fermented soymilk. In this study, we designed to develop a novel functional food by fermenting soymilk with Lactobacillus acidophilus (L. acidophilus), a probiotic bacterium that can improve microbiota present in intestine and modulate the immune system. We evaluated the physicochemical, microbiological and sensory attributes of the fermented soymilk, as well as its total phenolic, flavonoids, free amino acids, antioxidant and anticancer activities. The results revealed that L. acidophilus had ability to grow well and produce lactic acid in soymilk, resulting in a pH of 4.4 and a titratable acidity of 0.72 g of lactic acid per 100 mL after 12 h of fermentation. The fermented soymilk had a smooth texture, a pleasant aroma and a sour taste, and was well accepted by the panelists. The fermented soymilk also exhibited a good amount of total phenolic, flavonoids, free amino acids with high antioxidant activity towards DPPH free radicals (IC50 = 55.51 &amp;micro;g/mL) and the inhibition of human colorectal cancer cells (HCT-116) in a dose-dependent manner (IC50 = 67.13 &amp;micro;g/mL). Overall, these findings suggest that fermented soymilk with L. acidophilus is a novel functional food with potential therapeutic values for the prevention and treatment of oxidative stress, cancer and metabolic disorders.

Genetic aspects of taste formation

The article discusses the molecular genetic basis of taste development which determines the peculiarity of perception of sweet, salty, sour, bitter and high-protein food (umami). The genes TAS1R3, FTO, GLUT2, FGF21, GNAT3 are responsible for individual perception of sugar volume. Serum FGF21 levels are significantly elevated in obese patients and in patients with type 2 diabetes mellitus which presumably indicates a state of resistance to FGF21. Given the role of refined sugars in the development of diseases, the use of foods with a reduced content or complete absence of added sugar is a worldwide trend, especially necessary in the nutrition of children. During genome-wide sequencing for 39 patients aged 15-18 years, FGF21 gene polymorphism was detected in 27 adolescents (69 %) without gender identity. Almost all patients with FGF21 gene polymorphism showed a high addiction to sweet foods. Currently, the existence of a sixth taste is being debated, it is ammonium chloride, whose receptors are regulated by the Otop1 gene which is also responsible for the identification of sour taste.

Fungiform Papillae and Gustatory Function in Neurofibromatosis Type 1: A Case-Control Study.

Fungiform papillae enlargement is a common oral manifestation of neurofibromatosis type 1 (NF1). This study aimed to objectively evaluate the size, number, and symmetry of fungiform papillae in NF1 individuals and investigate the relationship between these alterations and taste perception, salivary flow, dietary habits, and BMI. A cross-sectional case-control study was conducted on 80 participants (40 with NF1 and 40 controls), matched by age and sex. Participants underwent quantitative and morphological evaluation of fungiform papillae, gustatory perception tests, sialometry, saliva analysis, xerostomia assessment, dietary assessments, and Body Mass Index calculations. The NF1 group exhibited significantly larger and more asymmetric fungiform papillae and exhibited a higher detection threshold for sweet and sour tastes, as well as hyposalivation and lower preference for healthy foods compared to the controls. No correlation was found between papillae morphology, gustatory perception tests, saliva properties, xerostomia, food preferences, or BMI in the NF1 group. Enlarged and asymmetric fungiform papillae, hyposalivation, heightened sensitivity to sweet and sour tastes, and reduced healthy eating habits were common in NF1. Although fungiform papillae alterations seem unrelated to taste sensitivity and food preferences, further investigation is needed to better understand the mechanisms underlying these changes.

Research Progress on Methods for the Deacidification of Small Berry Juice: An Overview

As some of the richest sources of natural antioxidants, small berry fruits have attractive colors and special tastes, with recognized benefits for human health. However, sour tastes in small berry juices result in a poor flavor and low acceptance among consumers, greatly limiting their marketability. Among the most commonly used deacidification methods, chemical deacidification methods can neutralize fruit juice via the addition of a deacidification agent, while physical deacidification methods include freezing deacidification, ion-exchange resin deacidification, electrodialysis deacidification, and chitosan deacidification. All of these methods can markedly improve the pH of fruit juice, but they introduce new substances into the juice that may have an influence on its color, taste, and stability. Biological deacidification can effectively remove malic acid from fruit juice, reducing the content from 15 g/L to 3 g/L; additionally, it maintains the taste and stability of the juice. Therefore, it is widely applied for fruit juice deacidification. On this basis, some compound deacidification technologies have also emerged, but they also present problems such as high costs and complicated working procedures. This review of deacidification methods for small berry juice provides a foundation for the industrial development of such juices.

Sifat Kimia dan Sensori Teh Celup Cascara Stevia dengan Metode Pengeringan Kulit Kopi dan Persentase Gula Stevia (Stevia rebaudiana Bertoni) yang Berbeda

Cascara is a dry tea made from coffee husk waste. Cascara is prepared in the shape of dip packets to make it easier for customers, and stevia (Stevia rebaudiana Bertoni) is added since consumers like sweet drinks and to promote consumer preference. The purpose of this study is to investigate the influence of the coffee skin drying process and cascara and stevia ratio on the physicochemical and sensory qualities of cascara tea bags. This research used a factorial completely randomized design where the first factor is the drying method, and the second is the percentage of added stevia. The research data obtained is then analyzed using Analysis of Variance (ANOVA) and followed with Duncan's Multiple Range Test (DMRT) if there are differences between treatments. The drying technique treatment variance influenced pH, total dissolved solids, and color hedonic. The research revealed that the pH of cascara dried in the oven was higher than that of sun drying, while the total soluble solids of sun drying were higher than that of oven drying. The pH and total soluble solids increased as the proportion of stevia added increased. The hedonic test mean result for fragrance was 3.49 (neutral), color was 3.47 (neutral), and taste was 3.13 (neutral). The cascara scent description test had a mean value of 2.74 (neutral), a cascara color description of 2.74 (light), a sweet taste description of 2.81 (neutral), a sour taste description of 2.24 (weak), a bitter taste description of 1.81 (weak), and an astringent taste description of 2.24 (weak). The total phenols value in sun drying with a 20% stevia addition yielded 139 mg GAE/mL

Enhancement of γ-aminobutyric acid content in Huangjiu through rice bran fermentation and its impact on the volatile organic compounds

Rice bran has high glutamic acid decarboxylase (GAD) activity and can be used to enrich and produce γ-aminobutyric acid (GABA). Glutinous rice was used as raw material to brew Huangjiu by liquefaction fermentation. Rice bran extract was added at different fermentation stages, then the content of GABA and basic physicochemical properties were tested, the changes of flavor substances and volatile organic compounds (VOCs) were observed in Huangjiu. The results showed the addition of concentrated GABA-enriched rice bran extract during the post-fermentation stage significantly increases the GABA content in Huangjiu. When the amount of rice bran used is 50 g, the GABA content in the Huangjiu can reach 592.44 mg/L after fermentation. The total sugar and pH of Huangjiu fermented with rice bran extract were higher than the control group, and the total acid and non-sugar solids were lower than the control group. Electronic tongue analysis showed that the addition of rice bran extract would affect the sourness, umami and saltiness taste of Huangjiu. Gas Chromatography-Ion Mobility Spectrometry (GC-IMS) analysis of Huangjiu made by adding rice bran extract at the post-fermentation stage showed increased isoamyl acetate, 2-heptanol, and other substances in comparison with the control group. The results of the study provide a cost-effective and rapid method for increasing the GABA content in Huangjiu. It also offers a theoretical basis and scientific guidance for the production of health-oriented Huangjiu.

Identification of Key Genes Controlling Sugar and Organic Acid Accumulation in Wampee Fruit (Clausena lansium) via Genome Assembly and Genome-wide Association Analysis.

Wampee (Clausena lansium) is an economically significant subtropical fruit tree widely cultivated in Southern China. To provide high-quality genomic resources for C. lansium, we report a chromosome-level genome sequence for the "JinFeng" cultivar. The 297.1 Mb C. lansium genome contained nine chromosomes with a scaffold N50 of 29.2 Mb and encoded 23,468 protein-coding genes. Selective sweep analysis between sweet and sour C. lansium varieties and genome-wide association analysis identified 14 candidate genes putatively involved in sugar and acid accumulation. ClERF061, encoding an ethylene response factor, and ClSWEET7, encoding a Sugars Will Eventually be Exported Transporters (SWEET) family protein, were proposed as key regulators of the sweet and sour tastes of the wampee fruit. ClERF061 and ClSWEET7 overexpression in tomatoes increased the total sugar and acid content in fruits. ClSWEET7 promoter activation by ClERF061 was confirmed via Nicotiana benthamiana transient expression. Our study provides valuable genomic resources for C. lansium genetics and breeding.

Sour taste perception in fluids: The impact of sweet tastant, fluid viscosity, and individual salivary properties

Binary taste perception is widely studied in aqueous solutions but less investigated in non-Newtonian fluid systems. In this study, the effect of sweet tastants on the dynamic sour taste perception in thickened fluids and its underpinning oral processing factors were investigated. Subjects were tested for taste thresholds and salivary biochemical properties. By using hydroxypropyl methylcellulose (HPMC) as a thickening agent, subjects conducted sour taste evaluation, with and without maltose and/or HPMC, using descriptive sensory analyses. A simulated fluid shear elicited by fixed-frequency mastication was applied on thickened fluid sample oral processing during time-intensity sour taste evaluation. Results showed that adding maltose to fluid samples enhanced sour taste perception, and increasing fluid viscosity generally suppressed perceived maximum sour taste. Moreover, subjects with lower sour taste sensitivity and higher salivary buffering capacity reported overall lower sour taste intensity in most samples, validating the hypothesis that salivary properties importantly affect sour taste perception.

Physico-chemical properties and organoleptic acceptability of star fruit (Averrhoa bilimbi Linn.) jam with variations of natural sweeteners

Belimbing wuluh (Averrhoa bilimbi Linn.) is a fruit plant from Indonesia that has a very sour taste because it contains citric acid and oxalic acid. This sour taste is why this fruit has yet to be optimally utilized. This study aimed to determine the effect of natural sweetener variations on wuluh star fruit jam's physico-chemical and organoleptic properties. This study used an experimental method in which the experiment was designed in a completely randomized design (CRD) with 4 treatments and 3 repetitions. The results of this study showed that the addition of natural sweeteners to wuluh star fruit jam had a significant effect (p &lt; 0.05) on viscosity (9143 – 9450 mpa.s), sineresis (1.295 – 4.592 mg), vitamin C test (17.540 – 25.629 mg/100g), moisture content (23.57 – 31.19%), total sugar content (58.01 – 69.41%wb) and which had no significant effect (p&gt;0.05) on pH (3.38 – 3.64%). Meanwhile, organoleptic testing did not significantly affect taste, color, texture, aroma, and spreadability parameters. Keywords: Belimbing wuluh, Cassava sugar, Corn sugar, Honey, Jam

KUALITAS ORGANOLEPTIK SUSU NABATI BIJI CEMPEDAK (Artocarpus Champeden) TERSUSPENSI PROBIOTIK BERDASARKAN SUHU PENYIMPANAN

Background: Cempedak (Artocarpus champeden) is a local fruit of Central Kalimantan that is oval with dark yellow and fibrous flesh and has a fragrant aroma when ripe. So far, cempedak seeds have only become organic waste, not used properly. The nutritional and mineral content of cempedak seeds can be used and processed into a healthy drink, namely vegetable milk. Methods: The method used is an experimental method to produce vegetable milk with cempedak seeds which is then carried out organoleptic tests to determine the quality of the aroma and taste of the vegetable milk made. Results: Based on the research carried out, the results showed that the taste quality of vegetable milk of cempedak seeds (Artocarpus champeden) that was most liked by the respondents/panelists was at the temperature of T1=20o C and T2=30o C, which was with a refreshing sweet and sour taste, while for the sour aroma and distinctive smell of cempedak seeds at the temperature of T3=30o C. Conclusion: Cempedak seeds can be used as probiotic plant-based milk with an optimal storage temperature of 30o C to get the distinctive taste, aroma and smell of cempedak seeds.

Gating elements for carvacrol activation of the OTOP1 proton channel

Otopetrin 1 (OTOP1) is a proton-activated channel crucial for animals’ perception of sour taste. Despite its significance, the gating mechanism of OTOP1 remains poorly understood. Here, we demonstrate that carvacrol activates the mouse OTOP1 (mOTOP1) channel under neutral and acidic conditions. Functional analysis showed that carvacrol enhances pH fluorescence signals in OTOP1-expressing cells, with reduced efficacy at lower pH levels. Carvacrol selectively activates mOTOP1, while mOTOP2, mOTOP3, and Chelonia mydas OTOP1 (CmOTOP1) are insensitive to carvacrol activation under neutral pH. Through chimera and point mutation experiments, swapping S134 in transmembrane segment 3 (TM3) and T247 in the TM5-6 linker abolished carvacrol activation of mOTOP1 and conferred activation on CmOTOP1, suggesting these two residues are critical for carvacrol sensitivity. These findings highlight TM3 and TM5-6 linker as pivotal gating apparatus of OTOP1 channels and potential docking sites for drug design.

Comparative Analysis of Taste Perception Among Airline Pilots, Construction Workers, and Office Employees.

Objective Occupational exposures may influence gustatory sensations through mechanisms such as fatigue, acute or chronic stress, circadian rhythm disruptions, and exposure to various chemicals. In this cross-sectional study, we sought to compare taste perception across three professional groups, namely airline pilots, construction workers, and office employees, by assessing taste identification times for sweet, salty, sour, and bitter flavors, alongside salivary pH levels. Methods The study cohort consisted of 90 healthy male participants, with 30 individuals in each occupational group, matched for age and professional experience. Salivary pH was measured using pH meter paper, whereas taste identification times were assessed using aqueous solutions applied to dissolvable strips for each taste. Results There were no significant differences in salivary pH among the study groups. However, airline pilots exhibited a significantly longer identification time for sweet taste (9.8 ± 3.9 seconds) compared to construction workers (7.0 ± 3.1 seconds, P < 0.05) and office employees (7.1 ± 3.3 seconds, P < 0.05). Conversely, construction workers demonstrated a significantly prolonged identification time for sour taste (6.1 ± 2.9 seconds) compared to pilots (4.2 ± 2.6 seconds, P < 0.05) and office employees (4.6 ± 2.5 seconds, P < 0.05). No significant differences were observed in the identification times for salty and bitter tastes across the groups. Conclusion We found significant differences in taste perception among airline pilots, construction workers, and office employees, particularly concerning sweet and sour tastes. These findings suggest that occupational factors may influence gustatory function in a complex manner. Further research is warranted to explore the underlying mechanisms and potential implications for dietary habits and health within specific occupational groups.

Lactiplantibacillus plantarum inoculation enhanced the color stabilization and aroma quality of blueberry wine

Inoculation of Lactiplantibacillus plantarum before yeast has the potential to affect the blueberry wine quality. The effects of four L. plantarum strains on the anthocyanins and volatile profile of blueberry wine were studied. Different L. plantarum inoculated wines presented a great color variation, and B3 strain was able to retain more bluish hue of blueberry wine. Compared with RF wine fermented by only Saccharomyces cerevisiae yeast, L. plantarum inoculated wines exhibited a better preservation of monomeric and acylated anthocyanins. More importantly, inoculation of L. plantarum, especially for B3 and B4 strains, enhanced the accumulation of pyranoanthocyanins, which may improve the color stability of blueberry wine. In addition, inoculation with L. plantarum favored the formation of lactate-related esters, acetoin, C6 alcohols, terpenes, aldehydes, and volatile phenols. Flash-Profile analysis indicated that B3, B4 and SS6 strains conferred wines more sour and astringent tastes, along with more ‘fruity’ and ‘chemical’ aromas.