The Taste of Caffeine

Thiazolidinediones are Partially Effective Bitter Blockers

PURPOSE

The bad bitter taste of some medicines is a barrier to overcoming noncompliance with medication use, especially life-saving drugs given to children and the elderly. Here, we evaluated a new class of bitter blockers (thiazolidinediones, TZDs).

METHODS

In this study, 2 TZDs were tested, rosiglitazone (ROSI) and a simpler form of TZD, using a high-potency sweetener as a positive control (neohesperidin dihydrochalcone, NHDC). We tested bitter-blocking effects using the bitter drugs tenofovir alafenamide fumarate (TAF), a treatment for HIV and hepatitis B infection, and praziquantel (PRAZ), a treatment for schistosomiasis, by conducting taste testing with 2 separate taste panels: a general panel (N = 97, 20-23 years, 82.5% female, all Eastern European) and a genetically informative panel (N = 158, including 68 twin pairs, 18-82 years, 76% female, 87% European ancestry). Participants rated the bitterness intensity of the solutions on a 100-point generalized visual analog scale.

FINDINGS

Person-to-person differences in drug bitterness were striking; TAF and PRAZ were weakly or not bitter for some people but moderately to highly bitter for others. Participants in both taste panels rated the bitter drugs TAF and PRAZ as less bitter on average when mixed with NHDC than when sampled alone. ROSI partially suppressed the bitterness of TAF and PRAZ, but effectiveness differed between the 2 panels: bitterness was significantly reduced for PRAZ but not TAF in the general panel and for TAF but not PRAZ in the genetically informative panel. ROSI was a more effective blocker than the other TZD.

IMPLICATIONS

These results suggest that TZDs are partially effective bitter blockers and the suppression efficacy differs from drug to drug, from person to person, and from panel to panel, suggesting other TZDs should be designed and tested with more drugs and on diverse populations to define which ones work best with which drugs and for whom. The discovery of bitter receptor blockers can improve compliance with medication use.

Prediction of bitterness based on modular designed graph neural network

Motivation

Bitterness plays a pivotal role in our ability to identify and evade harmful substances in food. As one of the five tastes, it constitutes a critical component of our sensory experiences. However, the reliance on human tasting for discerning flavors presents cost challenges, rendering in silico prediction of bitterness a more practical alternative.

Results

In this study, we introduce the use of Graph Neural Networks (GNNs) in bitterness prediction, superseding traditional machine learning techniques. We developed an advanced model, a Hybrid Graph Neural Network (HGNN), surpassing conventional GNNs according to tests on public datasets. Using HGNN and three other GNNs, we designed BitterGNNs, a bitterness predictor that achieved an AUC value of 0.87 in both external bitter/non-bitter and bitter/sweet evaluations, outperforming the acclaimed RDKFP-MLP predictor with AUC values of 0.86 and 0.85. We further created a bitterness prediction website and database, TastePD (https://www.tastepd.com/). The BitterGNNs predictor, built on GNNs, offers accurate bitterness predictions, enhancing the efficacy of bitterness prediction, aiding advanced food testing methodology development, and deepening our understanding of bitterness origins.

Availability and implementation

TastePD can be available at https://www.tastepd.com, all codes are at https://github.com/heyigacu/BitterGNN.

Thiazolidinediones are partially effective bitter blockers

Purpose

The bad bitter taste of some medicines is a barrier to overcoming non-compliance with medication use, especially life-saving drugs given to children and the elderly. Here we evaluated a new class of bitter blockers (thiazolidinediones; TZDs).

Methods

In this study, two TZDs were tested, rosiglitazone (ROSI) and a simpler form of TZD, using a high-potency sweetener as a positive control (neohesperidin dihydrochalcone, NHDC). We tested bitter-blocking effects using the bitter drugs tenofovir alafenamide fumarate (TAF), a treatment for HIV and hepatitis B infection, and praziquantel (PRAZ), a treatment for schistosomiasis, by conducting taste testing with two separate taste panels: a general panel (N=97, 20-23 yrs, 82.5% female, all Eastern European) and a genetically informative panel (N=158, including 68 twin pairs, 18-82 yrs, 76% female, 87% European ancestry). Participants rated the bitterness intensity of the solutions on a 100-point generalized visual analog scale.

Findings

Participants in both taste panels rated the bitter drugs TAF and PRAZ as less bitter on average when mixed with NHDC than when sampled alone. ROSI partially suppressed the bitterness of TAF and PRAZ, but effectiveness differed between the two panels: bitterness was significantly reduced for PRAZ but not TAF in the general panel and for TAF but not PRAZ in the genetically informative panel. ROSI was a more effective blocker than the other TZD.

Implications

These results suggest that TZDs are partially effective bitter blockers, suggesting other TZDs should be designed and tested with more drugs and on diverse populations to define which ones work best with which drugs and for whom. The discovery of bitter receptor blockers can improve compliance with medication use.

Coffee consumption decreases the connectivity of the posterior Default Mode Network (DMN) at rest

Habitual coffee consumers justify their life choices by arguing that they become more alert and increase motor and cognitive performance and efficiency; however, these subjective impressions still do not have a neurobiological correlation. Using functional connectivity approaches to study resting-state fMRI data in a group of habitual coffee drinkers, we herein show that coffee consumption decreased connectivity of the posterior default mode network (DMN) and between the somatosensory/motor networks and the prefrontal cortex, while the connectivity in nodes of the higher visual and the right executive control network (RECN) is increased after drinking coffee; data also show that caffeine intake only replicated the impact of coffee on the posterior DMN, thus disentangling the neurochemical effects of caffeine from the experience of having a coffee.

The effect of the chemical composition on the sensory characterization of Ecuadorian coffee

The study aims to test if Ecuadorean coffee's symbolic and material contents agree with the instrumental analysis and grading protocols. We studied the relationship between the chemical composition and the organoleptic characteristics of eight non-specialty and six specialty coffee samples. Firstly, the study addresses the grading following the Specialty Coffee American Association (SCAA) method. The second stage focuses on the qualitative composition of the coffee brews employing GC-MS and caffeine concentrations using HPLC. Then, we employed statistical tools such as Cohen's concordance coefficients, dissimilarity dendrograms, and linear correlations between the chemical compounds in the beverage and the attributes' scores. The grading panel consisted of 6 semi-trained-testers who would assess if the primary cultural capital can provide a criterion to identify specialty coffee. The variety of compounds allowed the evaluators to distinguish between commercial and specialty coffees. However, the composition analysis identified molecules that would imply greater gradation in the tasting, a prevision that was not reflected in the results. Finally, we confirmed that basic training could create cultural capital to distinguish non-specialties from specialty coffees through their chemistry and organoleptic attributes.

Ultrafast cold-brewing of coffee by picosecond-pulsed laser extraction

Coffee is typically brewed by extracting roasted and milled beans with hot water, but alternative methods such as cold brewing became increasingly popular over the past years. Cold-brewed coffee is attributed to health benefits, fewer acids, and bitter substances. But the preparation of cold brew typically needs several hours or even days. To create a cold-brew coffee within a few minutes, we present an approach in which an ultrashort-pulsed laser system is applied at the brewing entity without heating the powder suspension in water, efficiently extracting caffeine and aromatic substances from the powder. Already 3 min irradiation at room temperature leads to a caffeine concentration of 25 mg caffeine per 100 ml, comparable to the concentrations achieved by traditional hot brewing methods but comes without heating the suspension. Furthermore, the liquid phase’s alkaloid content, analyzed by reversed-phase liquid chromatography coupled to high-resolution mass spectrometry, is dominated by caffeine and trigonelline and is comparable to traditional cold-brewed coffee rather than hot-brewed coffee. Furthermore, analyzing the head-space of the prepared coffee variants, using in-tube extraction dynamic head-space followed by gas chromatography coupled to mass spectrometry, gives evidence that the lack of heating leads to the preservation of more (semi-)volatile substances like pyridine, which provide cold-brew coffee its unique taste. This pioneering study may give the impetus to investigate further the possibility of cold-brewing coffee, accelerated by more than one order of magnitude, using ultrafast laser systems.

Diet and Respiratory Infections: Specific or Generalized Associations?

Background: Based on our recently reported associations between specific dietary behaviors and the risk of COVID-19 infection in the UK Biobank (UKB) cohort, we further investigate whether these associations are specific to COVID-19 or extend to other respiratory infections. Methods: Pneumonia and influenza diagnoses were retrieved from hospital and death record data linked to the UKB. Baseline, self-reported (2006−2010) dietary behaviors included being breastfed as a baby and intakes of coffee, tea, oily fish, processed meat, red meat (unprocessed), fruit, and vegetables. Logistic regression estimated the odds of pneumonia/influenza from baseline to 31 December 2019 with each dietary component, adjusting for baseline socio-demographic factors, medical history, and other lifestyle behaviors. We considered effect modification by sex and genetic factors related to pneumonia, COVID-19, and caffeine metabolism. Results: Of 470,853 UKB participants, 4.0% had pneumonia and 0.2% had influenza during follow up. Increased consumption of coffee, tea, oily fish, and fruit at baseline were significantly and independently associated with a lower risk of future pneumonia events. Increased consumption of red meat was associated with a significantly higher risk. After multivariable adjustment, the odds of pneumonia (p ≤ 0.001 for all) were lower by 6−9% when consuming 1−3 cups of coffee/day (vs. <1 cup/day), 8−11% when consuming 1+ cups of tea/day (vs. <1 cup/day), 10−12% when consuming oily fish in higher quartiles (vs. the lowest quartile—Q1), and 9−14% when consuming fruit in higher quartiles (vs. Q1); it was 9% higher when consuming red meat in the fourth quartile (vs. Q1). Similar patterns of associations were observed for influenza but only associations with tea and oily fish met statistical significance. The association between fruit and pneumonia risk was stronger in women than in men (p = 0.001 for interaction). Conclusions: In the UKB, consumption of coffee, tea, oily fish, and fruit were favorably associated with incident pneumonia/influenza and red meat was adversely associated. Findings for coffee parallel those we reported previously for COVID-19 infection, while other findings are specific to these more common respiratory infections.

The effect of mouth rinsing with different concentrations of caffeine solutions on reaction time

Caffeine mouth rinsing (CAF-MR) has been shown to improve reaction time (RT). CAF-MR studies have generally used 1.2% CAF concentrations, but the effect of using different concentrations is unknown. Therefore, we compared the effect of different concentrations of CAF-MR on RT. Forty-five trained male athletes (age: 18 ± 3 y) volunteered to participate in this double-blind, randomized controlled crossover study. Participants completed five testing sessions (Control, Placebo (water)-MR, and 1.2%, 1.8%, and 2.4% CAF-MR), with hand and foot RTs assessed immediately after MR. All CAF-MR conditions resulted in significantly faster hand and foot RT compared to Control and Placebo (all p < 0.001, except for foot RT with 1.8% CAF-MR vs. Placebo: NS). For both hand and foot RT, 1.2% and 1.8% CAF-MR did not significantly differ, but RT for 2.4% CAF-MR was significantly faster than both (p < 0.001). Improvements in RT for 2.4% CAF-MR vs. Placebo were 22% for hand RT and 21% for foot RT. In conclusion, these findings demonstrate that higher CAF-MR concentrations than those typically used can result in greater improvements in RT. This has implications for the practical use of CAF-MR to enhance performance in sports in which optimal RT is a factor of success.

Anion-cation contrast of small molecule solvation in salt solutions

The contributions from anions and cations from salt are inseparable in their perturbation of molecular systems by experimental and computational methods, rendering it difficult to dissect the effects exerted by the anions and cations individually. Here we investigate the solvation of a small molecule, caffeine, and its perturbation by monovalent salts from various parts of the Hofmeister series. Using molecular dynamics and the energy-representation theory of solvation, we estimate the solvation free energy of caffeine and decompose it into the contributions from anions, cations, and water. We also decompose the contributions arising from the solute-solvent and solute-ions interactions and that from excluded volume, enabling us to pin-point the mechanism of salt. Anions and cations revealed high contrast in their perturbation of caffeine solvation, with the cations salting-in caffeine via binding to the polar ketone groups, while the anions were found to be salting-out via perturbations of water. In agreement with previous findings, the perturbation by salt is mostly anion dependent, with the magnitude of the excluded-volume effect found to be the governing mechanism. The free-energy decomposition as conducted in the present work can be useful to understand ion-specific effects and the associated Hofmeister series.

An update on extra-oral bitter taste receptors

Bitter taste-sensing type 2 receptors (TAS2Rs or T2Rs), belonging to the subgroup of family A G-protein coupled receptors (GPCRs), are of crucial importance in the perception of bitterness. Although in the first instance, TAS2Rs were considered to be exclusively distributed in the apical microvilli of taste bud cells, numerous studies have detected these sensory receptor proteins in several extra-oral tissues, such as in pancreatic or ovarian tissues, as well as in their corresponding malignancies. Critical points of extra-oral TAS2Rs biology, such as their structure, roles, signaling transduction pathways, extensive mutational polymorphism, and molecular evolution, have been currently broadly studied. The TAS2R cascade, for instance, has been recently considered to be a pivotal modulator of a number of (patho)physiological processes, including adipogenesis or carcinogenesis. The latest advances in taste receptor biology further raise the possibility of utilizing TAS2Rs as a therapeutic target or as an informative index to predict treatment responses in various disorders. Thus, the focus of this review is to provide an update on the expression and molecular basis of TAS2Rs functions in distinct extra-oral tissues in health and disease. We shall also discuss the therapeutic potential of novel TAS2Rs targets, which are appealing due to their ligand selectivity, expression pattern, or pharmacological profiles.

Caffeine Mouth Rinse Does Not Improve Time to Exhaustion in Male Trained Cyclists

This study investigated the effects of caffeine mouth rinse on cycling time to exhaustion (TTE) and physiological responses in trained cyclists. In a double-blinded randomized counterbalanced cross-over design, 10 recreationally trained male cyclists (mean ± SD: 32 ± 3 years, 72.8 ± 5.3 kg, 1.78 ± 0.06 m, 13.9% ± 3.3% body fat, peak power output = 289.4 ± 24.7 W) completed two TTE tests cycling at 75% of peak aerobic power following 24 hr of dietary and exercise standardization. Cyclists were administered 25-ml mouth rinses for 5 s containing either 85 mg of caffeine or control (water) every 5 min throughout the exercise tests. No significant improvement in TTE was shown with caffeine mouth rinse compared with control (33:24 ± 12:47 vs. 28:08 ± 10:18 min; Cohen's dz effect size: 0.51, p = .14). Caffeine mouth rinse had no significant effect on ratings of perceived exertion (p = .31) or heart rate (p = .35) throughout the cycling TTE protocol. These data indicate that a repeated dose of caffeinated mouth rinse for 5 s does not improve cycling TTE in recreationally trained male cyclists. However, these findings should be taken with caution due to the small sample size and blinding ineffectiveness, while further well-design studies with larger samples are warranted.

Chronic administration of caffeine alters acesulfame-K intake and features of fungiform taste buds in mice

The objective of this study was to investigate the effects of chronic administration of caffeine on the anatomical characteristics of taste buds, the expression level of taste receptor protein in mice, and preference for a palatable solution. We found that following a 21-day administration of caffeine, mice showed increased behavioural responses to sweet stimuli (acesulfame-K solution). Mirroring this behavioural change, chronic caffeine treatment evidently decreased the maximal cross-sectional area and height of the longitudinal axis of fungiform taste buds, the number of taste cells per fungiform taste bud, and the expression of G protein α-gustducin, while the expression of the sweet taste receptors T1R2 and T1R3 was reversed. Our findings demonstrate that chronic administration of caffeine has an impact on taste sensitivity and changes in taste bud features, which may contribute to the alteration of taste behaviour.

Caffeine: A potential strategy to improve survival of neonatal pigs and sheep

Caffeine is commonly used to treat pre-and postnatal injuries, including apnoea in premature infants, as well as neurological impairment caused by hypoxia or asphyxiation often associated with difficult birthing. As an adenosine antagonist, caffeine is metabolised rapidly and transported into many tissues. Caffeine stimulates the brain respiratory centre, improving respiratory function in immature infants or neonates, provides neuroprotection to the fetal brain, and initiates non-shivering thermoregulation increasing metabolic rates. Recently, potential benefits of caffeine for animal production have been investigated. This has particularly occurred in pig production, where large litters are associated with relatively long parturition durations, and piglets born near the end of the parturition period have an increased risk of mortality due to asphyxia-related birthing injury. Similarly, in sheep, dystocia or prolonged parturition is a significant problem, where neonatal injury, dystocia and death in utero contributes to approximately 46 % of lamb mortalities. Within these two livestock production systems, large prevalence's of neonatal mortality is a persistent issue contributing to lost revenue, as well as being a significant animal welfare concern. Pre-partum maternal caffeine supplementation is a promising strategy to reduce neonatal mortality; however, there needs to be refinement of appropriate quantities administered, duration and administration pathway to provide producers with an efficient and cost-effective method to reduce mortality rates and increase production output. The information in this review details effects, benefits and important considerations regarding caffeine use in animal production, and identifies areas of limited knowledge where further research is needed.

International society of sports nutrition position stand: caffeine and exercise performance

Following critical evaluation of the available literature to date, The International Society of Sports Nutrition (ISSN) position regarding caffeine intake is as follows: 1. Supplementation with caffeine has been shown to acutely enhance various aspects of exercise performance in many but not all studies. Small to moderate benefits of caffeine use include, but are not limited to: muscular endurance, movement velocity and muscular strength, sprinting, jumping, and throwing performance, as well as a wide range of aerobic and anaerobic sport-specific actions. 2. Aerobic endurance appears to be the form of exercise with the most consistent moderate-to-large benefits from caffeine use, although the magnitude of its effects differs between individuals. 3. Caffeine has consistently been shown to improve exercise performance when consumed in doses of 3-6 mg/kg body mass. Minimal effective doses of caffeine currently remain unclear but they may be as low as 2 mg/kg body mass. Very high doses of caffeine (e.g. 9 mg/kg) are associated with a high incidence of side-effects and do not seem to be required to elicit an ergogenic effect. 4. The most commonly used timing of caffeine supplementation is 60 min pre-exercise. Optimal timing of caffeine ingestion likely depends on the source of caffeine. For example, as compared to caffeine capsules, caffeine chewing gums may require a shorter waiting time from consumption to the start of the exercise session. 5. Caffeine appears to improve physical performance in both trained and untrained individuals. 6. Inter-individual differences in sport and exercise performance as well as adverse effects on sleep or feelings of anxiety following caffeine ingestion may be attributed to genetic variation associated with caffeine metabolism, and physical and psychological response. Other factors such as habitual caffeine intake also may play a role in between-individual response variation. 7. Caffeine has been shown to be ergogenic for cognitive function, including attention and vigilance, in most individuals. 8. Caffeine may improve cognitive and physical performance in some individuals under conditions of sleep deprivation. 9. The use of caffeine in conjunction with endurance exercise in the heat and at altitude is well supported when dosages range from 3 to 6 mg/kg and 4-6 mg/kg, respectively. 10. Alternative sources of caffeine such as caffeinated chewing gum, mouth rinses, energy gels and chews have been shown to improve performance, primarily in aerobic exercise. 11. Energy drinks and pre-workout supplements containing caffeine have been demonstrated to enhance both anaerobic and aerobic performance.

Taste Receptor Signaling

All organisms have the ability to detect chemicals in the environment, which likely evolved out of organisms' needs to detect food sources and avoid potentially harmful compounds. The taste system detects chemicals and is used to determine whether potential food items will be ingested or rejected. The sense of taste detects five known taste qualities: bitter, sweet, salty, sour, and umami, which is the detection of amino acids, specifically glutamate. These different taste qualities encompass a wide variety of chemicals that differ in their structure and as a result, the peripheral taste utilizes numerous and diverse mechanisms to detect these stimuli. In this chapter, we will summarize what is currently known about the signaling mechanisms used by taste cells to transduce stimulus signals.

Can taste be ergogenic?

Taste is a homeostatic function that conveys valuable information, such as energy density, readiness to eat, or toxicity of foodstuffs. Taste is not limited to the oral cavity but affects multiple physiological systems. In this review, we outline the ergogenic potential of substances that impart bitter, sweet, hot and cold tastes administered prior to and during exercise performance and whether the ergogenic benefits of taste are attributable to the placebo effect. Carbohydrate mouth rinsing seemingly improves endurance performance, along with a potentially ergogenic effect of oral exposure to both bitter tastants and caffeine although subsequent ingestion of bitter mouth rinses is likely required to enhance performance. Hot and cold tastes may prove beneficial in circumstances where athletes' thermal state may be challenged. Efficacy is not limited to taste, but extends to the stimulation of targeted receptors in the oral cavity and throughout the digestive tract, relaying signals pertaining to energy availability and temperature to appropriate neural centres. Dose, frequency and timing of tastant application likely require personalisation to be most effective, and can be enhanced or confounded by factors that relate to the placebo effect, highlighting taste as a critical factor in designing and administering applied sports science interventions.

Discovery and Development of S6821 and S7958 as Potent TAS2R8 Antagonists

In humans, bitter taste is mediated by 25 TAS2Rs. Many compounds, including certain active pharmaceutical ingredients, excipients, and nutraceuticals, impart their bitter taste (or in part) through TAS2R8 activation. However, effective TAS2R8 blockers that can either suppress or reduce the bitterness of these compounds have not been described. We are hereby reporting a series of novel 3-(pyrazol-4-yl) imidazolidine-2,4-diones as potent and selective TAS2R8 antagonists. In human sensory tests, S6821 and S7958, two of the most potent analogues from the series, demonstrated efficacy in blocking TAS2R8-mediated bitterness and were selected for development. Following data evaluation by expert panels of a number of national and multinational regulatory bodies, including the US, the EU, and Japan, S6821 and S7958 were approved as safe under conditions of intended use as bitter taste blockers.

Transcriptional profiling of genes in tongue epithelial tissue from immature and adult rats by the RNA-Seq technique

Children are more sensitive than adults to bitterness and thus dislike bitter tastes more than adults do. However, why children are more sensitive to bitterness has never been revealed. To elucidate the effects of age on taste perception, a double-bottle preference test was first performed with immature and adult rats. Then, RNA-Seq analysis was performed on tongues obtained from rats of the same ages as those in the double-bottle test. The immature rats exhibited a lower consumption rate of bitter solution than the adult rats. Bioinformatics analysis yielded 1,347 differentially expressed genes (DEGs) between male adult rats (MARs, 80 days old) and male immature rats (MIRs, 20 days old) and 380 DEGs between female adult rats (FARs, 80 days old) and female immature rats (FIRs, 20 days old). These DEGs were mainly associated with growth, development, differentiation, and extracellular processes, among other mechanisms. According to Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, the DEGs were enriched for bitter taste transduction. Specifically, the Gnb3 and TRPM5 genes were downregulated in FARs compared with FIRs and in MARs compared with MIRs, and the protein expression of TRPM5 was significantly downregulated in MARs compared with MIRs. The data presented herein suggest that transcriptional regulation of taste-associated signal transduction occurs differently in tongue epithelial tissue of rats at different ages, although additional analyses are needed to confirm this conclusion.

Taste Perception and Caffeine Consumption: An fMRI Study

Caffeine is ubiquitous, yet its impact on central taste processing is not well understood. Although there has been considerable research on caffeine’s physiological and cognitive effects, there is a paucity of research investigating the effects of caffeine on taste. Here we used functional magnetic resonance imaging (fMRI) to investigate group differences between caffeine consumers and non-consumers in blood-oxygenation-level-dependent (BOLD) activation during hedonic evaluation of taste. We scanned 14 caffeine consumers and 14 caffeine non-consumers at 3 Tesla, while they rated three tastes: caffeine (bitter), sucrose (sweet), and saccharin (sweet with bitter after taste), in aqueous solutions. Differences in BOLD activation were analyzed using voxel wise independent samples t-tests within Analysis of Functional Neuroimage (AFNI). Results indicated that during the hedonic evaluation of caffeine or sucrose, caffeine non-consumers had significantly greater activation in neuronal areas associated with memory and reward. During the hedonic evaluation of saccharin, caffeine consumers had significantly greater activation in areas associated with memory and information processing. The findings suggest caffeine consumption is associated with differential activation in neuronal areas involved in reward, memory, and information processing. Further research on intensity and hedonics of bitter and sweet stimuli in caffeine consumers and non-consumers will be of great interest to better understand the nature of differences in taste perception between caffeine consumers and non-consumers.

Quantitative Trait Loci Mapping for Theobromine and Caffeine Contents in Tea Plant ( Camellia sinensis)

Understanding the genetic basis of theobromine and caffeine accumulation in the tea plant is important due to their contribution to tea flavor. Quantitative trait loci (QTL) analyses were carried out to identify genetic variants associated with theobromine and caffeine contents and ratio using a pseudo-testcross population derived from an intervarietal cross between two varieties of Camellia sinensis. A total of 10 QTL controlling caffeine content (CAF), theobromine content (TBR), sum of caffeine and theobromine (SCT), and caffeine-to-theobromine ratio (CTR) were identified over four measurement years. The major QTL controlling CAF, qCAF1, was mapped onto LG01 and validated across years, explaining an average of 20.1% of the phenotypic variance. The other QTL were detected in 1 or 2 years, and of them there were four, two, and three for TBR, SCT, and CTR, respectively. The present results provide valuable information for further fine mapping and cloning functional genes and for genetic improvement in tea plant.