Target Flavor Research Articles

Preexposure to running attenuates rats' running-based flavour avoidance: Testing associative blocking with a cover cues or context change.

Voluntary running in activity wheels by rats leads to a Pavlovian conditioned aversion to the flavour consumed immediately before the running, causing the rats to avoid that flavour. This learning process, known as running-based flavour avoidance learning (FAL), is weakened when the rats have had repeated exposure to the wheels before. According to the associative account, the association between the background context and running established during the preexposure phase blocks the conditioning of the target flavour because the running is highly predictable by the background context from the outset of the FAL phase. Experiments 1 and 2 examined this account by introducing another flavour as a cue signalling wheel access during the preexposure phase. In the framework of the associative account, the introduction of this cue should impede the formation of the context-running association during the preexposure phase, thereby hindering the contextual blocking of aversive conditioning for the target flavour in the FAL phase. This would result in unweakened FAL. Although the results of Experiment 1 align with this prediction, in Experiment 2, when highly distinct flavours were used as the target and second cues, the preexposure effect was not eliminated. This contradicts the predictions of the associative account, indicating that Experiment 1 may have been influenced by stimulus generalisation. In Experiment 3, changing background contexts between the preexposure and FAL phases had no impact on the preexposure effect, contrary to the predictions of the associative account. In general, the associative account was not supported.

Male and Female Laboratory Rats Equally Acquire Running‐Based Flavor‐Aversion Learning1

AbstractLaboratory rats can be conditioned to shy away from a flavored substance consumed immediately before running in activity wheels, suggesting flavor‐aversion learning. We examined whether the factor of sex impacted running‐based flavor‐aversion learning. A differential conditioning procedure was employed in Experiment 1: The measure of learning was the degree of differentiation in the intake of a target flavor solution paired with running and an unpaired non‐target flavor solution. Flavor‐aversion learning was observed as a gradual decrease in the intake of the target solution, which was absent in that of the non‐target solution. Although females ran more than twice as fast as males, the degree of differential conditioning was similar for males and females. This was the case not only for absolute intake but also for intake per body weight and change from the initial intake (percentage decrease). The null effect of sex was replicated in Experiment 2, which employed a simple conditioning procedure. These results suggest that rats’ running‐based flavor‐aversion learning is a robust phenomenon, despite the subjects being male or female.

Comparative Analysis of Flavor, Taste, and Volatile Organic Compounds in Opossum Shrimp Paste during Long-Term Natural Fermentation Using E-Nose, E-Tongue, and HS-SPME-GC-MS.

The present study focused on the determination of color, flavor, taste, and volatile organic compounds (VOCs) changes of shrimp paste fermented for 1, 2, 3, and 8 years by E-nose, E-tongue, and headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS). During fermentation, the color of shrimp paste turned dark brown with decreases in L*, a*, and b* values. Inorganic sulfide odor was dominant in all fermented samples. The umami, richness, and aftertaste-B reached a maximum in year 3 of fermentation. A total of 182 volatiles, including long-chain alkanes, esters, aldehydes, olefins, ketones, acids, furans, and pyrazines, were detected. Sixteen VOCs including dimethyl disulfide, methional, trimethyl-pyrazine, (E,E)-2,4-heptadienal, benzeneacetaldehyde were selected as flavor markers. Correlation analysis showed that 94 VOCs were related to saltiness while 40, 17, 21, 22, and 24 VOCs contributed to richness, umami, aftertase-B, sourness, and bitterness, respectively. These novel data may help in optimizing fermentation duration to achieve target flavor indicators in opossum shrimp paste production.

Sucrose-based flavor preferences in rats: Factors affecting detection of extinction.

Rats that have consumed a novel target flavor added to a sucrose solution will develop a preference for that flavor. Such preferences appear to persist over the course of many presentations of the flavor alone when animals are not food-deprived. However, previous research indicates that an extinction effect (a reduction in preference) can be obtained when training or testing is carried out in animals that are hungry. In a series of experiments that produced flavor preferences in hungry rats by adding the flavor to a sucrose solution, three (Experiments 1, 2A, 2B) established that the concentration of sucrose and the nature of the flavor influenced the results but failed to detect extinction. Two-bottle choice tests showed some loss of preference but this occurred both in subjects given the extinction treatment (flavor-only presentations) and in control subjects given just water. A loss of preference in rats given an extinction treatment as opposed to controls given only water was, however, found in Experiments 3 and 4. These experiments differed from Experiments 1 and 2 in that the extinction stage involved the presentation of two bottles containing the flavor, thus matching the two-bottle procedure used in the test phase. These results confirm that experiencing a flavor alone can result in extinction of a conditioned flavor preference in hungry rats but indicate that the effect is highly context-specific, requiring the conditions of the test to match those of the extinction procedure. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Extinction makes acquisition context-specific in conditioned taste aversion regardless of the context where acquisition and testing take place.

Retrieval of a flavor-illness association has been found to show contextual dependence when the association is learned after a nontarget flavor-illness association has been extinguished in what has been named as the extinction makes acquisition context-specific (EMACS) effect. Four experiments were designed to further explore the EMACS effect in conditioned taste aversion. Experiments 1 and 2 replicated the EMACS effect using rats that did not experience extinction, and rats that underwent extinction of a different flavor as controls. Experiments 3 and 4 found that the experience of extinction with the nontarget Flavor X in a given context (A) led to context-specificity of performance to the target Flavor Y both, when Y was trained in a highly familiar context (B) and tested in the context where X had been trained (Context A, Experiment 3), and when the test was conducted in a less familiar context (C) where no cues or outcomes were presented before (Experiment 4). These results are consistent with the idea that the experience of extinction encourages organism's attention to the contexts, making retrieval of new learning context-specific. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Design Development for the Beam Dump Facility Target Complex at CERN

CERN has launched a study phase to evaluate the feasibility of a new high-intensity beam dump facility at the CERN Super Proton Synchrotron accelerator with the primary goal of exploring Hidden Sector models and searching for Light Dark Matter, but which also offers opportunities for other fixed target flavour physics programs such as rare tau lepton decays and tau neutrino studies. The new facility will require—among other infrastructure—a target complex in which a dense target/dump will be installed, capable of absorbing the entire energy of the beam extracted from the SPS accelerator. In theory, the target/dump could produce very weakly interacting particles, to be investigated by a suite of particle detectors to be located downstream of the target complex. As part of the study, a development design of the target complex has been produced, taking into account the handling and remote handling operations needed through the lifetime of the facility. Two different handling concepts have been studied and both resulting designs are presented.

Augmentation’s boundary conditions? Investigation of spatial contiguity, temporal contiguity, and target flavor familiarity

When a preconditioned flavor (A) is conditioned in compound with a novel target flavor (X), the aversion to the target X is increased; this enhanced aversion to X is called augmentation. In 6 experiments with rat subjects, we manipulated the spatial contiguity of cues during compound conditioning (AX+), the temporal contiguity of cues during compound conditioning (AX+), and the familiarity of the target. In all 6 studies, augmentation was recorded with spatially separated flavors. In Experiments 2–4, augmentation was not detected if the two flavors were temporally discontiguous, but augmentation still occurred if the cues were partially contiguous (i.e., the flavors co-occurred for 2 min of a 4-min exposure). Even though stimulus preexposure can often weaken subsequent conditioning, augmentation was observed following 1 or 4 preexposures to the target taste (Experiment 5A) or target odor (Experiment 5B). In sum, manipulations that should weaken, but not eliminate, the within-compound association formed during AX+ conditioning did not prevent augmentation, suggesting the robustness of the within-compound association when one of the elements is a preconditioned flavor.

Ratios and effect size.

Responding to a related pair of measurements is often expressed as a single discrimination ratio. Authors have used various discrimination ratios; yet, little information exists to guide their choice. A second use of ratios is to correct for the influence of a nuisance variable on the measurement of interest. I examine 4 discrimination ratios using simulated data sets. Three ratios, of the form a/(a + b), b/(a + b), and (a − b)/(a + b), introduced distortions to their raw data. The fourth ratio, (b − a)/b largely avoided such distortions and was the most sensitive at detecting statistical differences. Effect size statistics were also often improved with a correction ratio. Gustatory sensory preconditioning experiments involved measurement of rats’ sucrose and saline consumption; these flavors served as either a target flavor or a control flavor and were counterbalanced across rats. However, sensory preconditioning was often masked by a bias for sucrose over saline. Sucrose and saline consumption scores were multiplied by the ratio of the overall consumption to the consumption of that flavor alone, which corrected the bias. The general utility of discrimination and correction ratios for data treatment is discussed.

An expert system for automated flavour matching – Prioritizer

AbstractFlavour matching can be viewed as trying to reproduce a specific flavour. This is a time consuming task and may lead to flavour mixtures that are too complex or too expensive to be commercialized. In order to facilitate the matching, we have developed a new mathematical model, called Prioritizer. Based on the chemical composition of a mixture of volatiles (a target flavour profile), from a set of different ingredients, the model can suggest an initial selection of ingredients needed to reproduce the flavour. The model also allows the user to prioritize properties of the flavour, given the cost of the different raw materials, the allowed number of ingredients and relative importance of flavour components (represented e.g. by perception threshold values). The limit of detection of the equipment used to measure the target flavour profile puts a limit to what flavours can be matched, but it will be shown that the model offers a good initial estimate for reproducing flavour.

Characterization of the Authenticity of Pasta di Gragnano Protected Geographical Indication Through Flavor Component Analysis by Gas Chromatography–Mass Spectrometry and Chemometric Tools

An authentication study based on headspace solid-phase microextraction/GC-MS was performed with a set of 60 samples representative of traditional "Pasta di Gragnano protected geographical indication (PGI)" and the most common Italian pasta brands. Multivariate chemometric tools were used to classify the samples based on the chemical information provided from 20 target flavor compounds, including Maillard reaction and lipid oxidation products. Pattern recognition by principal component analysis and linear discriminant analysis showed a natural grouping of samples according to the drying process adopted for their production (i.e., the traditional Cirillo method versus a high-temperature approach). Subsequently, soft independent modeling by class analogy (SIMCA) and unequal dispersed classes (UNEQ) were used to build class models at 95% confidence and 100% sensitivity levels (forced models) for predictive classification purposes. The good performance obtained from the models in terms of cross-validation efficiency (SIMCA, 57.01%; UNEQ, 86.60%; 100% for both forced models) highlighted that targeted analysis of flavor profiles could be used to assess the authenticity of Pasta di Gragnano PGI samples. Hence, the proposed method may help to protect Pasta di Gragnano PGI from label frauds by verifying whether samples comply with statements concerning drying process conditions as stated in the product specification.

Flavor avoidance learning based on missing calories but not on palatability reduction

Avoidance of a target flavor can be produced by providing rats with a highly nutritious solution of 20 % maltodextrin (20 %Malto) in some sessions and a 3 % maltodextrin (3 %Malto) solution containing the target flavor in intermixed sessions. Since 20 %Malto is both more nutritious and more palatable than 3 %Malto, flavor avoidance could arise because the flavor signals either a reduction in calories or reduced palatability, or both. Pilot testing established that rats strongly preferred 3 %Malto plus 0.1 % saccharin to both unflavored 3 %Malto and unflavored 20 %Malto. The two main experiments tested whether the palatability difference, which the pilot data had suggested was larger than the difference between 20 %Malto and 3 %Malto, could produce flavor avoidance. In both experiments, one group of rats were given 3 %Malto plus 0.1 % saccharin on some days, intermixed with other days on which this group was given 3 %Malto plus the target flavor, almond. Neither when trained and tested under conditions of food deprivation (Experiment 1) nor when trained and tested sated (Experiment 2) did palatability reduction produce almond avoidance. In contrast, calorie reduction produced almond avoidance under both conditions. These results suggest that flavor avoidance can be produced by intermixed training involving solutions that differ in nutritious value and palatability, but not when they differ only in palatability.

Package images modulate flavors in memory: Incidental learning of fruit juice flavors

The effect of package images on incidental flavor memory for fruit juice was investigated. Ninety-two participants were allocated to three experimental conditions: (1) apple-label, (2) peach-label, and (3) control-label. In each condition, participants tasted a target flavor stimulus, a 1:1 mixture of 100% pure apple juice and 100% pure peach juice with pictures attached to the cups. Ten minutes later, participants were confronted with samples consisting of varying ratios of 100% peach to 100% apple juice, and were asked to rate their similarity to the target stimuli. Participants were also asked to rate how congruent the juice flavor and the image were at the initial tasting. Apple images modulated memories of the flavors of target stimuli: they shifted toward that of apples. This modulation occurred in participants who perceived the label and flavor as congruent. Peach images did not modulate memories, possibly because the subjects had significantly less experience of drinking peach juice than apple juice. These results reveal that flavor memory can be biased toward that of the image labels during initial tasting. However, memory bias depends on the perceived congruency between labels and flavors, and tasters’ prior experiences.

Posttraining flavor exposure in hungry rats after simultaneous conditioning with a nutrient converts the CS into a conditioned inhibitor

The present study investigated the decrement in nutrient-based conditioned flavor preference found in hungry rats exposed to a flavor following simultaneous flavor-sucrose conditioning while thirsty. Although a significant decrease in preference was found in the experimental group in each experiment, there was no evidence of either spontaneous recovery (Experiment 1) or reinstatement (Experiment 2). In addition, posttraining flavor exposure weakened the original flavor-sucrose association (Experiment 3). These results suggested that the flavor-US association might have been impaired after posttraining flavor exposure. Two further experiments assessed whether the flavor acquired the properties of a net inhibitor, using the retardation and summation tests for conditioned inhibition. Experiment 4 revealed that the flavor suffered retardation when retraining was conducted after the exposure phase. In Experiment 5, the target flavor decreased the preference shown for a different flavor previously paired simultaneously with sucrose when both were presented forming an unreinforced compound in the summation tests. None of these effects was found in a control group, which had received serial flavor → nutrient presentations during training. Together, these results suggest that a flavor simultaneously paired with sucrose acquires the properties of a net inhibitor when it is subsequently presented outside the compound to hungry animals.

Learned avoidance of flavors signaling reduction in a nutrient.

Food-deprived rats learned to avoid a flavor negatively correlated with access to a rich nutrient, 20% maltodextrin (20M) solution. This avoidance in two-bottle choice tests was produced by training consisting of either an unpaired condition where sessions of unflavored 20M were intermixed with sessions of 2 or 3% maltodextrin (2M or 3M) flavored with salt (Experiment 1) or almond (Experiments 3 and 4) or a differential conditioning procedure where one flavor was mixed with 20M and another with 2M (Experiment 2). Avoidance was counter-conditioned by mixing the target flavor with 20M (Experiment 1), generalized to a neutral context (Experiment 3), and displayed strong resistance to extinction (Experiment 4). The results demonstrated that food avoidance learning can occur in the absence of an aversive unconditioned stimulus and indicated that unpaired control groups and differential conditioning procedures may be misleading in flavor preference learning research when further control conditions are absent.

Use of network analysis to capture key traits affecting tomato organoleptic quality

The long-term objective of tomato breeders is to identify metabolites that contribute to defining the target flavour and to design strategies to enhance it. This paper reports the results of network analysis, based on metabolic phenotypic and sensory data, to highlight important relationships among such traits. This tool allowed a reduction in data set complexity, building a network consisting of 35 nodes and 74 links corresponding to the 74 significant (positive or negative) correlations among the variables studied. A number of links among traits contributing to fruit organoleptic quality and to the perception of sensory attributes were identified. Modular partitioning of the characteristics involved in fruit organoleptic perception captured the essential fruit parameters that regulate interactions among different class traits. The main feature of the network was the presence of three nodes interconnected among themselves (dry matter, pH, and °Brix) and with other traits, and nodes with widely different linkage degrees. Identification of strong associations between some metabolic and sensory traits, such as citric acid with tomato smell, glycine with tomato smell, and granulosity with dry matter, suggests a basis for more targeted investigations in the future.

Learned flavor preferences. The variable potency of post-oral nutrient reinforcers

The notion that preferences for flavors paired with various nutrients can be attributed simply to their energy content (“flavor-calorie learning”) is belied by variation in nutrient reinforcing potency. Fructose, fat and ethanol, all regarded as powerful contributors to food and fluid preferences, are less potent than glucose when their orosensory effects are bypassed. Conditioning studies in animals infused with nutrients as they consume target flavor solutions have shown that the weaker reinforcing effects of these nutrients can be enhanced by various methods that improve the opportunity for associating a flavor with post-oral effects. Until the nature of the reinforcing stimuli is understood, “flavor–nutrient learning” is a better label for these phenomena.

Solid‐phase microextraction for determining twelve orange flavour compounds in a model beverage emulsion

Solid-phase microextraction (SPME) coupled to gas chromatography has been applied for the headspace analysis (HS) of 12 target flavour compounds in a model orange beverage emulsion. The main volatile flavour compounds studied were: acetaldehyde, ethyl acetate, alpha-pinene, ethyl butyrate, beta-pinene, myrcene, limonene, gamma-terpinene, octanal, decanal, linalool and citral (neral plus geranial). After screening the fibre type, the effect of other HS-SPME variables such as adsorption temperature (25-55 degrees C), extraction time (10-40 min), sample concentration (1-100% w/w), sample amount (5-10 g) and salt amount (0-30% w/w) were determined using a two-level fractional factorial design (2(5-2)) that was expanded further to a central composite design. It was found that an extraction process using a carboxen-polydimethylsiloxane fibre coating at 15 masculineC for 50 min with 5 g of diluted emulsion 1% (w/w) and 30% (w/w) of sodium chloride under stirring mode resulted in the highest HS extraction efficiency. For all volatile flavour compounds, the linearity values were accurate in the concentration ranges studied (r(2) > 0.97). Average recoveries that ranged from 90.3 to 124.8% showed a good accuracy for the optimised method. The relative standard deviation for six replicates of all volatile flavour compounds was found to be less than 15%. For all volatile flavour compounds, the limit of detection ranged from 0.20 to 1.69 mg/L.

Influence of pectin and CMC on physical stability, turbidity loss rate, cloudiness and flavor release of orange beverage emulsion during storage

In the present work, the effect of type and concentration of two hydrocolloids namely pectin (1.5%, 3% and 4.5%) and CMC (0.1%, 0.3% and 0.5%) on physical stability, turbidity loss rate, cloudiness and flavor release of orange beverage emulsion was investigated during six months storage. From the turbidity loss rate results, the orange beverage emulsions containing 4.5% and 1.5% (w/w) pectin showed the highest and least storage stability, respectively. In contrast to the first two months storage, the replacement of both supplementary emulsion components resulted in a significant ( p < 0.05) increase in turbidity loss rate of all orange beverage emulsions, thus indicating a decrease in capability of beverage emulsion to maintain the cloudiness during storage. The cloudiness of all samples significantly ( p < 0.05) decreased during storage. The differences between the volatile release behaviors of target volatile compounds from orange beverage emulsions having different formulations indicated that the overall volatile flavor release was strongly influenced by the emulsion composition. This finding may be explained by the interactions between emulsion matrix and volatile flavor compounds. The release contents of most of target flavor compounds were significantly ( p < 0.05) decreased during storage, especially for the aldehyde compounds studied (i.e. octanal, decanal, neral, geranial).

Acquisition of a conditioned taste aversion becomes context dependent when it is learned after extinction

A conditioned taste aversion experiment tested context-switch effects on retrieval of conditioned stimulus (CS)-unconditioned stimulus (US) acquisition performance in rats. A context switch impaired performance when the target flavour was trained in a context where a different flavour underwent extinction. Conditioned taste aversion in the absence of previous extinction of the alternate flavour was not context dependent. It is suggested that the ambiguity in the meaning of the extinguished cue leads animals to pay attention to the context, so that the information learned in that context becomes context dependent.

Solid-phase microextraction for headspace analysis of key volatile compounds in orange beverage emulsion

Headspace solid-phase microextraction (HS-SPME) gas chromatography was used to analyze target flavor compounds in orange beverage emulsion. The effects of SPME fiber (PDMS 100 μm, CAR/PDMS 75 μm, PDMS/DVB 65 μm and DVB/CAR/PDMS 50/30 μm), adsorption temperature (25–45 °C), adsorption time (5–25 min), sample concentration (1–100%), sample amount (5–12.5 g), pH (2.5–9.5), salt type (K 2CO 3, Na 2CO 3, NaCl and Na 2SO 4), salt amounts (0–30%) and stirring mode were studied to develop HS-SPME condition for obtaining the highest extraction efficiency and aroma recovery. For the head space volatile extraction, the optimum conditions were: CAR/PDMS fiber, adsorption at 45 °C for 15 min, 5 g of diluted beverage emulsion (1:100), 15% (w/w) of NaCl with stirring and original pH 4. The main volatile flavor compounds were: limonene, 94.9%; myrcene, 1.2%; ethyl butyrate, 1.1%; γ-terpinene, 0.41%; linalool, 0.36%; 3-carene, 0.16%; decanal, 0.12%; ethyl acetate, 0.1%; 1-octanol, 0.06%; geranial, 0.05%; β-pinene, 0.04%; octanal, 0.03%; α-pinene, 0.03%; and neral, 0.03%. The linearity was very good in the considered concentration ranges ( R 2 ⩾ 0.97). Average recoveries ranged from 88.3% to 121.7% and showed good accuracy for the proposed analytical method. Average relative standard deviation (RSD) for five replicate analyses was found to be less than 14%. The limit of detection (LOD) ranged from 0.06 to 2.27 mg/l for all volatile flavor compounds and confirmed the feasibility of the HS-SPME technique for headspace analysis of orange beverage emulsion. The method was successfully applied for headspace analysis of five commercial orange beverage emulsions.