Ethanol perception and ingestion

Drinking of flavored solutions by high preferring (WHP) and low preferring (WLP) alcohol-drinking rats

BACKGROUND

Selective breeding alcohol-preferring (P) and alcohol-nonpreferring (NP) rats showed a strong preference for the sucrose solutions, whereas P rats intake greater amounts than NP rats. The aim of this study was the estimation of selectively bred ethanol-preferring (WHP - Warsaw High Preferring) and ethanol-nonpreferring (WLP - Warsaw Low Preferring) rats for their preference for various tastes.

METHODS

The oral drinking of the following substances was studied at a range of concentrations: sucrose (0.5-64.0 g/100 ml), NaCl (0.025-3.2 g/100 ml), citric acid (0.008-2.048 g/l), and sucrose octaacetate (0.002-0.512 g/l) solutions. Separate groups of 7-8 rats from each line were investigated of each of the four tastes. The investigated solutions were presented continuously keeping water and food always available. Concentrations of the various flavors were doubled every 48 h.

RESULTS

Rats from WHP and WLP lines clearly revealed the preference for the sucrose solution and the highest preference was at the 4.0 and 8.0 g/100ml sucrose concentration. Similar to sucrose, both lines exposed strong preference for the NaCl solution and this preference enhanced together with the increase of the NaCl concentration. Nevertheless their preference for the NaCl solutions decreased when the concentration of NaCl reached 1.600 g/100 ml. Both lines of rats did not differ in citric acid or sucrose octaacetate intake at any of the concentrations studied.

CONCLUSION

Selective breeding of rats (WHP) for high and rats (WLP) for low ethanol drinking is favorably correlated with the drinking of sweet and salty solutions and negatively correlated with the consumption of sour and bitter tastes.

Psychophysical assessments of sourness in citric acid-ethanol mixtures

The effect of ethanol in modulating the intensity and duration of the perceived sourness induced by citric acid was studied. Magnitude Estimation-Converging Limits method was applied to rate the sourness of seven solutions (3-70 mM) of citric acid in aqueous solution presented alone and mixed with 8% V/V or 15% V/V ethanol. Dynamic sourness ratings of 5, 15, and 45 mM citric acid alone and mixed with the same two ethanol levels were assessed by the Time Intensity Method (TI). Results were consistent with both methods. Sourness changed with citric acid concentration and ethanol levels. From TI measurements, a similar interactive pattern was obtained for parameters as duration, area under the curve, peak and average intensity.

Strategies to increase the stability of intermediate moisture foods towards Zygosaccharomyces rouxii: the effect of temperature, ethanol, pH and water activity, with or without the influence of organic acids

Intermediate moisture foods (IMF) are in general microbiologically stable products. However, due to health concerns consumer demands are increasingly forcing producers to lower the fat, sugar and preservatives content, which impede the stability of the IMF products. One of the strategies to counteract these problems is the storage of IMF products at lower temperatures. Thorough knowledge on growth/no growth boundaries of Zygosaccharomyces rouxii in IMF products, also at different storage temperatures is an important tool for ensuring microbiologically stability. In this study, growth/no growth models for Z. rouxii, developed by Vermeulen et al. (2012) were further extended by incorporating the factor temperature. Three different data sets were build: (i) without organic acids, (ii) with acetic acid (10,000 ppm on product basis) and (iii) with sorbic acid (1500 ppm on product basis). For each of these data sets three different growth/no growth models were developed after 30, 60 and 90 days. The results show that the influence of temperature is only significant in the lower temperature range (8-15 °C). Also, the effect of pH is negligible (pH 5.0-6.2) unless organic acids are present. More specific, acetic acid had only an additive effect to ethanol and aw at low pH, whereas sorbic acid had also an additive effect at the higher pH values. For incubation periods longer than 30 days the growth/no growth boundary remained stable but enlarged gradually between day 60 and 90, except for the lower temperature range (<12 °C) where the boundary shifts to more stringent environmental conditions.

Single bright light exposure decreases sweet taste threshold in healthy volunteers

INTRODUCTION

Bright light exposure can alter circulating serotonin levels, and alteration of available serotonin by acute selective serotonin reuptake inhibition significantly lowers sweet but not salt taste recognition thresholds. We tested the hypothesis that bright light exposure would increase sweet but not salt taste sensitivity in healthy adults.

METHODS

Fourteen healthy volunteers were exposed to bright (10,000 lux) and dim (<20 lux) light for 30 min each, in counterbalanced order. Measures of taste perception (salt and sweet) and mood were determined at baseline, and before and after each light exposure period.

RESULTS

Recognition thresholds for sucrose were significantly lower after bright but not dim light exposure. Thresholds for salt were unaffected by either condition. There were no significant changes in taste acuity, intensity or pleasantness for both the taste modalities and on visual analogue scales (VASs) for mood, anxiety, sleepiness and alertness, under either light condition.

CONCLUSION

Brief bright light exposure reduces sweet but not salt taste recognition thresholds in healthy humans.

Specific phenolic compounds and sensory properties of a new dealcoholized red wine with pomegranate (Punica granatum L.) extract

The pomegranate ( Punica granatum L.) fruit has a long history of human consumption and possesses notable antioxidant and cardiovascular properties. This work evaluated the feasibility to provide a new functional beverage based on a dealcoholized red wine matrix supplemented by a pomegranate extract. The potential bioactive compounds in the pomegranate extract, punicalagin A and B and ellagic acid, were analyzed during the downstream process in order to evaluate the functional dose in the final beverage. The addition of pomegranate extract to the dealcoholized red wine resulted in a product with more intense yeast odor, acidity, yeast flavor, and astringency and with a less intense berry flavor. Consumer acceptance of the product was also investigated and the results revealed the existence of a niche of consumers willing to consume dealcoholized wine enriched with pomegranate extract. After tasting, 50% and 40% of those consumers initially interested by this product concept declared to be interested to purchase the control sample and the functional beverage, respectively. The daily consumption of two servings of 250 mL of this new pomegranate-enriched dealcoholized wine provides 82 mg of total ellagitannins, corresponding to the sum of punicalagin A and B and ellagic acid.

Genetic analysis of chemosensory traits in human twins

We explored genetic influences on the perception of taste and smell stimuli. Adult twins rated the chemosensory aspects of water, sucrose, sodium chloride, citric acid, ethanol, quinine hydrochloride, phenylthiocarbamide (PTC), potassium chloride, calcium chloride, cinnamon, androstenone, Galaxolide™, cilantro, and basil. For most traits, individual differences were stable over time and some traits were heritable (h(2) from 0.41 to 0.71). Subjects were genotyped for 44 single nucleotide polymorphisms within and near genes related to taste and smell. The results of these association analyses confirmed previous genotype-phenotype results for PTC, quinine, and androstenone. New associations were detected for ratings of basil and a bitter taste receptor gene, TAS2R60, and between cilantro and variants in three genes (TRPA1, GNAT3, and TAS2R50). The flavor of ethanol was related to variation within an olfactory receptor gene (OR7D4) and a gene encoding a subunit of the epithelial sodium channel (SCNN1D). Our study demonstrates that person-to-person differences in the taste and smell perception of simple foods and drinks are partially accounted for by genetic variation within chemosensory pathways.

Monitoring gaseous CO2 and ethanol above champagne glasses: flute versus coupe, and the role of temperature

In champagne tasting, gaseous CO₂ and volatile organic compounds progressively invade the headspace above glasses, thus progressively modifying the chemical space perceived by the consumer. Simultaneous quantification of gaseous CO₂ and ethanol was monitored through micro-gas chromatography (μGC), all along the first 15 minutes following pouring, depending on whether a volume of 100 mL of champagne was served into a flute or into a coupe. The concentration of gaseous CO₂ was found to be significantly higher above the flute than above the coupe. Moreover, a recently developed gaseous CO₂ visualization technique based on infrared imaging was performed, thus confirming this tendency. The influence of champagne temperature was also tested. As could have been expected, lowering the temperature of champagne was found to decrease ethanol vapor concentrations in the headspace of a glass. Nevertheless, and quite surprisingly, this temperature decrease had no impact on the level of gaseous CO₂ found above the glass. Those results were discussed on the basis of a multiparameter model which describes fluxes of gaseous CO₂ escaping the liquid phase into the form of bubbles.

Carbon dioxide and ethanol release from champagne glasses, under standard tasting conditions

A simple glass of champagne or sparkling wine may seem like the acme of frivolity to most people, but in fact, it may rather be considered as a fantastic playground for any fluid physicist or physicochemist. In this chapter, results obtained concerning various steps where the CO₂ molecule plays a role (from its ingestion in the liquid phase during the fermentation process to its progressive release in the headspace above the tasting glass) are gathered and synthesized to propose a self-consistent and global overview of how gaseous and dissolved CO₂ impact champagne and sparkling wine science. Some recent investigations, conducted through laser tomography techniques, on ascending bubbles and ascending-bubble-driven flow patterns found in champagne glasses are reported, which illustrate the fine interplay between ascending bubbles and the fluid around under standard tasting conditions. The simultaneous monitoring of gaseous CO₂ and ethanol in the headspace of both a flute and a coupe filled with champagne was reported, depending on whether or not the glass shows effervescence. Both gaseous CO₂ and ethanol were found to be enhanced by the presence of ascending bubbles, thus confirming the close link between ascending bubbles, ascending-bubble-driven flow patterns, and the release of gaseous CO₂ and volatile organic compounds.

Simultaneous monitoring of gaseous CO(2) and ethanol above champagne glasses via micro-gas chromatography (μGC)

In champagne tasting, gaseous CO(2) and volatile organic compounds progressively invade the headspace above glasses, thus progressively modifying the chemical space perceived by the consumer. In this study, a novel, rapid, and nonintrusive method aimed to simultaneously determine the content in gaseous CO(2) and ethanol above a glass poured with champagne, using a micro-gas chromatography technique coupled with a thermal conductivity detector, was presented. The simultaneous quantification of CO(2) and ethanol in the headspace of a champagne glass was monitored, in real tasting conditions, all along the first 15 min following pouring, depending on whether or not the glass shows effervescence. Both CO(2) and ethanol were found to be enhanced by the presence of ascending bubbles, thus confirming the close link between rising bubbles and the release of gaseous CO(2) and volatile organic compounds.

Impact of swallowing on the dynamics of aroma release and perception during the consumption of alcoholic beverages

The consumption protocol used during alcoholic beverage tasting may affect aroma perception. We used an integrated approach combining sensory analysis and physicochemistry to investigate the impact of swallowing on aroma release and perception. A panel of 10 persons evaluated the dynamics of aroma perception during the consumption of a commercial flavored vodka, using the method of temporal dominance of sensations. Two protocols (spitting out or swallowing of the product) were tested. Nosespace analysis was simultaneously carried out by proton transfer reaction mass spectrometry to evaluate aroma release in the nasal cavity. Comparison of the results obtained with the 2 protocols highlighted significant differences in both the perception and the release of aroma: the swallowing of the product resulted in more complex perceptions but decreased the dominance rates of aromatic attributes. Ethanol perception also had an impact when the product was swallowed. Aroma release data partly accounted for the differences in perception, particularly as concerned ethanol release. The time at which dominance appears as well as the dominance duration of some attributes can be related to some temporal parameters of release data. But the lack of knowledge concerning the variety and complexity of mechanisms continues to limit our understanding of relationship between aroma release and perception.

The effect of taste familiarity on intake and taste reactivity in infant rats

With infant rats, unlike with adults, increased intake of a taste after mere exposure to this stimulus is not consistently found; this has sometimes been interpreted as a failure by the immature subject to recognize tastes as familiar. We studied the effect of preexposure to a tastant, measuring taste reactivity and intake in 14-day-old rats. Familiarity increased hedonic response to sucrose, but also increased aversive response to quinine and ethanol. With the sucrose-quinine compound, familiarity increased both the hedonic and the aversive reaction to the stimulus. In no case was a differential reactivity to water observed. Significant increased intake after familiarization was only found with quinine or the sucrose-quinine compound. Results indicate that in infant rats, and with the present parameters, taste familiarity enhances responsiveness to these stimuli, an effect not always accompanied by detectable changes in intake.

Fetal ethanol exposure increases ethanol intake by making it smell and taste better

Human epidemiologic studies reveal that fetal ethanol exposure is highly predictive of adolescent ethanol avidity and abuse. Little is known about how fetal exposure produces these effects. It is hypothesized that fetal ethanol exposure results in stimulus-induced chemosensory plasticity. Here, we asked whether gestational ethanol exposure increases postnatal ethanol avidity in rats by altering its taste and odor. Experimental rats were exposed to ethanol in utero via the dam's diet, whereas control rats were either pair-fed an iso-caloric diet or given food ad libitum. We found that fetal ethanol exposure increased the taste-mediated acceptability of both ethanol and quinine hydrochloride (bitter), but not sucrose (sweet). Importantly, a significant proportion of the increased ethanol acceptability could be attributed directly to the attenuated aversion to ethanol's quinine-like taste quality. Fetal ethanol exposure also enhanced ethanol intake and the behavioral response to ethanol odor. Notably, the elevated intake of ethanol was also causally linked to the enhanced odor response. Our results demonstrate that fetal exposure specifically increases ethanol avidity by, in part, making it taste and smell better. More generally, they establish an epigenetic chemosensory mechanism by which maternal patterns of drug use can be transferred to offspring. Given that many licit (e.g., tobacco products) and illicit (e.g., marijuana) drugs have noteworthy chemosensory components, our findings have broad implications for the relationship between maternal patterns of drug use, child development, and postnatal vulnerability.

Assessment of Upper Respiratory Tract and Ocular Irritative Effects of Volatile Chemicals in Humans

Accurate assessment of upper respiratory tract and ocular irritation is critical for identifying and remedying problems related to overexposure to volatile chemicals, as well as for establishing parameters of irritation useful for regulatory purposes. This article (a) describes the basic anatomy and physiology of the human upper respiratory tract and ocular mucosae, (b) discusses how airborne chemicals induce irritative sensations, and (c) reviews practical means employed for assessing such phenomena, including psychophysical (e.g., threshold and suprathreshold perceptual measures), physiological (e.g., cardiovascular responses), electrophysiological (e.g., event-related potentials), and imaging (e.g., magnetic resonance imaging) techniques. Although traditionally animal models have been used as the first step in assessing such irritation, they are not addressed here since (a) there are numerous reviews available on this topic and (b) many rodents and rabbits are obligate nose breathers whose nasal passages differ considerably from those of humans, potentially limiting generalization of animal-based data to humans. A major goal of this compendium is to inform the reader of procedures for assessing irritation in humans and to provide information of value in the continued interpretation and development of empirical databases upon which future reasoned regulatory health decisions can be made.

Reduced oral ethanol avoidance in mice lacking transient receptor potential channel vanilloid receptor 1

Ethanol is a known oral trigeminal stimulant and recent data indicate that these effects are mediated in part by transient receptor potential channel vanilloid receptor 1 (TRPV1). The importance of this receptor in orally mediated ethanol avoidance is presently unknown. Here, we compared orosensory responding to ethanol in TRPV1-deficient and wild type mice in a brief-access paradigm that assesses orosensory influences by measuring immediate licking responses to small stimulus volumes. TRPV1(-/-) and control mice were tested with six concentrations of ethanol (3, 5, 10, 15, 25, 40%), capsaicin (0.003, 0.01, 0.03, 0.1, 0.3, 1 mM), sucrose (0.003, 0.01, 0.03, 0.1, 0.3, 1 M), and quinine (0.01, 0.03, 0.1, 0.3, 1, 3 mM) and psychophysical concentration-response functions were generated for each genotype and stimulus. TRPV1 knockouts displayed reduced oral avoidance responses to ethanol regardless of concentration, insensitivity to capsaicin, and little to no difference in sweet or bitter taste responding relative to wild type mice. These data indicate that the TRPV1 channel plays a role in orosensory-mediated ethanol avoidance, but that other receptor mechanisms likely also contribute to aversive oral responses to alcohol.

Perception of sweet taste is important for voluntary alcohol consumption in mice

To directly evaluate the association between taste perception and alcohol intake, we used three different mutant mice, each lacking a gene expressed in taste buds and critical to taste transduction: alpha-gustducin (Gnat3), Tas1r3 or Trpm5. Null mutant mice lacking any of these three genes showed lower preference score for alcohol and consumed less alcohol in a two-bottle choice test, as compared with wild-type littermates. These null mice also showed lower preference score for saccharin solutions than did wild-type littermates. In contrast, avoidance of quinine solutions was less in Gnat3 or Trpm5 knockout mice than in wild-type mice, whereas Tas1r3 null mice were not different from wild type in their response to quinine solutions. There were no differences in null vs. wild-type mice in their consumption of sodium chloride solutions. To determine the cause for reduction of ethanol intake, we studied other ethanol-induced behaviors known to be related to alcohol consumption. There were no differences between null and wild-type mice in ethanol-induced loss of righting reflex, severity of acute ethanol withdrawal or conditioned place preference for ethanol. Weaker conditioned taste aversion (CTA) to alcohol in null mice may have been caused by weaker rewarding value of the conditioned stimulus (saccharin). When saccharin was replaced by sodium chloride, no differences in CTA to alcohol between knockout and wild-type mice were seen. Thus, deletion of any one of three different genes involved in detection of sweet taste leads to a substantial reduction of alcohol intake without any changes in pharmacological actions of ethanol.

Behavioral genetics and taste

This review focuses on behavioral genetic studies of sweet, umami, bitter and salt taste responses in mammals. Studies involving mouse inbred strain comparisons and genetic analyses, and their impact on elucidation of taste receptors and transduction mechanisms are discussed. Finally, the effect of genetic variation in taste responsiveness on complex traits such as drug intake is considered. Recent advances in development of genomic resources make behavioral genetics a powerful approach for understanding mechanisms of taste.

The relationship between PROP and ethanol preferences: an evaluation of 4 inbred mouse strains

Ethanol's taste attributes undoubtedly contribute to the development of drug preference. Ethanol's taste is both sweet and bitter. Taster status for bitter 6-n-propylthiouracil (PROP) has been proposed as a genetic marker for alcoholism; however, human results are conflicting. We collected preference scores for both tastants in 4 mouse strains selected on the basis of previously reported taste preference, with the generally accepted idea that inbred mice show minimal within-strain variation. Eighty-eight male mice (22 per strain) participated. The strains were as follows: C57BL/6J, ethanol preferring; BALB/cJ, ethanol avoiding; SWR/J, PROP avoiding; and C3HeB/FeJ, PROP neutral. Using a brief-access (1-min trials) 2-bottle preference test, we assessed the taste response of each strain to PROP and ethanol on separate days. Although PROP avoiding versus neutral mice could be segregated into significantly different populations, this was not the case for ethanol avoiding versus preferring mice, and all strains showed high variability. On average, only BALB/cJ, SWR/J, and C3HeB/FeJ mice conformed to their literature-reported preferences; nonetheless, there were a substantial number of discordant animals. C57BL/6J did not conform to previous results, indicating that they are ethanol preferring. Finally, we did not observe a significant relationship between PROP and ethanol preferences across strains. The high variability per strain and the number of animals in disagreement with their respective literature-reported preference raise concerns regarding their utility for investigations underlying mechanisms of taste-mediated ingestive responses. Absent postingestive consequences, the brief-access results suggest a possible degree of previously masked polymorphisms in taste preferences or a more recent drift in underlying genetic factors. The absence of a relationship between PROP and ethanol indicates that the bitter quality in ethanol may be more highly related to other bitter compounds that are mediated by different genetic influences.

Multiple routes of chemosensitivity to free fatty acids in humans

Selected free fatty acids (FFAs) are documented effective somatosensory and olfactory stimuli whereas gustatory effects are less well established. This study examined orthonasal olfactory, retronasal olfactory, nasal irritancy, oral irritancy, gustatory, and multimodal threshold sensitivity to linoleic, oleic, and stearic acids. Sensitivity to oxidized linoleic acid was also determined. Detection thresholds were obtained using a three-alternative, forced-choice, ascending concentration presentation procedure. Participants included 22 healthy, physically fit adults sensitive to 6-n-propylthiouracil. Measurable thresholds were obtained for all FFAs tested and in 96% of the trials. Ceiling effects were observed in the remaining trials. Greater sensitivity was observed for multimodal stimulation and lower sensitivity for retronasal stimulation. There were no statistically significant correlations for linoleic acid thresholds between different modalities, suggesting that each route of stimulation contributes independently to fat perception. In summary, 18-carbon FFAs of varying saturation are detected by multiple sensory systems in humans.

The Psychophysical Relationship between Bitter Taste and Burning Sensation: Evidence of Qualitative Similarity

Although it has long been studied as a pure sensory irritant, the ability of capsaicin to evoke, mask, and desensitize bitter taste suggests that burning sensations and bitter taste might be closely related perceptually. The current study investigated the psychophysical relationship between bitterness and burning using 2 different approaches. In Experiment 1, spatial discrimination of 4 taste stimuli was measured in the presence or absence of capsaicin. The subjects' task was to report which of 3 swabs, spaced 1 cm apart and presented to the tongue tip, contained a taste stimulus when 1) water was presented on the other 2 swabs or 2) when 10 muM capsaicin was presented on all 3 swabs. The presence of capsaicin did not change performance on the 3 alternative forced-choice (3-AFC) task for sweet, sour, and salty stimuli, while the localization error for 1.8 mM quinine sulfate (QSO(4)) increased significantly. In Experiment 2, the perceptual similarity/dissimilarity of taste stimuli and capsaicin was measured directly using pairs of stimuli applied to opposite sides of the tongue tip on swabs separated by 2 cm. Multidimensional scaling analyses showed that capsaicin fell nearer to QSO(4) than to any other taste stimulus. Cluster analysis corroborated this finding: capsaicin was closely linked with QSO(4) and the capsaicin-QSO(4) group was separated from the other taste stimuli. The latter result indicated that bitterness was more similar to burning than to the other tastes. These findings imply that despite being mediated by different sensory modalities, bitterness and burn are qualitatively similar. We speculate that this similarity reflects a common function of these 2 sensations as sensory signals of potentially harmful stimuli.

Bitter receptor gene (TAS2R38), 6-n-propylthiouracil (PROP) bitterness and alcohol intake

BACKGROUND

Phenylthiocarbamide (PTC) and 6-n-propylthiouracil (PROP), chemically related compounds, are probes for genetic variation in bitter taste, although PROP is safer with less sulfurous odor. Threshold for PROP distinguishes nontasters (increased threshold) from tasters (lower threshold); perceived intensity subdivides tasters into medium tasters (PROP is bitter) and supertasters (PROP is very bitter). Compared with supertasters, nontasters have fewer taste papillae on the anterior tongue (fungiform papillae) and experience less negative (e.g., bitterness) and more positive (eg, sweetness) sensations from alcohol. We determined whether the TAS2R38 gene at 7q36 predicted PROP bitterness, alcohol sensation and use.

METHODS

Healthy adults (53 women, 31 men; mean age 36 years)--primarily light and moderate drinkers--reported the bitterness of five PROP concentrations (0.032-3.2 mM) and intensity of 50% ethanol on the general Labeled Magnitude Scale. PROP threshold and density of fungiform papillae were also measured. Subjects had common TAS2R38 gene haplotypes [alanine-valine-isoleucine (AVI) and proline-alanine-valine (PAV)].

RESULTS

PROP bitterness varied significantly across genotypes with repeated measures ANOVA: 26 AVI/AVI homozygotes tasted less bitterness than either 37 PAV/AVI heterozygotes or 21 PAV/PAV homozygotes. The PAV/PAV group exceeded the PAV/AVI group for bitterness only for the top PROP concentrations. The elevated bitterness was musch less than if we defined the groups using psychophysical criteria. With multiple regression analyses, greater bitterness from 3.2 mM PROP was a significant predictor of greater ethanol intensity and less alcohol intake--effects separate from age and sex. Genotype was a significant predictor of alcohol intake, but not ethanol intensity. With ANOVA, AVI/AVI homozygotes reported higher alcohol use than either PAV/AVI heterozygotes or PAV/PAV homozygotes. When age effects were minimized, PROP bitterness explained more variance in alcohol intake than did the TAS2R38 genotype.

CONCLUSIONS

These results support taste genetic effects on alcohol intake. PROP bitterness serves as a marker of these effects.

Chemosensory factors influencing alcohol perception, preferences, and consumption

This article presents the proceedings of a symposium at the 2002 RSA/ISBRA Meeting in San Francisco, California, co-organized by Julie A. Mennella and Alexander A. Bachmanov of the Monell Chemical Senses Center. The goal of this symposium was to review the role that chemosensory factors (taste, smell, and chemical irritation) play in the perception, preference, and consumption of alcohol. The presented research focused on both humans and laboratory animals and used a variety of approaches including genetic, developmental, pharmacological, behavioral, and psychophysical studies. The presentations were as follows: (1) Introduction and overview of the chemical senses (Julie A. Mennella and Alexander A. Bachmanov); (2) Taste reactivity as a measure of alcohol palatability and its relation to alcohol consumption in rats (Stephen W. Kiefer); (3) Early learning about the sensory properties of alcohol in laboratory animals (Juan Carlos Molina); (4) Early learning about the sensory properties of alcohol in humans (Julie A. Mennella); (5) Genetic dissection of the ethanol-sweet taste relationship in mice (Alexander A. Bachmanov and Michael Tordoff); and (6) Human genetic variation in taste: connections with alcohol sensation and intake (Valerie B. Duffy and Linda M. Bartoshuk). The symposium concluded with a general discussion.

Effects of conditioned food aversions on nutritional behavior in humans

Conditioned food aversion (CFA) and taste aversion (CTA) are widely occurring phenomena mediating rejection of solids or liquids, the ingestion of which has induced the onset of post-ingestional malaise. It is a powerful and durable imprint learning that may influence food choice and intake in all animals, including humans. For ethical reasons, CTA has been extensively investigated in a wide variety of laboratory animal's species but only incidentally in humans. Nevertheless, convincing evidence has been provided that CFA and CTA learning are possible in a wide range of human subjects. The results in humans may have some limitations in accuracy since data are sparse, sometimes indirect, and poorly controlled. There is only limited information on the extent of CFA in the elderly since most studies have employed questionnaire and/or interview methods on young people (i.e. college students). The present review evaluates the literature derived both from laboratory animals and humans. In the first instance, the salient features of food and taste aversion learning and the neural mechanisms involved in this learning behavior will be examined. Then, the problems encountered when trying to assess the role of learned food and taste aversions in the nutritional status of healthy as well as sick young or elderly people will be considered. In particular, the importance of CFA on the nutritional status of cancer patients and treatment of alcoholism will be examined. It is concluded that the data are compelling enough to warrant further research and, some indications and recommendations are suggested.

Failure to reduce short-term appetite following alcohol is independent of beliefs about the presence of alcohol

Previously, it has been reported that energy consumed as alcohol prior to lunch does not result in subsequent reductions in voluntary food intake, and in some situations alcohol can increase subsequent appetite. The present study extends these findings by examining the effects of beliefs about alcohol content. Eighteen unrestrained men ate lunch 20 min after a preload of either water, an alcoholic beer or a non-alcoholic beer matched for energy content. Food intake was significantly less following the non-alcoholic beer than after alcohol or water, but when preload energy was included subjects had a higher overall energy intake on the day they consumed alcohol compared with both water and no-alcohol conditions. There were no significant differences in hunger or fullness ratings following the three drinks before or after the test meal, but the specific relationship between rated hunger and intake within the test meal was altered by the drink manipulation. The rate at which hunger decreased, and fullness increased, was slower after alcohol than after water or no-alcohol. The drinks did not alter the pleasantness of the test meal or increase hunger at the start of eating. When contrasted with previous work, these data confirm that alcohol consumed before lunch fails to reduce subsequent food intake, but also suggests that changes in rated appetite are influenced by beliefs about alcohol content.