Selective effects of naltrexone on food pleasantness and intake

The effects of 50 mg naltrexone on both pleasantness and intake of 10 common food items were investigated using a double-blind placebo-controlled study with 16 male volunteers. Rated food pleasantness was reduced significantly in the naltrexone condition compared with both controls (placebo and baseline). However, pleasantness ratings were not affected uniformly across foods, with sweetened, fatty, and high-protein foods being most affected. Changes in rated unpleasantness generally mirrored those for pleasantness, but evaluations of saltiness and sweetness were unaffected by naltrexone. Although total intake was reduced in the naltrexone condition, this was not significant compared with placebo. However, fat and protein intakes were significantly less following naltrexone. The effect of naltrexone on intake was also food dependent, but in this case intake of sweet foods was spared relative to other food categories. The apparent discrepancy between liking and intake data with sweet foods could be interpreted in terms of the likely influence of normal eating styles on food selection during a buffet-style meal, and may explain some contradictions in previous studies of this kind. The implications for understanding opioid involvement in food acceptability are discussed.     

Sensory-specific satiety: comparison of taste and texture effects

The respective contributions of taste (saltiness and sweetness) and texture (the hardness dimension) to sensory-specific satiety (SSS) were compared. Sixteen male and 16 female, young, normal-weight adults rated the pleasantness of taste, pleasantness of texture and desire to eat on visual analog scales for eight test foods, were then given one of the foods to eat ad libitum for lunch, and re-rated the same parameters for the eight foods 2 and 20 min after the end of the meal. The experimental sets of eight test foods and four lunch foods were balanced for taste quality (salty vs. sweet) and texture quality (hard vs. soft). Lunch foods were the hard and soft versions of a salty food (ham and cheese sandwich on baguette vs. white bread) or of a sweet food (apples vs. applesauce). Sensory-specific satiety was observed for both saltiness and sweetness (e.g. pleasantness of the taste of, and desire to eat sweet test foods decreased significantly after eating a sweet lunch food and similarly for salty foods), and to a lesser extent for texture (e.g. pleasantness of the texture of, and desire to eat hard test foods decreased after eating a hard lunch food and similarly for one of the soft foods). The authors conclude texture-specific satiety may be a significant component of satiety.     

Is pleasantness of biscuits and cakes related to their actual or to their perceived sugar and fat contents?

Perceptions of sugar, fat and moisture contents, as well as their influences on pleasantness were investigated in commercial foods. One-hundred-and-two-normal-weight men rated the "pleasantness", "flavour intensity", "moisture", "sweetness" and "fatness" of 39 different biscuits and cakes. Sugar content was accurately perceived up to a maximum content of about 33% weight/weight. The perception of fat content was less accurate and depended on both fat and sugar contents. High sugar contents seemed to decrease perception of fatness. Pleasantness was influenced mainly by sugar content and less by fat content. Pleasantness was better predicted by rated contents than by actual contents; it was even better predicted by the overall flavour intensity. Preferences for high fat stimuli did not appear to be based on conscious perception of their fat content. We conclude that the classical results obtained with simple experimental stimuli remain valid, as a first approximation, for commercial biscuits and cakes, despite their complex sensory characteristics.     

Hedonic and sensory characteristics of odors conditioned by pairing with tastants in humans.

Animals readily acquire positive odor-taste hedonic associations, but evidence for this in humans remains weak and was explored further. Retronasal pairing of odors with sucrose or salty stimuli (Experiment 1) increased the rated sweetness of sucrose-paired odors without altering liking, although changes in odor pleasantness correlated with sucrose liking. Experience of odors with sucrose or quinine by sweet likers (Experiment 2) found increased pleasantness and sweetness for sucrose-paired odors, whereas quinine-paired odors became less liked and more bitter. Odor-sucrose pairings in sweet likers and dislikers (Experiment 3) found increased sweetness in both groups but increased odor liking only in likers. These data suggest that evaluative and sensory learning are dissociable and that evaluative changes are sensitive to individual differences in sweet liking. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Carotenoid pigments in seafoods and aquaculture

Color plays a major role in the overall acceptability of food products. It is considered one of man's basic experiences that a particular foodstuff has to be of a distinct color in order to be edible. The color of a seafood is the first characteristic noted by the consumer and is directly related to the subsequent acceptance or rejection of it. Carotenoids contribute to the yellow, orange, and red colors of the skin, shell, or exoskeleton of aquatic animals. Indeed, they are the most widespread pigments found in nature, as they occur in bacteria, yeasts, mold, all green plants, and many animals, and therefore various functions have been attributed to them. From anthropocentric consideration, the most significant aspect of carotenoids is the color they impart to our food and environment. In animals, the carotenoids are also associated with reproductive organs and hence the hatching success and survival of alevins.     

Volatile flavor release from foods during eating

Classical analyses for volatile flavors (headspace or distillation/extract methods) give information on either the volatiles present in the air above a food before eating or the total volatile composition of the food. When foods are eaten, however, many changes take place (such as hydration/dilution with saliva, increase in surface area, etc.) that affect the release of volatiles from the food and therefore the profile of volatiles that are sensed in the nose. If we wish to study the relationship between flavor volatiles and the sensory properties of a food, it seems logical to measure the volatile profile that exists during eating. Although volatile flavor release during eating has been measured using a variety of sensory and psychophysiological analyses, only recently have instrumental methods been developed to measure the release of volatile compounds in humans as they eat. Whereas the sensory data give an overall measure of flavor perception, instrumental analyses can potentially follow the release of each and every flavor volatile and thus give a full picture of the aroma profiles generated during eating. From these instrumental measurements, a number of key factors have been identified. First, it has been shown that the volatile profile measured during eating is indeed different from the headspace profile of whole foods. Second, it is clear that the volatile profile in-mouth changes with time as the state of the food changes with chewing. Third, the volatile release from low-water foods is affected by the rate and extent of hydration in-mouth. The ability to measure aroma before, during, and after eating may lead to an understanding of the links between aroma release, interaction of volatiles with aroma sensors in the nose, and the overall perception of food flavor.     

Sweet tooth demonstrated: Individual differences in preference for both sweet foods and foods highly sweetened.

A total of 9 women and 9 men, aged 19–40 years, rated the sweetness of samples of chocolate, lime drink, and tomato soup relative to their personally ideal levels of sweetness for each food, with the conditions of each test session designed to eliminate various sources of bias. The method yielded precise estimates of the individual's most preferred concentration of sugar and of his or her tolerance of deviations from ideal. This linear precision allowed assessment of the degree to which the ideal food sugar level was a personal characteristic. We found that individuals differed significantly in peak-preferred levels of sugar, both generally across foods and with some variation relatively among foods. Also, the peak sweetness preferences for the three foods correlated significantly with several rated choices of sweet foods over nonsweet foods. This is evidence for the full construct of a sweet tooth—both a strong liking for sweet foods and a liking for strongly sweetened foods. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of sensory perception of foods on appetite and food intake: a review of studies on humans

OBJECTIVE: How much do the sensory properties of food influence the way people select their food and how much they eat? The objective of this paper is to review results from studies investigating the link between the sensory perception of food and human appetite regulation. CONTENT OF THE REVIEW: The influence of palatability on appetite and food intake in humans has been investigated in several studies. All reviewed studies have shown increased intake as palatability increased, whereas assessments of the effect of palatability using measures of subjective appetite sensations have shown diverging results, for example, subjects either feel more hungry and less full after a palatable meal compared to a less palatable meal, or they feel the opposite, or there is no difference. Whether palatability has an effect on appetite in the period following consumption of a test meal is unclear. Several studies have investigated which sensory properties of food are involved in sensory-specific satiety. Taste, smell, texture and appearance-specific satieties have been identified, whereas studies on the role of macronutrients and the energy content of the food in sensory-specific satiety have given equivocal results. Different studies have shown that macronutrients and energy content play a role in sensory-specific satiety or that macronutrients and energy content are not a factor in sensory-specific satiety. Sensory-specific satiety may have an important influence on the amount of food eaten. Studies have shown that increasing the food variety can increase food and energy intake and in the short to medium term alter energy balance. Further knowledge about the importance of flavour in appetite regulation is needed, for example, which flavour combinations improve satiety most, the possible connection between flavour intensity and satiety, the effect of persistence of chemesthetic sensation on palatability and satiety, and to what extent genetic variation in taste sensitivity and perception influences dietary habits and weight control.     

Glutamate and the UMAMI taste: sensory, metabolic, nutritional and behavioural considerations. A review of the literature published in the last 10 years

Monosodium glutamate (MSG) is used increasingly often in processed foods and in home cooking in the Western world. This substance is responsible for a pleasurable taste sensation, the Umami taste. This review covers recent developments in sensory studies of glutamate effects, and traces the Umami taste from sensory receptors on the tongue to the brain. The metabolism of glutamic acid, as revealed from recent literature, is described. A specific section is devoted to safety issues. In addition, effects of glutamic salts on nutrition and ingestive behaviours are shown to be potent. Animal and human works are treated separately, with special attention to the specific methods used in both cases. Future areas of research include further investigation of sensory physiology, role of glutamate as an excitatory substance in the brain, acquisition of food likes and impact on long-term food selection, food intake, and body weight control.     

Separate signals for orthonasal vs. retronasal perception of food but not nonfood odors.

There is a controversy concerning whether smelling via the nose (ortho-nasally) or the mouth (retro-nasally) represent two routes to the same modality or two distinct submodalities. Since olfactory coding is dependent upon experience, and since food odors are experienced retro-nasally, the authors tested the hypothesis that whether an odor represents a food may influence whether sensation via the two routes leads to separable responses. The authors demonstrate that salivary response to food odors decrease with repeated presentation and show that this response rebounds upon presentation of a novel food odor via the same route and upon presentation of the same food odor via a novel route. This finding indicates that the novel odor and the novel route represent distinct sensory signals. This effect is specific, in that it does not depend on differences in odor intensity or pleasantness and is selective, in that it occurs for food odors but not for equally pleasant and intense nonfood odors. These results demonstrate that separable signals are generated for the same food odor depending upon route and support the existence of category-specific processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Emotional perception and memory in amnesia.

The authors examined whether perception of emotional stimuli is normal in amnesia and whether emotional arousal has the same enhancing effect on memory in amnesic patients as it has in healthy controls. Forty standardized color pictures were presented while participants rated each picture according to emotional intensity (arousal) and pleasantness (valence). An immediate free-recall test was given for the pictures, followed by a yes-no recognition test. Arousal and valence ratings were highly similar among the amnesic patients and controls. Emotional arousal (regardless of valence) enhanced both recall and recognition of the pictures, and this enhancement was proportional for amnesic patients and controls. Results suggest that emotional perception and the enhancing effect of emotional arousal on memory are intact in amnesia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

In vivo characteristics and localisation of carotenoid pigments in psychrotrophic and mesophilic Micrococcus roseus using photoacoustic spectroscopy

The mesolimbic dopaminergic system (MDS) has been shown to be implicated in feeding behaviors. The present experiment was conducted to examine the effects of the sensory properties of food ingested on MDS activity. Microdialysis coupled to high-performance liquid chromatography with electrochemical detection was employed to measure the extracellular levels of dopamine (DA) and its main metabolites (DOPAC and HVA) in the nucleus accumbens of freely moving rats. During microdialysis sessions rats had access or not to powdered foods varying in palatability: short cakes as highly palatable (HP) food and regular chow as low palatable (LP) food. In the absence of food, there were no alterations in extracellular levels of DA, DOPAC, and HVA. During feeding, DA rose significantly with a greater rise for the HP than the LP food. Levels of DOPAC and HVA only reached significance with the HP food. The results indicate that the MDS is activated on ingestion of food, and suggest that MDS activity is related to the rewarding properties of foods.     

Acquisition of categorical color perception: A perceptual learning approach to the linguistic relativity hypothesis.

Color perception can be categorical: Between-category discriminations are more accurate than equivalent within-category discrimination. The effects could be inherited, learned, or both. The authors provide evidence that supports the possibility of learned categorical perception (CP). Experiment 1 demonstrated that observers' color discrimination is flexible and improves through repeated practice. Experiment 2 demonstrated that category learning simulates effects of "natural" color categories on color discrimination. Experiment 3 investigated the time course of acquired CP. Experiment 4 found that CP effects are acquired through hue- and lightness-based category learning and obtained interesting data on the dimensional perception of color. The data are consistent with the possibility that language may shape color perception and suggest a plausible mechanism for the linguistic relativity hypothesis. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The characteristics of the color perceptive space in protanomals

Color vision of three protanomal subjects was studied by means of direct paired comparison technique using 25 colors with different brightness. It was shown that the characteristics of their color vision could be completely and adequately described in the frames of the four-dimensional spherical model of color perception. The spatial axes could be identified as the two color-opponent mechanisms (red-green and blue-yellow) and the two achromatic mechanisms (brightness and darkness). Deformation of the color axes in protanomals (as compared with the normal trichromatics) was demonstrated in the "red" and "yellow" spectral region. The visual disturbance in protanomal subjects involves not only color but also achromatic mechanisms. This is manifested in the a deformation of perceptual brightness scale. In comparison with normal trichromatic subjects, the protanomals perceive the red and adjacent colors as achromatic while green, yellow-green, and orange as more bright but low-saturated colors.     

Multiple strains of Saccharomyces cerevisiae on a single grape vine

The opioid system plays an important role in feeding. In general, opioid agonists typically increase feeding and opioid antagonists decrease feeding in non-food restricted animals. In food restricted animals the effects of these drugs are substantially reduced. Opioid antagonists have shown a marked effectiveness at reducing consumption of sweet foods. Explanations for this robust effect have typically focused on drug induced changes in taste, taste perception, or palatability. The current study relates the effects of the opioid antagonist naloxone on motivation to obtain different sucrose concentrations to the drug's effects on unrestricted sucrose solution consumption. Changes in motivation to respond were assessed under a progressive ratio reinforcement schedule (PR) which required increased response cost for each successive unit of sucrose solution. Motivation, as measured by the PR, increased as sucrose concentration increased and naloxone produced a dose-dependent decrease in motivation to respond for a given sucrose concentration. Thus, the effectiveness of naloxone was indirectly related to strength of the sucrose concentration. Under unrestricted access to sucrose solutions, naloxone reduced consumption greatest under the higher concentrations. The data suggest at least part of naloxone's effects on sweet tasting food may be mediated through endogenous opioid reward systems that are reflected in measures of motivation.     

Leo M. Hurvich (1910–2009).

Leo M. Hurvich, a renowned figure in the field of human color vision, died on April 25, 2009, at age 98, in New York City. His research brought to the mainstream a theoretical framework for understanding human color perception in terms of underlying opponent-color mechanisms. When most psychologists and virtually all physiologists and physicists had sought principally to explain how physically different lights match in color, or how neural responses from photoreceptors combine to give the threshold of visually perceptible differences, Hurvich, together with his lifelong collaborator and wife, Dorothea Jameson, focused on understanding the appearance of hue, saturation, and brightness. The influence of their work has been profound and enduring. Their 1957 paper in Psychological Review (Hurvich & Jameson, “An Opponent-Process Theory of Color Vision”) has been referenced in 49 of the last 50 years and continues to be cited often. Hurvich lived a long and rich life, including more than 50 years in a scientific and personal partnership with Dorothea Jameson that blended independence and mutual support most wonderfully, enriching the lives of many in their circle of family, friends, and colleagues. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Modulation of synaptosomal plasma membrane-bound enzyme activity through the perturbation of plasma membrane lipid structure by bupivacaine

To determine whether young capuchin monkeys, Cebus apellaselectively interacted with others concerning novel foods, 11 infants (4.5-12 months) living in two groups were observed following presentation of familiar or novel foods. Foods were presented either to the whole group or to infants in a section of the home cage to which only they had access. Infants showed more frequent interest in others' food and picked up foods more frequently when foods were novel, and they tended to eat novel foods more frequently than familiar foods. The pattern was the same whether the foods were presented to the group or only to infants. Infants expressed interest in others' novel foods equally often before and after sampling these foods themselves. The frequency of interest in others' food correlated positively with age. It is concluded that acceptance of novel foods in these monkeys occurs readily regardless of socially provided information about edibility. Social interactions do not appear to make important contributions to acceptance of novel foods by infant capuchin monkeys.     

Diet palatability modulates sham feeding in VMH-lesion and normal rats: Implications for finickiness and evaluation of sham-feeding data.

Examined the capacity for taste cues to modulate the food intake of 24 ventromedial hypothalamic (VMH) and normal Long-Evans rats. Ss were implanted with a chronically indwelling gastric cannula and sham fed (cannula open) or normally fed (cannula closed) liquid diets varying in sucrose content. VMH Ss were maintained at control body-weight levels. For both groups, the discrepancy in consumption between sham and normal feeding situations depended on the sweetness of the diet. The implications of this finding for studies using sham feeding to assess putative feeding control signals are discussed. VMH lesions exaggerated the sensory control of food intake. Under sham-feeding conditions, increases in the sweetness of the diet led to disproportionately large increments of food intake in VMH Ss relative to controls. Data support the existence of a finickiness component in the VMH syndrome and allude to the nature of the physiological disturbance underlying this behavior change. (36 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)