Local Adaptation of Bitter Taste and Ecological Speciation in a Wild Mammal

Sensory systems are attractive evolutionary models to address how organisms adapt to local environments that can cause ecological speciation. However, tests of these evolutionary models have focused on visual, auditory, and olfactory senses. Here, we show local adaptation of bitter taste receptor genes in two neighboring populations of a wild mammal—the blind mole rat Spalax galili—that show ecological speciation in divergent soil environments. We found that basalt-type bitter receptors showed higher response intensity and sensitivity compared with chalk-type ones using both genetic and cell-based functional analyses. Such functional changes could help animals adapted to basalt soil select plants with less bitterness from diverse local foods, whereas a weaker reception to bitter taste may allow consumption of a greater range of plants for animals inhabiting chalk soil with a scarcity of food supply. Our study shows divergent selection on food resources through local adaptation of bitter receptors, and suggests that taste plays an important yet underappreciated role in speciation.     

Adult-infant food transfer in common marmosets: an experimental study

Infant marmosets and tamarins obtain solid food items from adults during and after the time of weaning. In addition to providing nutrients, food transfers may provide infants with the opportunity to learn about diet. The aim of this study was to investigate patterns of begging and food transfer in captive groups of common marmosets during tests with 1) palatable novel food, 2) unpalatable novel food, and 3) familiar food. Infants may gain an opportunity to learn about diet breadth by preferentially begging for novel rather than familiar items, while adults may facilitate infant learning by differing in their willingness to transfer food depending upon the food's novelty or palatability. In this study, infants exhibited more interest and begging with novel food items than with familiar ones. However, food transfers were not more likely to occur with novel foods than with familiar ones, and in fact adults were more likely to refuse infant begging attempts with novel foods. The palatability of the food also did not influence the rates of refusal and transfer: adults transferred palatable and unpalatable novel foods with similar frequencies. These results suggest that infant marmosets gain an opportunity to learn about diet breadth by begging for novel foods, but adults do not preferentially transfer novel or palatable food items.     

Rhesus macaques (Macaca mulatta) are not neophobic toward novel food with a high sugar content

While we know that food neophobia in nonhuman primates is affected by social factors, little is known about how palatability, and specifically sugar content, might ameliorate a monkey's hesitancy to eat a novel food. It is likely that an innate preference for sweet substances would alter an animal's typical neophobic response. To test this, I presented nine male rhesus macaques with novel foods that contained a low, high, or no amount of sugar. As expected, the monkeys exhibited a neophobic response to the no-sugar novel foods but not to the high-sugar novel foods. Previous research on food neophobia may need to be reevaluated in light of the effects of sugar content on the neophobic response.     

Modulation of sweet responses of taste receptor cells

Taste receptor cells play a major role in detection of chemical compounds in the oral cavity. Information derived from taste receptor cells, such as sweet, bitter, salty, sour and umami is important for evaluating the quality of food components. Among five basic taste qualities, sweet taste is very attractive for animals and influences food intake. Recent studies have demonstrated that sweet taste sensitivity in taste receptor cells would be affected by leptin and endocannabinoids. Leptin is an anorexigenic mediator that reduces food intake by acting on leptin receptor Ob-Rb in the hypothalamus. Endocannabinoids such as anandamide [N-arachidonoylethanolamine (AEA)] and 2-arachidonoyl glycerol (2-AG) are known as orexigenic mediators that act via cannabinoid receptor 1 (CB₁) in the hypothalamus and limbic forebrain to induce appetite and stimulate food intake. At the peripheral gustatory organs, leptin selectively suppresses and endocannabinoids selectively enhance sweet taste sensitivity via Ob-Rb and CB₁ expressed in sweet sensitive taste cells. Thus leptin and endocannabinoids not only regulate food intake via central nervous systems but also modulate palatability of foods by altering peripheral sweet taste responses. Such reciprocal modulation of leptin and endocannabinoids on peripheral sweet sensitivity may play an important role in regulating energy homeostasis.     

Personalised food: how personal is it?

Consumer goods became increasingly personalised, particularly during the last half of the 20th century. Foods and food products have been added a new flavour in this consumer trends with increasingly personalised values of convenience, cost, packaging, and taste. Now functional food industry is ready to take its next venture in a relatively new domain personalising health. Whether the goal of matching foods to individual genotypes to improve the health of those individuals can be attained, and personalised nutrigenomic foods enter the world’s food markets, depends on numerous hurdles being overcome: some scientific in nature, some technical and others related to consumer, market or ethical issues. Public adoption of new technologies is an important determinant for their success. Many of the drivers behind the trend in personalisation of food are now known, particularly ethical, legal and social issues (ELSI) are the major drivers. Future development in the field of nutrigenomics undoubtedly will place its seemingly huge potential in better perspective. Thus, the agriculture and food enterprise has an extraordinary opportunity to link individuals with foods that are personalised for their health.     

Food reward in the absence of taste receptor signaling

Food palatability and hedonic value play central roles in nutrient intake. However, postingestive effects can influence food preferences independently of palatability, although the neurobiological bases of such mechanisms remain poorly understood. Of central interest is whether the same brain reward circuitry that is responsive to palatable rewards also encodes metabolic value independently of taste signaling. Here we show that trpm5-/- mice, which lack the cellular machinery required for sweet taste transduction, can develop a robust preference for sucrose solutions based solely on caloric content. Sucrose intake induced dopamine release in the ventral striatum of these sweet-blind mice, a pattern usually associated with receipt of palatable rewards. Furthermore, single neurons in this same ventral striatal region showed increased sensitivity to caloric intake even in the absence of gustatory inputs. Our findings suggest that calorie-rich nutrients can directly influence brain reward circuits that control food intake independently of palatability or functional taste transduction.     

The role of novelty and fat and sugar concentration in food selection by captive tufted capuchins (Sapajus apella)

Capuchins, like other primates, use feedback from sensory cues and digestion to make decisions about which foods to consume and which to avoid. However, little is known about how capuchins make consumption decisions when simultaneously presented with novel and familiar foods, or how food familiarity and macronutrient concentration together influence food choice, topics with potential implications for developmental and health research. In this study, we evaluated the role of familiarity, as well as fat and sugar concentration, in the food selections of captive tufted capuchins (Sapajus apella). In the first experiment, over 10 sessions, subjects were assigned to either a group that chose between one familiar and one novel food item both high in fat or sugar (high condition), or to a group that chose between one familiar and one novel food item both low in fat or sugar (low condition). In the second experiment, subjects were divided into three groups, familiarized with food over five feeding sessions, and then offered the familiarized food and a novel food that varied in fat or sugar for 10 sessions. When offered foods high in fat, capuchins showed no clear signs of neophobia, forming an initial preference for the novel food, rejecting foods less frequently, and selecting foods faster than when offered foods low in fat. These trends were generally not observed in response to foods with sugar. When presented with options that varied in macronutrient concentration, subjects showed an initial interest in the novel food irrespective of whether it was high in fat or sugar, yet formed a final preference for the higher-concentration item. Findings suggest that the concentration of fat or sugar in novel foods may be an important mediator of exploratory behavior and that capuchins rely on immediate feedback from taste and other sensory cues to make consumption decisions.     

mu-Opioid receptor stimulation in the nucleus accumbens elevates fatty tastant intake by increasing palatability and suppressing satiety signals

Infusion of a μ-opioid receptor (MOR) agonist into the nucleus accumbens (NAcc) drives voracious food intake, an effect hypothesized to occur through increased tastant palatability. While intake of many palatable foods is elevated by MOR stimulation, this manipulation has a preferential effect on fatty food ingestion. Consumption of high-fat foods is increased by NAcc MOR stimulation even in rats that prefer a carbohydrate-rich alternative under baseline conditions. This suggests that NAcc MOR stimulation may not simply potentiate palatability signals and raises the possibility that mechanisms mediating fat intake may be distinct from those underlying intake of other tastants. The present study was conducted to investigate the physiological mechanisms underlying the effects of NAcc MOR stimulation on fatty food intake. In experiment 1, we analyzed lick microstructure in rats ingesting Intralipid to identify the changes underlying feeding induced by infusion of a MOR-specific agonist into the NAcc. MOR stimulation in the NAcc core, but not shell, increased burst duration and first-minute licks, while simultaneously increasing the rate and duration of Intralipid ingestion. These results suggest that MOR activation in the core increases Intralipid palatability and attenuates inhibitory postingestive feedback. In experiment 2, we measured the effects of MOR stimulation in the NAcc core on consumption of nonnutritive olestra. A MOR-specific agonist dose dependently increased olestra intake, demonstrating that caloric signaling is not required for hyperphagia induced by NAcc MOR stimulation. Feeding induced by drug infusion in both experiments 1 and 2 was blocked by a MOR antagonist. In experiment 3, we determined whether MOR activation in the NAcc core could attenuate satiety-related signaling caused by infusion of the melanocortin agonist MTII into the third ventricle. Suppression of intake caused by MTII was reversed by MOR stimulation. Together, our results suggest that MOR stimulation in the NAcc core elevates fatty food intake through palatability mechanisms dependent on orosensory cues and suppression of satiety signals inhibiting food intake.     

How Many Calories Are on Our Plate? Expected Fullness,Not Liking,Determines Meal‐size Selection

The availability of highly palatable food is thought to stimulate the selection of larger meals (leading to weight gain and obesity). In this article, we explore aspects of this proposition. Specifically, we scrutinize two basic assumptions: (i) palatable energy‐dense foods are more rewarding (desired), and (ii) these palatable foods are selected in relatively larger portions. In combination with palatability, we also consider the relative role for “expected satiation”—the extent to which a food is expected to deliver satiation. A total of 17 commonly consumed foods were assessed by 28 normal‐weight participants at lunchtime. Critically, our measure of food reward and expected satiation involves comparisons between foods based on equicaloric portions. When assessed in this way, we find that food reward and ideal portion sizes (in kcal) are both closely associated with expected satiation, but not with “expected liking.” Low expected satiation (not expected liking) predicts the selection of large portion sizes (in kcal) and foods with this characteristic tend to be more energy dense and are regarded as less (not more) rewarding (when compared calorie for calorie). Together, these findings challenge the role of palatability in meal‐size selection and they highlight the importance of expected satiation, a “nonaffective” component of food reward.     

Measuring Oral Fatty Acid Thresholds,Fat Perception,Fatty Food Liking,and Papillae Density in Humans

Emerging evidence from a number of laboratories indicates that humans have the ability to identify fatty acids in the oral cavity, presumably via fatty acid receptors housed on taste cells. Previous research has shown that an individual''s oral sensitivity to fatty acid, specifically oleic acid (C18:1) is associated with body mass index (BMI), dietary fat consumption, and the ability to identify fat in foods. We have developed a reliable and reproducible method to assess oral chemoreception of fatty acids, using a milk and C18:1 emulsion, together with an ascending forced choice triangle procedure. In parallel, a food matrix has been developed to assess an individual''s ability to perceive fat, in addition to a simple method to assess fatty food liking. As an added measure tongue photography is used to assess papillae density, with higher density often being associated with increased taste sensitivity.     

传统与未来的碰撞：食品发酵工程技术与应用进展

随着生物技术的飞速发展,作为食品生物工程的主要组成部分,食品发酵工程技术不断升级,在传统发酵食品的菌种、发酵过程、产品品质得到改善的同时,生物制造的功能食品组分、未来食品等新型产品也应运而生。首先概述了由生物技术和信息技术的进步带来的食品发酵研究手段与生产方式的多层面变革,并重点阐释了利用食品合成生物学设计构建细胞工厂的思路和方法,以及食品生物工程在微生物分析、过程工程和分离工程方面的智能化进程。其次,介绍了现代食品生物工程技术在改善传统发酵食品品质及安全性、生产功能食品组分、添加剂和酶制剂、创制未来食品和开发新型益生食品方面的应用进展。最后,对全球和我国食品发酵产业面临的挑战和未来发展趋势进行了总结和展望,以期为食品发酵的技术革新和工业化应用提供参考。     

Analyzing consumers' preferences towards GM food in southern Spain

In Europe, since the 1990s, food safety crises have heightened public concerns about and distrust towards the agro-food sector, making consumers wary of genetically modified (GM) foods. The application of gene technology to agricultural production has become a highly controversial scientific, political and social issue due to the uncertainty about the potential risks and benefits from GM food consumption. In this regard, public views influence consumers' demands and hence determine the future of this technology's development. Biotechnology proponents attribute the current consumer resistance to GM foods to the lack of tangible benefits for the consumers with higher functional properties. Thus, this paper estimates consumers' preferences regarding GM foods by simulating a market for GM functional cornflakes in southern Spain using the conjoint analysis method. Additionally, market segmentation was performed using a cluster analysis and the consumers' profile differences for each segment were identified. The main results indicate that consumers prefer the GM-free food; nonetheless, the market segmentation distinguishes a potential market niche for GM foods and indicates that businesses can develop strategies to target these segments. Therefore, the marketing strategies implemented in southern Spain should be focused on the health functional claims of second generation GM food.     

生物活性肽的生理功能及研究进展

随着人们生活水平的提高,伴随现代文明而来的各种富裕病如高血压、高血脂、肥胖病、糖尿病和癌症等越来越引起人们的关注,人们的消费观念已从单纯的吃饱吃好向防病治病方向转变。生物活性肽具有涉及神经、激素和免疫调节、抗血栓、抗高血压、抗胆固醇、抗细菌病毒、抗癌、抗氧化、清除自由基、改善氮素吸收关系和矿质运输、促生长、调节食品风味、口味、硬度等多种生理功能,被誉为21世纪人类健康的新宠儿。简述了生物活性肽的特点、生理功能及其研究进展。     

Physiological Adaptations in the Gastrointestinal Tract of Crayfish

SYNOPSIS. Crayfish are the dominant macrocrustacean in manyaquatic ecosystems and are the largest crustacean aquaculturalindustry in the United States, yet we know relatively littleabout their preferred and nutritionally important foods, aswell as their ability to utilize those foods. This review focuseson the ability of crayfish to detect foods, reduce food particlesize, digest macronutrients and the control of those functions.Of particular interest are the enzymatic capabilities of crayfish,especially trypsin, an alkaline protease, cellulase, muramidase,and possibly chitinase and chitobiase. The coordinated neuralcontrol of crayfish food location, ingestion and movement hasbeen well documented, while hormonal control mechanisms havenot. The conclusion we must draw from our current state of knowledgeis that crayfish have ample abilities to taste and locate potentialfoods and enzymatic adaptations developed in crayfish that allowuse of many of the foods they encounter in a benthic aquaticenvironment; other adaptations are lacking or have not beenelucidated.     

Vampire bats exhibit evolutionary reduction of bitter taste receptor genes common to other bats

The bitter taste serves as an important natural defence against the ingestion of poisonous foods and is thus believed to be indispensable in animals. However, vampire bats are obligate blood feeders that show a reduced behavioural response towards bitter-tasting compounds. To test whether bitter taste receptor genes (T2Rs) have been relaxed from selective constraint in vampire bats, we sampled all three vampire bat species and 11 non-vampire bats, and sequenced nine one-to-one orthologous T2Rs that are assumed to be functionally conserved in all bats. We generated 85 T2R sequences and found that vampire bats have a significantly greater percentage of pseudogenes than other bats. These results strongly suggest a relaxation of selective constraint and a reduction of bitter taste function in vampire bats. We also found that vampire bats retain many intact T2Rs, and that the taste signalling pathway gene Calhm1 remains complete and intact with strong functional constraint. These results suggest the presence of some bitter taste function in vampire bats, although it is not likely to play a major role in food selection. Together, our study suggests that the evolutionary reduction of bitter taste function in animals is more pervasive than previously believed, and highlights the importance of extra-oral functions of taste receptor genes.     

Response toward novel stimuli in a group of tufted capuchins (Cebus libidinosus) in Brasília National Park, Brazil

We investigated responses toward novel foods and novel objects by wild capuchins that routinely exploit visitors' foods in Brasília National Park. Given the capuchins' daily exposure to human foods and objects, we expected them to be more explorative toward novel foods and objects compared to capuchins that are not habituated to visitors. However, since the safety and palatability of potential foods have to be learned, we also expected the capuchins to be cautious about eating novel foods, as has been reported for wild and captive capuchins. Stimuli were presented on a platform in four experimental conditions: familiar food (FF), novel food (NF), familiar food plus novel object (FF+O), and novel food plus novel object (NF+O). Latencies to approach and contact the platform, and to approach and to ingest food did not differ across conditions. Nevertheless, the capuchins were significantly more responsive (measured in terms of interest, manipulation, etc.) toward familiar foods than novel foods, and ate significantly more of the former. In other words, their explorative response toward novel foods led to little consumption. Our results do not support the "readiness to eat" hypothesis, according to which a lower readiness to eat and food neophobia are the consequences of the presence of a distracting novel object. The finding that capuchins explore novel stimuli but remain cautious about eating novel foods supports the view that neophilia and neophobia are motivationally independent responses.     

Deactivation of dietary wariness through experience of novel food

When a forager encounters an unfamiliar type of food, it mustdecide whether to eat it and risk being poisoned or avoid eatingit and risk forfeiting a potentially valuable resource. Birdstypically respond to such situations with "dietary wariness";they show a transient aversion to approaching new food (neophobia),and many individuals also show a much longer lasting reluctanceto consume the new food (dietary conservatism), even once neophobiahas waned. Very little is known about how these processes, togethertermed "wariness," are controlled. We therefore present a seriesof experiments investigating how wariness of novel foods indomestic chicks, Gallus gallus domesticus, can be deactivatedand reactivated by different experiences of colored foods, varyingin their degree of novelty and palatability. We found that priorexperience of a single novel color of palatable chick crumbswas sufficient to deactivate both neophobia and dietary conservatismof any other novel color of crumbs tested. Relatively littleprior experience of a novel training food was needed to deactivateneophobia, after which the birds would peck at any other novelfood. In contrast, much more extensive experience of eatinga novel training food was needed before the birds would incorporateother novel foods into their diet. Chicks needed direct physicalcontact with the training food before they overcame their warinessto eat another novel food. However, observational learning wassufficient to encourage them to peck at the food (overcomingtheir neophobia). Reinstating wariness was much more easilyachieved than its deactivation. We discuss these surprisingresults in relation to the foraging behavior of wild and domesticbirds.     

Effect of domestic processing on bioactive compounds

Nowadays, most of the consumed foods are rarely ready for direct consumption. Food can be purchased at the local supermarket as fresh raw product such as meat, fruit, fish etc. or as manufactured product after an industrial processing (canned meat, dried fish, packed fruit etc.). But later on, both food types are usually submitted to culinary treatments which will transform the selected food into a cooked dish ready to eat. Domestic methods of food processing have been developed over the centuries to make the final product more attractive in flavour, appearance, taste and consistency. But, until the last centuries, none of the gourmets realize that at the same time, the cooking process was making their foods more digestible, microbiologically safer and more or less nutritive depending on the selected cooking technology. Besides consumer preferences, the selected cooking method is an important factor affecting not only the food chemical composition, but also the intake of bioactive compounds under normal dietary conditions. Therefore, in this work, the different culinary treatments and domestic cooking methods will be compared to define the optimal process to reduce the degradation of biologically active metabolites present in foods commonly consumed as an elaborated dish. Compounds such as carotenoids, glucosinolates, flavonoids and other phenolic compounds, ω-3 fatty acids, tocopherols, phytosterols, etc. have been pointed as bioactive compounds beneficial for human health. Apparently, they are able to prevent cardiovascular diseases (CVD), tumour formation, hiper-cholesterolemia in blood and other deleterious disorders. An adequate domestic practice might help to increase in taking of those functional molecules enhancing their functionality and reducing the risk of chronic diseases.     

Functional food science in Japan: state of the art

In 1984, a new science related to functional food was initiated by a National Project team under the auspices of the Japan Ministry of Education and Science. It was followed by a great many academic and industrial studies to occupy a central position in the field of food and nutritional sciences. In 1993, the Ministry of Health and Welfare established a policy of "Foods for Specified Health Uses" (FOSHU) by which health claims of some selected functional foods are legally permitted. Up to now (November 22. 1999), 167 FOSHU products have been born. Since the time (1984) when the concept of functional food" was proposed, it seems that the science in Japan has been progressing along, among others, a unique path of development. The uniqueness is seen in the development of functional foods by minimizing undesirable as well as maximizing desirable food factors. Hypoallergenic foods, developed from their materials by removing allergens, offer a good example. Another characteristic may be found in the field of sensory science which aims at elucidating a molecular logic of the senses of taste and smell in reference to their effects on physiological systems in the body. The paper discusses some characteristics of functional food science in Japan, with special emphasis on these topics.