Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

    We have a manual that explains all the features 

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The interplay between mouth and mind : explaining variation in taste-related brain activation
Rijn, Inge van - \ 2016
Wageningen University. Promotor(en): Kees de Graaf, co-promotor(en): Paul Smeets. - Wageningen : Wageningen University - ISBN 9789462579040 - 156
taste research - magnetic resonance imaging - brain - patterns - satiety - hunger - calories - smaakonderzoek - kernspintomografie - hersenen - patronen - verzadigdheid - honger - calorieën

Food does not always ‘taste’ the same. During hunger, for example, food may be tastier compared to during satiety. Many other internal and external factors affect the way we experience our food and make it a dynamic process. Our brain is responsible for weighing and integrating these factors and forms the final consumption experience. Mapping the impact of all factors that influence the consumption experience is of fundamental importance for understanding why we eat the way we eat. Important drivers for food consumption are its rewarding capacity, healthiness and caloric content. Furthermore, in the current supermarket environment, advertisements and food claims are omnipresent, and may exert influence on our consumption experience by triggering all kinds of cognitive processes. Therefore, in this thesis we aimed to assess the effect of food content (caloric content and sugar type), character (personality trait reward sensitivity and attitude health-interest) and cognitive effects (labeling/claim effects and selective attention to food properties) on brain activation during tasting. Such taste-related brain responses were obtained with the use of functional Magnetic Resonance Imaging while administering small sips of liquid to young, normal weight female participants in a MRI scanner.

To begin with, we focussed on the effect of caloric content on taste responses (Chapter 2). An important function of eating is ingesting energy, and the ability to sense energy in the oral cavity would therefore be biologically relevant. However, in this thesis we showed that oral exposure to caloric (maltodextrin and maltodextrin + sucralose) and non-caloric (sucralose) stimuli does not elicit discriminable responses in the brain when averaged over hunger and satiety. Nevertheless, energy content did interact with hunger state in several brain regions involved in inhibition (approach-avoidance behaviors) and gustation: the middle cingulate cortex, ventrolateral prefrontal cortex, anterior insula and thalamus. Thus, brain activation in response to oral calories, irrespective of sweetness, seems to be dependent on hunger state.

In addition to the detection of oral calories in general, we examined whether different sugar types, glucose and fructose, can be sensed in the oral cavity (Chapter 3). Tasting glucose compared to fructose evoked greater food reward (anterior cingulate cortex, ACC) activation during hunger and greater food motivation (precentral gyrus) activation during hunger and satiety. Responses to oral fructose relative to glucose were greater only during satiety in an area associated with inhibitory control (superior frontal gyrus). It appears that oral glucose and fructose evoke differential brain responses, independent of sweetness.

Secondly, we investigated in how far reward sensitivity, a personality trait, affected brain responses to calories in the oral cavity (Chapter 4). This because a food’s reward value is highly dependent on its caloric content. Sensitivity to rewards was measured with the Behavioral Activation System Drive scale and was correlated with oral calorie activation from a simple maltodextrin solution and a sucrose sweetened soft drink. Oral calorie activation was obtained by subtracting activation by a non-caloric solution (sucralose solution/non-caloric soft drink) from that by a caloric solution (maltodextrin + sucralose/sucrose sweetened soft drink). We found that neural responses to oral calories from a maltodextrin solution are modulated by reward sensitivity in reward-related areas such as the caudate, amygdala, and ACC. For soft drinks, we found no correlations with reward sensitivity in any reward related area. This discrepancy may be due to the direct detection of maltodextrin, but not sucrose in the oral cavity. However, the absence of this effect in a familiar soft drink warrants further research into its relevance for real life ingestive behavior.

In the last part of this thesis we explored how cognitions modulate the consumption experience. Perceived, rather than actual caloric content, inflicted by calorie food labels, induces cognitive processes that may influence the consumption experience on their own. We tested this in an experiment and found that receipt of a beverage perceived as low- compared to high-caloric induced more activation in the dorsal striatum, a region involved in coding food reward (Chapter 5). As low-calorie labels may appeal especially to the health-minded consumers, we correlated brain responses to the receipt of a beverage perceived as low- compared to high-caloric with health interest (measured with the General health interest subscale of the Health and Taste Attitude Scales). Indeed, health interest scores correlated positively with activation in the dorsal striatum.

Rather than focussing participants’ attention on differences within one food aspect, in Chapter 6 we focussed on selective attention to different food aspects, i.e. pleasantness versus taste intensity versus calories. In the supermarket, food labels and claims often do the same. In the first place, paying attention to hedonics, caloric content or taste intensity predominantly resulted in common brain activation in regions involved in the neural processing of food stimuli, e.g. the insula and thalamus. This likely resulted from ‘bottom-up’ sensory effects, which are more prominent than ‘top-down’ attentional effects. However, small differences were also observed; taste activation was higher during selective attention to intensity compared to calories in the right middle orbitofrontal cortex and during selective attention to pleasantness compared to intensity in the right putamen, right ACC and bilateral middle insula. Overall, these results indicate that statements regarding food properties can alter the consumption experience through attention-driven effects on the activation of gustatory and reward regions.

Finally, the general discussion (Chapter 7) describes main finding and conclusions of this thesis. In sum, we showed that food energy content, sugar type, trait reward sensitivity, health interest, food labels and selective attention all modulate taste-related brain activation. In conclusion, these findings indicate that the formation of the final consumption experience is a very multifaceted process that dependents on numerous factors integrated by the brain, of which we are just beginning to grasp its complexity.

De permanente groene revolutie van Swaminathan
Fresco, L.O. ; Rabbinge, R. - \ 2015
Vork 2 (2015)3. - ISSN 2352-2925 - p. 66 - 71.
green revolution - genetic engineering - human feeding - hunger - food supply - scientific research - scientists - society - fertilizers - pesticides - environmental impact - india - netherlands - potatoes - wheat - groene revolutie - genetische modificatie - humane voeding - honger - voedselvoorziening - wetenschappelijk onderzoek - wetenschappers - samenleving - kunstmeststoffen - pesticiden - milieueffect - nederland - aardappelen - tarwe
Het weekblad Time kwalificeerde hem als een van de twintig meest invloedrijke Aziaten van de twintigste eeuw: ‘The father of the Green Revolution used his skills in genetic engineering and his powers of persuasion to make famine an unfamiliar word in Asia’. Tegelijkertijd wees hij al vroeg op de gevaren van een te grote afhankelijkheid van kunstmest en bestrijdingsmiddelen en milieugevolgen daarvan. Dr. Monkombu Sambasivan Swaminathan is een fervent pleitbezorger van de Evergreen Revolution, de permanente groene revolutie. Op 7 augustus werd hij 90 jaar. Louise Fresco en Rudy Rabbinge schetsen zijn enorme betekenis voor wetenschap en samenleving.
Inequalities in Food Security and Nutrition. A Life Course Perspective
Bras, H. - \ 2015
Wageningen : Wageningen University - ISBN 9789462571891 - 36
voedselzekerheid - voeding - slechte voeding - gezondheidsongelijkheden - honger - levensloop - wereld - food security - nutrition - malnutrition - health inequalities - hunger - life course - world
Relying on satiety cues in food consumption : studies on the role of social context, appearance focus, and mindfulness
Veer, E. van de - \ 2013
Wageningen University. Promotor(en): Hans van Trijp, co-promotor(en): Erica van Herpen. - S.l. : s.n. - ISBN 9789461736895 - 240
voedselconsumptie - sociale psychologie - consumenten - voedselopname - verzadigdheid - eetlust - eetlustcontrole - honger - fysiologie - bewustzijn (consciousness) - eten - maaltijden - snacks - food consumption - social psychology - consumers - food intake - satiety - appetite - appetite control - hunger - physiology - consciousness - eating - meals
Consumers eat at various sequential occasions throughout the day. The current thesis addresses the question of how one consumption episode can affect the amount of consumption at a subsequent episode. The thesis focuses specifically on how the social context during a consumption episode affects subsequent consumption, and on when consumers rely on hunger and satiety cues in sequential consumption episodes.
Integrated Food and Nutrition Security Programming to Address Undernutrition : The Plan Approach
Boer, F.A. de; Verdonk, I. - \ 2012
Wageningen : Wageningen UR Centre for Development Innovation (Report / Wageningen UR Centre for Development Innovation CDI-12-014) - 34
voedselzekerheid - slechte voeding - honger - ondervoeding - food security - malnutrition - hunger - undernutrition
From a technical point of view, it is widely recognised that an integrated approach to food and nutrition security is an effective way to promote child nutritional well-being. In this desk review, based on project documents of the countries which took part in the PLAN NL supported Food and Nutrition Security Support Programme (FNSSP), what kind of interventions were undertaken and their strengths and weaknesses are compared with the lessons learned from the World Bank. Report number CDI-12-014.
Minder honger door minder verspilling? Het kan!
Waarts, Y.R. ; Meijerink, G.W. ; Timmermans, T. - \ 2010
Den Haag : Schuttelaar & Partners
voedselvoorziening - voedselverspilling - voedselafval - verliezen - honger - wereldvoedselproblemen - food supply - food wastage - food wastes - losses - hunger - world food problems
Publieksgerichte brochure voor Wereldvoedseldag 16 oktober 2010. Hebben mensen die honger lijden er wat aan als bij ons thuis minder eten verspild wordt? Ja, als we in westerse landen minder voedsel weggooien en er aan wennen dat goed voedsel er niet perfect uit hoeft te zien, dan zorgen we er met z'n allen voor dat consumenten in ontwikkelingslanden meer en beter eten kunnen kopen.
A green revolution from below? : science and technology for global food security and poverty alleviation
Richards, P. - \ 2010
Wageningen : Wageningen University - ISBN 9789085858850 - 21
wetenschap - technologie - ontwikkeling - landbouwontwikkeling - armoede - honger - voedselzekerheid - landbouw bedrijven - plattelandsontwikkeling - ontwikkelingslanden - science - technology - development - agricultural development - poverty - hunger - food security - farming - rural development - developing countries
Constrain constraints! : a study into real and perceived constraints and opportunities for the development of smallholder farmers in Sub-Sahara Africa
Becx, Gertjan - \ 2009
farmers - poverty - hunger - agricultural development - africa south of sahara - africa - development cooperation
Climate change versus development: trade-offs and synergies
Swart, R.J. - \ 2009
London, United Kingdom : Policy Network - 12
klimaatverandering - opwarming van de aarde - ontwikkeling - armoede - honger - climatic change - global warming - development - poverty - hunger
Voedselzekerheid : een beschouwing vanuit drie dimensies
Berkhout, P. - \ 2009
Den Haag : LEI Wageningen UR (LEI-rapport 2009-086) - ISBN 9789086153657
voedselzekerheid - landbouwproductie - voedselvoorziening - honger - voeding - voedselprijzen - biomassa - instellingen - wereld - food security - agricultural production - food supply - hunger - nutrition - food prices - biomass - institutions - world
To combat hunger is one of the biggest challenges the world is facing today. Currently around 1 billion people are suffering from hunger. Improving food security, with a still increasing world population, is a difficult and complex task. It is a problem with multiple dimensions, a technical, an institutional and an economic dimension. This report offers three articles, each article covering one of these dimensions
Long-term global availability of food: continued abundance or new scarcity?
Koning, N.B.J. ; Ittersum, M.K. van; Becx, G.A. ; Boekel, M.A.J.S. van; Brandenburg, W.A. ; Broek, J.A. van den; Goudriaan, J. ; Hofwegen, G. van; Jongeneel, R.A. ; Schiere, J.B. ; Smies, M. - \ 2008
NJAS Wageningen Journal of Life Sciences 55 (2008)3. - ISSN 1573-5214 - p. 229 - 292.
voedselzekerheid - voedselprijzen - productiemogelijkheden - voedselvoorziening - honger - armoede - populatiegroei - biobrandstoffen - food security - food prices - production possibilities - food supply - hunger - poverty - population growth - biofuels - precision agriculture - use efficiency - climate-change - bioenergy production - developing-countries - economic-development - production systems - specialized dairy - green-revolution - soil degradation
During the 20th century hunger has become a problem of poverty amidst plenty rather than absolute food scarcity. The question is whether this will remain so or whether the hunger of the poor will once more be exacerbated by rising food prices. In this paper we discuss biophysical conditions, social forces and non-linear interactions that may critically influence the global availability of food in the long term. Until 2050, the global demand for primary phytomass for food will more than double, while competing claims to natural resources for other purposes (including biobased non-foods) will increase. A sober assessment of the earth¿s biophysical potential for biomass production, which recognizes competing claims and unavoidable losses, suggests that this is in itself still large enough for accommodating this rising demand. However, the exploitation of this biophysical potential proceeds through technical paradigms that set a relative maximum to food production. In addition, socio-economic mechanisms make the food economy run up against a ceiling even before this maximum is reached. As a consequence, current developments may well entail a new trend change in international markets. These developments include the depletion of land and water reserves, the stagnation of the potential yields of major crops, the rise in energy prices, and the way in which systemic socio-economic factors lead to a strong underutilization of production possibilities in the developing world. Given these conditions, the avoidance of steep rises in food prices may depend on the timely relaxation of socio-economic constraints in developing countries and on timely breakthroughs in sustainable yield increases, biorefinement and non-farm production systems. Myopic expectations make it doubtful whether spontaneous market forces will provide the necessary incentives for this, which may be reason for societal actors to consider the need for more active policies
Eetgedrag, de verleiding voorbij
Graaf, C. de - \ 2006
Wageningen : Wageningen Universiteit - 32
eten - voedingsgedrag - voedselopname - eetpatronen - metabolisme - verzadigdheid - eetlust - honger - sensorische evaluatie - neurobiologie - eating - feeding behaviour - food intake - eating patterns - metabolism - satiety - appetite - hunger - sensory evaluation - neurobiology
Effect of low-density diets on broiler breeder and offspring performance
Enting, H. - \ 2005
Wageningen University. Promotor(en): Martin Verstegen, co-promotor(en): P.J. van de Aar. - s.l. : S.n. - ISBN 9085042283
vleeskuikens - nageslacht - voer - samenstelling - honger - energiegehalte - voedingsstoffengehalte - dierenwelzijn - vleeskuikenresultaten - pluimveevoeding - vleeskuikenouderdieren - broilers - progeny - feeds - composition - hunger - energy content - nutrient content - animal welfare - broiler performance - poultry feeding - broiler breeders
Regulation of food intake : a focus on ghrelin
Blom, W.A.M. - \ 2005
Wageningen University. Promotor(en): Frans Kok; G. Schaafsma, co-promotor(en): H.F.J. Hendriks. - - 216
voedselopname - eetlustcontrole - verzadigdheid - honger - maagdarmhormonen - food intake - appetite control - satiety - hunger - gastrointestinal hormones
The number of people with (severe) overweight is increasing. More insight into the mechanism of food intake may help to develop foods for weight maintenance. There are indications that ghrelin is an important hunger signal. The role of ghrelin in the regulation of food intake was investigated in human volunteers at TNO Quality of Life in Zeist, in collaboration with the department of Human Nutrition of Wageningen University. Our studies showed that changes in ghrelin concentrations were related to changes in appetite, but these changes did not predict food intake. Suppression of ghrelin concentrations, however, did predict initiation of the next meal. Such suppression of ghrelin appears to depend on type of macronutrient and energy content of a meal. We conclude that ghrelin is a hunger signal that does not determine meal size (satiation), but that regulates next meal initiation (satiety). Foods that contain nutrients (for example dairy protein) that effectively suppress ghrelin concentrations, may help prevent overweight and obesity.
Wageningen views on food security
Koning, N.B.J. ; Bindraban, P.S. ; Essers, A.J.A. - \ 2002
Wageningen : Wageningen Platform for Food Security (Report Wageningen Views 1) - ISBN 9789067546270 - 42
voedselproductie - voedselconsumptie - honger - voeding - economische ontwikkeling - landbouwbeleid - voedselzekerheid - food production - food consumption - hunger - nutrition - economic development - agricultural policy - food security
Report that integrates the proceedings of a number of multidisciplinay expert workshops on food security at Wageningen UR
Wageningse visies op voedselzekerheid
Koning, N.B.J. ; Bindraban, P.S. ; Essers, A.J.A. - \ 2002
Wageningen : Studium Generale - ISBN 9789067546577 - 44
landbouwproductie - voeding - honger - landbouwontwikkeling - voedselzekerheid - agricultural production - nutrition - hunger - agricultural development - food security
Landbouw en armoedebestrijding, voedselproductie. Uiteindelijk formuleert men vijf doelen en tien strategieën
Enige fysiologische en psychofysische waarnemingen op het gebied van de smaakgevoeligheid van proefpersonen
Kouwenhoven, T. - \ 1974
Landbouwhogeschool Wageningen. Promotor(en): C. den Hartog. - Wageningen : Veenman - 86
smaak - honger - hongersnood - dorst - besluitvorming - intermenselijke relaties - gewoonten - voedsel - voedingsmiddelen - consumenteninformatie - consumenten - onderzoek - vraag - invloeden - taste - hunger - famine - thirst - decision making - interpersonal relations - habits - food - foods - consumer information - consumers - research - demand - influences

Man is not merely a physiological organism, but is also a rational and social being. Therefore, problems of food choice and of other behaviour related to food have to be considered from a physiological, as well as from a social, cultural or economic point of view.

In the first chapter of this thesis a review is given of the principal cues of food behaviour and of the factors determining food choice.

Hunger appears to be the main physiological motive for food intake, while appetite is more related to its psychological regulation. The mechanisms reponsible for these cues are not totally understood. Evidence, however, is available that hormonal signals from the bloodstream and the fat tissues play an important role. Further is known that ventromedial and -lateral nuclei of the hypothalamus are involved in the regulation of food intake and that satiety feelings are evoked by the sense of taste in the mouth. Certain elasticity senses in the gastrointestinal tract are suggested to play a role as well.

As to the regulation of the quality and the quantity of the foods to ingest, some (older) authors suggested the existence in man of an inborn quality by which he is able to select adequately the right foods in the right amounts.

Food acceptance, however, is so strongly controlled by psychosocial, cultural and other factors that this selfselection quality is practically totally overshadowed by them. Consequently no practical meaning can be ascribed to it, at least in our society.

Since in food behaviour studies sensory experiments are commonly used tools, in chapter 2 a number of general and specific motives are given for further taste research. They are:
1. The important role of taste and odour in food selection and other behavioural phenomena.
2. Apart from its physiological function food has aesthetic functions, as well.
3. The consumer exhibits preferences and avoidances towards specific sensory food properties and is willing to pay considerable amounts of money for palatability and flavour.
4. The term 'quality' is gradually getting the meaning of 'sensory quality' in our countries.

The applicability of the sensory research on different fields forms another category of motives for taste research:

1. For the food technologist it is of great importance to have at his disposal possibilities for testing the sensory quality of his products and for evaluating the chances of acceptability a new product is likely to meet when it appears on the market.
2. For those concerned with planning and execution of nutritional and health projects, insight in and knowledge of the patterns of tastes and preferences of the target groups and categories are of great use.
3. Taste research has shown itself to be a tool for the tracing of ethnic relations between a variety of races and tribes.
4. It can be demonstrated that clear relations exist between taste sensitivity and some physiological and pathological variables. Although in these fields sensory experiments are rather common, frequently one is struck bij the lack of fundamental knowledge about taste sensitivity. Among others this is caused by the fact that between the different disciplines an exchange of thoughts is very difficult to obtain. The purpose of this thesis is therefore to integrate taste testing experiences from different application fields as much as possible and to make them accessible for others.

As usual in taste sensitivity research a restriction was made as regards the threshold value determination of the four primary taste qualities.

In chapter 3 a review is given of the main types of thresholds. The great variety of threshold data in the literature is discussed. The differences are due to variations in definitions, methodology, quality and purity of the taste substances used, solvent media, and so on. It is needless to say that differences in experimental subjects play an important role, too.

In this chapter attention is also drawn to the discussion about the possible existence of either one receptor system, in which all receptors respond to all taste stimuli or of a receptor system in which at least 4 types of receptors are present to respond selectively to any one of the primary tastes.

In a series of identification experiments (chap. 4) was shown that the mean threshold values resulting out of an arbitrarily increasing series of 15 concentrations of taste substances, were totally identical with those obtained from a series in which 12 concentrations were offered in a mathematically increasing order. Both series were caried out 4 times with sucrose, lactic acid and sodium chloride, with 10 and 15 tasters respectively in the 2 experimental groups. The mean threshold values for the 3 taste substances were 0,016 ± 0,012; 0,0072 ± 0,0038 and 0,016 ± 0,008 Mols/l, respectively. A positive, but weak correlation between the several sensitivities could be demonstrated so that lineair regression equations could be calculated.

Since the methods of determination of the threshold values as described appeared to be very laborious and time consuming, in the next experiment a design was developed in which at least 6 panel members could be examined for their taste sensitivity in the same time, This design actually consisted of a randomized presentation scheme in which were assembled all concentrations, repetitions, placebo's for the 4 taste substances under consideration. As taste substances were chosen 7 concentrations of sucrose, sodium chloride, citric acid an quinine sulphate. The experimental -design was planned in such a way that also the possible influence of the colour of a few kinds of artificial light could be studied (chap. 5). The total project consisted of presenting 7 concentrations of every taste substance in twelve fold, including 96 samples of demineralized water. Sixteen tasters completed the project (= 72 sessions). The mean threshold values of these tasters were in Mots per liter: 0,0091 ± 0,0047 (sucrose), 0,0078 ± 0,0054 (NaCl), 0,00023 ± 0,00022 (citric acid) and 0,000 00167 (quinine sulphate). All judges showed the following order of decreasing sensitivity: quinine sulphate>citric acid>NaCl>sucrose.

Analysis of the responses to the given placebo's made it possible to discriminate between relatively 'good' and relatively 'bad' tasters, according toe their capacity to describe and recognize the samples as water. Both categories showed a different pattern of incorrect responses:
1. All tasters are inclined to describe the demineralized water erroneously as 'bitter'.
2. The good tasters, moreover, seem to describe it frequently as 'sweet'.
3. A decrease in capacity to describe and to recognize the water correctly, is accompanied by a decrease in inclination to call it 'sweet', and an increase in mistakingly calling it 'bitter', 'sour' or 'salty'.
4. Consequently the ratios (incorrectly) sweet: bitter, sweet: sour, and/or sweet: salty, decrease. Probably this is also valid for the ratio salty: sour.

In chapter 4 the effects of training and experience are also studied. An active training period in which the taster gets instructions and advice is usually rather short (4 or 5 sessions) but its effects are very clear. Frequently it is followed by a period during which no further instructions are given, but in which a taster builds up his own experience. Although the effects are usually rather small, they last much longer. Training periods are necessary whenever one starts a new method of research, but experiences appeared to persist for more than half a year.

In the experiment described, the process of building up experience was manifest during the first 50 sessions. The number of correct responses (y) appeared to increase with the number of sessions (x) according to the regression equation y = 57,27 + 0,176x. The correlation coefficient r = 0,489 is significantly different from 0, with p < 0,01. Differences were observed between the tasters as well as in the taster themselves (inter- and intra taster differences). From taster to taster the number of correct responses varied from 53,2 % to 75,2 %.

For an estimation of the intra-individual differences a mathematical treatment of the results obtained was needed. With help of the method of maximum likelyhood it could be shown that the relation between the concentration and the fraction correct responses can be described by the equation for the cumulative normal frequency distribution.

With help of this relation and the observed number of correct responses estimations could be made of the individual parameters p o , μan σfor the different taste substances (table 28).

Finally an analysis is made of the frequencies with which taste qualities the panel members are inclined to confuse the presented samples. In general, tasters appear to confuse relatively seldom the given taste substances with salt or sour, but relatively often with demineralized water or bitter. Probably the degree of familiarity with primary tastes plays a role. From the incorrect responses an order of decreasing familiarity could be deducted: salt>sour>sweet>bitter>demineralized water. Deviations of this order are connected with the research design used, the circumstances during the experiments, and the 'quality' of the tasters. In tasting subthreshold concentrations of quinine sulphate or of sodium chloride, good tasters do describe them much more frequently as sweet than as sour, while the less good judges confuse them as often with sour as wich sweet.

The effects of colours on taste perception are discussed in chapter 5. These effects are partly associative, partly physiological in character. While the associative character of colours in relation to foods is well known, the physiological aspects in this context need further experimentation. A critical discussion of the scarce data in the literature shows that knowledge about this is mainly empirical. From the experiments of chapter 4 it appears that the physiological action of the different colours in relation to the individual results of the panel members is so weak, that as to the inspected results on an individual basis the influence is negligible, but for the panel members as a group, one ought to take it into account.

Analysis of the group data shows that colour effects are significantly present. Application of identical intensities of sodium light (yellow) and mercury light (blueish) resulted for the panel as a group in a significantly higher amount of correct responses compared with artificial daylight of the same intensity. This was valid at least for the taste substances sucrose, citric acid and sodium chloride. For the bitter substance quinine sulphate this phenomenon was not observed.

It could be demonstrated that the colour effects manifest themselves especially in the steep parts of the log dose response curves. As a consequence of the chosen experimental design this meant for the salt and sour taste substances an influence in the lower range of concentrations used and for the sweet substance an influence in the higher range. The steepness of the curve (a) plays an important role in this. As a consequence of the applied colours the curves showed a shift towards the lower concentrations; in other words: the panel members seemed to be a bit more sensitive. Finally attention is drawn to the fact that the observed phenomena do not form an isolated case, but that in the physiological and psychological literature analogous heteromodal interactions are discussed. According to this literature weak interacting stimuli can result into an enhancement of the cortical alertness in general, and as a consequence into a lowering of the threshold values. Strong interacting stimuli should have the opposite effects. It is concluded that the observed fall in threshold values and its accompanying features can result from the interacting effect of the applied light and that in comparison with the intensity of the taste stimuli, the light stimuli probably are perceived as very weak. The results seem to support YOUNG and HELMHOLTZ'S conception about the existence of several systems of coulour vision.

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