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.

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    Identifying odorants in mixtures : synthetic task instructions favour performance compared to analytical task instructions
    Bult, J.H.F. ; Schifferstein, H.N.J. ; Kroeze, J.H.A. - \ 2006
    Chemical Senses 31 (2006)8. - ISSN 0379-864X - p. E39 - E39.
    Sensory and instrumental analysis of food aromas
    Bult, J.H.F. - \ 2006
    Wageningen University. Promotor(en): J.H.A. Kroeze; Fons Voragen, co-promotor(en): H.N.J. Schifferstein; J.P. Roozen. - [S.l.] : S.n. - ISBN 9789085045236 - 172
    aroma - aromatische verbindingen - geur en smaak - geurstoffen en smaakstoffen - zintuiglijke waarneming - sensorische evaluatie - gaschromatografie - aroma - aromatic compounds - flavour - flavour compounds - organolepsis - sensory evaluation - gas chromatography

    Food aromas are generally perceived as unitary aromas, i.e. fried potatoes smell like fried potatoes and roasted coffee smells like roasted coffee. Nonetheless, nearly all food aromas are produced by a multitude of volatile components that contribute to an extensive collection of aromas in various compositions. Of the hundreds of volatiles released from fried potatoes and roasted coffee a major se!ection does not produce an odour, many others do produce an odour that contributes to one of both aromas, many others contribute to both. In spite of this, food aromas are not being perceived as collections of discernable odours.

    Central theme of this thesis is a method used to fractionate, identify and characterise the odorous components in mixtures of odorants: gas chromatography olfactometry (GCO). GCO entails the pressurised transfer of volatiles through a capillary column, after capturing these from the headspace of a foodstuff. Since the column delays volatiles differentially, panellists may sniff these volatiles sequentially on their release from the capillary. This allows the separate sensory evaluation of components in the aroma mixture.

    A well-established practice in technological studies is that measurement reliability of instruments is estimated and minimised. Although sniffing panels are generally employed as instruments that assess the odour impact of chemical components in food aromas, reliability assessment is generally not applied to their application. Paradoxically, there are no practically available valid methods that may assess the reliability of panel responses. In addition, studies of systematic bias of panel responses in GCO studies are not available, although some common assumptions in GCO studies are not valid psychologically. For instance, intense odorants that arc qualitatively similar to the aroma quality are generally identified as character impact components. However, perception studies showed that odorants may affect (viz. suppress) each others odour contribution in a mixture. Therefore, assumptions regarding the contribution of singular odorants to aromas on basis of GCO, is premature.

    This thesis introduces methodology to estimate GCO response reliability and reports the empirical testing of this methodology (chapters 2, 3 and 4). In addition, several GCO assumptions considered psychologically disputable, are evaluated in empirical studies. These studies entail the effect of stimulus context on the estimated reliability of GCO results (chapter 4), the evaluation of the contribution of GCO-identified 'character impact components' to an apple model aroma (chapter 5), the effects of task instruction on the identification of odorants in food aromas (chapter 6), the effects of peri-threshold components on a supra-threshold food aroma (chapter 7) and the effects of sequentially presented odorants on their mutual odour intensities as a function of qualitative odour similarity (chapter 8). The general conclusions of this thesis are, that panel responses in the temporary absence of odorants must be used to estimate the reliability of panel odour detections, and that mechanisms that systematically affect response variation should be known and considered m GCO.

    Modeling panel detection frequenties by queing system theory: An application in gas chromatography olfactrometry.
    Bult, J.H.F. ; Putten, B. van; Schifferstein, H.N.J. ; Roozen, J.P. ; Voragen, A.G.J. ; Kroeze, J.H.A. - \ 2004
    Perception and Psychophysics 66 (2004)7. - ISSN 0031-5117 - p. 1125 - 1146.
    rehydrated french beans - signal-detection-theory - sniffing port analysis - odor thresholds - vigilance decrement - bell peppers - flavor - identification - detectability - probability
    In continuous vigilance tasks, the number of coincident panel responses to stimuli provides an index of stimulus detectability. To determine whether this number is due to chance, panel noise levels have been approximated by the maximum coincidence level obtained in stimulus-free conditions. This study proposes an alternative method by which to assess noise levels, derived from queuing system theory (QST). Instead of critical coincidence levels, QST modeling estimates the duration of coinciding responses in the absence of stimuli. The proposed method has the advantage over previous approaches that it yields more reliable noise estimates and allows for statistical testing. The method was applied in an olfactory detection experiment using 16 panelists in stimulus-present and stimulus-free conditions. We propose that QST may be used as an alternative to signal detection theory for analyzing data from continuous vigilance tasks.
    The signal function of thematically (In)congruent ambient scents in a retail environment
    Schifferstein, H.N.J. ; Blok, S.T. - \ 2002
    Chemical Senses 27 (2002)6. - ISSN 0379-864X - p. 539 - 549.
    context-dependent memory - odor-evoked memories - implicit memory - cues - identification - experiences - behavior - distinctiveness - performance - congruency
    An odor emitted by an object signals the presence of that object and may draw attention to it. Can odors that are not actually emitted by an object also function as a signal? We investigated whether the degree of thematic congruency between an ambient odor and a magazine affected magazine sales in a retail store. We selected two odors: a grass odor, congruent with soccer, animal/nature and gardening magazines; and a sunflower odor, congruent with personal care and women's magazines. In a field study in three bookstores, the ambient odors did not increase sales for thematically congruent magazines, nor did they decrease sales for incongruent magazines. Several explanations for these unexpected findings are discussed.
    Sensory evaluation of character impact components in an apple model mixture
    Bult, J.H.F. ; Schifferstein, H.N.J. ; Roozen, J.P. ; Boronat, E.D. ; Voragen, A.G.J. ; Kroeze, J.H.A. - \ 2002
    Chemical Senses 27 (2002)6. - ISSN 0379-864X - p. 485 - 494.
    multicomponent odor mixtures - intensity interaction - sub-threshold - taste - identification - suppression - perception - resolution - profiles - quality
    Food aromas generally are complex mixtures of volatiles. In the present study, we investigated the joint effects of hexyl acetate, trans-2-hexenal and 1-hexanol on the multi-attribute perception of an apple aroma. The first two substances were identified earlier as positive contributors to the apple aroma (high character impact), whereas the third component was identified as an irrelevant or negative contributor (low character impact). Aroma quality was quantified using a set of eight graphic rating scales. All three components had significant effects on the aroma profiles. These effects consist mainly of an effect of each component on the attribute that described its individual character and an effect of all three components on ratings on the main character attribute `apple'. As expected, the high impact components increased `apple' ratings, whereas the low character impact component decreased `apple' ratings. Furthermore, intensity ratings on the attribute that corresponded with the odour of the low impact component were suppressed by the presence of high impact components. These results indicate that the contributions of odorants to the mixture's aroma are not linear combinations of separate odour intensities, because sensory interactions were observed. In addition, humans detect components in complex mixtures more accurately than studies on identification performance have suggested. We conclude that for an adequate assessment of the effects of multiple mixture components on changes in aroma perception, it is sufficient to employ multiple response scales measuring intensities of attributes that are distinctive with respect to the expected qualitative changes. Results of this approach should be subjected to multivariate methods of statistical analysis
    Range and nummer-of-levels effects in derived and stated attribute importances
    Verlegh, P.W.J. ; Schifferstein, H.N.J. ; Wittink, D.R. - \ 2002
    Marketing Letters 13 (2002)1. - ISSN 0923-0645 - p. 41 - 52.
    We study how the range of variation and the number of ttribute levels affect five measures of attribute importance: full profile conjoint estimates, ranges in attribute level attractiveness ratings. regression coefficients. graded paired comparisons. and self-reported ratings, We find that all importance measures are affected by the range manipulation. The number of attribute levels affects only two measures. The results allo,; us to benchmark the magnitude of the number-of-levels effect against the range effect conjoint importance estimates were approximately equally affected by a threefold increase in the range of attribute variation and by the insertion of two intermediate attribute levels, Our findings show that the number-of-levels effect is most likely due to respondents' tendencies to distribute their mental stimulus representations and their responses uniformly over the corresponding continua.
    Effects of appropriate and inappropriate odors on product evaluations
    Schifferstein, H.N.J. ; Michaut, A.M.K. - \ 2002
    Perceptual and Motor Skills 95 (2002). - ISSN 0031-5125 - p. 1199 - 1214.
    Range, frequency, and number-of-levels effects in derived and stated measures of attribute importance
    Verlegh, P.W.J. ; Schifferstein, H.N.J. ; Wittink, D.R. - \ 2001
    Unknown Publisher (Mansholt paper 3) - 11 p.
    To eat or not to eat? A multidisciplinary perspective on the determinants of human food choice
    Schifferstein, H.N.J. ; Frewer, L.J. ; Risvik, E. - \ 2001
    In: Food, People and Society. A European Perspective of Consumers' Food Choices / Frewer, L.J., Risvik, E., Schifferstein, H.N.J., Berlin Heidelberg : Springer - p. 3 - 7.
    Effects of product beliefs on product perception and liking
    Schifferstein, H.N.J. - \ 2001
    In: Food, People and Society. A European Perspective of Consumers' Food Choices / Frewer, L.J., Risvik, E., Schifferstein, H.N.J., Berlin Heidelberg : Springer - p. 73 - 96.
    The influence of olfactory concept on the probability of detecting sub- and peri-threshold odorants in a complex mixture
    Bult, J.H.F. ; Schifferstein, H.N.J. ; Roozen, J.P. ; Voragen, A.G.J. ; Kroeze, J.H.A. - \ 2001
    Chemical Senses 26 (2001). - ISSN 0379-864X - p. 459 - 469.
    The headspace of apple juice was analysed to obtain an ecologically relevant stimulus model mixture of apple volatiles. Two sets of volatiles were made up: a set of eight supra-threshold volatiles (MIX) and a set of three sub-threshold volatiles. These sets were used to test the hypothesis that sub-threshold components can change the quality of a familiar smelling mixture of odorants when added to this mixture. In order to test this hypothesis, three successive dilutions of the sub-threshold volatiles were prepared in such a way that the strongest was at the threshold concentration and the two lower concentrations were below the threshold. The detection probabilities of the sub-threshold components in a blank stimulus were compared with the detectabilities in MIX. The sub- and peri-threshold volatiles were detected no better in MIX than in a blank. On the contrary, sub- and peri-threshold volatiles were better detected alone than when added to MIX. However, when the group of subjects was split into two sub-groups, employing either a rough or a detailed concept definition of the target stimulus, respectively, the subjects with highly refined concepts were better able to detect the presence of sub-threshold volatiles in MIX than those with poorly refined stimulus concepts. The effect of stimulus concept definition occurred independently of the proportions of correct detections of sub-threshold volatiles in a blank
    Food, People and Society. A European Perspective of Consumers' Food Choices
    Frewer, L.J. ; Risvik, E. ; Schifferstein, H.N.J. - \ 2001
    Berlin : Springer Verlag - 462 p.
    Method of stimulation, mouth movements, concentration and viscosity : effects on the degree of taste adaptation
    Theunissen, M.J.M. ; Kroeze, J.H.A. ; Schifferstein, H.N.J. - \ 2000
    Perception and Psychophysics 62 (2000). - ISSN 0031-5117 - p. 607 - 614.
    Although sensory adaptation, the gradual loss of sensation during prolonged stimulation, has been demonstrated in laboratory taste experiments, a comparable loss of taste intensity is not experienced in real-life eating situations. This discrepancy may be due to differences in the proximal stimuli or to differences in the ways the taste receptors are stimulated. In two experiments, the effects of four potentially relevant variables were investigated: stimulus intensity, stimulus viscosity, mouth movements, and presentation method. During the initial seconds of stimulation, adaptation to the weakest of the two solutions was faster. Although more viscous stimuli were less sweet, viscosity as such did not affect adaptation rate, nor did mouth movements. Among the three presentation methods, a sucrose-soaked filter paper on the tongue produced more adaptation than either sipping the solution or flowing it over the tongue. This suggests that even mouth movements far more subtle than those still present in the no-movement condition of a sip-and-spit experiment can disrupt the adaptation process.
    Taste adaptation during the eating of sweetened yoghurt
    Theunissen, M.J.M. ; Polet, I.A. ; Kroeze, J.H.A. ; Schifferstein, H.N.J. - \ 2000
    Appetite 34 (2000). - ISSN 0195-6663 - p. 21 - 27.
    Taste adaptation, a gradual decline of taste intensity with prolonged stimulation, is frequently observed in laboratory experiments. However, during normal eating the taste of food does not seem to decrease or disappear. During eating, the presence of saliva, the interactions between tastants and odorants, and mouth movements can influence the time course of taste intensity. Therefore, results from standard laboratory adaptation experiments about adaptation seem of limited relevance to the prediction of the time course of taste intensity when eating real foods. We studied whether taste adaptation occurs when subjects eat yogurt, sweetened with two concentrations of sucrose (3.75 and 7.5Ž In addition, we examined whether this adaptation is related to taste adaptation measured with a filter paper method. During the eating of yogurt, sweetness intensity declined with time, whereas sourness intensity did not. As expected, taste adaptation in the ″yogurt task″ was only slightly correlated to adaptation measured with filter paper.
    Olfactory stimulus concept and the discriminability of nearly identical apple aroma's
    Bult, J.H.F. ; Schifferstein, H.N.J. ; Roozen, J.P. ; Voragen, A.G.J. ; Kroeze, J.H.A. - \ 2000
    In: Book of Abstracts 13th International Symposium Olfaction & Taste, ISOT 2000 and 14th European Chemoreception Research Organisation Congress / Persaud, K.C., van Toller, S., Brighton : European Chemoreception Res. Organisation - p. 190 - 190.
    Asymmetry in the disconfirmation of expectations for natural yogurt
    Schifferstein, H.N.J. ; Kole, A.P.W. ; Mojet, J. - \ 1999
    Appetite 32 (1999). - ISSN 0195-6663 - p. 307 - 329.
    Effects of (in)congruent product odors on buying decisions
    Schifferstein, H.N.J. ; Michaut, A.M.K. - \ 1999
    In: Marketing and Competition in the Information Age : Proceedings of the 28th EMAC Conference, Berlin, Germany, 11 - 14 May / L. Hildebrandt e.a. (eds.) - Berlin : Humboldt Universität, 1999 - (on CD-ROM)
    Verborgen verleiders : geur als marketinginstrument. Hidden persuaders : odor as marketing instrument
    Schifferstein, H.N.J. - \ 1999
    Tijdschrift voor Marketing 33 (1999)1. - ISSN 0165-1439 - p. 24 - 28.
    An empirical comparison of various individual-level hybrid conjoint analysis models
    Lans, I.A. van der; Verlegh, P.W.J. ; Schifferstein, H.N.J. - \ 1999
    In: Marketing and Competition in the Information Age : Proceedings of the 28th EMAC Conference, Berlin, Germany, 11-14 May / L. Hildebrandt e.a. (eds.) - Berlin : Humboldt Universität, 1999 - (on CD-ROM)
    Contextual Effects in Attribute Importances derived from Conjoint Analysis
    Schifferstein, H.N.J. ; Verlegh, P.W.J. ; Wittink, D.R. - \ 1998
    In: Proceedings of EU-AIR III project "Food and the Consumer" 4. - [S.l.] : [s.n.], 1998 - p. 10 - 13.
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