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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    Loss of Olfactory Function and Nutritional Status in Vital Older Adults and Geriatric Patients
    Toussaint, N. ; Roon, M. de; Campen, J.P.C.M. van; Kremer, S. ; Boesveldt, S. - \ 2015
    Chemical Senses 40 (2015)3. - ISSN 0379-864X - p. 197 - 203.
    mild cognitive impairment - odor identification - normative data - taste - malnutrition - smell - discrimination - dysfunction - prevalence - validation
    The aim of this cross-sectional study was to assess the association of olfactory function and nutritional status in vital older adults and geriatric patients. Three hundred forty-five vital (mean age 67.1 years) and 138 geriatric older adults (mean age 80.9 years) were included. Nutritional status was assessed using the mini nutritional assessment-short form. The Sniffin’ Sticks was used to measure olfactory function. Eleven percentage of the vital older adults were at risk of malnutrition, whereas 60% of the geriatric participants were malnourished or at risk. Only 2% of the vital older adults were anosmic, compared with 46% of the geriatric participants. Linear regression demonstrated a significant association (P = 0.015) between olfactory function and nutritional status in the geriatric subjects. However, this association became insignificant after adjustment for confounders. Both crude and adjusted analysis in the vital older adults did not show a significant association. The results indicate that, in both groups of elderly, there is no direct relation between olfactory function and nutritional status. We suggest that a decline in olfactory function may still be considered as one of the risk-factors for malnutrition in geriatric patients—once co-occurring with other mental and/or physical problems that are more likely to occur in those patients experience.
    Differences in taste in button mushroom strains (Agaricus bisporus)
    Baars, J.J.P. ; Stijger, I. ; Kersten, M. ; Sonnenberg, A.S.M. - \ 2014
    Wageningen : Wageningen UR Plant Breeding (Report / Plant Breeding Wageningen UR 2015-3) - 17
    mushrooms - edible fungi - taste - agaricus bisporus - agaricus - taste research - taste panels - postharvest quality - dry matter - paddestoelen - eetbare paddestoelen - smaak - agaricus bisporus - agaricus - smaakonderzoek - smaakpanels - kwaliteit na de oogst - droge stof
    This report describes the results of a screening of genetically diverse strains of mushroom Agaricus bisporus for differences in taste. Eight different strains were grown on regular commercial compost and casing soil. Two of these strains were also grown on a casing with calcium chloride added to increase osmotic value. The intension was to increase the dry matter content of the mushrooms that might affect the “bite” sensation of mushrooms.
    Landschapsvarken Bonte Bentheimer, Feestvaken of nieuw model voor verdienen
    Holster, Henri - \ 2014
    breeds - pig breeds - biodiversity - sustainability - taste - nature management - natural landscape - overijssel - landscape - economic viability
    Een kwestie van smaak - interview met Gerben Messelink en Wouter Verkerke
    Messelink, G.J. ; Verkerke, W. - \ 2014
    Buitenstebinnen : halfjaarlijkse uitgave van Naktuinbouw December (2014)3. - p. 18 - 19.
    tuinbouw - glastuinbouw - groenten - fruit - consumentenpanels - nieuwe cultuurgewassen - spaanse pepers - testen - smaakpanels - smaak - smaakonderzoek - voedingsmiddelen - horticulture - greenhouse horticulture - vegetables - fruit - consumer panels - new crops - chillies - testing - taste panels - taste - taste research - foods
    Naast dat consumenten voor groente en fruit kiezen op basis van het uiterlijk, bijvoorbeeld de vorm en de kleur, wordt de smaak van het product steeds belangrijker. Wageningen UR onderzoekt dan ook steeds meer producten (vooral nieuwe rassen) op smaak.
    Uitwerking interview workshop Onderscheid in Vers : Gerben Splinter in gesprek met drie deelnemers van het project PPP Paprika
    Splinter, Gerben - \ 2014
    horticulture - sweet peppers - program evaluation - sales promotion - consumer economics - cooperation - taste - merchandise information - knowledge - differentiation - varieties
    Smediger kaas door juiste voer
    Hettinga, K.A. ; Dijkstra, J. - \ 2014
    De zelfkazer 66 (2014)6. - ISSN 0166-4549 - p. 10 - 11.
    kazen - smaak - eiwitgehalte - vetgehalte - voersamenstelling - onverzadigde vetten - vetzuren - melk - melkvet - cheeses - taste - protein content - fat content - feed formulation - unsaturated fats - fatty acids - milk - milk fat
    Veel kaasmakers willen smedige (zachte, smeuïge) kaas maken, want de gemiddelde consument vindt die kaas het lekkerst. Kasper Hettinga en Jan Dijkstra van Wageningen Universiteit vertellen hoe de smedigheid van kaas kan worden beïnvloed door de samenstelling van het veevoer.
    Olfactory Imagination and Odor Processing: Three Same-Different Experiments
    Koster, E.P. ; Stelt, O. van der; Nixdorf, R.R. ; Linschoten, M.R.I. ; Mojet, J. ; Wijk, R.A. de - \ 2014
    Chemosensory Perception 7 (2014)2. - ISSN 1936-5802 - p. 68 - 84.
    reaction-times - betts questionnaire - imagery vividness - mental mixtures - visual-imagery - shortened form - error rates - food memory - perception - taste
    Do people who claim to have olfactory imagination process odors more efficiently? In three same–different experiments, using all possible combinations of odors and odor names as primes and targets, selected high imagers (n¿=¿12) were faster (±230 ms; P¿
    Vetarm en toch lekker romig
    Wolkers, H. ; Quataert, M.C.J. - \ 2014
    WageningenWorld (2014)4. - ISSN 2210-7908 - p. 32 - 33.
    kazen - smaak - vetgehalte - voeding en gezondheid - smakelijkheid - vetarme producten - productontwikkeling - kaasrijping - cheeses - taste - fat content - nutrition and health - palatability - low fat products - product development - cheese ripening
    Kaasspecialist Zijerveld wilde een smaakvolle geitenkaas met slechts 30 procent vet in het assortiment. Met ambachtelijke technieken lukte dat niet. Wageningen UR Food & Biobased Research vond een nieuwe receptuur voor het kaasje. Gezonder en net zo lekker.
    Salivary lipase and a-amylase activities are higher in overweight than in normal weight subjects: Influences on dietary beharior
    Mennella, I. ; Fogliano, V. ; Vitaglione, P. - \ 2014
    Food Research International 66 (2014). - ISSN 0963-9969 - p. 463 - 468.
    alpha-amylase - food-consumption - oral-sensitivity - lingual lipase - fat perception - taste - questionnaire - responses - humans - women
    Mounting evidence shows that hedonic eating, leading to overeating just for pleasure, can be driven by oro-sensory factors through the activation of reward processing and learning in the brain. Foods rich in sugars and fats are potent rewards and saliva composition influences oral taste, texture and aroma perception. A role for salivary a-amylase and lipase in the gustatory system and a link between salivary a-amylase activity and dietary habits were recently hypothesized. The objective of this study was to verify the relationship among salivary lipase and a-amylase activities as well as zinc concentration with food preference and choice of people with different body mass indices. Forty-two (23 normal weight and 19 overweight) healthy subjects participated in the study. Data showed that a-amylase and lipase were 1.8 and 2.4 folds higher in overweight than in normal weight subjects, respectively. On the other hand, overweight subjects showed a 33% reduced salivary zinc concentration compared to normal weight subjects. Only lipase activity positively correlated with individual preference for high-fat foods and with fat content of the diets. All in all data suggested that high salivary lipase activity in overweight subjects could be an adaptive response to the low fat-taste perception related to the reduced zinc concentration. It cannot be ruled out that other factors but diet might influence salivary a-amylase activity in overweight subjects.
    Human protein status modulates brain reward responses to food cues1–3
    Griffioen-Roose, S. ; Smeets, P.A.M. ; Heuvel, E.M. van den; Boesveldt, S. ; Finlayson, G. ; Graaf, C. de - \ 2014
    American Journal of Clinical Nutrition 100 (2014)1. - ISSN 0002-9165 - p. 113 - 122.
    leverage hypothesis - energy-intake - taste - breakfast - appetite - satiety - carbohydrate - mechanisms - receptors - choice
    Background: Protein is indispensable in the human diet, and its intake appears tightly regulated. The role of sensory attributes of foods in protein intake regulation is far from clear. Objective: We investigated the effect of human protein status on neural responses to different food cues with the use of functional magnetic resonance imaging (fMRI). The food cues varied by taste category (sweet compared with savory) and protein content (low compared with high). In addition, food preferences and intakes were measured. Design: We used a randomized crossover design whereby 23 healthy women [mean SD age: 22 +/- 2 y; mean +/- SD body mass index (in kg/m(2)): 22.5 +/- 1.8] followed two 16-d fully controlled dietary interventions involving consumption of either a low-protein diet (0.6 g protein center dot kg body weight(-1) center dot d(-1), similar to 7% of energy derived from protein, approximately half the normal protein intake) or a high-protein diet (2.2 g protein center dot kg body weight(-1) center dot d(-1), similar to 25% of energy, approximately twice the normal intake). On the last day of the interventions, blood oxygen level-dependent (BOLD) responses to odor and visual food cues were measured by using fMRI. The 2 interventions were followed by a 1 -d ad libitum phase, during which a large array of food items was available and preference and intake were measured. Results: When exposed to food cues (relative to the control condition), the BOLD response was higher in reward-related areas (orbitofrontal cortex, striatum) in a low-protein state than in a high-protein state. Specifically, BOLD was higher in the inferior orbitofrontal cortex in response to savory food cues. In contrast, the protein content of the food cues did not modulate the BOLD response. A low protein state also increased preferences for savory food cues and increased protein intake in the ad libitum phase as compared with a high-protein state. Conclusions: Protein status modulates brain responses in reward regions to savory food cues. These novel findings suggest that dietary protein status affects taste category preferences, which could play an important role in the regulation of protein intake in humans. This trial was registered at as NTR3288.
    The influence of olfactory impairment in vital, independently living older persons on their eating behaviour and foodliking
    Kremer, S. ; Holthuysen, N.T.E. ; Boesveldt, S. - \ 2014
    Food Quality and Preference 38 (2014). - ISSN 0950-3293 - p. 30 - 39.
    age-related-changes - flavor amplification - nutritional-status - functional foods - salt reduction - taste - smell - malnutrition - consumption - perception
    These two studies investigated eating behaviour and food liking of independently living Dutch older people with and without olfactory impairment. In the first study, an internet survey was conducted in relation to their olfactory status (n = 512; age 55–91). Hyposmic older people reported eating the same meal more often within a week than their unimpaired peers, and they also differed in some of the types of foods they reported eating as snacks (i.e. fewer cookies and nuts, more candy). In the second study, various strategies to increase food liking among older consumers were investigated, as well as their liking of reformulated foods with an expected reduced palatability. The strategies included (1) combined visual enrichment and flavour enrichment of mashed potatoes, (2) enhancement of taste intensity and thickness of gravy, and (3) flavour enrichment of stews. The reformulation encompassed (1) salt reduction of meatballs and (2) protein enrichment of bread. Thirty-eight young consumers (age 32.3 ± 8.9 y), 41 normosmic older consumers (age 65.1 ± 5.2 y), and 43 hyposmic older consumers (age 68.5 ± 5.9 y) assessed food liking on a 100 mm visual analogue scale. Both older groups increased their food liking in response to the changes made in the mashed potatoes and gravies, decreased their food liking in response to the salt reduction in the meatball and increased their product liking once information was given on the reduction. In conclusion, older persons – regardless of their olfactory status – may respond positively to multi-sensory enrichment in warm meal components. At the same time, certain types of foods may still appeal more or less to hyposmic older persons which in turn may lead to the development of different dietary intake patterns.
    The Sum of lts Parts-Effects of Gastric Distention, Nutrient Content and Sensory Stimulation on Brain Activation
    Spetter, M.S. ; Graaf, C. de; Mars, M. ; Viergever, M.A. ; Smeets, P.A.M. - \ 2014
    PLoS ONE 9 (2014)3. - ISSN 1932-6203 - 10 p.
    body-weight regulation - food-intake - feeding-behavior - eating behavior - human amygdala - appetite - humans - satiety - taste - fat
    During food consumption the brain integrates multiple interrelated neural and hormonal signals involved in the regulation of food intake. Factors influencing the decision to stop eating include the foods' sensory properties, macronutrient content, and volume, which in turn affect gastric distention and appetite hormone responses. So far, the contributions of gastric distention and oral stimulation by food on brain activation have not been studied. The primary objective of this study was to assess the effect of gastric distention with an intra-gastric load and the additional effect of oral stimulation on brain activity after food administration. Our secondary objective was to study the correlations between hormone responses and appetite-related ratings and brain activation. Fourteen men completed three functional magnetic resonance imaging sessions during which they either received a naso-gastric infusion of water (stomach distention), naso-gastric infusion of chocolate milk (stomach distention + nutrients), or ingested chocolate-milk (stomach distention + nutrients + oral exposure). Appetite ratings and blood parameters were measured at several time points. During gastric infusion, brain activation was observed in the midbrain, amygdala, hypothalamus, and hippocampus for both chocolate milk and water, i.e., irrespective of nutrient content. The thalamus, amygdala, putamen and precuneus were activated more after ingestion than after gastric infusion of chocolate milk, whereas infusion evoked greater activation in the hippocampus and anterior cingulate. Moreover, areas involved in gustation and reward were activated more after oral stimulation. Only insulin responses following naso-gastric infusion of chocolate milk correlated with brain activation, namely in the putamen and insula. In conclusion, we show that normal (oral) food ingestion evokes greater activation than gastric infusion in stomach distention and food intake-related brain areas. This provides neural evidence for the importance of sensory stimulation in the process of satiation.
    Aroma exposure time and aroma concentration in relation to satiation
    Ramaekers, M.G. ; Luning, P.A. ; Ruijschop, R.M.A.J. ; Lakemond, C.M.M. ; Bult, J.H.F. ; Gort, G. ; Boekel, M.A.J.S. van - \ 2014
    The British journal of nutrition 111 (2014)03. - ISSN 0007-1145 - p. 554 - 562.
    sensory-specific satiety - food-intake - repeated consumption - flavor retention - release - size - orthonasal - perception - behavior - taste
    The present study investigated the effect of aroma exposure time and aroma concentration on ad libitum intake and subjective satiation. In a within-subject study, thirty-eight unrestrained, healthy female participants (age: 18-39 years; BMI: 18·5-26·0 kg/m2) were asked to consume tomato soup during lunchtime, until they felt comfortably full. Every 30 s, the participants consumed 10 g of a bland soup base while tomato soup aroma was delivered separately through the nose via a retronasal tube that was attached to an olfactometer. This gave the impression of consuming real tomato soup. For each sip, the aroma varied in exposure time (3 and 18 s) and concentration (5 × ), resulting in four different test conditions. Ad libitum food intake and appetite profile parameters were measured. A 9 % lower food intake was observed when the participants were exposed to the condition with 18 s exposure time and a high concentration than when exposed to the other three conditions. These results indicate that changing the retronasal aroma release by aroma concentration and aroma exposure time affects food intake
    Laat de varkens los : nieuw perspectief voor boer en landschapsbeheer in Overijssel
    Holster, H.C. ; Mul, M.F. - \ 2013
    Lelystad : Livestock Research Wageningen UR - 20
    varkens - landschapsbeheer - scharrelhouderij - slachtdieren - overijssel - nederland - dierhouderij - rassen (dieren) - smaak - natuurlandschap - gezondheid - pigs - landscape management - free range husbandry - meat animals - overijssel - netherlands - animal husbandry - breeds - taste - natural landscape - health
    Wat zijn precies de functies die een varken in het landschap kunnen vervullen? Kan dat zomaar, varkens in het wild; waar moet je dan rekening mee houden? Is het wel rendabel om varkens te houden? Dit e-book geeft antwoorden, beelden en richting op deze vragen, specifiek voor de provincie Overijssel.
    Cooking time but not cooking method affects children's acceptance of Brassica vegetables
    Poelman, A.A.M. ; Delahunty, C.M. ; Graaf, C. de - \ 2013
    Food Quality and Preference 28 (2013)2. - ISSN 0950-3293 - p. 441 - 448.
    health-promoting compounds - primary-school children - food neophobia - antioxidant capacity - preferences - retention - broccoli - fruit - taste - information
    The home environment potentially presents a simple means to increase acceptance of sensory properties of vegetables by preparation. This research investigated how preparation can effectively impact upon children's acceptance for vegetables. Five- and six-year old children (n = 82, balanced for vegetable consumption) tasted and evaluated two Brassica vegetables, broccoli and cauliflower, each prepared in six different ways via variations in cooking method (boiling versus steaming) and cooking time (3 levels, ranging from 2 to 14 min). Children rated samples for liking and a trained descriptive panel assessed the samples' sensory properties. Across vegetable types, medium cooking times were liked more than short and long cooking times (p <0.0001), and these samples were medium firm and cohesive, with a balance of green and cooked flavour notes. Boiled samples were less intense in flavour and taste than steamed samples, but overall did not differ in acceptance. Significant interactions were found. Cooking method played a role in acceptance of broccoli but not cauliflower, with medium steamed broccoli liked the most. There was no difference in acceptance between low and high vegetable consumers, although high vegetable consumers were more discriminating in acceptance for cauliflower. In conclusion, children's acceptance of Brassica vegetables may be altered by preparation. There may be advantage in promoting steaming of Brassica vegetables to children, as they do not object to the flavour, and steaming is nutritionally preferable to boiling. Very short cooking times lead to an undesirable sensory profile and should be avoided. Recommendations are applicable to children regardless of their vegetable intake. (C) 2012 Elsevier Ltd. All rights reserved.
    Improved acceptance of Chromonaela odorata by goat kids after weaning is triggered by in utero exposure but nog consumption of milk
    Hai, P.V. ; Schonewille, J.T. ; Tien, D.V. ; Everts, H. ; Hendriks, W.H. - \ 2013
    Applied Animal Behaviour Science 146 (2013). - ISSN 0168-1591 - p. 66 - 71.
    chromolaena-odorata - feeding-behavior - food preference - amniotic-fluid - maternal diet - tropical weed - pregnant ewes - fetal - sheep - taste
    The aim of the current study was to determine whether the improved post-weaning intake of Chromonaela odorata by goat kids is related to either the in utero period of the goat kids or the subsequent suckling period. It was hypothesized that kids born to dams fed C. odorata during pregnancy and receiving milk from dams not exposed to C. odorata during pregnancy show an improved acceptance to consume this plant. Twenty female goats were successfully synchronized and divided into 4 groups. Two groups (1 and 3) were offered 50 g of dried C. odorata leave meal (COLM) mixed with a basic diet for the last 3 months of pregnancy until 1 week before parturition. At birth the kids from the goats in group 1 and 2 were cross fostered without colostrum or milk from their own mother. While waiting for the delivery of kid from another goat, the kid was fed milk replacer or milk from any goat dam in the same treatment. Kids from groups 3 and 4 remained with their mothers. After weaning (2.5 months old), one kid from each goat dam was selected for COLM intake which was measured for 30 min over a 4 week period. Feeding activities of the individually housed goat kids was monitored with a camera system. Kids born to dams receiving COLM during pregnancy consumed higher amounts of the COLM supplemented test feed during all feeding preference tests compared to kids from the control group, particularly during week 3 and 4 (P <0.001). Shorter latency, longer time spent on each meal and total eating time, chewing time and higher meal size (P <0.05) were different in the kids born from does that ingested COLM during pregnancy. It is concluded that prenatal exposure to C. odorata via maternal ingestion significantly increases the intake of C. odorata by weaned goat kids. This improved intake is due to the in utero learning and not the transfer of (secondary) components via the milk of the mothers fed C. odorata during pregnancy.
    Effect of Replacing Sugar with Non-Caloric Sweeteners in Beverages on the Reward Value after Repeated Exposure
    Griffioen-Roose, S. ; Smeets, P.A.M. ; Weijzen, P.L.G. ; Rijn, I. van; Bosch, I. van den; Graaf, C. de - \ 2013
    PLoS ONE 8 (2013)11. - ISSN 1932-6203
    body-weight - artificial sweetener - energy density - food-intake - satiety - brain - choice - flavor - adults - taste
    Background: The reward value of food is partly dependent on learned associations. It is not yet known whether replacing sugar with non-caloric sweeteners in food is affecting long-term acceptance. Objective: To determine the effect of replacing sugar with non-caloric sweeteners in a nutrient-empty drink (soft drink) versus nutrient-rich drink (yoghurt drink) on reward value after repeated exposure. Design: We used a randomized crossover design whereby forty subjects (15 men, 25 women) with a mean +/- SD age of 21 +/- 2 y and BMI of 21.5 +/- 1.7 kg/m(2) consumed a fixed portion of a non-caloric sweetened (NS) and sugar sweetened (SS) versions of either a soft drink or a yoghurt drink (counterbalanced) for breakfast which were distinguishable by means of colored labels. Each version of a drink was offered 10 times in semi-random order. Before and after conditioning the reward value of the drinks was assessed using behavioral tasks on wanting, liking, and expected satiety. In a subgroup (n=18) fMRI was performed to assess brain reward responses to the drinks. Results: Outcomes of both the behavioral tasks and fMRI showed that conditioning did not affect the reward value of the NS and SS versions of the drinks significantly. Overall, subjects preferred the yoghurt drinks to the soft drinks and the ss drinks to the NS drinks. In addition, they expected the yoghurt drinks to be more satiating, they reduced hunger more, and delayed the first eating episode more. Conditioning did not influence these effects. Conclusion: Our study showed that repeated consumption of a non-caloric sweetened beverage, instead of a sugar sweetened version, appears not to result in changes in the reward value. It cannot be ruled out that learned associations between sensory attributes and food satiating capacity which developed preceding the conditioning period, during lifetime, affected the reward value of the drinks.
    Prei: teeltsystemen uit de grond: Onderzoek 2012
    Os, E.A. van; Bruins, M.A. ; Wilms, J.A.M. ; Verhoeven, J.T.W. ; Weel, P.A. van - \ 2013
    Wageningen : Wageningen UR Glastuinbouw (Rapport / Wageningen UR Glastuinouw 1247) - 48
    teeltsystemen - hydrocultuur - preien - bladgroenten - vollegrondsgroenten - plantmateriaal - rassenproeven - smaak - proeven op proefstations - landbouwkundig onderzoek - cropping systems - hydroponics - leeks - leafy vegetables - field vegetables - planting stock - variety trials - taste - station tests - agricultural research
    Het 2012 onderzoek van prei op water, binnen het programma Teelt de Grond Uit, richtte zich op virusverspreiding, sorteren van plantmateriaal, plantleeftijden en rassenvergelijking, de smaak van de geoogste prei en wat te doen met het jaarlijks neerslagoverschot. Water en meststofverbruik per teelt over de afgelopen jaren is geanalyseerd om de besparing te berekenen (50% minder NO3 nodig). Plantdichtheid, buislengte en buisdiameter waren een voortzetting van eerder onderzoek en gaven geen andere uitkomsten. Binnen de rassen zijn grote verschillen, terwijl een oudere plant een hogere opbrengst geeft. Sorteren is een noodzaak voor een uniforme oogst. Het jaarlijks neerslagoverschot moet in eerste instantie via een aangepast systeemontwerp worden afgevoerd, andere opties kosten meer geld.
    Met elkaar in gesprek over voedseltechnologie
    Molder, H.F.M. te; Swierstra, T. ; Sneijder, P.W.J. ; Haen, D. - \ 2013
    [S.l.] : YouTube
    voedseltechnologie - innovaties - consumenten - houding van consumenten - voedselconsumptie - smaak - voeding en gezondheid - food technology - innovations - consumers - consumer attitudes - food consumption - taste - nutrition and health
    Het publieke vertrouwen in voedseltechnologie is fragiel. De maatschappelijke dialoog over voedsel en voedseltechnologie zou een stuk beter kunnen; technologen en consumenten praten nogal vaak langs elkaar heen. In deze video, gebaseerd op onderzoek van de Universiteit Maastricht en Wageningen Universiteit, wordt uitgelegd hoe dat komt.
    A taste of pepper: genetics, biochemistry and prediction of sweet pepper flavor
    Eggink, P.M. - \ 2013
    Wageningen University. Promotor(en): Richard Visser, co-promotor(en): Arnaud Bovy; Chris Maliepaard; J.P.W. Haanstra. - S.l. : s.n. - ISBN 9789461737243 - 159
    capsicum annuum - paprika's - wilde verwanten - genotypen - chemische samenstelling - smaak - geur en smaak - capsicum baccatum - introgressie - plantenveredeling - capsicum annuum - sweet peppers - wild relatives - genotypes - chemical composition - taste - flavour - capsicum baccatum - introgression - plant breeding

    This PhD project started with the composition of a diverse panel of genotypes that represented, (i) roughly the flavor variation in the commercial Capsicum annuum breeding program of Rijk Zwaan, (ii) parents of available mapping populations and (iii) some genotypes that were expected to have extraordinary flavors. The complete set consisted of 35 genotypes of which 24 genotypes were non-pungent. Volatile and non-volatile compounds as well as some breeding parameters were measured in mature fruits of all genotypes throughout the growing season. In addition, from three harvests the non-pungent genotypes were evaluated for taste by a trained descriptive sensory panel.

    The biochemical profiling with use of SPME-GC-MS allowed visualization of between- and within-species volatile compound variation. Principal components analysis (PCA) on the intensity patterns of 391 putative volatile compounds revealed individual grouping of C. chinense, C. baccatum var. pendulum and C. annuum, indicating potentially interesting volatile variation present in the former two groups. A large group of saturated and unsaturated esters were mainly responsible for the individual grouping of the C. chinense accessions. Due to the elevated acid concentrations and aberrant volatile profiles of the C. baccatum var. pendulum accessions PEN45 and PEN79, the two BIL populations derived from these accessions were identified as interesting candidates for further study. Compared to e.g. Mazurka the citrate concentration of the C. baccatum accessions was 2.5-3 times higher and the malate concentrations were even up to 12 times higher (Chapter 2).

    Based on the non-pungent genotypes, we found highly correlated clusters of volatiles and non-volatiles, which could be related to metabolic pathways and common biochemical precursors (Chapter 3). Contrasts between genotypes were caused by both qualitative and quantitative differences in these metabolic clusters, with the phenolic derivatives, higher alkanes, sesquiterpenes and lipid derived volatiles forming the major determinants. For the description of the non-pungent genotypes the panelists used fourteen attributes to describe the flavor sensation in the mouth/throat, which were the texture attributes crunchiness, stickiness of the skin, toughness and juiciness, the basic taste attributes sweetness and sourness and the retronasal flavor attributes aroma intensity, grassiness, green bean, carrot, fruity/apple, perfume, petrochemical and musty. The variation in flavor could be reduced into two major sensory contrasts, which were a texture related contrast and the basic sweet-sour contrast. The structure of the PCA plots resulting from the analysis with one harvest (Chapter 3) and the analysis with the combined three harvests (Chapter 4) remained almost identical, indicating the stability of these contrasts. To relate the sensory attributes to the metabolite data and to determine the importance of the individual compounds we used Random Forest regression on the individual harvests and on the three harvests together. Several predictors for the attributes aroma, fruity/apple, sourness and sweetness were found in common between harvests, which we proposed as key-metabolites involved in flavor determination of sweet pepper (Chapter 4). This list contains compounds with known relations to attributes, like sweetness and sugars, but also several compounds with new relations. In this respect we have demonstrated for the first time, that the metabolites p-menth-1-en-9-al, (E)-β-ocimene, (Z)-2-penten-1-ol, and 1-methyl-1,4-cyclohexadiene are related to fruity/apple taste and/or sweetness of pepper. For sourness the only compound with a consistent significant contribution was an unknown C6H8O2 compound. We postulated therefore the hypothesis that in pepper the effect of sourness related metabolites is masked by other volatile and non-volatile compounds or texture differences (Chapter 3). Subsequently in Chapter 4 we described a clear sweetness-sourness interaction and demonstrated that the masking effect of fructose and other sugars explained why we did not find organic acids contributing to the prediction of sourness. The major sensory attributes were also predicted between harvests. The Random Forest predictions of the texture related attributes (juiciness, toughness, crunchiness and stickiness of the skin) and sweetness were very good. The predictions of the attributes aroma intensity, sourness and fruity/apple were somewhat lower and more variable between harvests, especially in the second harvest. In general, we concluded that prediction of attributes with higher heritabilities works better and is more consistent over harvests (Chapter 4).

    Based on the results of the initial experiments (Chapter 2) the species C. baccatum was chosen for further study. To exploit the potential flavor wealth of C. baccatum PEN45 we combined interspecific crossing with embryo rescue, resulting in a multi-parent BC2S1 population, that was characterized for sensory and biochemical variation (Chapter 5). We developed a population specific genetic linkage map for QTL mapping of characterized traits. Because of the complex structure of our BC2S1 mapping population we encountered several limitations, such as accidental co-segregation, underrepresentation of color linked markers and pre-selection leading to skewness, which might have resulted in false positive or missed QTLs. Despite these limitations, we were still fairly well able to map several biochemical, physical and sensory traits, as demonstrated at first for the (monogenic) control traits red color and pungency in the BC2S1 mapping population and in second instance by validation of genetic effects via an experiment with near-isogenic lines (NILs).This two-step approach turned out to be very powerful, since it led to the identification of the main results from this thesis: (i) Asmall C. baccatum LG3 introgression causing an extraordinary effect on flavor, which resulted in significantly higher scores for the attributes aroma, flowers, spices, celery and chives. In an attempt to identify the responsible biochemical compounds few consistently up- and down-regulated metabolites were detected, including the well-known pepper compound 2-isobutyl-3-methoxypyrazine (down) and 6-methyl-4-oxo-5-heptenal (up); (ii) Two introgressions (LG10.1 and LG1) had major effects on terpenoid content of mature fruits, affecting at least fifteen different monoterpenes; (iii) A second LG3 fragment resulted in a strong increase in Brix (total soluble solids) without negative effects on fruit size (Chapter 5).

    In Chapter 6 some extra sensory results of the pungent genotypes are given and a comparison between the two C. baccatum pendulum BILs (PEN45 and PEN79 derived) is made in light of the overall results. Finally the perspectives for breeding are discussed and presented in the form of a flowchart for flavor improvement.

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