Are you P. Walstra?

Claim your profile

Publications (35)8.39 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The aim of the present study (part of an EU AIR programme on boar taint) was to make objective the perception of boar taint in entire male pork, and to relate the perception to skatole and androstenone levels. Trained analytical sensory panels in seven European countries assessed pig meat with known levels of androstenone and skatole. The panels performed a sensory profiling using the attributes pig, urine, manure/stable, naphthalene/mothballs, rancid, sweet, sweat and abnormal, both for odour and flavour in separate sessions. It turned out to be difficult to harmonise sensory methodology for seven sensory panels throughout the EU, especially with respect to the exact level of training the panellists received. Sensory panels in general were able to differentiate between the two compounds and between different levels of the compounds, though substantial differences between the panels in the different countries existed. Androstenone was found to relate mostly to the urine attribute, while skatole related mostly to manure and, to a lesser extent, to naphthalene.
    Meat Science 03/2000; 54(3):261-9. · 2.75 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: An international study, involving 11 participants in 7 European countries, was conducted to provide scientific evidence for an objective measurement of boar taint in entire male pigs and its possible variation between countries. The specific objectives were to determine the respective contributions of androstenone and skatole to boar taint and their possible variations according to production systems and consumer populations. Over 4000 entire male pigs and 200 gilts were raised and slaughtered in 6 countries. Meat samples were taken from the loin and backfat samples were used for the rapid measurement of androstenone and skatole. A sub-population of 377 entire males and 42 gilts was then selected in such a way as to represent all combinations of skatole and androstenone levels. Androstenone and skatole levels in the selected samples were checked, using established reference methods. Meat samples from the selected animals were used for sensory evaluation by trained panels and for consumer surveys in 7 European countries. The present paper gives a general presentation of the programme and reports the main characteristics of the samples. Three companion papers present the results of the evaluation by trained sensory panels [Dijksterhuis, G., Engel, B., Walstra, P., Font i Furnols, M., Agerhem, H., Fisher, K., Oliver, M. A., Claudi-Magnussen, C., Siret, F., Béague, M. P., Homer, D. B., & Bonneau, M. (2000). An international study on the importance of androstenone and skatole for boar taint: II. Sensory evaluation by trained panels in seven European countries. Meat Science54, 261-269], the results of the consumer surveys [Matthews, K. R., Homer, D. B., Punter, P., Béague, M. P., Gispert, M., Kemspter, A. J., Agerhem, H., Claudi-Magnussen, C., Fischer, K., Siret, F., Leask, H., Font i Furnols, M., & Bonneau, M. (2000). An international study on the importance of androstenone and skatole for boar taint: III. Consumer survey in seven European countries. Meat Science, 54, 271-283] and the main conclusions and recommendations [Bonneau, M., Walstra, P., Claudi-Magnussen, C., Kempster, A. J., Tornberg, E., Fischer, K., Diestre, A., Siret, F., Chevillon, P., Claus, R., Dijksterhuis, G., Punter, P., Matthews, K. R., Agerhem, H., Béague, M. P., Oliver, M. A., Gispert, M., Weiler, U., von Seth, G., Leask, H., Font i Furnols, M., Homer, D. B., & Cook, G. L. (2000). An international study on the importance of androstenone and skatole for boar taint: IV. Simulation studies on consumer dissatisfaction with entire male pork and the effect of sorting out carcasses on the slaughter line, main conclusions and recommendations. Meat Science, 54, 285-295]. Seasonal effects and differences between countries in skatole and androstenone levels are presented elsewhere [Walstra, P., Claudi-Magnussen, C., Chevillon, P., von-Seth, G., Diestre, A., Matthews, K. R., Homer, D. B., & Bonneau, M. (in press). An international study on the importance of androstenone and skatole for boar taint: Levels of androstenone and skatole according to country and season. Livestock Production Science]. A supplementary paper considers the effects of human sensitivity to androstenone and skatole on the consumer acceptance of entire male pork [Weiler, U., Font i Furnols, M., Fischer, K., Kemmer, H., Oliver, M. A., Gispert, M., Dobrowolski, A., & Claus, R. (in press). Influence of differences in sensitivity of Spanish and German consumers to perceive androstenone on the acceptance of boar meat differing in skatole and androstenone concentrations. Meat Science]. A study of possible other compounds contributing to boar taint was also carried out within this programme.
    Meat Science 03/2000; 54(3):251-9. · 2.75 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: An international study has been conducted in order to determine the respective contributions of androstenone and skatole to boar taint and their possible variations according to production systems and consumer populations. The presentation of the study and the main results concerning skatole and androstenone levels and data from sensory evaluation or consumer surveys are reported in companion papers. The present paper summarises the main conclusions of the study and gives tentative recommendations. A simulation study was conducted, based on the skatole and androstenone levels currently observed in European populations of entire male pigs and on the results of the consumer surveys. The first part of the simulation study demonstrated that, overall, 6.5% (odour) and 3.0% (flavour) more consumers were dissatisfied with entire male than with gilt pork. The differences were, however, very variable according to countries. Consumer dissatisfaction for the odour of entire male pork was mostly associated with high skatole levels, while androstenone had little influence on it. On the other hand, androstenone and skatole had similar contributions to the level of dissatisfaction for flavour. From the present study it is not possible to determine clear cut-off levels for androstenone/skatole. The regression equations presented in [Matthews, K. R., Homer, D. B., Punter, P., Béague, M. P., Gispert, M., Siret, F., Leask, H., Fonti i Furnols, M., & Bonneau, M. (2000). An international study on the importance of androstenone, skatole for boar taint: III. Consumer survey in seven European countries. Meat Science, 54, 271-283] provide a basis for decision making. However, due to methodological limitations, the results may underestimate consumer reaction to entire male pork. The second part of the simulation study demonstrated that sorting carcasses on the basis of androstenone/skatole would reduce, but not eliminate, differences in consumer dissatisfaction between entire male and gilt pork. For odour, taking androstenone into account did not improve the efficiency obtained from sorting using skatole only. For flavour, sorting using both compounds was more efficient than sorting using skatole only. Sorting out 15% of the entire males, on the basis of skatole only, would result in a difference in the proportion of dissatisfied consumers of 4.2% (odour) or 2.0% (flavour) between entire male and gilt pork. The results of the last part of the simulation study demonstrated that decreasing skatole in entire male pig populations, to levels as low as 0.10 ppm, would still result in a difference in the proportion of dissatisfied consumers of 3.2% (odour) or 1.6% (flavour). To reduce this difference further, the levels of both compounds would have to be reduced still further. The lowest difference that can be achieved is 2.3% (odour) or 0.4% (flavour). The conclusions of the present study may differ according to whether immediate commercial applications or long-term goals are considered. On the basis of the skatole and androstenone levels currently observed in entire male pig populations, sorting out procedures based on skatole is the easiest way to rapidly achieve a significant decrease in consumer dissatisfaction with entire male pork. In most countries, however, this will not be sufficient to obtain the same level of acceptability as with gilts. In the long term, a sharp reduction in both skatole and androstenone would have to be achieved in entire male pig populations to obtain low differences in acceptability between entire male and gilt pork.
    Meat Science 03/2000; 54(3):285-95. · 2.75 Impact Factor
  • B. Hulsegge, G.S.M. Merkus, P. Walstra
    Animal science 71, 2000, 253-257. 01/2000;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Fat samples from 43,13 entire males taken from six European countries were measured for androstenone and skatole using rapid ELISA and colourimetric methods, respectively. The samples were collected during summer (replicate 1) and during the following winter period (replicate 2). A sub-population of over 400 samples was further measured for androstenone and skatole using laboratory methods. For skatole, there were only small differences between rapid and laboratory measurements; therefore, the rapid measurements were used throughout. Rapid measurements of androstenone could not be used because of large differences with the laboratory measurements in replicate 2. Therefore, the rapid values of androstenone for the whole population were corrected based on the laboratory ELISA measurements. Mean skatole concentration differed between replicates, but there was no overall difference for androstenone. Significant country by replicate interactions were observed for both androstenone and skatole. Skatole levels were higher in replicate 1 than replicate 2 for the United Kingdom (0.15 vs. 0.11 μg/g), Sweden (0.13 vs. 0.10 μg/g) and the Netherlands (0.19 vs. 0.16 μg/g), whereas they did not differ between replicates for the other countries (Denmark, France and Spain). Androstenone levels were higher in replicate 2 than replicate 1 only for the Netherlands (0.69 vs. 0.86 μg/g), while the reverse was found in the United Kingdom (0.91 vs. 0.72 μg/g). Overall, the correlation coefficient between androstenone and skatole was 0.30. Apart from the interaction between countries and replicates, various countries within replicates differed for mean androstenone and skatole concentrations due to the different frequency distributions for both. Overall, the United Kingdom (0.81 and 0.54 μg/g), France (0.80 and 0.53 μg/g) and the Netherlands (0.79 and 0.53 μg/g) had the lowest mean and median concentrations for androstenone, whereas Sweden (1.22 and 0.82 μg/g) and Spain (1.27 and 0.85 μg/g) had the highest. The lowest mean concentration for skatole was found in Denmark (0.10 μg/g), while it was highest in the Netherlands (0.17 μg/g) and Spain (0.17 μg/g). Androstenone and skatole concentrations increased with increasing carcass weight and decreased with increasing lean meat percentage. However, the correlation coefficients were very low; about 0.10 for carcass weight and −0.15 for lean meat percentage. Overall, more than 60% of the entire males had androstenone levels above 0.5 μg/g and about 30% had levels above 1.0 μg/g. For skatole, 15% of the entire males had levels above 0.2 μg/g and more than 10% had levels above 0.25 μg/g, but there was a large variation between countries. In the Netherlands and Spain, about 20% of the entire males had skatole levels above 0.25 μg/g, while this was lower than 2% in Denmark.
    Livestock Production Science 12/1999;
  • Animal science 68, 1999, 641-645. 01/1999;
  • 'Boar taint in entire male pigs', No. 92 edited by M. Bonneau, K. Lundström, B. Malmfors, 01/1998: pages 7-10; EAAP Publication.
  • P. Walstra, B. Hulsegge
    Meat automation newsletter 1st issue, 1998. 01/1998;
  • In: Boar taint in entire male pigs. Proceedings of a meeting of the EAAP working group "Production and utilisation of meat from entire male pigs", Stockholm, Sweden 1-3 October 1997 / Michel Bonneau, Kerstin Lundström and Brigitta Malmfors (editors). - Wageningen : Wageningen Pers, 1997. - (EAAP Publication ; 92). - pp. 20-28. 01/1997;
  • In: Boar taint in entire male pigs. Proceedings of a meeting of the EAAP working group "Production and utilisation of meat from entire male pigs", Stockholm, Sweden 1-3 October 1997 / Michel Bonneau, Kerstin Lundström and Brigitta Malmfors (editors). - Wageningen : Wageningen Pers, 1997. - (EAAP Publication ; 92). - pp. 7-10. 01/1997;
  • Praktijkonderzoek Varkenshouderij. Proefverslag nummer P.181 (1997) 52 pp. 01/1997;
  • Kints, Ch, E. Kanis, J. Huiskes, P. Walstra, Boer, Tj
    Praktijkonderzoek Varkenshouderij 7,3 (1993) 23-27. 01/1993;
  • Kints, Ch, E. Kanis, J. Huiskes, P. Walstra, Boer, Tj
    Vleesdistributie & Vleestechnol. 8 (1993) 12-15. 01/1993;
  • [Show abstract] [Hide abstract]
    ABSTRACT: A long-distance international transport of live pigs was simulated by transporting 216 pigs (± 100 kg live weight) around through The Netherlands for two days; 100 control pigs were slaughtered at start. The experimental pigs were allocated to groups with and without access to water and three different loading densities (0.66, 0.44 and 0.33 m2 per pig) during the transport. The watered pigs used 5.4 ] per pig during the 44 h of transport, part of which was wasted by leaning on the bite waternipples. Hence, water consumption was very low. In the high density compartments not all pigs could lie down at the same time, involving continuous alternation of lying down and standing up. During the two days the weather was warm (on average 22°C).After transport pigs had lost 8 kg live weight, half of which was lost carcass weight. The latter was mainly due to water loss, as illustrated by the increased fat/water ratio in the backfat (5.3 versus 4.1 in controls). It should be noted that the weight loss was a little higher in the watered groups than in the non-watered ones.Physiological parameters determined after slaughter in blood and urine did not indicate physiological imbalance due to non-watering or high loading density. These factors had no significant effect on meat quality parameters, except for higher pH1 and pH2 values in the high loading density group, indicating that these animals had got more fatigued. The experiment has shown that watering during transport by means of bite nipples is ineffective. It is suggested that loading densities should not exceed 235 kg body weight m−2 (0.44 m2 per pig of 100 kg) for reasons of animal welfare and meat quality.RésuméUn transport international à longue distance de porcs vifs a été simulé en faisant voyager 216 (± 100 kg de poids vif) pendant deux jours à travers les Pays-Bas, 100 porcs témoins ont été abattus au départ. Pendant le transport, les porcs expérimentaux étaient entre des groupes de concentration différentes de chargement (0.66, 0.44 ou 0.33 m2/porc) ayant ou non accès à l'eau. Les animaux abreuvés ont utilisé 5.4 l/porc au cours des 44 h. du transport; mais ils en ont gaspillé une partie en s'appuyant sur les poussoirs des têtines. Aussi la consommation d'eau a-t-elle été très faible. Dans les compartiments à densitéélevée, tous les porcs ne pouvaient pas se coucher simultanément, ce qui provoquerait des changements parmanents de position entre les stations debout et couchée. Pendant les deux jours, le temps était chaud (22°C en moyenne).Après le transport, les animaux avaient perdu huit kg de poids vif, dont la moitié au détriment de la carcasse, Celle-ci était principalement dûe à une perte d'eau, comme l'illustrait l'augmentation du rapport lipides/eau dans la graisse sous-cutanée (5.3, vs 4.1 chez les témoins). On peut noter que la perte de poids était légérement supérieure dans les groupes abreuvés que dans les autres.Les paramètres physiologiques déterminés dans le sang et l'urine après l'abattage n'indiquaient pas de déséquilibre dûà l'absence d'abreuvement ou à la densité de chargement élevé. Ces facteurs n'affectaient pas significativement les paramètres de qualité de viande, sauf les valeurs de pH1 et pH2 supérieures dans le groupe à densité de chargement la plus élevée indiquant que ces animaux étaient plus fatigués. Cette expérience montre que l'abreuvement pendant le transport au moyen de poussoirs est inefficace. Il est suggéré que la densité de chargement ne doit pas excéder 235 kg de poids vif/m2 (0.44 m2/porc de 100 kg) pour des raisons de bien être des animaux et de qualité de viande.ZusammenfassungUm einen internationalen Transport lebender Schweine über grosse Entfernungen zu simulieren, wurden 216 Schweine (± 100 kg Lebendgewicht) zwei Tage durch die Niederlande gefahren; 100 Kontrollschweine wurden geschlachtet, als die Fahrt der Versuchstiere begann. Für die Zeit des Transportes erfolgte eine Aufteilung der Versuchsschweine in Gruppen mit und ohne Zugang zur Tränke sowie in drei Gruppen mit unterschiedlicher Lade-Dichte (0.66, 0.44, 0.33 m2 pro Schwein). Die mit Wasser versorgten Schweine verbrauchten während des 44-stündigen Transportes 5.4 1 pro Tier, wobei jedoch ein Teil nicht aufgenommen wurde, sondern durch das Anlehnen an die Nippeltränken verloren ging. Folglich war die eigentliche Wasseraufnahme sehr gering. In den Abteilungen mit hoher Lade-Dichte konnten sich nicht alle Schweine zur gleichen Zeit hinlegen, so dass es zu einem beständigen Wechsel von Niederlegen und Aufstehen kam. Während der zwei Tage waren die Aussentemperaturen relativ hoch (φ 22°C).Nach dem Transport hatten die Schweine 8 kg Lebendgewicht bzw. 4 kg Schlachtkörpergewicht verloren. Dass der Verlust an Schlachtkörpergewicht hauptsächlich auf einen Wasserverlust zurückzuführen war, wurde anhand des erhöhten Fett/Wasser-Verhältnisses im Rückenspeck deutlich (5.3 im Vergleich zu 4.1 bei den Kontrolltieren). Es sollte noch erwähnt werden, dass der Gewichtsverlust bei den Gruppen mit Zugang zur Tränke geringfügig höher war als bei den Gruppen ohne Wasseraufnahmemöglichkeit.Die physiologischen Parameter, die nach der Schlachtung im Blut und im Harn bestimmt worden waren, zeigten kein gestörtes physiologisches Gleichgewicht aufgrund fehlender Wasserversorgung oder hoher Lade-Dichte. Diese Faktoren hatten — bis auf veränderte pH1 und pH2 Werte — keinen signifikanten Einfluss auf die Fleischqualität. Die erhöhten pH1 und pH2 Werte in den Gruppen mit hoher Lade-Diche waren ein Zeichen für den grösseren Erschöpfungszustand dieser Tiere.In der vorliegenden Untersuchung hat sich die Wasserversorgung von Tieren mit Hilfe von Nippeltränken während eines Transportes als ineffektiv erwiesen. Es wird vorgeschlagen, eine Lade-Dichte von 235 kg Korpergewicht/m2 (0.44 m2 pro Schwein mit 100 kg Lebendgewicht) aus Gründen des Tierschutzes und der Fleischqualität nicht zu überschreiten.
    Livestock Production Science. 01/1985;
  • P Walstra, G Mateman, P C Moerman
    Tijdschrift voor diergeneeskunde 09/1977; 102(15):857-70. · 0.13 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Onderzoek naar de voorspelbaarheid van de vleeskwaliteit van varkenskarkassen heeft aangetoond dat er een relatie bestaat tussen de HGP-meting en de vleeskwaliteit
    Praktijkonderzoek varkenshouderij 8 (1994) 5.
  • Lelystad : ID-Lelystad, 2000. - (intern rapport ; 2084).
  • Vleeskrant 20 februari (1998) 16.
  • In: Boar taint in entire male pigs. Proceedings of a meeting of the EAAP working group "Production and utilisation of meat from entire male pigs", Stockholm, Sweden 1-3 October 1997 / Michel Bonneau, Kerstin Lundström and Brigitta Malmfors (editors). - Wageningen : Wageningen Pers, 1997. - (EAAP Publication ; 92). - pp. 11-15.
  • Schweinezucht und Schweinemast 43, 1995, 12-14.