A sensory description of boar taint and the effects of crude and dried chicory roots (Cichorium intybus L.) and inulin feeding in male and female pork

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MEAT SCIENCE Meat Science 79 (2008) 252–269 www.elsevier.com/locate/meatsci

A sensory description of boar taint and the effects of crude and dried chicory roots (Cichorium intybus L.) and inulin feeding in male and female pork Derek V. Byrne

a,*

, Stig M. Thamsborg b, Laurits L. Hansen

c

a Department of Food Science, Faculty of Life Sciences, University of Copenhagen, Rolighedsvej 30, DK 1958 Frederiksberg C, Denmark Danish Centre for Experimental Parasitology, Department of Veterinary Pathobiology, Faculty of Life Sciences, University of Copenhagen, Dyrlaegevej 100, DK 1870 Frederiksberg C, Denmark Department of Food Science, Faculty of Agricultural Sciences, University of Aarhus, Blichers Alle´ 20, P.O. Box 50, DK-8830 Tjele, Denmark

b

c

Received 21 December 2006; received in revised form 11 September 2007; accepted 18 September 2007

Abstract Sensory profiling studies were carried out to evaluate the effects of chicory root (Cichorium intybus L.) and inulin bioactive feeding with respect to reducing the ‘off-flavour’ boar taint in intact male and female pork Longissimus dorsi and Psoas major. Feeding treatments significantly reduced perceived sensory boar taint in the cooked pork meat of intact males in both muscles. There were also indications that crude chicory was also effective in taint descriptor reduction in female pork, however not to the same systematic level as in male animals. Chemical measurements for skatole and androstenone were highly predictive of specific sensory descriptors of boar taint reduction. Feeding of crude, dried chicory and inulin were also determined not to impart negative sensory characteristics upon boar taint reduction. Chicory feeding therefore must be considered to have the potential for utilisation as part of a strategy for boar taint reduction in intact male pork.  2007 Elsevier Ltd. All rights reserved. Keywords: Chicory; Boar taint; Pork meat; Descriptive sensory profiling; Multivariate data analysis

1. Introduction Sensory boar taint is widely reported to have a distinctive and unpleasant character which evokes repulsion and rejection when perceived through a combination of odour, flavour and taste in pork and pork products during cooking and eating (e.g. Gunn et al., 2004). It has been described as consisting of key sensory characteristics reminiscent of ‘male pig’, ‘animal’, ‘urine’, ‘faecal’ and/or ‘sweat’ which are largely causal in terms of the negative reaction with respect to human sensory perception (e.g. Dijksterhuis et al., 2000; Gunn et al., 2004). It is widely considered that two compounds are largely causal in boar *

Corresponding author. Tel.: +45 35 33 31 99; fax: +45 35 33 31 74. E-mail address: [email protected] (D.V. Byrne).

0309-1740/$ - see front matter  2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.meatsci.2007.09.009

taint namely, 3-methyl indole and 5a-androst-16-3-one, commonly referred to as skatole and androstenone, respectively (e.g. Babol, Squires, & Gullet, 1996; Patterson, 1968; Vold, 1970; Walstra & Maarse, 1970). Sensory profiling, a method by which a panel uses a developed sensory vocabulary to describe perceived sensory boar taint characteristics in the sample sets has been utilised in the present research (see Byrne, O’Sullivan, Dijksterhuis, Bredie, & Martens, 2001a; Byrne et al., 2001b; ISO, 1985, 1994a, 1994b; Meilgaard, Civille, & Carr, 2007). The resultant profiles are perceptual maps of the variation in a sample type that can be employed alone or in combination with chemical/instrumental measurements and potentially consumer studies in the explanation and elucidation of underlying predictive and causal relationships (e.g. Bryhni et al., 2002, 2003).

D.V. Byrne et al. / Meat Science 79 (2008) 252–269

Boar taint is an issue which requires renewed attention as for welfare reasons it is likely that castration of male piglets without analgesia will most likely be prohibited in the future in the European Union (Gunn et al., 2004). Legislation prohibiting castration of pigs is already scheduled to take effect in Norway in 2009 (Landbruksdepartementet, 2002) and in Switzerland in 2009 (CSEC, 2005). A similar legislation is under discussion in relation to Danish organic pig production. Thus, there is a pressing need for alternative means and approaches to control or avoid boar taint in pig production. One such approach is the use of specific ‘bioactive’ ingredients i.e. foods that exert biological effects not directly related to the nutritive value. Chicory roots (Cichorium intybus L.) are a bioactive crop that has been shown to reduce skatole and androstenone in intact male and female pigs thus this may positively affect eating quality (Hansen et al., 2006a). The present research presents the sensory eating quality aspects with respect to a paper previously published which presents detailed feeding, production, growth and chemical results pertinent as background to the present articles feeding regimes (Hansen et al., 2006a). Hansen and co workers found that feeding chicory both in crude and dried form resulted in a significant reduction in boar taint related chemical compounds. The objectives of the present study were to investigate the sensory variation that resulted from the effects of various bioactive (crude/dried chicory and inulin) finishing feeding strategies in intact male and female cooked pork. Of specific focus was the effect of such bioactive feeding on the ‘off-odour/flavour’ referred to as boar taint in the meat samples. To achieve these aims descriptive sensory vocabularies were developed with expert sensory panels and subsequently these panels were utilised to develop a sensory profile for the sets of meat samples, derived from male and female animals fed chicory and inulin for differing periods of time prior to slaughter.

253

2. Materials and methods 2.1. Meat samples All experimental animals of two profiling investigations to be termed experiment 1 and 2, were Danish crossbred pigs of Duroc sire · zigzag crossbred dam of Danish Landrace · Large White (D· (L · Y) produced at Faculty of Agricultural Sciences, Tejle, University of Aarhus. In experiment 1 both intact male (total no. = 16) and female pigs (no. = 16) were used, intact male pigs only were used in experiment 2 (total no. = 32), (see Table 1 and Hansen et al., 2006a for additional details). The animals were treated in accordance with the guidelines outlined by The Danish Inspectorate of Animal Experimentation, which also gave permission to take blood samples. At the approved abattoir at Faculty of Agricultural Sciences, Tejle, University of Aarhus, the pigs were supervised by a veterinary surgeon before and after slaughter. Specific details of diet compositions are presented in Hansen et al. (2006a) and these conformed to Danish recommendations (Madsen, Petersen, and Soegaard, 1990). A summary of experiment 1 treatments, organic concentrate (control), (ConCtrl), organic concentrate + silage (OrgCtrl), and organic concentrate + crude chicory, 4 and 9 weeks (CC4 and CC9) are presented in Table 1. In the second experiment, pigs were allocated to the following four treatments organic concentrate + silage (control), (OrgCtrl) and organic concentrate + crude and dried chicory, 6 weeks (CC6, DC6) and Inulin, 6 weeks (I6) (Table 1). 2.2. Sample preparation for sensory profiling 2.2.1. Experiment 1. Profile Longissimus dorsi 1 (patties), intact male, and female animals All Longissimus dorsi 1 (LD 1) muscles were stored vacuum packed in darkness at 20 C until required for sen-

Table 1 Control and experimental diets for experiment 1, crude chicory feeding for 4 and 9 weeks and experiment 2, crude, dried chicory and inulin feeding for 6 weeks prior to slaughter Treatment

Treatment abbreviations

Organic concentrate

Clover grass silage

Chicory roots Crude (CC)

Dried (DC)

Inulinc (I)

Experiment 1 Organic concentrate (no silage) Organic concentrate + silage Organic concentrate + crude chicory 4w Organic concentrate + crude chicory 9w

ConCtrl OrgCtrl CC4 CC9

100d 95 95a/70b 70

– ad libitum ad libituma/–b –

– – –a/25b 25

– – – –

– – – –

Experiment 2 Organic concentrate + silage Organic concentrate + crude chicory 6w Organic concentrate + dried chicory 6w Organic concentrate + inulin 6w

OrgCtrl CC6 DC6 I6

95 70 70 70

ad libitum – – –

– 25 – –

– – 25 –

– – – 14

a

Control treatment (OrgCtrl) day 0 to 35 (i.e. 5 weeks). Supplemented with chicory (CC4) day 35 to 63 (i.e. the last 4 weeks (w) before slaughter). c RaftilineHP, Orafti Ltd., Belgium (produced from chicory roots). d According to Danish recommendations by Madsen et al. (1990) all energy values are given as % of total energy intake per day (see Hansen et al., 2006a). b

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sory analysis. Muscles were held at 4 C for approx. 12 h prior to handling to allow ease of cutting and grinding LD 1 muscles were cut into cubes (approx. 3 cm3) and mixed thoroughly. Muscles from a specific treatment (4 animals per treatment) were utilised, and mixed together thoroughly once cubed. Each treatment batch of muscle cubes was ground in a rotary screw mincer (Model X 70, Scharfen GmbH & Co. Maschinenfabrik KG, Germany) through a 4.5 mm plate. The minced samples were shaped into patties of 100 g and approx. 1 cm thickness using a commercial pattie maker (i.d. 9 cm). Plastic packaging film was used in the making of the patties to help maintain their shape prior to vacuum bagging. Patties were subsequently removed from their plastic film wrapping and vacuum packed in oxygen impermeable plastic laminate bags. The vacuum packed patties were then frozen at 30 C and stored for maximum of up to one week. Comminuted meat patties were used in the initial profile of experiment 1 as the focus was purely on the odour and flavour characteristics, their description and discriminative ability for the different samples. In addition, in comminuted form the sample preparation, presentation, cooking, and presentation were highly standardisable which was a requirement from the perspective that this initial study was of a model nature for determining the sensory characteristics of feeding chicory on boar taint (see Byrne et al., 2001b). 2.2.2. Experiment 1. Profile Psoas major 1 (whole cuts), intact male animals Based on the feeding effects determined for the LD 1 from the intact male animals PM of experiment 1 and all subsequent muscles were analysed as steaks/cutlets from whole muscles to introduce texture as a variable and to mimic treatment as the average consumer may prepare and consume this type of meat. Each muscle type was derived from animals fed treatments as per LD 1 (see Table 1). A total of 4 individual animals’ muscles were utilised for each feeding treatment. All muscles were stored vacuum packed in darkness at –20 C. Muscles were held at 4 C for approx. 12 h prior to handling to allow ease of cutting. Muscles were cut into individual ‘steaks’ (approx. 1 cm thickness). Individual samples were subsequently vacuum packed in oxygen impermeable plastic laminate bags. The vacuum packed chops were then frozen at 30 C and stored for up to one week prior to profiling. 2.2.3. Experiment 2. Profiles, Longissimus dorsi 2 (whole cuts) and Psoas major 2 (whole cuts), intact male animals Pork muscles Psoas major 2 (PM 2) and Longissimus dorsi 2 (LD 2) from entire male pigs were used for sensory profiling in experiment 2. Each muscle type was taken from animals fed one of four different feeding treatments (see Table 1). A total of 8 individual animals’ muscles were utilised for each feeding treatment. All muscles were stored vacuum packed in darkness at 20 C. Muscles were held at 4 C for approx. 12 h prior to handling to allow ease of cutting. Muscles were cut into chops (approx. 1 cm

thickness). Individual cutlets were subsequently vacuum packed in oxygen impermeable plastic laminate bags. The vacuum packed chops were then frozen at 30 C and stored for up to one week prior to use in profiling. 2.3. Heat treatment, storage and reheating for profiling Prior to heat treatment, all experiment 1 LD patties were placed in a 25 C water bath until a core temperature of between 18 and 20 C had been reached. Subsequently patties were removed from their plastic vacuum bags and batch cooked in convection ovens set to 150 C. The heating/cooking process took a total of 20 min and was carried out as per Byrne, Bak, Bredie, Bertelsen, & Martens, 1999a; Byrne, Bredie, & Martens, 1999b. The final internal temperature reached over all pattie batches was found to vary between 78 and 82 C. After cooking the samples were cooled to 5 C in oxygen impermeable plastic laminate bags for a short period (10–15 min) prior to reheating for sensory assessment. To prepare the samples for sensory profiling, patties were placed in a steel tray filled with water at ambient temperature. For reheating the tray was placed in a convection oven at 140 C for 19 min. The mean serving temperature of the vacuum packed samples was 65 C. In the case of experiment 1 PM1 and experiment 2 LD2 and PM2 the heating/cooking process at 150 C was determined to take a total of 8 min 4 minutes per side. After cooking the samples were immediately served to the panellists (within 3 min) such that the serving temperature of the samples varied between 65 and 68 C. 2.4. Sensory analyses 2.4.1. Selection of panellists The selection of judges per se for profiling was carried out in accordance with ISO 1993, 1994a, 1994b. Overall, panellists ultimately to be utilised in profiling were required to display sensitivity to skatole and androstenone, be able to describe each compound from the perspective of their common unpleasant sensory odour description and finally be able to detect each to a designated minimum concentration. A final selection of eight judges in experiment 1 was made based on those persons who were displayed the ability to detect minimum concentrations of at least 0.3 lg/ml androstenone and 0.1 lg/ml skatole. An identical selection process was carried out to obtain the 10 judges that were part of experiment 2 profiling. The methodology utilised in the panellist selection was based largely on the method previously presented by Banon, Costa, Gil, and Garrido (2003). 2.4.2. Descriptive sensory vocabulary development Prior to sensory profiling the sensory panels (Experiment 1, Profile 1 LD1 = 8 persons, Experiment 1 Profile 2 PM 1 and Experiment 2, Profile 3 LD2 and 4 PM2 utilised the same 10 persons) participated in the development of a sensory vocabulary to describe and discriminate the effects of

D.V. Byrne et al. / Meat Science 79 (2008) 252–269

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Table 2 List of 54 sensory descriptive characteristics plus overall impression, with definitions developed for the evaluation of cooked pork meat derived from entire male and female pigs fed either organic concentrate/less silage, organic control/plus silage, crude or dried chicory, or inulin Termc,d

Definitions and reference materialse

Odour 1. Fresh cooked pork meat-Oa/b 2. Sweet meaty-Ob 3. Nutty-Ob 4. Piggy/Animal-Oa/b 5. Gamey-Oa/b 6. Urine-Ob 7. Parsnip-Ob 8. Musty-Ob 9. Manure-Ob 10. Sweat-Ob 11. Chicory (fresh)-Ob 12. Feedy-Ob 13. Hay/Silage-Ob 14. Soapy-Ob 15. Linseed oil-Oa 16. Cardboard like-Oa

Aromatic associated with: Oven cooked pork meat with no on surface browning

Texture 17. Hardness-Txb 18. Tenderness-Txb 19. Juiciness-Txb 20. Fibrous-Txb

Textural impression associated with: Force required to bite completely through the sample with molars Ease with which the meat is divided into fine particles when chewed The amount of liquid exudate in the mouth when one has chewed the sample 5 times The amount of fibers appearing during mastication

Taste 21. 22. 23. 24. 25.

Taste associated with: Sodium chloride, 0.5 g/l solution in water Quinine chloride, 0.05 g/l solution in water Ymer/natural yoghurt/formage frais Sweet fresh cooked pork The ’blooming’ flavour enhancing taste of monosodium glutamate, a solution 0.5 g/l MSG in water

Flavour 26. 27. 28. 29. 30. 31. 32. 33.

Salt-Ta Bitter-Ta Sour-Ta/b Sweet-Ta/b Umami-Tb

34. 35. 36. 37. 38.

Metallic-Fa Herby-Fa Spicy-Fa Cooked Ham-Fa Lactic/Fresh sour-Fa White pepper-Fa Pork fat-Fa Fresh cooked pork meat-Fa/b Cooked pork fat-Fa/b Piggy/Animal-Fa/b Gamey-Fa/b Parsnip-Fb Manure-Fb

39. 40. 41. 42. 43. 44. 45. 46. 47.

Livestock/Barny-Fb Feedy-Fb Hay-Fb Spicy-Fa/b Chicory (water)-Fb Chicory (flakes)-Fb Cardboard like-Fa/b Serum/Metallic-Fb Cooked liver/Organy-Fb

Aftertaste 48. Astringent-ATa/b 49. Chemical medicinala 50. Fresh sour/Lactic-ATa/b 51. Flat Bitter-ATb 52. Heat/Spicy-ATa/b

Fresh cooked pork its sweetness characteristics Crushed roasted hazel nuts Cooked pork meat from entire male pigs/diluted skatole solution Freshly cooked game meat as exemplified by deer, pheasant or wild boar Male pig urine (presented in sealed vessel with perforated cover for assessment) Cooked parsnip/earthy/sweet Stale damp/moist old fabric/cloth sealed in plastic for 5 days/moist cellar Male pig excrement/faeces (presented in sealed vessel with perforated cover for assessment) Old human body sweat/Swiss cheese Flaked fresh chicory root Blended barley grains and water (50/50) Dry hay/fermented hay (silage) Non-perfumed liquid soap Warmed linseed oil/linseed oil based paint Wet cardboard

Aromatic taste sensation associated with: Ferrous sulphate, 0.1 g/l solution in water Dried mixed herbs Mixed spices Cooked ham Natural yoghurt White pepper Cooked pork fat Oven cooked pork meat with no on surface browning Freshly cooked pork fat Cooked pork meat from entire male pigs Freshly cooked game meat as exemplified by deer, pheasant or wild boar Cooked parsnip/earthy/sweet Male pig excrement/faeces. Reference presented in sealed vessel with perforated cover for assessment aim to allow it to evoke ‘flavour’ Flavour of white pepper just after the initial soapy notes and before the strong peppery notes Blended barley grains and water (50/50) Flavour of dried grass Spicy flavour from salami Water cooked with dried chicory root (4:1 w/v) Dried chicory root flakes after soaking in boiling water Wet cardboard Cooking losses from pan fried pork mince meat with high meat content (max 8–12% fat) Freshly cooked liver Aftertaste sensation associated with: Solution 0.02 g/l aluminum sulphate in water. Drying sensation in mouth and on teeth. Cough syrup Ymer/natural yoghurt Bitter aftertaste from chicory Salami heat 30 s after eating (continued on next page)

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Table 2 (continued) Termc,d 53. 54.

Definitions and reference materialse b

Salty-AT Fatty mouthcoatingATa/b

Preference 55. Overall Impressiona/b a b c d e

Sodium Chloride (NaCl) (basic salt) (0.5 g/l) aftertaste Residual fatty coating in mouth once meat expectorated Preference associated with: Question: to which degree do you like the pork sample you have just tasted? Scored as dislike very much to like very much on an unstructured 15 cm line scale

Experiment 1 – feeding description see Table 1 (derived from patties). Experiment 2 – feeding description see Table 1 (derived from whole cuts). Suffix to sensory terms indicates method of assessment by panellists; O = Odour; F = Flavour; T = Taste; AT = Aftertaste; Tx = Texture. Concentrations in g/l were devised to ensure panellists’ could recognise clearly the sensory note involved. Definitions of sensory terms as derived during vocabulary development.

organic control plus/minus silage and bioactive feeding on the sensory characteristics and in particular from the perspective of the boar taint sensory aspects in the pork meat of the present study (see Byrne et al., 2001a, 1999a, 1999b). All sensory work was carried out in the sensory laboratory at the University, which fulfills requirements according to the international standards (ASTM, 1986; ISO, 1988). The sensory descriptor lists developed for experiment 1 and 2 are presented in combination as Table 2. 2.4.3. Descriptive sensory profiling Each sensory descriptive profile in experiment 1 and 2 was carried out over four 2-h sessions by the trained panel (see Byrne et al., 2001b; ISO, 1985; Meilgaard et al., 2007). The sample sets presented at the profiling studies contained all four treatments in each of experiment 1 and 2. This sample set (4) was assessed by each of the 8 panel assessors 4 times, as replicates (4 · 8 · 4 = 128 ‘objects’) in the profile data set for each of the 25 sensory terms (Table 2), in the case of experiment 1 sample sets. For experiment 2 sample sets the 4 treatments were assessed by each of 10 panel assessors 4 times, as replicates (4 · 10 · 4 = 160 ‘objects’) in the profile data set for each of the 43 sensory terms (Table 2). In both experiment 1 and 2 profiles each replicate was presented on each of 4 days to each panellist, 4 samples per day. In all 4 days of panel sessions of 1.5 h each were carried out in the development of each profile. Sample presentation to individual panellists on each day of profiling was in a randomised order. 2.4.4. Data acquisition Quantitative vocabulary development and profiling data were collected using the FIZZ Network data acquisition software version 2.20C (BIOSYSTEMES, Couternon, France). Unstructured line scales of 15 cm anchored on the left side by the term ‘none’ and on the right side by the term ‘extreme’ were used for the scoring of each sensory term (Meilgaard et al., 2007). 2.5. Chemical analyses Blood samples from Vena jugularis for plasma were collected in heparinised vacuum tubes in weeks 0 and 8 in trial 1

and weeks 0 and 6 (the day before slaughter) in experiment 2 for analysis of androstenone and skatole. Androstenone was measured by direct immunochemical analysis of the blood plasma samples (Tuomola, Harpio, Knuuttila, Mikola, & Lo¨vgren, 1997). Skatole in blood plasma was measured according to the HPLC method described by HansenMøller (1998) and modified by omitting the column switching procedure and injecting the protein-precipitated plasma directly on a Hypersil 3 lm 3 · 60 mm column. The lower limit of quantification was 0.12 lg L 1. Indole analyses were performed as per the skatole analyses in plasma. In both experiments backfat samples were collected 45 min post slaughter and skatole equivalents measured by the automatic spectrophotometric method described by Mortensen and Sørensen (1984). 2.6. Data analyses 2.6.1. Univariate analysis of variance, ANOVA Analysis of Variance (ANOVA) on chemical measurements for skatole in backfat/blood and androstenone in blood with respect to feeding treatments in experiment 1 and 2 was carried out using the Statistical Analysis System release 8.20 and the procedure, general linear model (GLM), (SAS Institute., 2000; see Hansen et al., 2006a). 2.6.2. Multivariate analysis To visualize and determine the descriptive ability of the sensory profiling data sets for the sample treatments quantitative ANOVA Partial Least Squares Regression (APLSR) was performed where the X-matrix was set as design main effect 0/1 variables for feeding treatments and the Y-matrix was designated sensory data (Martens & Martens, 2001). In this analysis the sensory data were preprocessed with Generalised Procrustes Analysis (GPA) using Matlab 6.5 (MathWorks Inc., USA), such that assessor level and range of scale used effects were removed (see Byrne et al., 2001a; Dijksterhuis & Gower, 1991; Martens & Martens, 2001). To determine the predictive ability of the sensory data for selected boar taint relevant chemical measurements (skatole in blood and back fat, androstenone in blood), Partial Least Squares Regression (PLSR) was performed where the X-matrix was set as the level of

D.V. Byrne et al. / Meat Science 79 (2008) 252–269

scale use corrected sensory characteristics (odour/flavour/ taste/aftertaste) and the Y-matrix was designated as selected boar taint relevant chemical measurements. To derive significance indications for the relationships determined in the quantitative APLSR and predictive PLSR, regression coefficients were analysed by jack-knifing which is based on cross-validation and stability plots (Martens & Martens, 2001). For reasons of focus and brevity key boar taint descriptors only are included in Tabulated form in the present article while the remaining relationship significances presented in the text where relevant. All multivariate analyses were performed using the Unscrambler Software, Version 9.6 (CAMO ASA, Trondheim, Norway). In all regression analysis data were analysed unstandardised, centered and with full cross-validation. 3. Results 3.1. Sensory descriptive profiling, experiment 1: crude chicory 3.1.1. M. Longissimus dorsi, experiment 1 – intact males Fig. 1 presents the APLSR correlation loadings plot (PC1 versus PC2) for LD1 male for the model based on X-matrix = experimental feeding treatments 1, ConCtrl, OrgCtrl, CC4 and CC9 and Y-matrix = sensory characteristics (Tables 1 and 2). This model presented 3 significant PCs, PC1 (39% Y-explained variance) was spanned by the feeding strategies ConCtrl versus CC4 and CC9. PC2 (31%) was spanned by the OrgCtrl and the third compo-

nent (30%) described the specific differences between CC4 and CC9 sensory variation. With respect to ConCtrl, these samples were described by pork meatiness-flavour (P < 0.001), sweet-taste (P < 0.001), pork fat-flavour (P < 0.001), cooked ham-like flavour (P < 0.001) and lactic/fresh flavour (P < 0.01). Of key importance here was the additional association of these samples was a high level of boar taint as described by Piggy/Animaly-flavour and odour. For Piggy/Animal-flavour this was determined to be significant at the 5% level (Table 3). In the case of OrgCtrl, these samples appear not as ‘fresh’ in relation to meatiness compared to ConCtrl, with a significantly low level of pork meat flavour (P < 0.05) and relatively, significantly high levels of the sensory boar taint off-characteristics, Piggy/Animal odour and flavour both at the P < 0.01 level (Table 3).With respect to crude chicory CC4 and CC9, these samples collectively can be described as having fresh pork meat odour (CC4 = P < 0.01, CC9 = P < 0.05), bitter-taste (CC4 = P < 0.0001) and astringent-aftertaste (CC9 = P < 0.001). Overall, both were found, relative to ConCtrl and OrgCtrl diets, to have lower scores for the boar taint descriptor Piggy/Animal-flavour. This was significant in the case of CC4 (P < 0.001) (Table 3). For the boar taint characteristic Piggy/Animal odour, feeding of crude chicory for 9 weeks was also found to be significantly lower than controls (P < 0.001). In relation to overall impression both CC4 and CC9 were found to display higher overall impression, CC4 significantly so (P < 0.05). As for the ConCtrl and OrgCtrl diets both displayed significantly lower levels of

Fatty mouthcoating-AT

White pepper-F

1.0

Gamey-O

Principal Component 2 (Y-explained variance 31%)

OrgCtrl

Piggy/Animal-O Piggy/Animal-F

Heat/Spicy-AT

Chemical/medicinal-AT

Spicy-F

0.5

257

Herby-F Sour-T

Salt-T Cooked pork fat-F

Cardboard-F

0.0

Linseed oil-O

Fresh cooked pork meat-O

Fresh cooked pork meat-F

CC4

Sweet-T Cardboard-O

Bitter-T

ConCtrl

Metallic-F Cooked Ham-F Lactic/Fresh sour-AT

-0.5

Gamey-F

Lactic/Fresh sour-F

CC9

Overall Impression

Astringent-AT

-1.0 -1.0

-0.5

0.0

0.5

1.0

Principal Component 1 (Y-explained variance 39%) Fig. 1. Longissimus dorsi 1 – Male (LD 1) (PC 1 v 2). ANOVA Partial Least Squares Regression (APLSR) correlation loadings plot of feeding treatment design variables (X-matrix) versus sensory profiling variables (Y-matrix). Ellipses represent r2 = 50 and 100%.

I6

+0.141 ns +0.438** 0.850*** 0.097 ns 0.066 ns +0.087 ns 0.063 ns +0.141 ns +0.125 ns 0.439*** 0.933*** +0.301** 0.305* 0.596 ns 0.0191 ns 0.067 ns +0.117 ns 0.661*** +0.191 ns +0.263*** 0.492*** 0.172 ns 0.279 ns 0.522*** 0.245** 0.452 ns +0.568*** +0.107 ns +0.231** +1.040*** +0.576*** +0.405*** +0.453** +0.376** 0.107 ns 0032 ns 0.538** 0.132 ns 0.660*** 0.017 ns 0.340** +0.701*** 0.045 ns +0.209 ns +0.365*** 0.077 ns 0.121 ns +0.166 ns 0.084 ns 0.078 ns 0.306** +0.329** +0.18 ns +0.0311 ns +0.614*** +0.688*** +0.290** 0.376*** 0.141 ns 0.716*** 0.046 ns +0.216** +0.037 ns +0.001 ns 0.433 *** +0.203* +0.477*** +0.559*** +0.320* 0.237* 0.609*** 0.434*** +0.056*** +0.531*** 0.537*** 0.619*** 0.965*** 0.413*** 0.248* 0.229 ns +0.505***

Estimated regression coefficients including sign (±) for treatment correlation derived from ANOVA Partial Least Squares Regression (APLSR). b

a

na = not applicable.

***Significant at the 0.1% level (P < 0.001), **Significant at the 1% level (P < 0.01), *Significant at the 5% level (P < 0.05), ns = Non-significant (P > 0.05).

+0.002ns 0.343*** 0.179 ns +0.020 ns 0.412*** 0.732*** +0.001 ns +0.294* +0.151* 0.485*** +0.343* +0.143 ns +0.221* +1.076*** +0.740*** 0.225* +0.304* 0.128 ns 0.311** +0.221 ns +0.394*** +0.535*** na na na na 0.254 ns 0.887*** 0.027 ns 0.397* 0.429** na na na na 0.049* +0.450* 0.111 ns +0.018 ns +0.549*** na na na na +0.158 ns +0.749*** 0.082 ns 0.016 ns 0.655*** na na na na +0.145 ns +0.278* 0.564*** 0.794*** 0.267 ns na na na na +0.563 ns +0.530** 0.072ns +0.109 ns 0.391*** na na na na +0.153* 0.024 ns 0.325* +0.454** +0.426** na na na na 0.378*** 0.784*** +0.96*** +0.230 ns +0.231* na na na na 0.338**

CC4 OrgCtrl

overall impression, (P < 0.01) and (P < 0.001), respectively when compared to feeding of crude chicory for 4 and 9 weeks (Fig. 1, Table 3).

0.078 ns 0.531*** +0.573*** +0.378*** +0.300* +0.405* +0.473*** 0.369* 0.528***

CC4 OrgCtrl ConCtrl CC9 CC4 ConCtrl ConCtrl

OrgCtrl Profile 1 Profile 1

CC9

Female LD 1 Male LD 1

Experiment 1a,b crude chicory Terms

Pork meat-O Pork meat-F Piggy/Animal-O Piggy/Animal-F Manure-O Manure-F Sweat-O Urine-O Overall Impression

Profile 2

OrgCtrl I6 DC6 CC6 OrgCtrl

Profile 2 Profile 2

CC9

Male LD 2 Male PM 1

Experiment 2 crude/dried chicory and inulin

Male PM2

CC6

DC6

D.V. Byrne et al. / Meat Science 79 (2008) 252–269

Table 3 Longissimus dorsi (LD) and Psoas major (PM) from experiment 1 and 2, significance of APLSR derived estimated regression coefficients for the relationships of key boar taint relevant sensory descriptors to the design indicators as derived by jack-knife uncertainty testing

258

3.1.2. M. Longissimus dorsi, experiment 1 – females The sensory profiling results are presented as an APLSR correlation loadings plot (Fig. 2, PC1 versus PC2) for LD 1 female meat for the model based on X-matrix = experimental feeding treatments as per males and Y-matrix = sensory characteristics (see Tables 1 and 2). This model presented 3 significant PCs, were PC1 (43% Y-explained variance) differentiated the feeding strategies ConCtrl and CC4, PC2 (34%) the OrgCtrl and CC9 versus ConCtrl and the third component (24%) described the subtle sensory differences between OrgCtrl and CC9 sensory variation. A qualitative and quantitative change in the sensory properties of the female meat was apparent for both CC4/CC9 and OrgCtrl feeding, when compared to ConCtrl (Fig. 2). However, this did not result in a significant decrease in scores for the boar taint descriptors Piggy/Animal odour/flavour, particularly in the case of CC9. On the contrary, CC9 was found along with OrgCtrl to result in a significant increase in boar taint scores (Table 3). Moreover, the ConCtrl is the treatment which presented the highest correlation to fresh pork meat characteristics. This is highly significant (P < 0.001) with respect to Pork meat odour. Of the crude chicory feeding regimes CC4 alone resulted in a significant decrease in the boar taint descriptors Piggy/Animal odour (P < 0.05) and Piggy/Animal-flavour (P < 0.01). Thus, an indication that chicory feeding does indeed reduce aspects of boar taints influence in terms of off-flavour in female animals. However, this was not translated in to an elevated overall impression, CC4 in fact presented a significantly negative correlation to overall impression when compared to ConCtrl (Table 3). 3.1.3. M. Psoas major, experiment 1 – intact males Fig. 3 presents the APLSR correlation loadings plot (Fig. 3, PC1 versus PC2) for PM 1 intact males for the model based on X-matrix = experimental feeding treatments as per LD 1 and Y-matrix = sensory characteristics (see Tables 1 and 2). This model presented 3 significant PCs, PC1 (44% Y-explained variance) was spanned by the feeding strategies ConCtrl and OrgCtrl versus CC4 and CC9 crude chicory feeding. PC2 (31%) was spanned by the specific sensory differentiation of CC4 versus CC9. PC 3 (24%) was determined to describe the specific sensory differences between ConCtrl/OrgCtrl and CC9. As found in the LD 1 intact male samples, Fig. 3, displayed PM 1 samples from animals fed ConCtrl to be positively correlated and therefore higher in sensory terms that can be ascribed as boar taint related, significantly so in the case of e.g. manure/stable odour (P < 0.05)/flavour (P < 0.05), piggy/animal odour (P < 0.001)/flavour (P < 0.001) and sweat odour (P < 0.001) (see Table 3). Similar associations were found for OrgCtrl, except in the case of sweat odour which was significantly (P < 0.05) nega-

D.V. Byrne et al. / Meat Science 79 (2008) 252–269

1.0

259

Piggy/Animal-F Lactic/Fresh sour-AT

Principal Component 2 (Y-explained variance 34%)

Fatty mouthcoating-AT

CC9

Piggy/Animal-O

Gamey-F

Fresh cooked pork meat-F

Cardboard-F

Sour-T

Metallic-F

Spicy/Heat-AT

0.5

Astringent-AT

Herby-F

Linseed oil-O

OrgCtrl Gamey-O

0.0 Chemical/medicinal-AT

Fresh cooked pork meat-O

White pepper-F

Cardboard-O

-0.5

Cooked pork fat-F

CC4

Spicy-F Salt-T Overall Impression

ConCtrl

Cooked Ham-F

Bitter-T

Lactic/Fresh sour-F Sweet-T

-1.0 -1.0

-0.5

0.0

0.5

1.0

Principal Component 1 (Y-explained variance 43%) Fig. 2. Longissimus dorsi 1 – Female (LD 1) (PC 1 v 2). ANOVA Partial Least Squares Regression (APLSR) correlation loadings plot of feeding treatment design variables (X-matrix) versus sensory profiling variables (Y-matrix). Ellipses represent r2 = 50 and 100%.

Juciness-Tx

1.0

Principal Component 2 (Y-explained variance 31%)

Sweet-T Lactic/Fresh sour-AT

Tenderness-Tx

CC4 Sour-T Parsnip-O

Urine-O

Cooked liver/Organy-F

Serum/Metallic-F

0.5

Gamey-F

Astringent-AT Feedy-F Spicy-F

Hay-F

Piggy/Animal-F

Heat/Spicy-AT Manure/Stable-O

0.0

Overall Impression Gamey-O

Chicory (flakes)-F Salty-AT

OrgCtrl

Fibrous-Tx

Piggy/Animal-O Livestock/Barney-F

Sweat-O Flat bitter-AT

Fresh cooked pork meat-O

-0.5

Fresh cooked pork meat-F

Chicory (fresh)-O

Cardboard-F

Manure/Stable-F

ConCtrl

Feedy-O

Musty-O

Chicory (water)-F

CC9

Soapy-O Sweet meaty-O Parsnip-F Nutty-O Hardness-Tx

Fatty mouthcoating-AT Hay/Silage-O Cooked pork fat-F

-1.0 -1.0

-0.5

0.0

0.5

1.0

Principal Component 1 (Y-explained variance 44%) Fig. 3. Psoas major 1 – Male (PM 1) (PC 1 v 2). ANOVA Partial Least Squares Regression (APLSR) correlation loadings plot of feeding treatment design variables (X-matrix) versus sensory profiling variables (Y-matrix). Ellipses represent r2 = 50 and 100%.

tively correlated and therefore low in these samples (Table 3). In contrast animals fed crude chicory CC4 and CC9, were determined to be significantly negatively correlated

with these boar taint descriptors and therefore crude chicory feeding had a significant boar taint reducing ability as per LD 1 intact males (Fig. 1 and Table 3). Specifically,

260

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bite than CC4 and control feeding. This however, did not appear to contribute to reducing the overall impression in the case of CC9, on the contrary CC9 scored higher in this respect in the present profile. Thus, indicating that the changes in texture in the PM 1 profiling sample set were relatively less important compared with the levels of boar taint reduction in terms of overall impression.

CC9 was determined to be the most effective in relation to boar taint reduction, in that after 9 weeks of feeding the samples were, e.g. significantly higher in fresh pork meat odour/flavour (P < 0.001) and sweet meaty odour (P < 0.01) characteristics relative to the control fed samples. This was also found for CC4 however, in comparison to 9 weeks crude chicory feeding, CC4 appeared not as effective in boar taint reduction such that a number of taint descriptors were less significantly reduced (Table 3). Moreover, CC4 was only significantly correlated with fresh pork descriptor for flavour. In addition, CC4 was found positively correlated to sweat odour, which is a reflection of its lesser effectiveness in boar taint reduction compared with CC9. Not withstanding, both CC4 and CC9 displayed significantly improved overall impression scores compared to ConCtrl/ OrgCtrl controls, CC4 to a lesser extent with a significance of (P < 0.05) versus CC9 at (P < 0.001) (Table 3). In terms of the added dimension of texture descriptors in this profile, chicory feeding for 4 and 9 weeks resulted in significant changes in scoring of hardness/fibrous (both significantly negatively correlated at P < 0.01 for CC9) and tenderness/juiciness (both significantly positively correlated at P < 0.01 for CC4) (Tabulated results not shown). Of note with respect to these correlations was the clear significant involvement of these texture terms in differentiating CC4 and CC9 (Fig. 3). Overall, CC4 was determined to have significantly higher tenderness scores when compared to CC9 and compared to OrgCtrl. Concurrently, CC9 displayed significantly higher levels of hardness of first

Principal Component 2 (Y-explained variance 32%)

1.0

Sweet-T Juciness-Tx

3.2. Sensory descriptive profiling, experiment 2: crude, dried chicory and inulin 3.2.1. M. Longissimus dorsi, experiment 2 – intact males Fig. 4 presents the APLSR correlation loadings plot (PC1 versus PC2) for LD 2 intact males for the model based on X-matrix = experimental feeding treatments 2, OrgCtrl, CC6, DC6 and I6, and Y-matrix = sensory characteristics (Tables 1 and 2). This model (Fig. 4) presented 3 significant PCs, PC1 (45% Y-explained variance) was spanned by the feeding strategies OrgCtrl versus DC6 dried chicory feeding. PC2 (32%) was spanned by the specific sensory differentiation of I6 versus CC6. PC 3 (23%) was determined to describe the specific sensory differences between DC6 and CC6. APLSR of feeding treatment design variables versus for sensory profiling Longissimus dorsi 2 (LD 2), displayed that the animals fed treatments OrgCtrl were significantly (in the majority of cases P < 0.001) higher in boar taint terms such as, manure/stable odour/flavour and piggy/animal odour/flavour. Whereas animals fed CC6, DC6 and I6

Fresh cooked pork meat-O

CC6 Fresh cooked pork meat-F

Tenderness-Tx

Gamey-O

Piggy/Animal-O Salty-AT

0.5

Feedy-F

Cooked pork fat-F Nutty-O

Chicory (water)-F Lactic/Fresh sour-AT

Fatty mouthcoating-AT Umam-T

Fibrous-Tx

Musty-O Cardboard-F

0.0

Urine-O

Chicory (fresh)-O

Parsnip-O

Manure/Stable-O Cooked liver/Organy-F Astringent-AT Hay/Silage-O Flat bitter-AT Sour-T OrgCtrl

Gamey-F Parsnip-F Sweat-O Heat/Spicy-AT Overall Impression

Sweet meaty-O Soapy-O

Spicy-F

DC6

Hay-F Feedy-O

-0.5

Chicory (flakes)-F

Piggy/Animal-F

I6

Hardness-Tx

Manure/Stable-F

Serum/Metallic-F Livestock/Barney-F

-1.0 -1.0

-0.5

0.0

0.5

1.0

Principal Component 1 (Y-explained variance 45%) Fig. 4. Longissimus dorsi 2 – Male (LD 2) (PC 1 v 2). ANOVA Partial Least Squares Regression (APLSR) correlation loadings plot of feeding treatment design variables (X-matrix) versus sensory profiling variables (Y-matrix). Ellipses represent r2 = 50 and 100%.

D.V. Byrne et al. / Meat Science 79 (2008) 252–269

261

higher in terms of hardness (P < 0.05) and fibrousness (P < 0.001) when compared to both CC6/DC6 and I6 feeding. Of theses three feeding treatments CC6 was determined to be significantly the most tender (P < 0.001) and juicy (P < 0.001). However, as I6 displayed a significantly (P < 0.001) higher overall impression versus the organic control treatment, the influence of texture, appeared to be superseded by the sensory nature of boar taint reduction in terms, as was the case of PM 1 (Table 3).

were, relative to OrgCtrl (which was significantly lower (P < 0.001) in cooked pork meat flavour) not significantly high in boar taint descriptors (Table 3). This was in particular the case for crude chicory (CC6). Moreover, treatments, CC6 and DC6 appeared to be somewhat similar in their effectiveness in reducing bore-taint in LD 2 (Table 3). In relation to Inulin (I6), CC6 and DC6 had comparable effects in relation to boar taint reduction, however the nature of this change in sensory characteristics differed, in that each of the feeding treatments (CC6, DC6 and I6) had a unique combination of boar taint descriptors significantly (at least at the 5% level) negatively correlated (see Fig. 4, Table 3). In this respect, of note across all three treatments was the lack of reduction in relation to the terms sweat and urine odours particularly in the case of DC6 for sweat odour and CC6 in the case of urine odour. In addition, CC6 displayed significantly higher scores in cooked pork meatiness (P < 0.001), this was however, not the case for DC6 and I6 which were low in cooked pork odour/flavour, significantly (P < 0.01) so in the case of I6. Overall, OrgCtrl treatment displayed significantly the lowest scores for overall impression, versus the other feeding treatments and of these I6 was determined to result in a significant increase (P < 0.001) in overall impression. Thus, fresh cooked pork meat odour/flavour could not be assigned as most important for impression, the most likely a contributor was the significant (P < 0.001) positive correlation of I6 to sweet meaty odour in this muscle. With respect to textural terms in the case of LD 2 the OrgCtrl treatment was determined to be significantly

3.2.2. M. Psoas major, experiment 2 – intact males The sensory profiling results for Psoas major from the experiment 2 (PM 2) for intact males are presented in Fig. 5, an APLSR correlation loadings plot (PC1 versus PC2) for the model based on X-matrix = experimental feeding treatments, OrgCtrl, CC6, DC6 and I6, and Y-matrix = sensory characteristics (Tables 1 and 2). The resultant APLSR model revealed 3 significant PCs, PC1 (39% Y-explained variance) was spanned by the feeding strategies OrgCtrl versus CC6, DC6 and I6. PC2 (31%) was spanned by the specific sensory differentiation of I6 and CC6 versus OrgCtrl and DC6. PC 3 (30%) was determined to describe the specific sensory differences between DC6 and CC6, and I6 and OrgCtrl. Animals fed the organic control treatment (OrgCtrl) were significantly positively correlated to boar taint descriptors such as e.g. piggy/animal odour (P < 0.001) and flavour (P < 0.001), manure/stable odour (P < 0.001) and flavour (P < 0.01) and sweat odour (P < 0.01), however, not urine odour (Table 3). In contrast animals fed

Principal Component 2 (Y-explained variance 31%)

1.0 DC6 Livestock/Barney-F

Sour-T Astringent-AT

Flat bitter-AT Parsnip-O Feedy-F

0.5

Piggy/Animal-O Manure/Stable-F

Fibrous-Tx

Urine-O

Parsnip-F

Manure/Stable-O Sweat-O

Soapy-O

Chicory (flakes)-F Gamey-O

Hay-F Hay/Silage-O

Spicy-F Cardboard-F

0.0 Nutty-O Chicory (fresh)-O

Serum/Metallic-F

I6

Sweet meaty-O Musty-O

Hardness-Tx

-0.5

OrgCtrl

Heat/Spicy-AT Piggy/Animal-F Gamey-F Lactic/Fresh sour-AT

Sweet-T Feedy-O

Cooked liver/Organy-F Tenderness-Tx Salty-AT

CC6 Fresh cooked pork meat-F Juciness-Tx Chicory (water)-F Fatty mouthcoating-AT Fresh cooked pork meat-O Cooked pork fat-F

-1.0

Umami-T

-1.0

-0.5

0.0

Overall Impression

0.5

1.0

Principal Component 1 (Y-explained variance 39%) Fig. 5. Psoas major 2 – Male (PM 2) (PC 1 v 2). ANOVA Partial Least Squares Regression (APLSR) correlation loadings plot of feeding treatment design variables (X-matrix) versus sensory profiling variables (Y-matrix). Ellipses represent r2 = 50 and 100%.

ns na 3.5 na 27.0a na 23.2a na na * na 1.6 na 9.1b na 13.7ab na 13.5ab

0.227 0.033b 2.908 1.350ab

Androstenone blood (lg/l) Day 41-male na Day 56-male 17.7a

1.204 2.441a

ns = non significant. na = not applicable. a–c LSM Within trial and within rows not sharing a common superscript letter differ significantly (P < 0.05).

0.170 0.000b

0.56 0.56

*** **

27.0a na

27.1a na

*** na na 0.3 na na 0.68b na na 0.11b na na 0.32b na na 3.49a a a b ab

Skatole blood (lg/l) Day 41-male Day 56-male Day 56-female

*** na na 0.006 na na 0.026b na na 0.017b na na 0.023b na na 0.088a na na na *** * na 0.023 0.023 na 0.0004c 0.025ab na 0.0349bc 0.000b

s.e. CC9 CC4 OrgCtrl

na 0.132a 0.038a na 0.099ab 0.065a Skatole backfat (lg/g) Day 42&44-male Day 63-male Day 65-female

s.e. I6 DC6 OrgCtrl

CC6 Treatment

ConCtrl

Significance of treatment Treatment

In relation to the feeding treatments of experiment 1, chicory-fed pigs displayed skatole concentrations in backfat at slaughter (63 days of age) and skatole concentrations in blood plasma after 56 days on trial, that were not significantly different from zero (Table 4). Both CC6 and CC9 were determined similar in their effectiveness in reducing skatole in backfat and blood compared with ConCtrl and OrgCtrl. In the case of skatole in backfat the effect was at a significance level of (P < 0.001) for intact males and (P < 0.05) for female animals. For CC6 and CC9 reducing levels of skatole in blood, the significance levels were (P < 0.001) for intact males and (P < 0.01) for female animals (Table 4). Overall, it was found that backfat skatole concentrations for intact males were significantly (P < 0.05) higher than in females (Table 4). With respect to androstenone levels in blood at 56 days a significant decrease (P < 0.05) was observed in CC9 compared with ConCtrl (Table 4). CC4 also displayed a decrease but a significant difference to control could not be ascribed.

Experiment 2

3.3. Skatole and androstenone analyses

Experiment 1

crude chicory for 6 weeks were in general negatively correlated to all boar taint descriptors, significantly in the case of piggy/animal odour (P < 0.001), manure/stable flavour (P < 0.001) and sweat odour (P < 0.01). In the case of dried chicory feeding (DC6) piggy/animal flavour only was found to be significantly (P < 0.05) decreased, with the majority of the remaining taint terms displayed a tendency in this respect. In relation to inulin feeding (I6) piggy/animal odour was singularly the descriptor that significantly (P < 0.001) decreased in relation to boar taint reduction (Table 3). Of the 4 feeding treatments CC6 was found to display significantly the highest scores (P < 0.001) for overall impression. This is a reflection of the consistent and significant levels of reduction found in scores across the majority of boar taint terms for CC6 (Table 3). In this respect the contrasting lack of significant reduction in taint terms w.r.t. DC6 is reflected as a significant decrease (P < 0.001) in overall impression relative to the other feeding treatments for PM 2. For sensory textural effects in PM 2, the organic control was determined to have significantly higher tenderness scores (P < 0.001) and lower hardness and fibrousness scores (P < 0.001 in both cases) when compared to e.g. I6 which displayed a significantly higher level (P < 0.001) of hardness of first bite. Crude chicory, CC6 was determined, as per the organic control (OrgCtrl), to display a significantly higher level (P < 0.001) of tenderness compared to DC6 and I6 (Table 3). Again as CC6 was determined to be the most significantly appreciated feeding regime as per LD 2 and PM 1, tenderness was not the driving force in liking here also, as it is also significantly improved in OrgCtrl which did not have a high overall impression, thus this score appears largely related to level of boar taint reduction.

Significance of treatment

D.V. Byrne et al. / Meat Science 79 (2008) 252–269

Table 4 Slatole concentrations in backfat and blood and androstenone levels in blood for experiment 1 and 2, least square means (LSM) and standard error of LSM (s.e.)

262

0.018 ns +0.015 ns +0.001 ns 0.015 ns +0.022 ns 0.048* +0.085** +0.088*** +0.056* +0.054* +0.067** 0.039 ns +0.087** +0.089*** +0.056* +0.055* +0.068** 0.039 ns 0.065 ns 0.018 ns 0.022 ns +0.045 ns 0.089** 0.004 ns +0.031* +0.091*** +0.099*** +0.046* 0.044* 0.105*** +0.035* +0.094*** +0.102*** +0.044* 0.040* 0.108***

Estimated regression coefficients including sign (±) for treatment correlation derived from ANOVA Partial Least Squares Regression (APLSR). b

a

na = not applicable.

***Significant at the 0.1% level (P < 0.001), **Significant at the 1% level (P < 0.01), *Significant at the 5% level (P < 0.05), ns = Non-significant (P > 0.05).

+0.095*** +0.090*** +0.076** +0.046 ns +0.079* 0.002 ns +0.278 ns +0.050* +0.209*** +0.147*** 0.-044* +0.024 ns +0.062** +0.077*** +0.195*** +0.134*** 0.001 ns +0.018 ns na na na na na na 0.026 ns 0.077 ns na na na na 1.006 ns 0.094 ns na na na na +0.166*** +0.103* na na na na +0.150*** +0.192*** na na na na

Skatole blood Day 56 Skatole blood Day 56

Androstenone Blood Day 56

Skatole blood Day 56

Androstenone Blood Day 56

Skatole backfat Day 63 Skatole backfat Day 63 Skatole backfat Day 63

+0.189*** +0.194*** na na na na Piggy/Animal-O Piggy/Animal-F Manure-O Manure-F Sweat-O Urine-O

Androstenone blood day 41 Skatole blood day 41 Profile 2

Skatole backfat Day 42 & 44 Skatole backfat Day 42 & 44

Skatole blood day 41

Androstenone blood day 41

Male PM2

Androstenone Bood Day 56

Profile 2

Male LD 2

Profile 1 Profile 1

Profile 2

Experiment 2

Male PM 1 Female LD 1 Male LD 1

Partial least squares regression (PLSR) was utilised to investigate the relationships between the sensory characteristics and the chemical measurements (skatole in backfat and blood, androstenone in blood), which in PLSR were set as the X and Y matrices, respectively. Individual PLSR models were developed for each individual sensory profile which included individual muscles (LD 1, 2 and PM 1, 2), genders (intact male, female) and each of experiment 1 and 2. Each of the models displayed 2 significant principal components as validated for interpretation. Overall, all intact male samples from both LD and PM in experiment 1 and 2 for a number of key sensory boar taint descriptors were determined to be significantly positively correlated to the chemical measurements (see Table 5). In all cases skatole in both backfat and blood was significantly (at least P < 0.05) positively correlated in experiments 1 and 2 to a number of sensory boar taint related terms, e.g. Piggy/animal odour and flavour and manure/ stable odour and flavour (Table 5). No significance relationship however, could be assigned with respect to skatole in backfat nor blood with respect to the LD 1 female animals. This may be a reflection of the minor sensory changes w.r.t. boar taint effects previously discussed for this muscle. Of note for skatole in backfat/blood was that specifically in the case of experiment 2, the terms urine and sweat odour were determined to be significantly negatively correlated (PM 2) and/or lack significance in their relationship to skatole per se. This may be that these sensory characteristics were reflective of the androstenone aspects of sensory boar taint (Gunn et al., 2004). Thus, specific causality of skatole in relation to piggy/animal and manure odours and flavours can be said to have been clearly assigned in the present case (Table 5). Androstenone levels measured at 56 days of age in blood were also found to be highly predictive of the ‘skatole’ related sensory terms piggy/animal odour and flavour in the case of LD1 and PM 1 experiment 1 (Table 5). However, in direct contrast androstenone was determined not to be predictive of these terms in the experiment 2 muscles, i.e. LD 2 and PM 2. Thus, these contrasting findings

Experiment 1a,b

3.4. Significance testing of direct sensory-chemical prediction

263

Terms

In experiment 2 irrespective of formulation the chicoryfed entire male pigs (groups CC6 and DC6) showed a significant reduction in skatole concentrations in blood plasma compared with the control pigs (Table 4). Furthermore, skatole concentrations of the chicory-fed pigs were not significantly (P < 0.05) different from zero. Also the I6 treatment pigs had less (P < 0.001) skatole compared with the OrgCtrl treatment, however, this level was above (P > 0.05) zero. At the end of the 6-week trial period all chicory- and inulin-fed entire male pigs displayed lower skatole concentrations in backfat than those of corresponding control-fed pigs (P < 0.001). Plasma androstenone concentrations of chicory- and inulin-fed pigs in experiment 2 were not affected by treatment (Table 4).

Table 5 Longissimus dorsi (LD) and Psoas major (PM) from experiment 1 and 2, significance of PLSR derived estimated regression coefficients for the relationships of key boar taint relevant sensory descriptors to chemical measurements skatole and androstenone as derived by jack-knife uncertainty testing

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D.V. Byrne et al. / Meat Science 79 (2008) 252–269

between experiment 1 and 2 appear, in the case of experiment 2 to bear out the contention that, piggy/animal and manure descriptors are largely skatole predictive and causal related descriptors in relation to sensory boar taint. In relation to the generally reported androstenone specific terms urine and sweat odour PM 1 was the only case where sweat odour was found to be significantly positively linked, in experiment 2 androstenone in blood was determined not only unrelated significantly to these terms (urine and sweat odours) but even significantly negatively (P < 0.05) related in the case of PM 2. Thus, there would appear to be a lack of systematic clarity in terms of potentially expected correlations in relation to androstenone and its reported related sensory descriptors, i.e. urine and sweat like odours (Dijksterhuis et al., 2000;Gunn et al., 2004). To ensure the androstenone indications are given their total context with respect to sensory correlation reference is made to the actual chemical measurement values presented in Table 4. These results may reflect to a certain degree an aspect of the underlying reason for the lack of clarity in the androstenone sensory correlations in the case of experiment 2, in that measured androstenone across the feeding treatments did not vary significantly in these animals. In contract androstenone in blood was found to decrease significantly in the male animals of experiment 1. It may be conjectured that skatole is a clear predictor of specific sensory characteristics whereas androstenone cannot be said to be as defined in this respect, in the present experiments. 4. Discussion 4.1. Sensory impact and description of chicory and inulin feeding Chicory feeding in fresh and dried form significantly reduced sensory boar taint relative to control feeding per se in both PM and LD muscles of intact males (Figs. 1– 5). In terms of muscle type, dried chicory, important as the form which is most likely of interest in practical terms when one considers its applicability as a feed ingredient, appeared more effective in boar taint reduction in PM muscles versus LD muscles (Table 3). Inulin also appeared to be effective in the reduction of sensory boar taint in both PM and LD, but to a lesser degree relative to chicory feeding, particularly in the case of PM. With respect to intact male muscles of PM and LD in experiment 1 and 2, it was also apparent that PM in the case of crude chicory feeding displayed greater reduction in levels of quantitative boar taint (off-odour and off-flavour) when compared to the other feeding regimes (Table 3). The reason for these muscle differences was undetermined and could not be explained explicitly as literature data was not discovered regarding the concentration of skatole and androstenone in different lean tissues. However, it is assumed that the association of backfat with LD muscles was related to elevated meat or muscle concentrations of boar taint compounds compared with a muscle such as PM which is not

associated with backfat (e.g. Lawrie, Pomeroy, & Cuthbertson, 1963 and Lauridsen, Nielsen, Henckel, & Sørensen, 1998; Rius & Garcia-Regeiro, 2001). The concentration of boar taint causing compounds particularly skatole may be assumed higher in LD muscles then and the feeding regimes appear thus to be relatively less effective in sensory boar taint reduction in LD over PM. In female animals crude chicory feeding was also determined to reduce perceived boar taint but to a lesser and much less defined extent than that determined for the intact male animals (Table 3). Moreover, a discrepancy was apparent in this indication, in that 4 weeks of crude chicory feeding was determined more effective than 9 weeks. The exact reason for this was unclear from a sensory perspective given that the skatole concentrations in backfat and blood were reduced by both chicory feeding treatments for the female LD animals to levels close to zero (Table 3). It may be considered in part to be due to the fact that the female animals were low in taint to begin with and the changes were of a very subtle nature such that they went undetected from a sensory perspective in the case of 9 weeks of crude chicory feeding exemplified by a significant increase in boar taint descriptors for these samples (Table 3). This is supported by the level of skatole reduction in backfat in female animals where the 9 week samples (CC9) were not found to be significantly different to the control samples, whereas CC4 samples were determined to be quantitatively different, this appeared to be translated into a quantitative sensory perceptible different with respect to boar taint reduction (Table 4). In relation to specific sensory descriptive terms the control fed pigs both ConCtrl in and OrgCtrl were found to have significantly higher levels of boar taint as described by the terms manure/stable odour and flavour and piggy/ animaly-odour and flavour relative to the pigs fed chicory and inulin, which it must be noted additionally displayed a higher overall impression (Table 3). That crude, dried chicory and inulin, having clearly reduced boar taint from a sensory perspective, did not lead to the imparting of significant ‘new’ off-flavours in the cooked meat samples was critical. The bitter nature of chicory roots may potentially have been expected to be an issue, however, this proved not to be the case (Figs. 1–5). Byrne et al. (2001b) and Byrne, Bredie, O’Sullivan, and Martens (2002) have reported terms such as cardboard and linseed oil-like as lipid oxidation descriptors. In the present profiles these were found associated with the chicory feeding treatments in particular with feeding for 4 weeks (CC4) which was supplemented with clover grass silage (Table 1, Figs. 1–5). The underlying reason may be related to elevated levels of polyunsaturated fatty acids (PUFA x6, x3) in these samples as a result of dietary silage, with a corresponding susceptibility to develop lipid oxidation based off-characteristics (e.g. see Ho¨gberg, Pickova, Andersson, & Lundstro¨m, 2003; Ho¨gberg, Pickova, Stern, Lundstro¨m, & Bylund, 2004; Johansson, Lundstro¨m, & Jonsa¨ll, 2002; Wood et al., 2004). In addition, it can be said that the

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OrgCtrl samples, also supplemented with silage up to slaughter, appeared associated with lipid oxidation descriptors, however, more so in experiment 2 versus experiment 1 (Figs. 4 and 5). These oxidation type off-flavours/odours were not at a level described as rancid thus potentially consumer acceptability may not be detrimentally affected (see Bryhni et al., 2002; Bryhni et al., 2003). In relation to specific terms of relevance specifically to chicory feeding, bitter-taste was determined associated in a number of the profiles, however, it did not result in a corresponding negative overall impression. Thus, elevated levels of chicory derived bitter compounds such as sesquiterpene lactones were not determined to cause negative sensory effects (Bais & Ravishankar, 2001). Terms such as crude and dried chicory designed to monitor chicories overall sensory influence in the supplemented samples were found to be highly relevant for their discrimination as opposed to inulin description (Figs. 1–5). A key significant sensory note associated consistently with chicory feeding per se was that the samples exhibited gamey-like characteristics for odour and flavour. Moreover, the chicory samples were scored high for terms such as herby/ spicy, which may be contributing to the generally positive overall impression. Finally, chicory was judged to have high levels of lactic/sour and astringent notes, these once again did not appear to be at levels or impart characteristics that were determined to be negative by panelists (Figs. 1–5). With specific sensory reference to inulin as opposed to the chicory feeding treatments a number of terms appeared unique to significantly describing its sensory effects, namely feedy, umami and parsnip. No president was found in the literature with respect to such specific sensory description of inulin effects (Table 3). Also of note were the clear effects of chicory and inulin feeding on the sensory modality texture as exemplified by changes in levels of tenderness and hardness (Figs. 3–5). Overall, the effect of bioactive feeding per se was found to have conflicting effects on the textural aspect of the samples and thus a general systematic effect could not be ascribed in this respect. As to why chicory feeding would affect tenderness could be attributed or to some degree explained by previous results where tenderness was seen to be potentially negatively affected due to reduced muscle glycogen stores in slaughter pigs as a result of strategic finishing feeding with diets low in digestible carbohydrate and high in fermentable carbohydrate, like inulin extracted from chicory roots or potentially chicory roots per se (Rosenvold, 2002; Rosenvold et al., 2001). An additional point of note was the determination that chicory in some instances resulted in a perceived decrease in tenderness, though not per se, was not reflected by a decrease in overall impression. Indicating that the tenderness changes were relatively minor in sensory terms, such that the level of repulsion to taint by the panellists was more influential on liking relative to texture thus an indication of the impact of taint per se. This was interesting from the perspective that tex-

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tural change in cooked meat in many instances is the key modality with respect to the overall impression (e.g. Hansen, Therkildsen, & Byrne, 2006b). Finally, with respect to the hypothetical basis of the present experimental feeding regimes as presented by Hansen et al. (2006a), i.e. that the use of specific ‘bioactive’ ingredients such as Chicory (Cichorium intybus L.) may positively influence sensory eating quality has been determined to be clearly the case, with certain subtleties with respect to the level of feeding, of crude, dry chicory and pure inulin. The basis for chicories effects on the sensory properties of pork is conjectured to be based on the presence of fructo-oligosaccarides (inulin) (Claus, Weiler, & Herzog, 1994; Jensen, Cox, & Jensen, 1995) and to a lesser extent sesquiterpene lactones (bitter compounds) in the roots of chicory plants (Bais & Ravishankar, 2001). The mechanism proposed as involved by Hansen et al. (2006a) with respect to the positive effects of chicory is that the active ingredient of the roots, namely inulin, functions as a prebiotic in pigs due to fermentation in caecum and colon, resulting in a stimulation in the growth of positive bacteria such as Bifidobacteria and Lactobacillus (Tungland, 1998). This bacterial growth is considered the underlying reason for the significantly positive influence of the feeding treatments of the present studies on the sensory eating quality of the meat in general by reducing the levels of bacteria producing the boar taint related products skatole, indole, and p-cresol in the caecum and colon (Jensen & Hansen, 2006; Takahashi, Kadowaki, Tashiro, Takizawa, & Kinoshita, 1996). In addition, a direct effect of sesquiterpene lactones was also presented as very likely (see Choi et al., 1998; de-Kraker, Bouwmeester, Franssen, & de Groot, 1999; de-Kraker, Franssen, Dalm, de-Groot, & Bouwmeester, 2001; Hansen et al., 2006a; Rees & Harborne, 1985; Bais, Govindaswamy, & Ravishankar, 2000; Bais & Ravishankar, 2001). 4.2. Skatole/androstenone, specific sensory prediction and causality In terms of sensory description of the skatole aspect of boar taint, clear associations with respect to boar taint description were apparent for characteristics such as Piggy/Animal and Manure odour and flavour, as exemplified by correlation to skatole in blood and backfat (see Table 5). No significance of relationship however, could be assigned with respect to skatole in backfat or blood with respect to the LD 1 female animals. In contrast the association of commonly reported androstenone descriptors such as sweat and urine odours were not found to be as systematic (see Gunn et al., 2004).The androstenone concentration in the blood did not appear to be affected by feeding chicory or inulin in experiment 2 and no clear explanation was possible for the decrease in androstenone level in the four entire male pigs given crude chicory for 9 weeks before slaughter compared with the control treatment in experiment 1 (Table 4). However, it has been reported that die-

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tary fibre is capable of reducing the level of cholesterol in serum (Marlett et al., 1994), by interrupting the enterohepatic circulation of the steroid core of cholesterol. As androstenone and cholesterol follow the same biosynthetic pathway, a prolonged feeding period with a dietary fibre such as chicory/inulin may be postulated as able to affect the androstenone content in plasma in a similar manner to cholesterol (Hansen et al., 2006a). The issue of the relationship of androstenone to sensory terms and therefore an indication of an effect of feeding treatment on the androstenone aspect of boar taint was reflective of the plasma indications (Table 5). For Psoas major experiment 1 where a significant decrease was found in plasma androstenone with 9 weeks feeding a corresponding decrease in sweat odour scores was apparent (Table 5). In contrast, in experiment 2 a systematic decrease in reported androstenone related descriptors (urine and sweat odour) could not be generally assigned for chicory feeding (see Gunn et al., 2004). Crude chicory treatment 6 weeks was the only case where a reduction was found. This is clearly a reflection of the lack of significant decrease in measured androstenone in these samples (Table 4). The experimental feeding treatments replacing 25% of the recommended daily energy intake with crude or dried chicory had a pronounced effect on the skatole concentrations in blood and backfat after three and four weeks, and the effect clearly remained for the 9-week feeding period if results of experiments 1 and 2 are considered as a whole. Hansen et al. (2006a) also reported the effects on skatole are also found with just 1 week of feeding chicory. This result can be compared to effects determined by Claus, Lo¨sel, Lacorn, Mentschel, and Schenkel (2003) with respect to the effect on boar taint of feeding potato starch for a short period. In the second experiment, 14% inulin (corresponding to the amount of inulin (fructan) in 25% chicory) reduced the skatole concentrations in blood and backfat to the same extent as 25% of chicory, which suggests the level of inulin was likely the most important factor responsible for the reduction in skatole concentration in blood and backfat. High levels of correlation between skatole in backfat and blood plasma have been presented in a variety of experiments, ranging from r = 0.90 to 0.98 at a significance level of P < 0.001 (e.g. Agergaard, Jensen, Laue, & Jensen, 1998a; Agergaard & Laue, 1998b; Hansen, Larsen, Jensen, & Hansen-Møller, 1997; Tuomola, Vahva, & Kallio, 1996). With respect to androstenone, less systematic indications have been found for levels of correlation between blood and fat samples when the blood samples have been extracted with organic solvents prior to analysis. Indications for androstenone have ranged from a complete lack of association (Lundstro¨m, Malmfors, Hansson, Edqvist, & Gahne, 1978; Malmfors & Andresen, 1975) to a very high degree of correlation (Andresen, 1976; Babol, Squires, & Lundstro¨m, 1999; Booth, Williamson, & Patterson, 1986; Groth & Claus, 1977; Zamaratskaia, Babol, Andersson, & Lundstro¨m, 2004). Other than this, determinations

from direct immunochemical analysis of non-extracted blood samples, as per those of the present investigations, correlate highly with the levels measured in backfat, i.e. between, r = 0.78 to 0.89 at a significance of P < 0.001 (Tuomola, Harpio, Wirta, & Lo¨vgren, 2002; Tuomola et al., 1997). With respect to the skatole and androstenone measurements, if one considers a minor effect on androstenone in blood and backfat by relatively short term chicory feeding, the optimal effect of chicory roots against boar taint may be obtained when the intact male pigs have not yet reached full sexual maturity in the interval 85 to 100 kg live weight which is the reported range where levels of androstenone are lower and thus are a lesser issue in terms of contribution to boar taint (Claus et al., 1994; Godt, Kristensen, Poulsen, Juhl, & Bech, 1996). It is likely that with the extremely low levels of skatole obtained in the present studies as a result of 25% chicory feeding, taint characteristics from androstenone will not be enhanced and therefore may not result in large boar taint issues in the majority of cases between 85 and 100 kg, however, this would depend very much on the levels of androstenone present in the animals. 5. Conclusions Crude and dried chicory feeding were found to result in a significant reduction in boar taint sensory characteristics concurrent with a significant elevation in overall impression relative to the non-bioactive and organic control feed groups in intact male and to a degree in female animals. A key aspect with respect to these findings was that chicory feeding did not to impart negative sensory characteristics such as bitterness and sourness to unacceptable levels. Feeding of 25% of crude and dried chicory significantly reduced skatole in blood and backfat (to almost zero levels) irrespective of gender and feeding period (4 to 9 weeks). This is a reduction to levels below present published Danish boar taint ‘cutoff’ limits for consumer acceptability, of 0.25 lg/g to a proposed upper limit of 0.15 lg/g to avoid boar taint in more than 99% of all Danish entire male pigs slaughtered at 100 kg live weight (Godt et al., 1996). Skatole analysis overall was highly predictive of sensory boar taint reduction, however, in the case of androstenone correlation was not as systematic. Specific causality of skatole in relation to piggy/animal and manure odours and flavours were clearly assigned. While androstenone was related to descriptors urine and sweat. Levels of boar taint reduction and improved overall impression scores with chicory feeding may be considered as reflection of potential consumer response. However, many factors come into play with respect to consumer acceptability such as variation in sensitivity with respect to e.g. location, gender and anosmia (see Dijksterhuis et al., 2000; Font I Furnols, Gispert, Diestre, & Oliver, 2003; Gunn et al., 2004). Thus, the feeding treatments most certainly require evaluation in the consumer realm to determine the absolute level of efficiency and effective-

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ness of these feeding regimes in boar taint reduction. As one is going from high taint to very low or no taint with chicory/inulin feeding, it is safe to assume that at least with respect to the skatole aspect of boar taint, which reportedly 95% of the population are sensitive to (Gilbert & Wysocki, 1987), that chicory feeding would reduce the negative reaction of the consumer to this aspect of boar taint significantly. With respect to the androstenone aspect this is not such a surety. Chicory feeding must however be seriously considered to have the potential for utilisation as a major part of a commercial strategy for boar taint reduction in entire male pork. It can be said that feeding dried chicory for as little as 4 weeks (or for as little 1 week, as reported by Hansen et al., 2006a) provides a practically applicable way to significantly reduce the skatole element of boar taint. Moreover, this strategy would be most applicable at lower than average slaughter weights, 85 to 100 kg where androstenone is not considered as influential. In this respect the indication of influence of chicory on androstenone require further investigation. Finally, research may be focused effects of chicory feeding at different slaughter weights, with respect to percentage and feeding periods required to produce pork from entire male pigs on a commercial scale that is acceptable to the consumer. Acknowledgements The financial support for the projects PROSBIO/PROSQUAL from the Danish Research Centre for Organic Farming (DARCOF) is greatly acknowledged. References ASTM. (1986). Physical Requirements. Guidelines for Sensory Evaluation Laboratories. STP 913. Pennsylvania: American Society for Testing and Materials. Agergaard, N., Jensen, B. B., Laue, A., & Jensen, M. T. (1998a). Production and absorption of skatole to portal vein blood following tryptophan infusion to the hindgut. In W. Klinth Jensen (Ed.), Skatole and boar taint (pp. 97–110). Roskilde, Denmark: Danish Meat Research Institute. Agergaard, N., & Laue, A. (1998b). Absorption of skatole to portal vein blood and liver turnover in entire male pigs using an in vivo animal model. In W. Klinth Jensen (Ed.), Skatole and boar taint (pp. 77–96). Roskilde, Denmark: Danish Meat Research Institute. Andresen, Ø. (1976). Concentrations of fat and plasma 5 a-androstenone and plasma testosterone in boars selected for rate of body weight gain and thickness of back fat during growth, sexual maturation and after mating. Journal of Reproduction and Fertility, 48, 51–59. Babol, J., Squires, E. J., & Gullet, E. A. (1996). Investigation of factors responsible for the development of boar taint. Food Research International, 28, 573–581. Babol, J., Squires, E. J., & Lundstro¨m, K. (1999). Relationship between metabolism of androstenone and skatole in intact male pigs. Journal of Animal Science, 77, 84–92. Bais, H. P., Govindaswamy, S., & Ravishankar, G. A. (2000). Enhancement of growth and coumarin production in hairy root cultures of witloof chicory (Cichorium intybus L. cv. Lucknow local) under the influence of fungal elicitors. Journal of Bioscience and Bioengineering, 90, 648–653.

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