Acceptability of entire male pork with various levels of androstenone and skatole by consumers according to their sensitivity to androstenone

The results of meat quality traits and sensory characteristics according to the concentration of androstenone in uncastrated pigs

Pork quality is determined by several attributes, among which odor and taste are the utmost significant. Therefore, this study was aimed to assess the effects of boar odor hormone concentration on the quality traits and sensory acceptability of pork. A total twenty-six (26) non-castrated 3-way crossbred (Landrace × Yorkshire × Duroc) pigs were selected with an average body weight (ABW) 115.6 kg before to slaughter. The three treatment groups (low, medium and high) were divided according to the androstenone concentration. In experiment 1, for meat quality traits carcass was selected based on androstenone concentration: low (LC, 0.64-0.69 μg/g, n = 9), medium (MC, 0.70-0.99 μg/g, n = 7) and high (HC, 1.00-1.69 μg/g, n = 10). In experiment 2, for sensory evaluation carcasses were also selected based on the abovementioned conditions. Results revealed that androstenone concentration not effect on proximate components, meat quality traits and fatty acids except palmitoleic acid. Sensory evaluation data showed that boar taint and meat boar taint were significantly increased in a concentration-dependent manner from low to high, whereas, gravy and meat flavor preference were significantly increased in LC group than HC group. In addition, correlation analysis showed that boar taint and meat boar taint were positively, and gravy and meat flavor preference were negatively correlated with boar taint hormones. In essence, our findings indicate that androstenone concentration had no effect on meat qualities, but a high concentration of androstenone had a negative effect on the sensory characteristics in uncastrated pigs.

A Preliminary Evaluation of Sex and Dietary Field Pea Effects on Sensory Characteristics of Dry-Cured Loins

Two of the main issues related to cured meat products are castration to avoid boar taint and the hefty reliance on soybean meal to feed pigs. However, data on the effects of immunocastration in pigs and alternative crop protein feeds on the sensory traits and consumers' acceptance of dry-cured loin are still limited. A preliminary study was conducted on the effect of sex type (surgical castrated male pigs and immunocastrated male and female pigs, at approximately 140 kg in weight and 7 months of age) and animal diet (pea vs. soya) on dry-cured loins. The study involved a sensory evaluation of six treatments, with a 3 × 2 factorial design, conducted by trained panellists and untrained consumers in Spain (n = 126) and Portugal (n = 80). The consumers were also checked for their skatole sensitivity using a pure substance. The results showed that the pea-based diet was significantly different (p < 0.001) from the soy-based diet, as determined by a trained panel of surgically castrated male pigs, although the immunocastration treatments were not split. Dry-cured loin from immunocastrated male pigs fed with peas was considered tenderer and juicier (p < 0.05) than those fed soya-based diets. The untrained consumer panel scored higher on the sensory traits (flavour, juiciness, and overall liking) from the loin samples of surgically castrated male pigs fed a pea diet. All consumers scored similarly in boar taint detection. This study demonstrates the applicability of the pea-based diet for the feeding of pigs destined for cured meat and highlights immunocastration as a tool that does not compromise the skatole detection score.

The effects of different immunocastration protocols on meat quality traits and boar taint compounds in male Bísaro pigs

Immunocastration can be an alternative to surgical castration in Bísaro pigs when there is a need to keep animals on the farm until at least 8 months old. As an autochthonous breed, some particularities must be addressed when doing immunocastration, for which 3 different protocols were tested and two control groups were made with surgically castrated males (SC) and boars (Bo). Two protocols were made in prepubertal pigs, with two (E2) and three inoculations (L3) in the first cycle, and another in adults (A2) with only two inoculations. Physicochemical parameters and boar taint compounds quantification and sensory analysis of the meat from the studied pigs were assessed. Immunocastration provided intermediate values between surgically castrated pigs and entire males, with low levels of boar taint compounds. The L3 group provided closer results to SC, which was also corroborated by the sensory analysis. Although the other two protocols had no significant differences with Bo, there was a positive tendency towards them. As is, the L3 protocol was promising as a good alternative to surgical castration, maintaining the characteristic attributes of the Bísaro pig meat.

Effect of Immunocastration on Culled Sows-A Preliminary Study on Reproductive Tract, Carcass Traits, and Meat Quality

The Bísaro pig is a Portuguese autochthonous breed greatly appreciated for its meat quality and is mainly reared outdoors. Immunocastration could be a solution to avoid undesirable pregnancies and boar taint in cull sows. The present study tested three immunocastration protocols (with Improvac®) according to their reproductive cycle. The first inoculation was performed two weeks after farrowing (IM1, n = 5), at the beginning of estrus (IM2, n = 5), and one week after the end of estrus (IM3, n = 5), followed by a second administration four weeks apart. A control group (C, n = 5) was also included in the same housing conditions. The sample collection included the reproductive tract for morphometric evaluation, neck fat for the quantification of boar taint compounds, and a portion of the Longissimus thoracis et lumborum for meat quality trait assessment. The reproductive tracts from intact sows (C) were significantly heavier compared to the immunocastrated groups (p < 0.05) (1.403 kg C to 0.508 kg IM1, 0.590 kg IM2, and 0.599 kg IM3), suggesting the regression of the reproductive tract to nonstimulated conditions due to immunization against GnRH. The IM1 group exhibited significantly smaller reproductive tract measurements compared to group C for most of the evaluated segments (p < 0.05). No marked differences were observed in the meat quality traits. Therefore, immunocastration can be used in culling sows to avoid ovarian activity, and it is not detrimental to pork quality traits.

Novel gels and films to mask boar taint in entire male pork

Boar taint masking strategies were developed using hydrocolloids and spices to produce edible gels and films. Carrageenan (G1) and agar-agar (G2) were used for the gels and gelatin (F1) and alginate+maltodextrin (F2) for the films. The strategies were applied to both castrated (control) and entire male pork with high levels of androstenone and skatole. The samples were evaluated sensorially by a trained tasting panel through quantitative descriptive analysis (QDA). Lower hardness and chewiness of entire male pork, with high levels of boar taint compounds object of study, were found with the carrageenan gel, due to the better carrageenan gel adherence to the loin. The films showed that the gelatin strategy tended to have a certain "sweet" taste, and a higher overall masking than the alginate+maltodextrin film. In conclusion, a trained tasting panel found that gelatin film masked boar taint the most, followed by the alginate+maltodextrin film and the carrageenan-based gel.

Concentrations of Boar Taint Compounds Are Weakly Associated with Sexual Behavior of Young Boars

Strategies to control boar taint (BT) in meat relies on the reduction of skatole, indole, and androstenone concentration. This might have unfavorable effects on the libido of breeding boars. The association between BT compound concentration in backfat and libido was investigated in 391 commercial breeding boars. Six sexual behavior traits (SBT; sexual arousal, salivation, mounting performance, interest in the dummy sow, penis unsheathing, and overall libido score) were scored during the training of the boars with the dummy sow. Variation in SBT was analyzed by proportional-odds cumulative logistic models. Overall, indole, skatole, and androstenone concentrations were weakly associated with libido. Farm of origin, age at training or body weight, and BT compound levels were poor predictors of boar performance (the area under the ROC curve ranged from 0.60 to 0.69). This indicates that BT compound concentrations were weakly associated with libido, even though the probability of observing good SBT scores increased with high levels of androstenone, intermediate or low levels of skatole, and intermediate to high levels of indole. Hence, practices aiming at reducing androstenone, and controlling the concentrations of skatole and indole to intermediate levels are not expected to impair the libido of young boars.

Consumer evaluation of meat quality from barrows, immunocastrates and boars in six countries

The practice of surgical castration of piglets and its alternatives is still under debate. Production of boars may impair meat quality due to boar taint and reduced tenderness compared to meat from surgically castrated male pigs, while immunocastration reduces boar taint and may improve meat quality but seems to be less accepted by the pig chain. In this study, we aimed to evaluate the consumer's sensory appreciation of meat from barrows (BAs), immunocastrates (ICs) and boars (BOs) in six European countries, taking into account the selection of tainted carcass and consumers' appreciation of boar taint. Loin chops of 30 BAs, 30 ICs and 30 BOs were evaluated by 752 consumers in six countries: Belgium, Czech Republic, Poland, Portugal, Romania and Spain. Consumers rated odour, flavour, tenderness, juiciness, overall liking and willingness to buy and sensitivity to and liking of androstenone (AND) and liking of skatole (SKA) was also tested. In each of the six countries, consumers liked the odour of the BO samples less than that of BA, and IC intermediate. For flavour, tenderness, juiciness, overall liking and willingness to buy, liking scores given by the Czech, Polish and Portuguese consumers significantly differed between the BA, BO and IC. Willingness to buy was highest for BA by Czech and Polish consumers and for BA and IC by Portuguese consumers. The frequency of the negative check all terms that apply terms also differed, with a higher frequency of disgusting for BO compared to BA and IC and of off-flavour, irritating, manure, sweat, disappointing compared to BA, and intermediate for IC. 31% of the consumers disliked the odour of AND (NEG_AND), and 36% of them were not sensitive; in contrast, 77% of the consumers disliked SKA (NEG_SKA). The decrease in flavour liking score for BO compared to BA and IC was more outspoken by the NEG_AND consumer, while NEG_SKA consumers gave an overall lower liking score independent of the type of male pig. The results of this study indicate that IC can be a valid alternative for surgical castration.

Consumers’ Expectations about Meat from Surgical Castrated or Immunocastrated Male and Female Iberian Pigs

Simple Summary

Pig castration is a common practice in the Iberian breed (boar and gilts), known for the quality of its products. This work studies the effect of pig castration (surgically castrated females and males, immunocastrated females and males and entire females) on the sensory expectations and acceptability of the meat. Attitudes and beliefs towards castration and immunocastration were also evaluated. The study was carried out in Madrid and Barcelona, where consumers (n = 252) evaluated meat from the five sex types in blind and informed conditions. Results showed that consumers could be classified into three groups as “Indifferent”, “Against castration and immunocastration” and “Against immunocastration”. Meat from castrated males had higher overall liking scores than the other types of meat. Information provided to the consumers, together with their expectations, affects the overall liking scores. Thus, this needs to be considered to determine the best marketing strategy according to the type of pork produced.

Abstract

A common practice in Iberian pigs is the castration of both males and females, and it can be carried out surgically or by immunization against gonadotropin-releasing factor (GnRF). The aim of this work was to determine consumers’ overall liking and expectations towards Iberian pork from five different sex types (castrated females, entire females, GnRF-vaccinated females, castrated males and GnRF-vaccinated males), as well as to know the attitudes and beliefs of consumers towards castration and immunocastration. Loins from 83 Iberian pigs were collected and evaluated by 252 consumers in Barcelona and Madrid. Consumers evaluated the five types of meat in three situations: blind condition (tasting the product), expectations (without tasting) and informed condition. Finally, attitudes and beliefs towards castration and immunocastration were also determined. Results distinguished three segments of consumers labeled as “Indifferent”, “Against castration and immunocastration” and “Against immunocastration”. Meat from castrated males had higher overall liking scores in the blind condition. Expectations towards pork depending on its sex type affect consumer-informed acceptability; thus, it is important to consider marketing strategies to avoid or direct the effect of the information provided on the acceptability of the pork.

Dietary silage supplement modifies fatty acid composition and boar taint in pork fat

In organic pig husbandry, the use of roughage is mandatory as dietary supplement. This study investigated the effects of oat silage on the fatty acid composition, in entire males and gilts, as well as indole and skatole levels in perirenal adipose tissue of entire males. Entire males and gilts (forty-five to forty-eight pigs/sex) were assigned to two dietary roughage feeds (control with straw vs. oat silage). There was no significant effect of silage or sex on total SFA and MUFA in pork fat. However, the oat silage increased the total PUFA n-3 and decreased the PUFA n-6/n-3 ratio. The content of boar taint compounds (skatole and indole) in the entire male pigs did not differ between diets, although human nose scoring rejected in a greater extent more pork fat from entire males supplemented with oat silage, compared with those only supplied with straw. Approximately 50% of the entire males (90 to 97 kg of carcass) had low skatole values (≤0.1 μg/g), that were below the range of boar taint detection, regardless of the feeding regime. This finding indicates that more studies should be performed to avoid the problem of taint detection in entire males under organic production.

Sensory Profiling and Liking of Salami and Pancetta from Immunocastrated, Surgically Castrated and Entire Male Pigs

Simple Summary

Alternatives to surgical castration are an important issue in pig production due to societal concerns regarding animal welfare. Castration of piglets is a common practice to avoid boar taint, an unpleasant taste (urine/fecal like) of meat from uncastrated male pigs. In view of abandoning surgical castration and introduction of new alternatives, such as raising entire male pigs and applying immunocastration, several new issues are emerging. These include boar taint occurrence in case of entire male pigs and a deteriorated raw material (meat, fat) quality, which can affect consumer perception. Therefore, more information is needed about the consumer acceptance of products from the different alternatives. In the present study, two types of dry-cured meat products were assessed to give some insights into the sensory characteristic and consumers’ liking of the products coming from immunocastrated, entire male and surgically castrated animals.

Abstract

Consumer studies on acceptability of pork from immunocastrates (IC) and entire males (EM) are of primary importance, if these alternatives are to replace surgical castration (SC) of piglets. Data on the sensory traits and consumers acceptance of IC and EM meat products are still limited. Therefore, the purpose of the study was to (1) describe the sensory profile by quantitative descriptive analysis and (2) test the perception and consumer liking of salami (dry-fermented sausage) and pancetta (dry-cured belly) from EM, IC and SC animals. The consumer tests included the scaling method and check-all-that-apply. Profiling showed that EM products were scored lower in the overall sensory quality compared to IC or SC. EM products differed mainly from IC and SC in the intensity of the manure, sweat odor and flavor, persistent impression and texture (hardness, gumminess and easy to fragment). Salami samples did not differ in liking. In pancetta, the differences were significant for odor liking and visual quality (expected liking). Consumers did not perceive EM products as inferior in terms of liking, while sensory profiling indicated differences for boar taint presence and texture. Using meat originating from IC did not result in any differences in consumers acceptance as compared to products from SC.

Influence of Immunocastration on Slaughter Traits and Boar Taint Compounds in Pigs Originating from Three Different Terminal Sire Lines

Simple Summary

Due to the negative public opinion and welfare issues related to surgical castration, gradual introduction of alternatives like entire males and immunocastrates is taking place. Despite several economical and welfare advantages that the alternatives offer, numerous issues (i.e., boar taint, meat quality alterations), as well as their interactions with rearing and breeding (genetic) factors remain unanswered. Therefore, the focus of this study was to investigate the possibility of using different commercial sire lines in three male sex categories (entire males, immunocastrates, surgical castrates) and to compare their carcass traits, meat quality and boar taint compounds. A significant effect of terminal sire line and/or male category together with their interaction was observed for most of the investigated carcass and meat quality traits. The observed interaction should be taken into consideration when deciding on the production of a specific male category.

Abstract

The aim of the research was to investigate the influence of terminal sire line (TSL) and male category (MC) on carcass and meat quality of commercial fatteners. The study was performed on 180 pigs originating from three terminal sire lines: A (Pietrain × Large White), B (pure Pietrain), and C (Pietrain × Duroc × Large White), being assigned to three groups according to MC: immunocastrates (IC, n = 60), surgical castrates (SC, n = 60) and entire males (EM, n = 60). TSL affected most of the carcass and meat quality traits, together with the androstenone concentration. At the same time, MC had a significant effect on fat thickness, ham circumference, drip loss, cooking loss and androstenone and skatole concentrations. A significant interaction effect was observed for carcass length and ham circumference, as well as for most of the measured meat quality traits (except cooking loss, CIE L*, CIE b*, and Warner Bratzler Shear Force (WBSF)). Among the three investigated sire lines, immunocastration was shown to be most beneficial for fatteners sired by the TSL C. However, if deciding to raise EM, fatteners from the TSL B are recommended in terms of carcass and meat quality, although strategies for avoiding boar taint in their carcasses must be taken into consideration.

Recent genetic advances on boar taint reduction as an alternative to castration: a review

Boar taint is an unpleasant odor in male pig meat, mainly caused by androstenone, skatole, and indole, which are deposited in the fat tissue. Piglet castration is the most common practice to prevent boar taint. However, castration is likely to be banished in a few years due to animal welfare concerns. Alternatives to castration, such as genetic selection, have been assessed. Androstenone and skatole have moderate to high heritability, which makes it feasible to select against these compounds. This review presents the latest results obtained on genetic selection against boar taint, on correlation with other traits, on differences in breeds, and on candidate genes related to boar taint. QTLs for androstenone and skatole have been reported mainly on chromosomes 6, 7, and 14. These chromosomes were reported to contain genes responsible for synthesis and degradation of androstenone and skatole. A myriad of work has been done to find markers or genes that can be used to select animals with lower boar taint. The selection against boar taint could decrease performance of some reproduction traits. However, a favorable response on production traits has been observed by selecting against boar taint. Selection results have shown that it is possible to reduce boar taint in few generations. In addition, modifications in diet and environment conditions could be associated with genetic selection to reduce boar taint. Nevertheless, costs to measure and select against boar taint should be rewarded with incentives from the market; otherwise, it would be difficult to implement genetic selection.

Discrimination of Complex Odor Mixtures: A Study Using Wine Aroma Models

There are key unanswered questions when it comes to multicomponent odor discrimination. This study was designed to assess discrimination of odorant mixtures that elicit a singular percept. We collected data to address the following two questions: (1) What odor features do humans notice when attempting to discriminate between subtly different odor mixtures? (2) Are odor mixtures easier to discriminate when an odorant is added, compared with when a component is removed? Using modern aroma chemistry techniques, an odor mixture resembling a generic white wine was constructed. This wine odor mixture was modified using a series of three esters which are commonly found in white wines that vary in chain length and branching. Participants performed a sequence of discrimination tasks for the addition/subtraction of modifiers to the base wine at different concentrations. Only one of the esters (ethyl propanoate) led to a discriminable odor mixture. As concentration of the modifying odorant was increased, discrimination of odor mixtures was first reported because of changes in odor mixture familiarity and then intensity. We found similar sensitivity to changes in odor mixtures regardless whether the modifying compound was added or subtracted, suggesting that perceptual stability of odor mixtures is equally dependent on both imputing missing information (pattern completion) and disregarding extraneous information.

Consumer acceptance of minced meat patties from boars in four European countries

A consumer study was performed in four EU countries to further clarify the acceptability of meat with boar taint. In Denmark, France, Italy and Poland, a total of 476 female consumers evaluated 8 meat patties from boars with varying levels of skatole (0.10-0.40μg/g fat tissue) and androstenone (0.47-2.00 μg/g fat tissue), in a pair-wise comparison with patties from castrates. Boar meat patties were always less preferred than the castrate meat patties, regardless of the level of androstenone and skatole. Acceptability of the boar meat patties decreased with increasing skatole level. In samples with low skatole levels, higher levels of androstenone also reduced acceptability among androstenone sensitive consumers. No clear threshold levels for androstenone and skatole could be identified. Maps presenting the reduction in preference due to increasing levels of skatole and androstenone, and corrected for the general acceptance of the meat product were developed, taking into account androstenone sensitivity. Further work is needed, covering the whole range of androstenone and skatole levels found in entire male pigs and for a wider set of meat products.

Sensory evaluation of boar meat products by trained experts

Rearing entire male pigs, one of the alternatives for surgical castration, entails the possible occurrence of boar taint. This study aimed at the investigation of the acceptability of meat from entire male pigs in 8 different meat products (cutlets, bacon, blade loin, tenderloin, dry fermented sausage, cooked ham, dry-cured ham and minced meat) by trained assessors. Generally, the sensory evaluation of meat samples was affected the most in the androstenone (AEON) group, indicating that AEON is the most offensive boar taint compound for sensitive assessors. Differences between the meat products showed the highest potential for processing tainted meat in cold meat products, which was most likely due to the serving temperature on the one hand and production-related influences on the other. However, more insights regarding reducing and masking effects of production-related factors on boar taint are necessary.

Fatty acid composition and its association with chemical and sensory analysis of boar taint

A certain level of disagreement between the chemical analysis of androstenone and skatole and the human perception of boar taint has been found in many studies. Here we analyze whether the fatty acid composition can explain such inconsistency between sensory evaluation and chemical analysis of boar taint compounds. Therefore, back fat samples (n=143) were selected according to their sensory evaluation by a 10-person sensory panel, and the chemical analysis (stable isotope dilution analysis with headspace solid-phase microextraction and gas chromatography-mass spectrometry) of androstenone and skatole. Subsequently a quantification of fatty acids using gas chromatography-flame ionization detection was conducted. The correlation analyses revealed that several fatty acids are significantly correlated with androstenone, skatole, and the sensory rating. However, multivariate analyses (principal component analysis) revealed no explanation of the fatty acid composition with respect to the (dis-)agreement between sensory and chemical analysis.

Hydrolysable tannin-based diet rich in gallotannins has a minimal impact on pig performance but significantly reduces salivary and bulbourethral gland size

Tannins have long been considered ‘anti-nutritional’ factors in monogastric nutrition, shown to reduce feed intake and palatability. However, recent studies revealed that compared with condensed tannins, hydrolysable tannins (HT) appear to have far less impact on growth performance, but may be inhibitory to the total activity of caecal bacteria. This in turn could reduce microbial synthesis of skatole and indole in the hindgut of entire male pigs (EM). Thus, the objective of this study was to determine the impact of a group of dietary HT on growth performance, carcass traits and boar taint compounds of group housed EM. For the study, 36 Swiss Large White boars were assigned within litter to three treatment groups. Boars were offered ad libitum one of three finisher diets supplemented with 0 (C), 15 (T15) or 30 g/kg (T30) of HT from day 105 to 165 of age. Growth performance, carcass characteristics, boar taint compounds in the adipose tissue and cytochrome P450 (CYP) isoenzymes CYP2E1, CYP1A2 and CYP2A19 gene expression in the liver was assessed. Compared with C, feed efficiency but not daily gain and daily feed intake was lower (P<0.05) in T15 and T30 boars. Except for the percentage carcass weight loss during cooling, which tended (P<0.10) to be greater in T30 than C and T15, carcass characteristics were not affected by the diets. In line with the numerically lower androstenone level, bulbourethral and salivary glands of T30 boars were lighter (P<0.05) than of T15 with intermediate values for C. Indole level was lower (P<0.05) in the adipose tissue of T30 than C pigs with intermediate levels in T15. Skatole levels tended (P<0.10) to be lower in T30 and C than T15 pigs. Hepatic gene expression of CYP isoenzymes did not differ between-treatment groups, but was negatively correlated (P<0.05) with androstenone (CYP2E1 and CYP1A2), skatole (CYP2E1, CYP2A) and indole (CYP2A) level. In line with the numerically highest androstenone and skatole concentrations, boar taint odour but not flavour was detected by the panellists in loins from T15 compared with loins from C and T30 boars. These results provide evidence that HT affected metabolism of indolic compounds and androstenone and that they affected the development of accessory sex glands. However, the effects were too small to be detected by sensory evaluation.

Urinary signature of pig carcasses with boar taint by liquid chromatography-high-resolution mass spectrometry

Boar taint is an offensive odour that can occur while cooking pork or pork products and is identified in some uncastrated male pigs that have reached puberty. It is widely held that boar taint is the result of the accumulation in back fat of two malodorous compounds: androstenone and skatole. The purpose of this study is to assess a mass spectrometry-based metabolomics strategy to investigate the metabolic profile of urine samples from pig carcasses presenting low (untainted) and high (tainted) levels of androstenone and skatole in back fat. Urine samples were analysed by LC-ESI(+)-HRMS. Discrimination between tainted and untainted animals was observed by the application of multivariate statistical analysis, which allowed candidate urinary biomarkers to be highlighted. These urinary metabolites were positively correlated to androstenone and skatole levels in back fat. Therefore, the study suggests that the measurement of these urinary metabolites might provide information with regard to androstenone and skatole levels in live pigs.

Effect of piglet castration with nonsurgical sterilant on the zootechnical performance and pork carcass quality

ABSTRACT A non-surgical sterilant (NSS) was used with the objective of assessing the zootechnical performance, carcass and meat quality, and hormone levels. 90 male piglets were selected with birthweights varying between 1.5kg to 2.0kg. The control group was constituted of 45 males castrated by the conventional surgical method, at the seventh day of age, and the treated group was constituted of 45 males castrated with NSS (active principle of zinc gluconate in the concentration of 26.2mg/mL associated to the dimethyl sulfoxide at 0.5%), with the application of the first dose on the seventh day of age and the second dose on the fourteenth day of age. The zootechnical assessments were carried out on the farm and consisted: weight gain in the periods per animal and feed conversion. The slaughter of the animals and the assessment of the carcass and meat quality and hormone levels were carried out in a slaughterhouse and the municipality of Campinas (SP). The study demonstrated that the use of NSS was a viable alternative in relation to the zootechnical performance and the carcass quality. In relation to the meat quality there was no significant difference in the majority of the assessed parameters.

Consumers' sensitivity to androstenone and the evaluation of different cooking methods to mask boar taint

Boar taint is an unpleasant odour and flavour present in some entire male pigs that is due to the presence of androstenone and skatole. The aim of the study was to assess the sensitivity of 150 consumers to androstenone and to compare the acceptability and liking of meat from castrated and entire pigs, cooked with different cooking methods. Meat samples consisted of loins from castrated (CM) and entire male pigs (EM) with high levels of androstenone cooked by two cooking methods: sous-vide and fried/breaded with garlic and parsley. Consumers evaluated smell and flavour acceptability, and overall liking of CM and EM for each cooking method. The results of the study showed that dislike of androstenone odour increased significantly with sensitivity. The results of acceptability and overall liking were similar in CM and EM for both cooking methods. Therefore, the two cooking methods used in the study may be useful to mask boar taint.

Genetic relationships between measures of sexual development, boar taint, health, and aggressiveness in pigs

Breeding intact boars is a promising alternative to surgical castration of piglets. Genetic selection should enable farmers to solve problems due to boar taint and aggressiveness while taking into account potential consequences on other traits of interest. The aim of the study was to estimate genetic relations between sexual development, boar taint, health, and aggressiveness. About 1,600 Pietrain (purebred) or Pietrain × Large White (crossbred) boars were raised in a testing station. Blood samples were collected at about 105 kg BW for measuring sex hormones (testosterone and estradiol) and indicators of the inflammatory status (C-reactive protein [CRP], pig major acute-phase protein [pigMAP], and blood formula). Animals were slaughtered 9 d later and measured for boar taint compounds present in fat (androstenone and skatole) and skin lesions on carcass, an indicator of aggressiveness. For both genetic types, heritability was moderate for sex hormones (from 0.17 to 0.29) and skatole (0.24 for purebred and 0.37 for crossbred) and high for androstenone (0.63 and 0.70 for purebred and crossbred, respectively). Genetic correlations between sex hormones and boar taint compounds were moderate to high (from 0.31 to 0.95). Heritability was moderate for CRP (0.24 and 0.46 for purebred and crossbred, respectively) and very low for pigMAP (0.06 and 0.05 for purebred and crossbred, respectively. Numbers of leukocytes had moderate to high heritabilities according to the genetic type (from 0.21 to 0.52). Heritability of skin lesions was moderate for both genetic types (0.31). Genetic correlations were negative between sex hormones and inflammatory measures (from -0.46 to -0.05), positive between testosterone and number of lesions (0.43 and 0.53 for purebred and crossbred, respectively), and low between androstenone and lesions (-0.06 and -0.17 for purebred and crossbred, respectively). Overall, both breeds of pigs had very similar estimations of heritabilities, but estimates of genetic correlations were different for some pairs of traits. It would be possible to select boars based on their plasma concentration of sex hormones to decrease boar taint and aggressiveness without important consequences on the immune response. However, because of the strong links between boar taint and reproductive function, the possible consequences on the reproductive performance should be evaluated.

Interaction of Skatole and Androstenone in the Olfactory Perception of Boar Taint

This study analyzed odor-odor interactions of two malodorous volatile substances, androstenone and skatole, that may accumulate in fat and meat of uncastrated male (boar) pigs. Therefore, fat samples were collected from 1000+ entire male pig carcasses for sensory evaluation and quantification of boar taint compounds using gas chromatography-mass spectrometry (GC-MS). Each sample was sniffed by 10 trained assessors, resulting in 11 000+ individual ratings, which were subjected to statistical analysis. Pearson correlations of chemical traits and sensory traits (panel average) were higher for skatole [r(1029) = 0.59; p < 0.001] than for androstenone [r(1029) = 0.44; p < 0.001]. Linear terms of androstenone and skatole as well as their interaction significantly (p < 0.05) contributed to perception of deviant smell (R(2) = 0.43). Standardized regression coefficients illustrate the higher importance of skatole (β = 0.68) than androstenone (β = 0.39). Interindividual differences in the responses of assessors to androstenone and skatole are confirmed. A new curved approach is suggested because it better accounts for the interaction of androstenone and skatole than the "safe box" approach. On the basis of these data, sorting strategies using instrumental measurements are discussed. An automated detection based on only skatole measurements is recommended because its performance is only slightly inferior to a sorting based on both androstenone and skatole. Sorting thresholds need to be calibrated against consumer acceptance though.

Russian and Chinese consumers' acceptability of boar meat patties depending on their sensitivity to androstenone and skatole

The aim of this work was to study the sensitivity of Chinese and Russian female consumers to androstenone and skatole and to identify their preference for pork patties from entire male pigs compared with those from castrated pigs. One-hundred-twenty women in each country were enrolled. The sensitivity of the consumers to both compounds was tested using smell strips and triangular tests. Pairwise tests were performed comparing patties from castrated male pigs with patties from boars with different levels of androstenone and skatole. Approximately 70% of the Russian and 60% of the Chinese consumers were sensitive to skatole and 37% and 32% were sensitive to androstenone, respectively. Nevertheless, a higher percentage of sensitive Russian consumers compared to Chinese consumers disliked the smell of both compounds. In Russia, the consumers' preferences were higher for patties with low levels of both compounds, while no differences were found in China. In both countries, consumers who were sensitive to skatole also preferred patties with low levels of both compounds. Thus, the levels of androstenone and skatole affect boar patty preferences.

Consumers' perception and acceptance of boiled and fermented sausages from strongly boar tainted meat

Characteristic off-flavours may occur in uncastrated male pigs depending on the accumulation of androstenone and skatole. Feasible processing of strongly tainted carcasses is challenging but gains in importance due to the European ban on piglet castration in 2018. This paper investigates consumers' acceptability of two sausage types: (a) emulsion-type (BOILED) and (b) smoked raw-fermented (FERM). Liking (9 point scales) and flavour perception (check-all-that-apply with both, typical and negatively connoted sensory terms) were evaluated by 120 consumers (within-subject design). Proportion of tainted boar meat (0, 50, 100%) affected overall liking of BOILED, F (2, 238)=23.22, P<.001, but not of FERM sausages, F (2, 238)=0.89, P=.414. Consumers described the flavour of BOILED-100 as strong and sweaty. In conclusion, FERM products seem promising for processing of tainted carcasses whereas formulations must be optimized for BOILED in order to eliminate perceptible off-flavours. Boar taint rejection thresholds may be higher for processed than those suggested for unprocessed meat cuts.

Evaluation of different strategies to mask boar taint in cooked sausage

The use of smoking and/or spices was evaluated for their ability to mask boar taint in frankfurters manufactured from entire pigs with high levels of androstenone. Five frankfurter types were considered: control, smoked, flavouring+smoked, spicy and spicy+smoked. A trained panel in androstenone perception carried out a sensory profile on the different sausages. The highest scores for androstenone perception (odour, flavour and aftertaste) were found in frankfurters that included no masking strategy which indicated the effectiveness of the evaluated strategies. Regarding masking strategies, the contribution of spices and smoking to sensory perception of frankfurters was detected by the panellists. Smoking was the best strategy to mask androstenone odour, while the use of spices masked androstenone odour to a greater extent than androstenone flavour. Only the combined use of spices and smoking was able to eliminate the perception of androstenone. The application of this strategy in frankfurters could be an alternative in the commercialization of entire pigs.

Consumers' segmentation based on the acceptability of meat from entire male pigs with different boar taint levels in four European countries: France, Italy, Spain and United Kingdom

Two consumer studies were conducted to know the acceptability of pork with different boar taint levels: test 1 performed in Spain (n=126) and United Kingdom (n=146), and test 2 performed in France (n=139) and Italy (n=140). Each test had 3 types of pork: 'Female meat', 'Low boar tainted meat', and a third type was 'Medium boar tainted meat' or 'High boar tainted meat'. Three main clusters were identified on the basis of 'How delicious do you find this meat?': 1-Pork lovers, 2-Boar meat lovers, 3-Reject boar tainted meat. Additionally, in test 2, a fourth cluster was identified: 'Reject low tainted meat'. A group of 16.2-38.2% of consumers rejected meat from boars, and another group of 12.4-21.7% rated the meat with medium or high levels of boar taint better than the meat from females, identifying a niche for meat from medium and high levels of boar taint, and suggesting the need to select carcasses on the basis of boar taint.

Prevalence of boar taint in commercial pigs from Spanish farms

The presence of boar taint can affect the sensory quality of pork because the "off" odours and flavours can be detected by consumers. The aim of this study was to determine the prevalence of boar taint in pig carcasses from 30 Spanish farms located in different regions of the country. Hot carcass weight and subcutaneous fat thickness means were 79.4±8.19 kg and 18.4±5.09 mm, respectively. Subcutaneous fat samples were classified into different levels according to androstenone and skatole concentrations in adipose tissue measured using GC-MS and HPLC. Androstenone results were: 87.4% of the carcasses below 0.50 μg/g, 7.1% from 0.50 to 1.00 μg/g (medium level), and 5.5% ≥1.00 μg/g (high level). Skatole results were: 88.9% of the carcasses below 0.10 μg/g, 4.5% from 0.10 to 0.20 μg/g (medium level), and 6.6% ≥0.20 μg/g (high level). Given these results, a future online method to classify carcasses according to boar taint is strongly recommended.

Validation of boar taint detection by sensory quality control: relationship between sample size and uncertainty of performance indicators

To prevent impaired consumer acceptance due to insensitive sensory quality control, it is of primary importance to periodically validate the performance of the assessors. This communication show cases how the uncertainty of sensitivity and specificity estimates is influenced by the total number of assessed samples and the prevalence of positive (here: boar tainted) samples. Furthermore, a statistically sound approach to determining the sample size that is necessary for performance validation is provided. Results show that a small sample size is associated with large uncertainty, i.e., confidence intervals and thus compromising the point estimates for assessor sensitivity. In turn, to reliably identify sensitive assessors with sufficient test power, a large sample size is needed given a certain level of confidence. Easy-to-use tables for sample size estimations are provided.

Preliminary study of FMO1, FMO5, CYP21, ESR1, PLIN2 and SULT2A1 as candidate gene for compounds related to boar taint

An association study between polymorphisms of six genes and boar taint related compounds androstenone, skatole and indole was performed in a boar population (n=370). Significant association (P<0.05) was detected for SNP of FMO5 (g.494A>G) with all boar taint compounds, SNP of CYP21 (g.3911T>C) with skatole and indole, and SNP of ESR1 (g.672C>T) with androstenone and indole. mRNA expression of CYP21 and ESR1 was higher in CAB (castrated boar) compared to non-castrated boars; whereas, the expression of FMO5 and ESR1 was higher in LBT (low boar taint) compared to HBT (high boar taint) in liver tissue. FMO5, CYP21 and ESR1 proteins were less detectable in HBT compared with LBT and CAB in liver tissues. These findings suggest that FMO5, CYP21 and ESR1 gene variants might have effects on the boar taint compounds.

Evaluating the performance of sensory quality control: the case of boar taint

Detection of malodours referred to as 'boar taint' in entire male pigs is essential for quality control when refraining piglet castration. This study analysed the sensitivity and specificity of sensory evaluation by trained assessors (n=18) compared to chemical analysis of two marker compounds (androstenone, skatole) in backfat (n=794). Taking the measurement uncertainty into consideration, several cut-off thresholds for chemical analysis were exemplarily evaluated. Using the panel average score, sensitivity and specificity of sensory analysis ranged from 61 to 69% and 77 to 85%, respectively. Performance of individual assessors varied highly (sensitivity: 47 to 86%; specificity: 45 to 88%) and correlated to olfactory acuity to the compounds. According to receiver operating characteristic-curves, the average panel performed better than single assessors regardless of the sensory criterion shift. Agreement plots illustrate that high skatole levels are better detected than high androstenone levels (useful for assessor feedback). The agreement between sensory and chemical analyses was moderate. Assessors need to be selected carefully.

How olfactory acuity affects the sensory assessment of boar fat: a proposal for quantification

Due to animal welfare concerns the production of entire male pigs is one viable alternative to surgical castration. Elevated levels of boar taint may, however, impair consumer acceptance. Due to the lack of technical methods, control of boar taint is currently done using sensory quality control. While the need for control measures with respect to boar taint has been clearly stated in EU legislation, no specific requirements for selecting assessors have yet been documented. This study proposes tests for the psychophysical evaluation of olfactory acuity to key volatiles contributing to boar taint. Odor detection thresholds for androstenone and skatole are assessed as well as the subject's ability to identify odorants at various levels through easy-to-use paper smell strips. Subsequently, fat samples are rated by the assessors, and the accuracy of boar taint evaluation is studied. Considerable variation of olfactory performance is observed demonstrating the need for objective criteria to select assessors.

Object concepts in the chemical senses

This paper examines the applicability of the object concept to the chemical senses, by evaluating them against a set of criteria for object-hood. Taste and chemesthesis do not generate objects. Their parts, perceptible from birth, never combine. Orthonasal olfaction (sniffing) presents a strong case for generating objects. Odorants have many parts yet they are perceived as wholes, this process is based on learning, and there is figure-ground segregation. While flavors are multimodal representations bound together by learning, there is no functional need for flavor objects in the mouth. Rather, food identification occurs prior to ingestion using the eye and nose, with the latter retrieving multimodal flavor objects via sniffing (e.g., sweet smelling caramel). While there are differences in object perception between vision, audition, and orthonasal olfaction, the commonalities suggest that the brain has adopted the same basic solution when faced with extracting meaning from complex stimulus arrays.

Fast and solvent-free quantitation of boar taint odorants in pig fat by stable isotope dilution analysis-dynamic headspace-thermal desorption-gas chromatography/time-of-flight mass spectrometry

Boar taint is a specific off-odour of boar meat products, known to be caused by at least three unpleasant odorants, with very low odour thresholds. Androstenone is a boar pheromone produced in the testes, whereas skatole and indole originate from the microbial breakdown of tryptophan in the intestinal tract. A new procedure, applying stable isotope dilution analysis (SIDA) and dynamic headspace-thermal desorption-gas chromatography/time-of-flight mass spectrometry (dynHS-TD-GC/TOFMS) for the simultaneous quantitation of these boar taint compounds in pig fat was elaborated and validated in this paper. The new method is characterised by a simple and solvent-free dynamic headspace sampling. The deuterated compounds d3-androstenone, d3-skatole and d6-indole were used as internal standards to eliminate matrix effects. The method validation performed revealed low limits of detection (LOD) and quantitation (LOQ) with high accuracy and precision, thus confirming the feasibility of the new dynHS-TD-GC/TOFMS approach for routine analysis.

On the relationship between an Asian haplotype on chromosome 6 that reduces androstenone levels in boars and the differential expression of SULT2A1 in the testis

Background

Androstenone is one of the major compounds responsible for boar taint, a pronounced urine-like odor produced when cooking boar meat. Several studies have identified quantitative trait loci (QTL) for androstenone level on Sus scrofa chromosome (SSC) 6. For one of the candidate genes in the region SULT2A1, a difference in expression levels in the testis has been shown at the protein and RNA level.

Results

Haplotypes were predicted for the QTL region and their effects were estimated showing that haplotype 1 was consistently related with a lower level, and haplotype 2 with a higher level of androstenone. A recombinant haplotype allowed us to narrow down the QTL region from 3.75 Mbp to 1.94 Mbp. An RNA-seq analysis of the liver and testis revealed six genes that were differentially expressed between homozygotes of haplotypes 1 and 2. Genomic sequences of these differentially expressed genes were checked for variations within potential regulatory regions. We identified one variant located within a CpG island that could affect expression of SULT2A1 gene. An allele-specific expression analysis in the testis did not show differential expression between the alleles of SULT2A1 located on the different haplotypes in heterozygous animals. However a synonymous mutation C166T (SSC6: 49,117,861 bp in Sscrofa 10.2; C/T) was identified within the exon 2 of SULT2A1 for which the haplotype 2 only had the C allele which was higher expressed than the T allele, indicating haplotype-independent allelic-imbalanced expression between the two alleles. A phylogenetic analysis for the 1.94 Mbp region revealed that haplotype 1, associated with low androstenone level, originated from Asia.

Conclusions

Differential expression could be observed for six genes by RNA-seq analysis. No difference in the ratio of C:T expression of SULT2A1 for the haplotypes was found by the allele-specific expression analysis, however, a difference in expression between the C over T allele was found for a variation within SULT2A1, showing that the difference in androstenone levels between the haplotypes is not caused by the SNP in exon 2.