Development of a quantitative method for the simultaneous analysis of the boar taint compounds androstenone, skatole and indole in porcine serum and plasma by means of ultra-high performance liquid chromatography coupled to high resolution mass spectrometry

Enhanced HPLC Method for Boar Taint Quantification

Boar taint is an unpleasant odour found in the carcasses of entire male pigs, resulting from androstenone and skatole accumulation during pubertal development, and impacting pork quality. This study proposes the validation of an adapted chromatographic method for quantifying skatole and androstenone in the pigs' liquid fat using fluorescence detection. A good chromatographic separation was achieved, with skatole (SKA) and androstenone (AND) elution at 4.4 and 9.9 min., respectively. An external calibration method was applied, with calibration curves correlation coefficient of 0.9999 for both analytes. Detection limit values were 1.53 and 16.02 ng/g for SKA and AND, respectively. SKA recovery was 99.72±2.34 % (2.34 % RSD) and 102.84±1.62 % (1.57 % RSD) for AND. Results showed good precision values (repeatability <2.46 % RSD for SKA, <6.85 % RSD for AND; intermediate precision <2.87 % RSD for SKA, <6.98 % RSD for AND). The method's robustness was tested and the values were within the reference ranges. The validation results proved that the adaptation of an existing method resulted in good assessments of robustness, reliability and accuracy.

q value and parent energy optimization using a low-voltage ionization approach increases resolution in linear ion trap mass spectrometry

In this work, the isolation step in the linear ion trap was performed using different "q values" conditions at a low collision-induced dissociation (CID) energy leading to the parent ion resolution improvements, reasonably due to better ion energy distribution. According to the results, we obtained a greater resolution and mass accuracy operating in both traditional electrospray and low voltage ionization near the q value = 0.778 and with a CID energy of 10%. This effect was evaluated with low-molecular-mass compounds (skatole and arginine). The proposed optimization yielded a superior instrument performance without adding technological complexity to mass spectrometry analyses.

A sensitive electrochemical method for indole based on the signal amplification strategy by gold/iron-oxide composite nanoparticles

Indole is a major metabolite of tryptophan, which plays an important role in the intestinal microecological balance and human physiological activities. The determination of indole becomes important for its researches. So, it is urgent to establish a sensitive and cost-effective method for indole detection. Herein, a sensitive electrochemical method was constructed to determine the concentration of indole using screen-printed carbon electrode (SPCE) with the signal amplification strategy by gold/iron-oxide composite nanoparticles (Au/Fe₃O₄). Au/Fe₃O₄ nanoparticles were successfully synthesized under the irradiation by high-energy electron beams. 4-aminothiophenol (4-ATP) was connected to Au/Fe₃O₄ via Au-S bond. And then NaNO₂ reacted with 4-ATP to form the azo bond, which could form the final product of Au/Fe₃O₄@ATP-azo-indole by the coupling reaction. Thus, the concentration of indole was detected by the electrochemical signal produced by Au/Fe₃O₄@ATP-azo-indole indirectly. The detection sensitivity was greatly improved by the large specific surface area provided by Au/Fe₃O₄ after the modification. The linear range of indole was from 0.50 to 120.00 μg L^-1 and the limit of detection (LOD) was as low as 0.10 μg L^-1 (S/N = 3). Furthermore, the developed method exhibited acceptable intra-day and inter-day precisions with the coefficient of variations (CV) less than 4.9% and 8.2%, respectively. And the recoveries were from 97.2% to 105.4%. An innovative, sensitive, cost-effective method was established for indole determination in human plasma matrix in this manuscript, which provides a promising way for indole detection in conventional laboratories.

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.

Evaluation of the Effect of Surgical and Immunological Castration of Male Pigs on Boar Taint Compounds in Oral Fluid and Fat Tissue by LC-MS/MS Method

Introduction

An effective way of preventing undesirable boar taint in pork meat caused by the presence of androstenone, skatole and indole is surgical castration of piglets. This, however, arouses growing social opposition. An alternative method of inhibiting the development of unpleasant odour is immune castration. The aim of the study was to compare the effectiveness of both methods of castration for the elimination of the compounds responsible and to assess the suitability of oral fluid for pre-slaughter predictive testing for boar taint.

Material and Methods

The research material was pooled oral fluid and fat samples taken from gilts and surgically and immunologically castrated piglets. The samples were tested with a liquid chromatography– tandem mass spectrometry method developed in this research.

Results

The compounds giving rise to boar taint were found only sporadically above the accepted limits; only one sample of oral fluid contained skatole at a concentration above 200 μg L⁻¹ and one contained indole more concentrated than 100 μg L⁻¹. Indole above the limit value was also detected in one fat sample. In none of the tested samples was androstenone found.

Conclusion

The results indicate the similar effectiveness of both methods of piglet castration on the reduction of compounds generating boar taint. The usefulness of testing oral fluid for the ante-mortem prediction of boar taint has not been fully confirmed and further investigation is needed.

Application of gas sensors for modelling the dynamic growth of Pseudomonas in pork stored at different temperatures

Pseudomonas have a faster growth rate over other bacteria in chilled meat under aerobic conditions. A non-destructive method for modelling the dynamic growth of Pseudomonas in pork stored at different temperatures using gas sensors was presented in our work. Based on selected gas sensor data, the first-order kinetic equations (Gompertz and Logistic Functions) combined with the secondary model (Square-root Function) effectively simulated Pseudomonas growth in pork at different temperatures with R² and RMSE values of 0.71-0.97 and 0.27-0.84, respectively. Additionally, these models showed high accuracy with correlation coefficients greater than 0.90, in addition to several individual accuracy values. Furthermore, HS-SPME/GC-MS results demonstrated the presence of identified key volatiles in samples inoculated with Pseudomonas, including three amine compounds (mercaptamine, 1-octanamine and 1-heptadecanamine), phenol and indole. Our work showed that gas sensors are a rapid, easy and non-destructive method with acceptable feasibility in modelling the dynamic growth of spoilage microorganisms in meat.

Mechanistic insight into the role of immunocastration on eliminating skatole in boars

The accumulation of skatole in fat tissue is one of the predominant factors, causing boar taint. The present study was aimed to understand the mechanism whereby active immunization against GnRH (immunocastration) eliminates skatole in boars. Thirty-six boars were assigned within litter into three groups (n = 12): control, surgically castrated, or immunized against GnRH at 10 wk of age (with a booster 8 wk later). Faecal and blood samples (for skatole and skatole-regulatory hormone profiles) were collected at 4-wk intervals until boars were slaughtered (26 weeks). Immunocastration reduced (P < 0.05) serum levels of androstenone, 17β-estradiol and IGF1 especially after the booster immunization, and down-regulated (P < 0.05) mRNA expressions of both IGF1 and IGF1receptor (IGF1R) in mucosa of ileum as well as colon at slaughter. Compared to intact controls, immunocastration substantially decreased (P < 0.05) faecal skatole contents subsequent to the decrease of serum IGF1 levels, which persisted in boars after surgical castration. In parallel with the decreased formation of skatole in the intestine, levels of skatole in serum and then in fat tissue were also decreased (P < 0.05). On the other hand, deprivation of testicular steroids, especially androstenone and 17β-estradiol accelerated skatole degradation metabolism in the liver by increasing (P < 0.05) hepatic CYP2E1, CYP2A, CYP2C49 and CYB5A expressions. Collectively, our results suggested that immunocastration decreased skatole formation in the intestine and meanwhile accelerated skatole degradation metabolism in the liver, resultantly eliminating skatole accumulation in male pigs. Decreased intestinal skatole formation by immunocastration appeared to be associated with the attenuated actions of IGF1 on the turnover of both ileal and colon mucosa.

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.