Within Europe the castration of male piglets without anesthesia has been common practice for decades to prevent the occurrence of boar taint - an offensive off-flavor in pork. This practice, however, is increasingly questioned and refused by the majority of the public, since it is evident that piglets suffer pain and serious distress during and after castration. To allow for future animal welfare, all stakeholders along the pork chain have therefore declared to voluntarily ban surgical castration without anesthesia by 2018. Instead, pork industry successively switches to the production of entire male pigs, which appears as the most suitable alternative to surgical castration. This change in production, however, is very likely to result in a remarkable amount of tainting carcasses entering the food chain.

To prevent consumers from tainting pork and to investigate the occurrence of boar taint in detail, the pork industry as well as scientific research demand for reliable boar taint detection methods. Thus, the main objective of this thesis was to develop a candidate reference method for the quantitation of both major and minor boar taint compounds, i.e., androstenone, skatole, indole, 3α-androstenol and 3β-androstenol, in porcine tissue. As the compounds of interest accumulate in fat tissue, back fat samples were selected as the matrix of choice for the intended boar taint analysis. To comply with the general requirements of a potential reference method, a special focus was put on fast and simple sample preparation, precise and simultaneous quantitation of the respective boar taint compounds, and proper validation of the novel method. All requirements are fulfilled by the newly developed GC/MS procedure that is especially characterized by the application of isotopically labeled internal standards in a stable isotope dilution assay (SIDA). Thereby, commonly used internal standards, being only fair structural analogs of the analytes, are replaced by isotopically labeled counterparts of the respective analytes, which exhibit almost identical physicochemical properties such as solubility, polarity or volatility. In consequence, the application of such isotopomers generally guarantees a virtually identical behavior of analyte and internal standard during sample treatment, chromatography and detection, and thereby delivers very reliable results. As suitable isotopically labeled internal standards were commercially not available, synthesis of the required deuterium labeled isotopomers was performed. After successful synthesis, the obtained isotopomers d3-androstenone, d3-skatole, d6-indole and d3-3β-androstenol were characterized in detail by NMR and MS techniques and subsequently applied for SIDA.

Based on the developed SIDA–GC/MS procedure for back fat analysis, a second GC/MS procedure was elaborated, allowing for the selective quantitation of skatole in porcine meat juice. Meat juice itself is obtained as drip loss when thawing muscle tissue and is currently explored as an alternative matrix in pork quality assessment, e.g., for Salmonella monitoring or haptoglobin measurement. After successful method development, a comparative measurement was performed investigating the correlation of skatole between meat juice and back fat samples in a set of entire male boars. High correlation between both matrices was found, thus confirming that meat juice is a suitable substitute-matrix for skatole analysis. Using this novel skatole analysis, a further quality-related parameter is now detectable in meat juice.

Finally, a small study was performed exploring the back fat concentrations of androstenone, skatole, indole, 3α- and 3β-androstenol in a set of entire wild boars. The investigation was focused on wild boars, because no or only negligible complaints about boar taint are usually observed with respect to the meat of entire wild boars. However, wild boars are the genuine form of our domestic pig breeds and hence should be likewise susceptible to boar taint. The performed back fat analysis, though, revealed significant differences in the concentrations of major and minor boar taint compounds between both subspecies with special emphasis on skatole. In this context, possible factors explaining these differences between wild and domestic boars such as their intestinal flora and anatomy, dietary composition, housing or genetic predisposition are discussed.

Schlagwörter: boar taint; androstenone; skatole; GC-MS; SPME; SIDA

Berichte aus der Lebensmittelchemie