Boar taint detection through volatile organic compounds sampling - A study on its optimisation through the use of SPME-GC-MS

Abstract

Surgical castration of piglets is known to be stressful and painful for piglets. Alternatives have hence gained a lot of interest in the recent years. These include immunocastration and rearing of entire males. However, an unpleasant odour, called boar taint can appear when cooking the meat of some entire males. Many researches are hence being undertaken to find reliable and fast methods to distinguish tainted from untainted carcasses in slaughterhouses. Amongst these methods are the VOCs-sensor based methods. The objective of this work is to contribute to the development of such sensor by optimising the extraction of the targeted molecules skatole and androstenone, performed through heating of pork fat where they are stored. Given that a multitude of VOCs are released when heating fat, sensor poisoning could easily occur. Another objective is hence to fully characterise the VOC profiles generated during this extraction. Firstly, the fat matrix was characterised. Skatole and androstenone content were determined to understand whether the fat obtained in the slaughterhouse is tainted or not. Once the tainted samples were identified, their fatty acids composition was analysed. Next, the work focused on studying the extraction of VOCs from pig fat at 150 °C and 180 °C by SPME-GC-MS. Although significant correlations existed between the content and the headspace concentrations at these temperatures, this study concluded that higher heating temperatures should be tested to extract more of these molecules and that working in a closed and controlled environment should be tested to limit lipid oxidation. This work was hence carried on by testing an innovative heating device coupled with SPME-GC-MS analysis. The fat was heated at temperatures up to 450 °C and the device’s air was replaced in various trials by argon and nitrogen to limit the formation of lipid oxidation products. Through multivariate data analysis tools, such as PCA, an impact of both temperatures and atmospheres on the VOC profiles was pointed out. Indeed, aldehydes relative abundance, among the main lipid oxidation products, decreases from 62.57% for air at 450 °C to 24.85% for nitrogen and 22.09% for argon. Concerning the temperature changes, heatmaps indicate a very highly significant distinction of the VOC profiles between 450 °C and the other temperatures. Additionally, this study confirmed that temperature had an impact on the extraction of skatole and androstenone. Indeed, although thorough validation is still on-going for the analytical method used to quantify these targeted molecules, increasing concentrations can clearly be observed from heating temperature 150 to 450 °C. In conclusion, this work greatly contributed to the on-going optimisation of skatole and androstenone extraction from pork fat. For the first time, the impact of modulating the heating atmosphere on the VOC profile generated when heating was proved. Further research must be performed to validate these findings and to test other sampling methods such as vacuum assisted sampling of the generated VOCs.