Simultaneous quantification of the boar-taint compounds skatole and androstenone by surface-enhanced Raman scattering (SERS) and multivariate data analysis

Abstract

This study investigates the feasibility of using surface-enhanced Raman scattering (SERS) for the quantification of absolute levels of the boar-taint compounds skatole and androstenone in porcine fat. By investigation of different types of nanoparticles, pH and aggregating agents, an optimized environment that promotes SERS of the analytes was developed and tested with different multivariate spectral pre-processing techniques, and this was combined with variable selection on a series of analytical standards. The resulting method exhibited prediction errors (root mean square error of cross validation, RMSECV) of 2.4 × 10(-6) M skatole and 1.2 × 10(-7) M androstenone, with a limit of detection corresponding to approximately 2.1 × 10(-11) M for skatole and approximately 1.8 × 10(-10) for androstenone. The method was subsequently tested on porcine fat extract, leading to prediction errors (RMSECV) of 0.17 μg/g for skatole and 1.5 μg/g for androstenone. It is clear that this optimized SERS method, when combined with multivariate analysis, shows great potential for optimization into an on-line application, which will be the first of its kind, and opens up possibilities for simultaneous detection of other meat-quality metabolites or pathogen markers. Graphical abstract Artistic rendering of a laser-illuminated gold colloid sphere with skatole and androstenone adsorbed on the surface.

Recent developments in quantitative SERS: Moving towards absolute quantification

“…With respect to other food safety concerns, several potentially carcinogenic substances that may be present in food have also been targeted for quantitation with SERS and these include aflatoxins in maize [34], Sudan I spiked in chili powder [35] and Rhodamine B in chili oil [36]. Finally, although not hazardous to health the boar-taint compounds skatole and androstenone, which alter the flavor of meat, have also been recently detected and quantified in pork fat using SERS [37].…”

Summaries

“…On-line boar taint evaluation of skatole with a colorimetric method was developed in Denmark to sort out carcasses with high levels of skatole and in few EU countries, some abattoirs use the human nose to classify male carcasses according its boar taint level. Several works aimed to evaluate rapid methods for boar taint detection like human nose quality control , as well as some technologies were tested for boar taint evaluation like sensors (Hart et al, 2016), Raman spectroscopy (Sørensen et al, 2015;Liu et al, 2016) and mass spectroscopy (Borggaard et al, 2017) providing promising results.…”

Feasibility of on/at Line Methods to Determine Boar Taint and Boar Taint Compounds: An Overview

“…The best way to compare and validate the method performance, would be to use standardized reference samples for all the technologies in a slaughter house setting. Data show that methods such as LDTD-MS/MS is robust and accurate [ 61 ] while other methods like REIMS and Raman spectroscopy are not that accurate [ 38 , 75 , 78 ] and since they are also calibration dependent, they will probably be less robust when implemented in different conditions.…”

“…Based on Raman spectroscopy, Sørensen et al [ 78 ] used a surface-enhanced Raman scattering (SERS). This modification of the Raman technique is carried out in an improved environment (nanoparticles, a determined pH and aggregating agents) that allows an indirect quantification using multivariate techniques such as partial least-square (PLS) and interval PS (iPLS).…”

“…Comparatively to the regular Raman spectroscopy, SERS has the advantage of measuring androstenone and skatole levels. However, in the present stage of development of the technique, the observed prediction errors are much too high (0.17 μg/g for skatole, 1.46 μg/g for androstenone) [ 78 ] to make the method of any use in boar taint detection.…”