For the analysis of complex samples, such as agricultural products and foods, comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC � GC �  TOFMS) is applied in conjunction with statistical data mining techniques to assess the differences between well-defined sample classes, e.g., a high quality versus a low quality food product. The Fisher-ratio (F-ratio) method, a data mining technique, comprehensively analyzes the GC � GC �  TOFMS data to find 2D locations in the GC � GC separation space of marker compounds that statically distinguish the sample classes. The discovered locations are referred to as hits, and a hit list is produced, from highest F-ratio to lowest, with a metric expressing the statistical quality of each hit. The data corresponding to significant hits are subsequently subjected, in hit order, to Parallel Factor Analysis (PARAFAC) for deconvolution, identification, and quantification of the differentiating marker compounds at each 2D chromatographic location. We demonstrate that this analytical platform is successful at finding marker compounds in complex samples such as cacao beans, the principal ingredient in chocolate. Cacao beans that are exposed to water during storage or transportation exhibit a loss of quality due to water damage; however, water damage is not always visibly apparent, and we instead seek chemical indications of water damage. Cacao beans from multiple origins were water damaged and subsequently monitored by sampling the headspace volatiles with solid-phase micro extraction (SPME) followed by GC � GC �  TOFMS analysis. The F-ratio method was applied to find marker compounds that indicate water damage, and thus provide chemical indicators of the resulting loss of quality. The discovered marker compounds may be used for determining whether cacao has been water damaged, even prior to visible evidence.

Development of discovery-based techniques for the comprehensive analysis of complex samples with GC � GC � TOFMS: Biomarker discovery for food products

247th National Meeting (2014)

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