In-depth analysis of pistachio aroma compounds utilizing high-capacity concentration tools coupled with GC×GC-MS

The quality and consumer acceptance of pistachio are heavily influenced by its key organoleptic characteristics and aroma is one of these. This attribute is connected to various factors like cultivar, geographical origins, harvesting conditions, and storage, as is common with natural products. This study focused on evaluating the volatile organic compounds (VOCs) of pistachios from diverse geographic locations. The evaluation was conducted using a high-capacity concentration tool called HiSorb. Various HiSorb probes were tested to optimize results, considering factors such as temperature and extraction time, by means of a design of experiment. The extracted VOCs of 18 pistachio samples belonging to different geographic areas were subsequently analyzed using two-dimensional comprehensive gas chromatography - triple quadrupole mass spectrometry (GC×GC-QQQ-MS) equipped with a reversed fill/flush flow modulator. For the GCGC separation, a conventional (non-polar/polar) set of columns was used. The first dimension (1D) column used was a 20m  0.18 mm i.d.  0.18 µm film thickness; equivalent in polarity to 5% phenyl / 95% dimethyl polysiloxane, while the (2D) column was a 50ms 3m  0.25 mm i.d.  0.25 film thickness equivalent in polarity to 50% phenyl / 50% dimethyl polysiloxane. The MS was operated in single-Q mode, using electron-impact ionization (EI) at 70 eV. The ion source and transfer line temperatures were 200 °C and 250 °C, respectively. The scan range was set to 35–350 m/z, with an acquisition frequency of 50 Hz. A core of 15 volatile molecules able to discriminate the different geographic origins of pistachio samples was also established using classification algorithms (random forest). The use of GC×GC enhances separation power, maximizing the extraction of information and providing a chromatographic fingerprint of the VOCs in pistachios.