Physicochemical properties, volatile compounds, and oxidative stability of cold pressed kernel oils from raw and roasted pistachio (Pistacia vera L. Var Kerman)

Pistachio kernel oil (PKO) was prepared by cold-pressing from raw (RPKO), conventional (CRPKO), and microwave (MRPKO) roasted kernels for Kerman pistachio. Physicochemical properties, bioactive compounds, antioxidant activities, and thermal behaviors of extracted oils were determined in this study. Volatile compounds were tentatively identified and semi-quantified by headspace solid-phase micro-extraction combined with gas chromatography-mass spectrometry technique. The results showed that there was no significant difference between oil samples for some physicochemical parameters and fatty acid profiles. Roasting treatments caused an increase in total phenolics and antioxidant capacity and a decrease in levels of total tocopherols and chlorophylls. The thermal transition temperatures of the RPKO were -47.15 and -19.85 degrees C for crystallization, and -13.11 and 3.11 degrees C for melting. Among the 43 volatile compounds identified, the major compounds were limonene, -pinene, -myrcene, hexanoic acid, and nonanal in RPKO. The levels of these compounds decreased after roasting. However, concentrations of pyrazines, furans, and pyrroles increased significantly as a result of roasting, especially for CRPKO. Using a PV of 15meq/kg oil as a quality criterion, PKO stored in transparent glass bottles after exposed to fluorescent light (720 Lux) and room temperature conditions had an acceptable quality for only 30 days of storage. Practical applications: Pistachios are normally consumed as salted and roasted snacks or as an ingredient in bakery and confectionery products, desserts, and ice-creams. With the increasing consumption and demand for novel edible oils, the market is expanding and creating space for the production of the pistachio kernel oil. After analyzing the physicochemical characteristics and volatile compounds, roasting treatments may provide additional volatile compounds in the pistachio kernel oil. The research results suggest that cold-pressed pistachio kernel oil is highly susceptible to photo-oxidative degradation, and must be stored in containers with light-barrier properties together with the addition of some appropriate natural antioxidants. Physicochemical properties, volatile compounds, and oxidative stability of pistachio kernel oils obtained from different treated pistachio kernels (raw, conventional, and microwave roasting) by cold pressing method were analyzed. Results indicate that pistachio kernel oil can be produced by the cold pressing technique giving edible quality, which does not require chemical refining, and only a simple filtering or centrifugation to remove suspended plant materials may be needed. Conventional or microwave roasting treatments before pressing did not change the oil specifications significantly.