Drying temperature and extraction method influence physicochemical and sensory characteristics of pistachio oils

Abstract

Drying is an important operation in pistachio processing to ensure good quality. Study of drying parameters is important since they affect the quality, mainly in color, flavor and nutritional value. Hence, drying parameters could also affect pistachio oils. Pistachios of variety Larnaka were dried at different temperatures (room, 30, 50, and 70°C). Changes in physicochemical quality parameters, stability, and chemical composition of the extracted oils were evaluated. Sensory evaluation was also performed. An increase in the peroxide value was observed when pistachios were dried at 70°C or when screw press was used to extract the oil, remaining low in the rest of oils extracted with the hydraulic press. A similar pattern was observed for K270 extinction coefficient. In addition, the oils from pistachios dried at higher temperatures (50°C, 70°C) showed an increase in polyphenol content and a decrease in stigmasterol. The oxidative stability was slightly higher when screw press was used. Changes in drying temperature and extraction system had no significant effects on fatty acid composition. Color sensory tests indicated a consumer preference for oils from pistachios dried at 70°C, which produced greenish oils. Pistachio oils with different characteristics are obtained depending on the drying temperature used, both of them acceptable by consumers.Practical applicationsPistachios are considered nuts with the most nutritional value and a rich source of natural antioxidants. Drying is an important stage during pistachio processing, as it affects their oil fraction. The extraction system may also influence the characteristics of the final product. The combination of the drying temperature and extraction system may produce oils with different characteristics, which could be an interesting alternative in order to fit any consumer preferences.Physicochemical parameters and chemical composition of pistachio oils obtained by means of two pressure systems were analysed. The effect of drying temperature of the pistachios was mitigated in the oils extracted with the screw press, whereas it was clearly visible in the oils obtained with the hydraulic press. The combination of drying temperature and extraction system produces oils with different characteristics.