Subcritical Fluid Extraction of Antioxidant Phenolic Compounds from Pistachio (Pistacia vera L.) Nuts: Experiments, Modeling, and Optimization.

A process to obtain phenolic compounds with antioxidant properties from pistachio nuts using water/ethanol mixture under high temperature and pressure conditions was carried out. To optimize extraction conditions and antioxidant activity of bioactive compounds, theoretical models were scanned against experimental data. Phenolic profile was dominated by several flavonoids and gallic acid derivatives. A fitted model for phenolic compounds extraction presented a maximum predicted value under the following conditions: 220 °C extraction temperature, 6.5 MPa pressure, and 50% ethanol. Beneath these conditions, phenolic extracts gave the highest radical scavenging capacity, similar to that reached by using commercial antioxidants. A mathematical model, namely two-site desorption kinetic model, showed to be suitable for the description of extraction kinetics under the optimal operation conditions. Overall, the process described in this study shows a potential alternative method for extraction of pistachio bioactive compounds. PRACTICAL APPLICATION: Pistachio nuts are known to contain a vast array of phenolic and polyphenolic substances having strong antioxidant properties. Currently, the use of natural antioxidants in the food industry has increased, in consequence there is a growing interest in improving the extraction processes using GRAS (general recognize as safe) solvents. This study describes a safe, inexpensive, and short-time method (subcritical fluid extraction) to obtain antioxidant extracts from defatted pistachio nuts. This type of process may be adapted toward applications at industrial scale.