A. Rajaei - Department of Food Science and Technology, College of Agriculture, Tarbiat Modares University, P. O. Box: ۱۴۱۱۵-۳۳۶, Tehran, Islamic Republic of Iran.
M. Barzegar - Department of Food Science and Technology, College of Agriculture, Tarbiat Modares University, P. O. Box: ۱۴۱۱۵-۳۳۶, Tehran, Islamic Republic of Iran.
Z. Hamidi - Department of Food Science and Technology, College of Agriculture, Tarbiat Modares University, P. O. Box: ۱۴۱۱۵-۳۳۶, Tehran, Islamic Republic of Iran.
M. A. Sahari - Department of Food Science and Technology, College of Agriculture, Tarbiat Modares University, P. O. Box: ۱۴۱۱۵-۳۳۶, Tehran, Islamic Republic of Iran.

Phenolic compounds, especially those of plant origin, constitute an essential part of the human diet, and are of considerable interest due to their antioxidant properties. In this study, Ultrasound-Assisted Extraction (UAE), Microwave-Assisted Extraction (MAE), as well as Maceration Extraction (ME) methods were applied for phenolic compounds’ extraction from pistachio green hull. Response surface methodology was employed to optimize the extraction conditions as regards the yield of the compounds. A Central Composite Design (CCD) was employed to investigate the effects of three independent variables, namely liquid-to-solid ratio (۸-۲۰ times), temperature (۲۵-۶۵ °C) and time (۵-۴۵ minutes) on the dependent variable (level of total phenolic compounds). The results indicated that within the same extraction time, the extraction yield through UAE was higher than those in ME and MAE methods. Correlation coefficients (R۲) of the models for UAE, MAE and ME methods were ۰.۹۵, ۰.۹۶ and ۰.۹۴, respectively. The optimal conditions for extraction of phenolic compounds from pistachio green hull through ME, UAE, and MAE methods were ۲۰(v/w), ۶۵°C, ۴۵ minutes; ۲۰(v/w), ۶۵°C, ۲۵ minutes; and ۲۰(v/w), ۶۵°C, ۴۵ minutes, respectively. Under optimized conditions the experimental values well agreed with the values predicted by the proposed models.

Phenolic compounds, Maceration method, Microwave-assisted extraction, RSM, Ultrasound-assisted extraction