Optimization of cold plasma and pulsed ultrasound conditions in the extraction of phenolic compounds from pomegranate seed meal

The waste generated during the processing and production of food products is one of the major problems in the food industry. Disposing of waste leads to the loss of valuable bioactive compounds, which, if identified and extracted, can have many applications in food products. Pomegranate is one of the fruits whose processing generates a significant amount of waste, and this waste is usually discarded without any reuse. In this study, the preparation of phenolic extract from pomegranate seed meal obtained by cold pressing was investigated. For this purpose, the microwave-roasted meal was treated with cold plasma for 10 min as a pretreatment for extracting phenolic compounds, and the conditions of voltage (16, 18, and 20 kV) and time (5, 10, and 15 min) were optimized in terms of achieving an appropriate amount of total phenolic content and antioxidant activity. Optimization of power (100, 200, and 300 W) and time (5, 10, and 15 min) was also conducted for the extraction of compounds using pulsed ultrasound. In the end, the type and amount of phenolic compounds were analyzed using HPLC. Based on the results, applying a cold plasma pretreatment with a voltage of 20 kV for 15 min and extraction with ultrasonic waves at 200 W for 15 min were the best conditions for extracting phenolic compounds. HPLC results also indicated a high amount of gallic acid compared to other compounds in the extract.