Extraction of polyphenols and antioxidants from pomegranate peel using ultrasound: influence of temperature, frequency and operation mode

The objective of this research was to investigate the effects of temperature (40-70 degrees C), frequency (37 and 80 kHz) and ultrasonic operation mode (normal, pulse and sweep), and their interactions on the recovery of phenolic compounds and antioxidants present in pomegranate peel using ultrasound-assisted extraction. The content of individual phenolic compounds, total phenolic compounds (TPC), antioxidant capacity (AC) and total extract yield (X-0) were analysed. Significant effects were observed between some sources of variation in recovery of individual compounds at TPC and X-0, and no significant effect was observed for AC. The process and conditions studied shown to be interesting to extract antioxidants, since a high antioxidant capacity was verified in the extracts. Temperatures around 50-60 degrees C, using 37 kHz frequency, and normal or pulse modes were the conditions that provided better yields of phenolic compounds and X-0. Regarding AC, the best condition observed was at 70 degrees C, 80 kHz frequency and continuous mode.