Effect of ultrasound pretreatment and solvent type on antioxidant capacity and phenolic compounds of coffee

Coffee is a rich source of methylxanthines, especially caffeine, hydroxy-cinnamic acids, especially chlorogenic acids and, for health benefits has been considered. In this research the effect of ultrasound pretreatment and then roasting process on extraction of phenolic compounds, flavonoids and free radicals scavenging capacity as well as the effect of solvent composition on the extraction phenolic and flavonoid contents were evaluated. The results of this research showed that ultrasound pretreatment can increase the extraction of phenolic compounds up to the 11.99% for a frequency of 20 kHz, 22.89% for 40 kHz and 13.52% for frequencies of 60 kHz frequency. The results also showed that ultrasound pretreatment can increase flavonoid extraction for the frequencies 20, 40 and 60 kHz; 13.65, 18.47 and 30.04 percent respectively compared to the control sample. The highest extraction of phenolic compounds related to the frequency of 60 kHz and isopropanol 60%, which was 31.51 mg per gram of Gallic acid. Ultrasound pretreatment had significant effect on the percentage of free radicals scavenging of DPPH (p