Effect of ultrasound extraction conditions on yield and antioxidant properties of the fennel seed(Foeniculum vulgare) extract

Conventional extraction methods such as soxhlet, are time consuming and there is a risk of damage for heat-sensitive components. In this study, the new method of ultrasound and the conventional method of soxhlet were compared regarding to the yield and antioxidant properties of fennel seed extract. The soxhlet method conditions were temperature of85 °C, and duration of 240 minutes, while in ultrasound method the samples were examined at two temperatures (40 and 60 °C), three durations (15, 30 and 45 min) and three powers (100, 200 and 300 W). The results showed that the highest value of the extract yield, equivalent to 8.79 g dry extract/100 g of fennel seeds was obtained at 60 °C, 45 min and 300 W. There was no significant difference between soxhlet and ultrasound methods but ultrasound method caused an increase of 3.9 % than the soxhlet method. The highest amount of phenolic compounds equivalent to 3.15 mg/ml fennel seed extract was obtained at 60 °C, 45 min and 200 W, which was significantly different compared to soxhlet method and the ultrasound method caused an increase of 50.8 % of the phenolic compounds compared to the soxhlet. The percentage of DPPH free radical scavenging was highest at 60 °C, 15 min and 300 W, with 98.88% that there was no significant difference compared to soxhlet method and it only caused an increase of 0.18 % compared to the ultrasound method. Regarding to the time and low temperature, the superiority of the ultrasound method was proved.