Effects of ultrasound frequency and process variables of modified ultrasound-assisted extraction on the extraction of anthocyanin from strawberry fruit

The aim of this work was to evaluate the effects of ultrasound frequencies from 18 to 90 kHz on the extraction of anthocyanin from strawberry fruit by using an approach of modified ultrasound-assisted extraction (MUAE) that was based on a frequency search device with six extraction tanks controlled by a computer. According to the obtained optimal frequency of 62-64 kHz, the effects of other different process variables, such as treatment time, temperature, ultrasound power and solvent to solid ratio, on the extraction of anthocyanin were also studied in comparison with heat assisted extraction (HAE) and ultrasound-assisted extraction (UAE). The obtained results showed that the maximum yield of 796.9 mu g/g of anthocyanin was obtained at the optimized conditions of ultrasound frequency of 62-64 kHz, solvent to solid ratio of 6 mL/g, ultrasound power of 120 W, temperature of 45 degrees C and treatment time of 12 min with 55% ethanol as the solvent. The application of MUAE showed that anthocyanin yield increased by about 42% and 22% higher than that of HAE and UAE, respectively. These findings demonstrated MUAE is not only an effective and feasible method for extracting anthocyanin from strawberry fruit, but also promising for extracting active components from natural materials in industry.