Ultrasound-assisted extraction of bioactive compounds from black currant and chokeberry pomaces.

Constantly growing amounts of food wastes encourages to find new solutions to recover valuable components. Fruit industry by-products such as pomaces obtained after juice pressing are a source of bioactive compounds e.g., polyphenols, which are known as anti-oxidative molecules. The process of bioactive compounds extraction may be however harmful to environment and energy-consuming. In the following study sonication was used to improve the extraction efficiency and decrease energy and organic solvents consumption. Black currant and chokeberry pomaces obtained as by-products of juice pressing were dried. Bioactive extracts were collected in ultrasound-assisted process applying different parameters of ultrasound amplitude and time of sonication and using water as an extractant. Total polyphenol content of extracts was determined in Folin-Ciocalteu assay and antioxidant capacity of them was determined in ABTS study. Values of total polyphenol content were significantly higher when sonication was applied, reaching over 1.7-fold higher value of polyphenol content in chokeberry extract when 80% amplitude and 10 min time of ultrasound treatment were implemented, comparing to control. According to the literature main groups of polyphenols found in chokeberry pomace are anthocyanins followed by phenolic acids and flavonols and black currant pomace consists mainly of anthocyanins. Differences in antioxidant capacity values were also significant reaching maximum level of 0.27 μmol Trolox equivalent/ml of chokeberry extract and 0.33 μmol Trolox equivalent/ml of black currant extract. Both highest results were noted when 80% amplitude and 10 min time of ultrasound treatment were applied. Alternative extraction methods accelerate the extraction process and let obtain bioactive compounds-rich extracts from berry fruit by-products.