Ultrasound-assisted extraction of polyphenols from potato peels: profiling and kinetic modelling

Ultrasound-assisted extraction (UAE) at 33 and 42kHz has been investigated in the extraction of polyphenols from peels of two potato varieties, cream-skinned Lady Claire (LC) and pink-skinned Lady Rosetta (LR), commonly used in snack food production. Extraction efficacy between the UAE-untreated (control) and the UAE-treated extracts was assessed on the total phenolic content and antioxidant capacities (DPPH and FRAP). Application of UAE showed significantly higher recovery of phenolic compounds compared to solid-liquid extraction process alone. Lower ultrasonic frequency (33kHz) was more effective in recovering polyphenols compared to 42kHz ultrasonic treatment. The liquid chromatography-tandem mass spectrometry revealed that chlorogenic acid and caffeic acid were the most prevalent phenolics in LR peels, whereas caffeic acid was dominant in LC peels. Peleg's equationshowed a good correlation (R-2>0.92) between the experimental values and the predicted values on the kinetics of UAE of phenolic compounds.