Standardization of ultrasound-assisted extraction of bioactive compounds from kinnow mandarin peel

Citrus reticulata (kinnow mandarin) peels, which contain a plethora of bioactive compounds having nutraceutical properties, are discarded as waste, by the citrus processing industries. This organic waste holds a tremendous potential to be converted into nutritious value-added products, using various extraction approaches. Extraction helps in isolation of bioactive phytochemicals from the by-products that could be used as nutritional supplements in food systems. This study was carried out to standardize process parameters of probe sonicator, using response surface methodology, for separation of bioactives from kinnow mandarin peels. The crude extract obtained was analyzed for total phenolic content as well as antioxidant activity, using spectrophotometric analysis. Maximum TPC (36.17 mg GAE/g extract), DPPH radical scavenging activity (64.70% DPPH reduction), ferric reducing antioxidant power assay (28.17 mM/100 g), superoxide radical scavenging activity (57.37%) and hydroxyl radical scavenging activity (60.30%), were observed at an amplitude of 31%, liquid to solid ratio of 30:1 at 41 °C temperature after treatment time of 15 min. The extract obtained at optimized conditions was also analyzed via Fourier Transform Infrared Spectroscopy (FTIR) to validate various functional groups observed in the extract. This study can be helpful for developing a scale-up process, for utilization of nutraceutical potential of kinnow peels and development of functional foods. Thus, biorefining of kinnow mandarin peels can be beneficial for waste management in citrus industry.