Sequential Extraction of Functional Compounds from Citrus reticulata Pomace Using Ultrasonication Technique

•Kinnow pomace is profuse with phenolic compounds and dietary fiber•Ultrasonication has emerged as an efficient tool for the extraction of bioactives•Temperature, amplitude, time, and liquid/ solid ratio affect the extraction yield•Extracted bioactive compounds can be used for the preparation of functional foods Kinnow (Citrus reticulata) pomace, a primary residue discarded by kinnow processing industries is profuse with phenolic, antioxidant compounds, and dietary fiber. These compounds can be separated from the by-products and utilized as functional ingredients. In this study, the process parameters of the probe sonicator were optimized, to enhance the extraction yield of bioactive compounds from kinnow pomace. At optimized parameters of amplitude (40%), liquid to solid ratio (38:1), temperature (40°C), and sonication time (12 min), total phenolic content of 7.89 ± 0.09 mg GAE/g pomace, DPPH reduction of 68.63 ± 0.79%, and ferric reducing antioxidant power assay of 31.17 ± 0.23 mM Fe2+/100 g, were observed. The biomass obtained after extraction of phenolic compounds contained 33.18-45.12% total dietary fiber, 68-72% of total dietary fiber was represented by insoluble dietary fiber. Analytical instruments such as FT-IR and GC-EI-MS were used to identify the functional groups in the extract, and physicochemical characterization of dietary fiber was performed using FT-IR, XRD. The oil and water holding capacities of dietary fiber proved that it can be utilized for the preparation of functional foods. The work-done in this research can be scaled-up to extract large volume of functional compounds from kinnow pomace for their utilization in development of functional/ health foods. Ultrasound-assisted extraction is an economical green technique used to extract bioactive compounds from plant materials. Since inadequate research is available on the value-addition of kinnow pomace using ultrasound-assisted extraction, the present research focused on the extraction of bioactive phytochemicals from kinnow pomace using ultrasonication. In this study, the wet pellet obtained after extraction of phenolic and antioxidant compounds has been utilized for extraction of dietary fiber to approach zero-waste waste management. This study can be applied to various citrus processing by-products and can be helpful for scale-up studies for the value-addition of these by-products using an extraction approach.