Green extraction of bioactive components from carrot industry waste and evaluation of spent residue as an energy source

Carrot processing industries produce 25–30% of waste in the form of carrot rejects, peels, and pomace which contain a large amount of high-value bioactive components. Green extraction of the bioactive components from carrot rejects with green solvents using closed-vessel energy-intensive microwave-assisted extraction was the objective of this work. In this work, three experimental studies were implemented. One uses 8 different green solvents for maximum yield of bioactive using green technology, and the other for the optimization of Microwave-assisted Extraction (MAE) parameters to enhance the bioactive components yield. Response Surface Methodology was employed to optimize the processing parameters including temperature, time, solid to solvent ratio, and solvent type. The optimized extraction conditions: treatment temperature of 50 °C for 5 min gave a significantly higher yield of total carotenoids (192.81 ± 0.32 mg carotenoids/100 g DW), total phenolic (78.12 ± 0.35 g GAE/100 g DW), and antioxidants by FRAP (5889.63 ± 0.47 mM TE/100 g DW), ABTS (1143.65 ± 0.81 mM TE/100 g DW), and DPPH (823.14 ± 0.54 mM TE/100 g DW) using a solvent combination of hexane and ethanol (1:3) with solid to solvent ratio of 1:40 (w/v). This green technology in combination with GRAS solvents promoted the best recovery of bioactive from carrot rejects. Moreover, the solid residue remained after the extraction of bioactive components exhibited higher carbon content (46.5%) and calorific value (16.32 MJ/kg), showcasing its potential to be used as an energy source.