Effect of microwave pretreatment on the extraction of antioxidant‐rich red color betacyanin, phenolic, and flavonoid from the crown of Cylindra‐type beetroot (Beta vulgaris L.)

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AbstractIn the context of “waste valorization,” recovery of biomolecules from agri‐food wastes by the innovative extraction technique has come to the forefront. In this investigation, the effect of microwave pretreatment on aqueous extraction of betacyanin (BC), phenolic, flavonoid, and antioxidant from the crown part of Cylindra‐type beetroot (Beta vulgaris L.) has been studied. Two major operating parameters of leaching, such as temperature and extraction time have been varied, ranging from 30°C to 60°C and 20–60 min, respectively to optimize the extraction of mentioned biomolecules through the response surface methodology technique. Moreover, the extraction of mentioned biomolecules by leaching was increased by microwave pretreatment (at 800 W for 3 min). As an example: the microwave‐assisted aqueous leaching process provided BC color compound 17.12 ± 0.37 mg/g dry matter (DM), total phenolic compounds (TPC) 57.89 ± 1.14 mg gallic acid equivalent (GAE)/g DM, total flavonoids content (TFC) 10.37 ± 0.00 mg quercetin equivalent (QUE)/g DM and total antioxidant activity (AA) 56.13 ± 0.92 mg ascorbic acid equivalent (ASE)/g DM. Whereas, BC, TPC, TFC, and AA were 3.04 ± 0.07 mg/g DM, 2.81 ± 0.11 mg GAE/g DM, 2.43 ± 0.41 mg QUE/g DM, and 4.38 ± 0.18 mg ASE/g DM by aqueous leaching process without microwave pretreatment. Subsequently, the existence of two major different BC, such as betanin and iso‐betanin have been examined by high‐performance liquid chromatography‐diode array detector‐electrospray ionization‐quadrupole‐time‐of‐flight. In addition, changes in the morphology of the plant matrix were pointed out by field emission scanning electron microscope. Our investigation has proven the positive impacts of microwave pretreatment on the extraction of mentioned bioactive compounds by infusion and maceration processes as well.Practical ApplicationsThe application of innovative emerging technologies for the effective scavenging of bioactive compounds from agro‐industrial discharges has been focused on. Under the study range, microwave‐assisted leaching extraction was found to be the most efficient method as it exhibited the utmost amounts of betacyanin, phenolic, flavonoid, and antioxidants in microwave‐assisted maceration and infusion processes. This investigation encourages the short‐time microwave pretreatment before the performance of traditional solid–liquid extractions in order to improve the extraction efficacy of plant compounds.