Ultrasound-Assisted Extraction of Betalains from the Amaranthus Using Natural Deep Eutectic Solvents

Due to increasing consumer awareness, there is a growing demand for healthy foods by replacing synthetic colorants with natural alternatives. Amaranthus is a sustainable rich source of one such natural colorant, namely, betalains. Conventional extraction methods have various challenges, such as high solvent requirements and low extraction yield. To overcome these problems, the present study aims at developing a green extraction method for betalains from Amaranth by ultrasound-assisted extraction (UAE) employing natural deep eutectic solvents (NADES). Of the three Amaranth species screened, the leafy Amaranth is found to have the highest betalains content (24.79 ± 2.88 mg/100 g FW). Among the five NADES screened, lactic acid: fructose was identified as the most efficient solvent with a betalains yield of 79.68 ± 4.81 mg/100 g FW. The Box-Behnken Design (BBD) was employed to identify the best combinations of extraction process parameters. This approach enabled optimization through a reduced number of experiments. Subsequently, a machine learning model was employed to predict yield for all possible process parameter combinations. On identifying the most effective combination process parameters that resulted in the highest possible yield (306.72 mg/100 g FW), the same is experimentally validated (297.28 ± 10.76 mg/100 g FW). UAE employing NADES has resulted in a 3.7-fold increase in the yield of betalains over extraction with NADES alone and a 12-fold increase over conventional extraction. HPLC analysis confirmed that the structure remained intact even after processing. Based on the results, UAE employing NADES was demonstrated to be an attractive extraction methodology for downstream processing of betalains in particular and biomolecules, in general.