Ultrasound assisted extraction of betacyanin from dragon fruit (Hylocereus polyrhizus) for sustainable natural colorant production

Abstract

Betacyanin, a natural pigment with potential antioxidant properties, is widely used in the food, cosmetic and pharmaceutical applications. However, it is sensitive to heat and light, presenting challenges in extraction and processing. This study comparatively evaluated conventional extraction and ultrasound-assisted extraction (UAE) for recovering betacyanin from Hylocereus polyrhizus flesh and peel. The novelty of this work lies in its integrated assessment of extraction efficiency, betacyanin yield, thermal degradation kinetics and bioactive compound profiles across two distinct plant matrices. Both methods were analyzed at varying solvent ratios and temperatures, and their effects on betacyanin yield were analyzed using three-way ANOVA, which revealed significant main and interaction effects. Spectrophotometric quantification, antioxidant assays, total phenolic content (TPC), total flavonoid content (TFC) and HPLC profiling were used to characterize extract quality. The highest betacyanin content was obtained using UAE with water as solvent at 45 °C for 10 minutes and 2.5 W g⁻¹ for flesh (430.25 mg/100 g), and 0.5 W g⁻¹ for peel (117.989 mg/100 g) respectively. UAE shortened the extraction time from 60 min to 10 min, an 83% reduction, indicating substantial energy savings while eliminating organic solvents and supporting green processing principles. Betacyanin showed marked degradation above 60 °C, especially under light exposure, confirming its thermolabile, photosensitive behavior. First-order-kinetics predominated under all thermal and photochemical conditions. Peel extracts exhibited slightly greater thermal stability, whereas flesh extracts demonstrated stronger antioxidant activity (66.61%). HPLC profiling confirmed betanin as the dominant pigment in the extract. Overall, UAE effectively enhances betacyanin recovery while retaining pigment integrity, offering a rapid, energy efficient and sustainable approach suitable for food grade natural colorant production.