Ultrasound Extraction and Microencapsulation for Increasing Stability of Anthocyanins Extracted from Purple Sweet Potato.

Abstract

The purple sweet potato is an adaptable and fast-growing crop that thrives in various soil conditions, making it efficient and accessible. Its high post-harvest durability and elevated anthocyanin content (≈ 1202.70 mg cya-3-glu/100 g w.b.) make it a promising source of natural pigments. However, anthocyanins are unstable due to physical and environmental factors, limiting their application. This study evaluated the stability of anthocyanins extracted from purple sweet potato using ultrasound for 4, 6, 8, and 10 min and amplitudes of 20, 40, 60, and 80%, and their microencapsulation by spray drying with maltodextrin. The microencapsulation efficiency was 81.93%. The infrared spectroscopy analysis confirmed the protection of the extract, while calorimetric analysis demonstrated its thermal stability. After two months of storage in the dark at room temperature (22-25 °C), 67.47% retention of anthocyanins was achieved, with a t_1/2 of 99.88 days. Physicochemical and rehydration properties of the microencapsulated were maintained over two months of storage. The results suggest that microencapsulation significantly improves the stability of purple sweet potato anthocyanin extract, offering a natural colorant with potential for the food industry.