Drying kinetics, extraction kinetics and microencapsulation of antioxidant bioactive compounds of pitaya (Hylocereus undatus) peel

The prospects of commercialization in the market for exotic fruits are increasingly promising in Brazil. Pitaya, for instance, is a fruit that can be consumed either fresh or processed. During the processing of its pulp, there is generation of residues, mainly from the peel. The aim of this study was to evaluate the convective drying of pitaya peel and the extraction of bioactive compounds by cold maceration and ultrasound-assisted methods, as well as the microencapsulation (ME) process. The peels were cut and dried in an air circulation oven at 60 degrees C. Some empirical mathematical models were used to describe the drying process (Henderson & Pabis, Page, Peleg, Silva et al., Wang & Singh). The powders obtained from drying were subjected to ultrasound-assisted and cold maceration (4 degrees C) extractions and ME. Fresh peels (FR), extract obtained by ultrasound (US), extract obtained by cold maceration (CM) and microencapsulated extract (ME) were characterized for the Folin-Ciocalteu reducing capacity (FCRC), antioxidant capacity and phenolic compound profile by High-Performance Liquid Chromatography ( HPLC). According to the results, the Peleg model showed the best description for the convective drying of pitaya peel at 60 degrees C. ME extract showed the highest values for antioxidant capacity by DPPH and FCRC. US and CM extracts showed significant results at 5% probability level for antioxidant capacity by ABTS and FRAP, respectively. The main group of phenolic compounds quantified was flavonols, among which quercetin 3-glucoside had the highest concentration (70.25-361.45 g 100 g(-1)), and high levels were quantified for the betalains betanin and isobetanin, between 167.23 and 326.43 g 100 g(-1). The ME sample had the highest content of total phenolics quantified (TPQ) (1017.18 g 100 g(-1)), highlighting its technological potential for food production. [GRAPHICS] .