Maturity-dependent changes in the nutritional, functional, mineral, and structural properties of dragon fruit peel (Selenicereus spp.).

INTRODUCTION

Dragon fruit peel (Selenicereus spp.), a major by-product of fruit processing, is a source of dietary fibre, minerals, and bioactive compounds; However combined effect of maturity stage and variety on nutritional, functional, antioxidant, mineral, anti-nutritional and structural properties of dragon fruit peel is limited. Thus, this study aimed to analyze the physicochemical properties, antioxidant activities, anti-nutritional activities, functional properties, mineral and structural analysis of dragon fruit peel powder obtained from different maturity stages and varieties.

METHODS

Dragon fruit peels from four varieties (C, CM Pink, Taiwan Pink and Jumbo Red) at three maturity stages (25th,35th and 45th days after anthesis; DAA) were hot-air dried and analyzed for proximate composition, antioxidant activity [2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and ferric reducing antioxidant power (FRAP)], anti-nutritional factors, mineral composition, and functional properties. Structural characteristics were evaluated using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD).

RESULTS

The functional properties, such as oil absorption capacity, water-holding capacity, and swelling capacity also improved with maturity, from 1.33-1.66 g/g, 1.12- 1.13 g/mL, and 3.43-4.19 g/g, respectively, to 2.66-3.97 g/g, 2.05-2.31 g/mL, and 6.20-6.32 g/g, respectively. Dietary fibre and mineral contents increased with maturity, whereas total phenolic content, flavonoid content, and antioxidant activities declined. Phytic acid decreased, while oxalate and tannin contents increased moderately. The results of structural analyses showed a higher porosity and maturational changes in the functional groups and crystallinity.

DISCUSSION: Overall, mature dragon fruit peel had better nutritional and technological functionality, making it suitable as a food ingredient with additional fibre and mineral contents. In addition, bioavailability, digestibility, safety and formulation evaluation studies are needed to enable use in functional food systems.