Characterization of Pectin Extracted from the Peel of Dragon Fruit (Selenicereus cf. guatemalensis ‘Queen Purple’)

The dragon fruit (Selenicereus sp.) peel is a viable plant source for the extraction of polysaccharides such as pectin, the demand for which has increased significantly in the food and pharmaceutical industries. In Nayarit, Mexico, the Queen Purple variety of dragon fruit (Selenicereus cf. guatemalensis) is commonly cultivated. The peel is typically discarded, while only the pulp is utilized for direct consumption or processed into derivative products. The objective of this study was to characterize the properties of pectin extracted from the peel of dragon fruit (Selenicereus cf. guatemalensis ‘Queen Purple’). The yield, molecular weight, anhydrouronic acid content, betalain content, antioxidant capacity, and phenolic compounds were determined using gravimetric, volumetric, spectrophotometric, and colorimetric techniques, among others. Furthermore, the functional groups and degree of esterification of the pectin were identified using Fourier-transform infrared spectroscopy. The pectin presented a yield of 12.8%, esterification degree of 49.85%, molecular weight of 645 kDa, anhydrouronic acid, phenolic acid and betalain content of 98.27%, 195.7 mg EAG/100 gDW and 4.26 mg/100 gDW respectively and an antioxidant capacity of 149.6, 192.76 and 20.5 mg EAA/100 gDW by the DPPH, ABTS and FRAP methods respectively, classified as high-purity, low-methoxyl, intermediate-molecular-weight, with an important betalain content and antioxidant capacity. Based on these findings, the extracted pectin complies with the Food and Agriculture Organization specifications and shows promise as a functional ingredient in the food industry.