Chemical and antioxidant analysis of peels from two red-purple cactus pears (Opuntia streptacantha) from Altos Norte of Jalisco, Mexico

Resumen

The cactus pears, fruits of the Opuntia genus, exhibit a wide variety of colors and feature a juicy, fleshy pulp with numerous seeds enclosed within a thick peel. The peel, which accounts for approximately 50% of the fruit's weight, contains valuable components, including pigments, dietary fiber, and antioxidants. However, it is currently regarded as a waste product. The objective of the present research was to evaluate the chemical composition and antioxidant capacity of the peel from "Redondilla" (Opuntia streptacantha cv. Dojä) and "Cardona" (O. streptacantha cv. Jocoquillo), which are abundant in the Altos Norte of Jalisco, Mexico. The fruit cultivars were collected and assessed for their physical characteristics, including size, weight, and peel content. The peels were then analyzed for their chemical composition (proximate composition, qualitative phytochemical profile, total phenolic and betalain contents), as well as their antioxidant properties (DPPH, iron-reducing power), using spectrophotometric techniques. The fruits of the "Cardona" cultivar were larger and heavier (83 g) than those of the "Redondilla" (40 g). In both cultivars, 54% of the fruit weight is derived from the peel. The moisture (88%) and protein (1.0%) content of the peel of both Opuntia cultivars was found to be similar. However, the total dietary fiber (41.4% DW) and ash (10.9% DW) contents were higher in "Redondilla". The phytochemical profile of by-products of both cultivars was found to be similar, with the presence of alkaloids, sterols, tannins, flavonoids, and saponins. The aqueous extracts of the peels were used for antioxidant properties determination. The pigments content, comprising betacyanins and betaxanthins (131.86 and 102.81 mg/100 g DW, respectively), and the iron-reducing power (1,116.67 mmol TE/kg DW) were found to be greater in “Cardona”. In contrast, the total phenolic content (1,197.04 mg gallic acid eq./100 g DW) and DPPH antiradical capacity (39.19 mmol Trolox eq./kg DW) were higher in “Redondilla”. The results demonstrate that peels from Opuntia cultivars native to Altos Norte of Jalisco, Mexico, represent a source of biologically active molecules, including dietary fiber, betalains, and phenolic compounds with high antioxidant value and potential for use as antioxidant fiber and for the extraction and application of natural pigments and antioxidants in pharmaceutical, food and manufacturing industries with benefits in terms of health and sustainability.