Sustainable valorization of tropical fruit peels for sustainable production of natural antioxidants and functional food ingredients†

Abstract

Tropical fruit peels, frequently discarded during agricultural and food processing, represent an underutilized source of natural antioxidants and bioactive compounds. This study aimed to valorize tropical fruit peels, namely mango, banana, dragon fruit, pineapple, and papaya, by transforming them into functional food ingredients. Ethanol-based ultrasound-assisted extraction was applied to enhance the bioactive compounds and their antioxidant potentials. The variation in physicochemical characteristics, bioactive components, and antioxidant capacity of various fruit peel powders was investigated. 2,2-Diphenyl-1-picrylhydrazyl (DPPH), ferric-reducing antioxidant power (FRAP), and total antioxidant capacity assays were used to evaluate the antioxidant activities. The qualitative method was used for the phytochemical screening. Additionally, reverse-phase high-performance liquid chromatography (RP-HPLC) analysis reveals their phenolic compositions. Then, the selected high-potential components were incorporated into biscuits. The digestion method was conducted following the INFOGEST protocol. Comparing all tested powders, the mango peel powder (MPP) had the highest total phenolic content (TPC) with 69.81 mg GAE per g and the highest antioxidant activity, which corresponded with the presence of gallic acid (13.95 mg g⁻¹), chlorogenic acid (9.62 mg g⁻¹), and quercetin (11.59 mg g⁻¹). The incorporation of MPP (5–15%) into biscuits improved nutritional composition and antioxidant potential while maintaining acceptable sensory characteristics at lower inclusion levels. Simulated in vitro digestion confirmed the retention and bioaccessibility of phenolics and flavonoids, indicating their functional relevance. This study addresses a gap in bioaccessibility and sensory acceptability of tropical fruit peel-fortified functional foods. This valorization framework also adopts circular economy principles, using residual biomass for composting. The findings demonstrate a green, scalable approach to transform fruit peel waste into health-promoting, functional ingredients aligned with sustainable food production.