Valorization of red dragon fruit peel (Hylocereus polyrhizus) as a functional ingredient for fortified biscuits: physicochemical, nutritional, and sensory implications
Mrityunjoy Biswas, Mahfujul Alam, Md. Akhtaruzzaman, Shafi Ahmed, MM Uddin, Atia Sanjida Talukder, Md. Asraful Alam, Bikramjit Biswas
Abstract
This study valorizes red dragon fruit peel (an agro-industrial byproduct) as a useful ingredient in biscuits. Proximate analysis of the Red dragon fruit peel powder (RDFPP) revealed a high crude fiber (23.68%), ash (10.60%), and carbohydrates (43.32%), along with bioactive components such as total phenolic content (0.34 mg GAE/g), flavonoids (53.32 mg QE/g) and antioxidant activity: 43.22%). Fourier transform infrared spectroscopy identified functional groups associated with polysaccharides, phenolic content, flavonoids, and lipids in both peel and biscuits. Biscuits containing 0-9% RDFPP were evaluated for physicochemical, bioactive, sensory, and microbiological qualities. Increasing RDFPP substitution increased ash (0.71% to 2.27%) and fiber (0.08% to 0.74%), while decreasing moisture (5.58% to 4.21%) and pH (5.34 to 5.03), enhancing shelf stability. Antioxidant activity and bioactive compounds increased proportionally, with 9% RDFPP showing the highest values (total phenolic content: 0.50 mg GAE/g; total flavonoids: 1.99 ± 0.02 mg QE/g; DPPH: 38.79%). Sensory evaluation indicated that 6% RDFPP was the ideal acceptability level, after which color (darker, L*: 36.61) and taste declined due to betacyanin pigments and acidic significance. Scanning electron microscopy analysis revealed structural porosity at higher RDFPP levels, correlating with texture changes. Microbial shelf-life studies showed that RDFPP has antimicrobial properties, reducing bacterial growth in 9% RDFPP biscuits (8.09 log 10 CFU/g) compared to the control (8.45 log 10 CFU/g) after 15 days. These findings highlighted the ability of RDFPP to enhance nutritional and functional properties of baked products. A 6% RDFPP substitution optimized antioxidant enrichment, fiber fortification, and consumer acceptance, providing a sustainable solution for repurposing agricultural waste into value-added foods.