Gymnema sylvestre-fortified spheres and beads from waste biomass: a circular bioeconomy approach for functional food delivery

Abstract

A novel circular bioeconomy approach was developed for formulating functional food delivery platforms with antidiabetic potential by combining brown seaweed, Sargassum cinctum, avian eggshell waste, and Gymnema sylvestre extract. S. cinctum yielded 25% of sodium alginate, whereas calcium chloride recovered from eggshells demonstrated 89.14% efficiency. FTIR spectroscopy confirmed structural integrity with characteristic carboxylate peaks (1600 and 1400 cm⁻¹) for alginate and Ca–Cl stretching (689.66 and 516.92 cm⁻¹) for calcium chloride. According to thermogravimetric analysis, calcium chloride exhibited heat stability up to 700 °C and alginate breakdown at 220–230 °C. G. sylvestre-fortified spheres (3.87 ± 0.31 cm) and beads (0.54 ± 0.06 cm) were made by ionic gelation at an optimal sodium alginate concentration of 4%. The spheres had a total phenolic content of 27.77 ± 1.29 mg GAE per g, a flavonoid content of 19.16 ± 0.56 mg QE per g, and a nitric oxide scavenging activity of 72.66% at 10 mg mL⁻¹. At 100 µg mL⁻¹, enzyme inhibition tests showed α-amylase (30.1%) and α-glucosidase (31.1%) inhibition, which was much less than acarbose (>90%). Studies on pH-dependent release showed that phenol was released more quickly at pH 1.2 (80.53 ± 0.87% by 120 min) and more slowly at pH 6.8 (59.13 ± 0.83% by 180 min). Korsmeyer–Peppas investigation revealed anomalous transport mechanisms (n = 0.94–0.98), and kinetic modelling revealed the Higuchi model as the best relevant descriptor (R² > 0.97). Despite lower taste scores (6.38–6.87), sensory analysis revealed acceptable consumer perception (total acceptability of 8.07–8.5 on a 9-point scale). This integrated approach effectively turns multiple waste streams into biodegradable functional carriers with pH-responsive release characteristics, even if bioactive loading adjustment is still required for commercial viability.