Hesperidin-enriched extracts for active food packaging from tangerine agro-industrial by-products using subcritical water extraction and resin purification

This study investigates the extraction and purification of polyphenols, particularly hesperidin (HE), from agro-industrial by-products (stems and leaves) for application in active food packaging. Subcritical water extraction (SWE) as an extraction technique and macroporous resin adsorption as a purification process were tested and optimized. At 140 °C (ASE, 15 min; solid-to-liquid ratio 1:20), SWE achieved ∼88% of the hesperidin (HE) yield compared to EtOH 70% (14.0 vs 15.9 mg g⁻¹ dry matrix, DM). Scale-up optimisation in a pressurised Parr reactor (140 °C, 5 min; solid-to-liquid ratio 1:20) afforded 11.3 mg HE·g⁻¹ DM, ∼80% of ASE performance. For purification, seven macroporous resins were screened; XAD-7 delivered the highest HE purity (≈25 g per 100 g extract) with a concentration factor of 5.4, while enriching total phenolics and radical-scavenging activity by 4.5- and 8.8-fold, respectively, and effectively removing simple sugars. HE adsorption onto XAD-7 exhibited pseudo-second-order kinetic behavior and was best fitted by the Freundlich isotherm. In dynamic (fixed-bed) mode at 5 bed volumes per hour (BV·h⁻¹), the adsorption capacity reached 132.8 mg·g⁻¹ resin, with a 50% saturation volume of 54 BV, and > 94% HE recovery at ∼24.6% purity. The HE-enriched fraction exhibited bacteriostatic effects against both Gram-positive and Gram-negative strains and strongly inhibited multi-species surface adhesion on plastic film (to <5% coverage), indicating anti-biofilm potential. Overall, the SWE–XAD-7 workflow provides a sustainable, scalable route to valorise citrus by-products into HE-rich functional ingredients aimed at active food packaging for food products.