**Background:** Procyanidins (PCs) are phenolic compounds with potent antioxidant, anti-cancer, anti-inflammatory, and cardioprotective properties, but their low bioavailability limits commercial application. Dietary fiber, particularly inulin, can improve polyphenol stability and bioaccessibility. However, the natural adsorption of polyphenols onto inulin is limited. Pulsed electric field (PEF) treatment, a non-thermal technology, can modify macromolecular structures and enhance molecular interactions. This study investigates whether PEF treatment can improve the complexation between litchi pericarp oligomeric procyanidins (LPPC) and inulin, and characterizes the resulting complex's physicochemical and processing properties.
**Methods:** Inulin (Fibruline® XL, average DP ≥23, purity >94.5%) was dissolved in water at 80°C and mixed with LPPC extracted from litchi pericarp. The mixed solution (conductivity 1523 μS/cm) was subjected to PEF treatment (exponential pulse width 50 μs, frequency 1.02 kHz). Electric field intensity (6.7–26.7 kV/cm), flow rate (1.25–2 mL/s), and sample cycles (1–9) were optimized for adsorption capacity (Qe). The complex was dialyzed (1 kDa membrane) against water for 48 h, concentrated, alcohol-precipitated, and freeze-dried. Adsorption isotherms were modeled using Langmuir, Freundlich, Redlich-Peterson, and Toth equations. Characterization included UV spectroscopy (200–400 nm), FT-IR (4000–400 cm⁻¹), DSC (50–270°C at 10°C/min), and SEM. Processing properties evaluated were water solubility (20–70°C), water holding capacity, steady shear viscosity (10–100 s⁻¹, 1–100 mg/mL), and texture profile analysis (TPA) of 40% gels. All experiments were performed in triplicate; significance was assessed by Duncan's multiple range test (p < 0.05).
**Key Results:** Optimal PEF conditions were electric field intensity 13.3 kV/cm, flow rate 1.25 mL/min, and 3 sample cycles, yielding a maximum adsorption capacity of 103.46 ± 0.27 μg/mg—a 31.71% increase over the untreated complex. Adsorption capacity increased with electric field intensity up to 13.3 kV/cm but declined at higher intensities (>13.3 kV/cm). The Redlich-Peterson isotherm model provided the best fit (R² = 0.99688), indicating multilayer adsorption on a heterogeneous surface. UV spectroscopy showed disappearance of the LPPC peak at 280 nm in the complex, suggesting bound (not free) procyanidins. FT-IR revealed disappearance of aromatic nucleus peaks (1610, 1518, 1415, 1283 cm⁻¹) and weakening of the inulin C₆-OH band at 985 cm⁻¹ in the complex, indicating hydrogen bonding and hydrophobic interactions. DSC showed disappearance of inulin's melting (185°C) and degradation (200°C, 230°C) peaks in the PEF-treated complex, indicating enhanced thermal stability. SEM revealed the PEF-treated complex had a flaky, porous, compact, and oriented structure versus inulin's larger spherical particles (10–70 μm). Water solubility of the complex (2.30–6.74% over 20–70°C) was lower than inulin (4.81–8.96%), but water holding capacity was higher (complex: 401.73 ± 6.01% vs. inulin: 347.47 ± 8.29% at 70°C). The complex exhibited higher apparent viscosity than inulin at all concentrations (e.g., consistency index kc = 92.718 vs. 1.415 mPa·s at 100 mg/mL) and greater shear-thinning behavior (flow behavior index n = 0.301 vs. 0.984 at 100 mg/mL). TPA showed the complex gel had significantly higher hardness (93.247 ± 4.970 g vs. 20.813 ± 2.121 g, +348%), gumminess (28.251 ± 1.953 g vs. 8.183 ± 0.686 g, +245%), and chewiness (25.615 ± 1.716 g vs. 7.908 ± 1.093 g, +224%) compared to inulin gel (p < 0.05). Springiness, cohesiveness, and resilience were not significantly different.
**Clinical Implications:** While this is a food science study without direct clinical data, the enhanced physicochemical and processing properties of the PEF-treated inulin-procyanidin complex suggest potential for developing functional food ingredients with improved stability, texture, and water retention. The complex could serve as a fat substitute, thickener, gelling agent, or stabilizer in food products. The improved thermal stability and binding capacity may also enhance the delivery of bioactive polyphenols to the colon, potentially improving their bioavailability and health benefits (e.g., antioxidant, anti-inflammatory, prebiotic effects). Further in vivo studies are needed to confirm the bioaccessibility and bioefficacy of the complex.