Enhancing the solubility and pH stability of curcumin through polyvinylpyrrolidone conjugation for improving their bioavailability and use in fruit preservation

Abstract

Curcumin, a natural antioxidant and antimicrobial compound, shows great potential in food preservation due to its ability to inhibit microbial growth and oxidation. However, its limited water solubility and pH instability hinder its practical applications. To address these issues, curcumin was conjugated with polyvinylpyrrolidone (PVP) using a solid dispersion technique, resulting in a water-dispersible and stable formulation. The PVP-curcumin conjugate was characterized using Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), and Scanning Electron Microscopy (SEM), confirming the successful formation of an amorphous complex. Solubility studies showed that the conjugate entirely dissolved in water, whereas native curcumin mainly remained insoluble. Stability tests across a pH range of 1–12 demonstrated that PVP significantly enhanced the stability of curcumin, particularly under alkaline conditions. The antimicrobial activity of the PVP/Cur conjugate was assessed using the well diffusion method against Escherichia coli, Salmonella enterica, Pseudomonas aeruginosa, and Staphylococcus aureus. The inhibition zones ranged from 24 to 29 mm. Additionally, its application as a peach coating under non-ideal storage conditions (27–40°C) resulted in a significant reduction in moisture loss and microbial spoilage, thereby extending the shelf life to 12–24 days. This study highlights the multifunctional benefits of PVP/Cur, including enhanced solubility, bioavailability, and antimicrobial efficacy. These findings suggest its potential as a sustainable and innovative solution for food preservation and improving the post-harvest quality of perishable products.