Structural and physiochemical characterization of novel hydrophobic packaging films based on pullulan derivatives for fruits preservation

Pullulan acetate (PLAc), pullulan propionate (PLPr) and pullulan butylate (PLBu) with various degrees of substitution (DS) were synthesized from pullulan and different carboxylic anhydrides (acetic anhydride, propionic anhydride and butyric anhydride). The structure of PLAc, PLPr and PLBu were determined by Fourier Transform Infrared Spectrometer (FT-IR) and H-1 Nuclear Magnetic Resonance Spectroscopy (H-1-NMR) spectroscopy. Pullulan ester films were obtained by solvent casting. The water vapor permeability, oxygen permeability, surface hydrophobicity, color and mechanical properties were investigated. Compared with native pullulan, all pullulan esters film showed a lower TS. TS and EAB declined with the increase of DS. PLBu3 achieved the lowest water vapor permeability property at 0.792 x 10(-11) g/m s Pa and lowest oxygen permeability property of 0.625 x 10(-3) g/m(2) s. The onset of ripening was monitored in terms of reduction in flesh firmness loss and weight loss. Package fruits with pullulan ester films delayed the ripening and senescence and hence could be used as an effective edible coating for extending their shelf life.