Development of active packaging films based on quaternary ammonium chitosan, polyvinyl alcohol and litchi (Litchi chinensis Sonn.) pericarp extract

Litchi (Litchi chinensis Sonn.) pericarp contains abundant polyphenols that are suitable materials for developing active packaging films. In this study, 1 wt%, 3 wt% and 5 wt% of litchi pericarp extract (LPE) was added into quaternary ammonium chitosan (QAC) and polyvinyl alcohol (PVA) matrix to develop active packaging films. The structural, physical and functional properties of QAC-PVA (QP) films were compared with LPE (QP-LPE films) and without LPE (QP films). Results showed QP film had a heterogenous cross-section whereas QP-LPE films displayed rough and uneven cross-sections. After adding LPE, the N-H, O-H, C-H and C=O stretching bands of QP films shifted due to the formation of intermolecular interactions between LPE and film matrix. LPE made the colorless QP film turned brown. QP-LPE films presented lower ultraviolet-visible light transmittance than QP film. After adding LPE, film thickness increased from 0.091 to 0.103 mm, film water vapor permeability increased from 14.98 x 10(-11) to 17.21 x 10(-11) g m(-1) s(-1) Pa-1, film oxygen permeability increased from 0.16 to 0.22 cm(3) mm m(-2) day(-1) atm(-1), film tensile strength increased from 14.10 to 17.41 MPa, and film elongation at break decreased from 36.94% to 25.13%. QP-LPE films quickly released polyphenols in distilled water within 4 h and displayed potent antioxidant activity. The antimicrobial ratio of the film against Escherichia coli, Salmonella typhimurium, Staphylococcus aureus and Listeria monocytogenes was elevated from 50.40-68.04% to 58.93-91.38% after adding LPE. Results suggested QP-LPE films could be utilized as antioxidant and antimicrobial packaging materials in food industry.