Development of pullulan bioactive packaging and evaluation on frozen Tilapia fillets

In this study, trisodium trimetaphosphate (STMP) was used as a crosslinking agent to improve the water resistance and physical properties of pullulan. The decreasing O-H stretching vibration(3, 300 cm'¹) of crosslinking pullulan in FT-IR spectra indicate a higher degree of crosslinking was formed with increasing concentration of crosslinking reagent. In addition, nisin, a bacteriocin that produced by Lactococcus lactics, was incorporated into the pullulan film to develop an antibacterial food package system. The antibacterial activity of active pullulan film was also tested for common strains: E. coli, S. aureus, L. monocytogenes and V. parahaemolyticus, utilizing in vitro and on the meat. Results demonstrated that nisin and EDTA incorporated pullulan hydrogel could at least reduce 1.12 and 2.72 log of cfu in the S. aureus and L. innocua. In the frozen tilapia food package, frozen tilapia with active pullulan package could surely inhibit the growth of L. innocua and V. parahaemolyticus by at least 2.11 and 1.66 log of cfu in a 10-day test. In summary, the crosslinking strategy effectively improve the hydrophobic property of pullulan, and expect the active pullulan-nisin absorbend pad could apply to food package to extend the shelf life of meat.