In this study, the nano chitosan particles were produced by ionotropic gelation between sodium tripolyphosphate and chitosan. The effect of nano chitosan with or without sodium lactate coating was evaluated on physicochemical (pH, thiobarbituric acid, total volatile basic nitrogen, and peroxide), microbial (total mesophilic and psychrotrophic viable counts, lactic acid bacteria, yeasts, and molds), and sensorial properties of beef burgers within 24 days of storage at 4°C. The solutions of 1% nano chitosan (T1), 2% nano chitosan (T2), 2.5% sodium lactate (T3), 1% nano chitosan+2.5% sodium lactate (T4), and 2% nano chitosan+2.5% sodium lactate (T5) were used for the coating. Although the results showed the increment of microbial growth of all treatments during storage time, the T4 and T5 samples had the lowest microbial counts, which indicates the synergistic effect of sodium lactate and nano chitosan. The pH of all samples was acidic to neutral (5.48-7.15) and increased during 24 days of storage, and the pH value of T4 and T5 samples increased with a lower slope. On the other hand, the evaluation of peroxide and TBARS values exhibited that nano chitosan had a more efficient preservative effect than sodium lactate, and both of them individually had lower antioxidant activity than their combined form. Furthermore, T4 and T5 samples had the best sensorial scores. These results indicated that nano chitosan and sodium lactate had synergistic effects and could be effectively applied to expand the shelf life of beef burgers.
Keywords: Chitosan; Hamburger; Nanoparticles; Shelf life; Sodium lactate.