Thermal and antimicrobial properties of chitosan–nanocellulose films for extending shelf life of ground meat

• Addition of nanocellulose decreased glass transition temperature of chitosan polymers.
• Decreasing glycerol concentration significantly decreased glass transition temperature and melting point of the nanocomposites.
• Two constituent layers including chitosan matrix and dispersed nanocellulose were merged and united very well.
• Influence of the nanocomposite on improving shelf life of ground meat was significant.

Chitosan–nanocellulose biocomposites were prepared from chitosan having molecular weight of 600–800 kDa, nanocellulose with 20–50 nm diameters and various levels of 30, 60 and 90% (v/wCHT) for glycerol. Agitation and sonication were used to facilitate even dispersion of particles in the polymer matrix. The nanocomposites were examined by differential scanning calorimetry, X-ray diffraction and agar disc diffusion tests; finally, the film was applied on the surface of ground meat to evaluate its performance in real terms. Chitosan–nanocellulose nanocomposites showed high Tg range of 115–124 °C and were able to keep their solid state until the temperature (Tm) range of 97–99 °C. XRD photographs revealed that nanocellulose peak completely disappeared after their addition to chitosan context. Agar disc diffusion method proved that the nancomposite had inhibitory effects against both gram-positive (S. aureus) and gram-negative (E. coli and S. enteritidis) bacteria through its contact area. Application of chitosan–nanocellulose nanocomposite on the ground meat decreased lactic acid bacteria population compared with nylon packaged samples up to 1.3 and 3.1 logarithmic cycles at 3 and 25 °C after 6 days of storage, respectively.