The effect of chitosan on the properties of microfibrillated cellulose (MFC) film used in food packaging

Nowadays, safe food packaging is very important for consumers; because it is directly related to people health. Environmental issues have become more important in the production of food packaging. Plastic materials made from fossil polymers cause environmental pollution. For this reason, the use of green polymers, a suitable substitute for fossil polymers in the packaging industry is increasing rapidly. As an eco-friendly material, MFC has some properties required for active food packaging, such as low permeability to oxygen and high tensile strength. Chitosan is also a biodegradable material that antioxidant and antibacterial effects have been recently noticed in food packaging. This study was conducted with the aim of investigating the effect of adding chitosan on the properties of MFC film used in food packaging. At first, the bleached pulp from eucalyptus was converted into MFC with a consistency of 3% using a super disc grinder. To prepare starch, 40 g of starch was added to 1000 mL of water and turned into starch gel using heat. Then, starch gel was added to the bleached eucalyptus pulp with a ratio of 40 to 60% and after passing through the super disk grinding, the prepared gel was stored in the refrigerator. One gram of chitosan was stirred in 100 ml of 1.5 M acetic acid for 24 h, and after preparation, it was added to the bleached eucalyptus pulp and passed through the super disk grinding. Glycerol was also added to the gels as a plasticizer agent. After preparing the films with different compounds by casting method, antioxidant, antibacterial, tensile strength, oxygen and water vapor transmission rate (WVTR) tests and morphological examination with field emission scanning electron microscope (FE-SEM) ) and fourier transform infrared spectroscopy (FTIR) was performed. The results of the antioxidant test using DPPH and ABTS methods showed that films containing chitosan have the free radical scavenging activity. Also, films containing chitosan had an inhibition effect against gram-negative and gram-positive bacteria, Escherichia coli and Staphylococcus aureus. The tensile strength of pure MFC films was more than other films, and films containing chitosan and starch had lower tensile strength than pure MFC film. The addition of glycerol to the films caused a significant decrease in tensile strength. The oxygen and WVTR in pure MFC film was less than other films. The films containing chitosan, starch and especially glycerol had higher oxygen and WVTR. The results of this study showed that the MFC/chitosan film is a film with active properties and it is possible to prepare eco-friendly active food packaging films using these materials.