Improvement of application properties of chitosan-based food packaging films by lavender essential oil

Abstract: Ecological and environmental issues caused by traditional plastic packaging materials, and increasing food safety awareness have resulted in alternative packaging materials. Chitosan (CS) is a potential biodegradable material due to its edibility, film-forming capacity, non-toxicity, antibacterial activity, biocompatibility and biodegradability. Traditional chitosan-based composite films are made by the casting-evaporation method. However, inferior waterproof and mechanical properties limit their applications in food package industries. Many researches have been conducted to improve the CS film. Incorporating one or several substancesinto CS film have been widespreadly used. Moreover, acetic acid and chitosan-acetate can be removed from traditionally prepared CS film by alkali leaching, resulting in lower film water-solubility. Lavender essential oil (LEO) can be used as sedative, antispasmodic, antiviral and bacteriostat in industries of perfume, aromatherapy and pharmacy. LEO can also be used as a natural spice in drink, ice cream, candy, bakery and chewing gum. In order to improve the physical and mechanical properties of conventional chitosan-based food packaging films, lavender essential oil/chitosan composite films were made with CS by casting-evaporation-alkali leaching method in this study. The films microstructures were characterized by Fourier transform infrared reflectance spectroscopy (FTIR), X-ray diffraction (XRD). The impacts of LEO content on the thickness, mechanical properties, volatiles content, water contact angle, water solubility and swelling property of films were investigated. The results indicated that the partial functional group's locations of CS matrix were occupied by the LEO ingredients with reduced vibration intensity of covalent bond of CS. Reduced free hydrogen group could form hydrophilic bonds with water, then resulted in the loss of moisture content of films. Moreover, Chitosan-acetate content increased by incorporating LEO. The thicknesses of all films ranged from (20.60±0.34) μm to (23.35±0.65) μm. There was no linear relationship between the film thickness and LEO concentration. Tensile strength (TS) and elongation at break (E) behaved similarly when LEO was incorporated into the CS matrix. When the LEO content was 8%, broken tensile strength and elongation reached their maximum levels as (123.44±0.33) MPa and 3.74%±0.02%, respectively. The LEO/CS composite films had lower volatiles mass fraction compared with the CS film. The volatiles mass fraction decreased significantly and reached its minimum level as 8.98%±0.05% after incorporating of 2% of LEO into the CS film. The incorporation of LEO increased film water-solubilities . The films were classified as an insoluble matter due to their low water-solubilities, less than (1.21±0.04) mg/100 g. Water contact angle (WCA) and swelling index (SI) of films decreased with increasing LEO content. The minimum WCA and SI as 80.73°±0.32° and 0.62±0.01, were reached by CS-LEO (10%) film. The incorporation of LEO improved the physical and mechanical properties of chitosan-based composite films by casting-evaporation-alkali leaching method. As for physical or mechanical properties of the film, their optimal LEO contents were not identical. Therefore, the optimal LEO content needs to be verified with the field data. The CS-LEO (8%) film had the best mechanical properties, while CS-LEO (10%) film had the best waterproof properties. The cost of raw materials also need to be considered. It is expected that this study will assist in the production and application of LEO/CS composite films.