| Food simulants（distilled water,3%acetic acid,10%ethanol,50%ethanol and 95%ethanol）can simulate the characteristics of various foods and are widely used to study the migration of active ingredients from packaging materials to food.Antibacterial packaging materials are one of the development trends in the field of food preservation in the future.The composite film prepared from chitosan and plant essential oil has good antibacterial properties,but the migration behavior and mechanism of essential oil from composite film to food are still unclear.In this study,the chitosan composite film prepared from three essential oils of thyme,cinnamon and lemon was used to study the migration characteristics of essential oils in the food simulants.The relationship between the migration of essential oils and the properties and structure of the composite film was analyzed.The effects of drying conditions on the properties and migration of essential oils were also investigated.In addition,the effects of three active components of thyme essential oil such as thymol,linalool and carnation on the performance and structure of chitosan film were investigated in order to clarify the migration behavior in food stimulants.The study provided reference for the application of antibacterial chitosan active packaging film in food preservation.The main results are as follows:（1）The types of essential oil and food simulants affected the migration of essential oil in the composite film.Plant essential oils had good solubility in low-polar food simulants（50%ethanol and 95%ethanol）,and the partition coefficient of cinnamon essential oil was the larger than lemon and thyme essential oil.In contrast,the migration of essential oil was positively correlated with the solubility of composite film in food simulants,but negatively correlated with the swelling degree in 95%ethanol.In addition,in 3%acetic acid,the structure of chitosan composite films was seriously damaged,resulting in rapid swelling,solubility and migration of essential oil.Scanning electron microscopy showed that the presence of essential oil in the chitosan composite film varied with the type of food simulants,and distilled water and 3%acetic acid had a great influence on the essential oil composite film.FTIR analysis showed that 3%acetic acid and 95%ethanol had a great influence on the O-H bond of the essential oil chitosan composite film,and 95%ethanol caused the peak at 1552 cm-1（N-H）to shift to the high frequency band.（2）Drying treatment reduced the water content of the essential oil chitosan composite films and decreased water vapor permeability,the swelling and solubility in food stimulants.The migration rate of essential oil from the film was significantly slowed down,and the migration equilibrium time was significantly prolonged.（3）Thyme essential oil and its three main components significantly affect the properties of chitosan film solution and film.Thyme essential oil,thymol and caryophyllene improved the water resistance of chitosan film,reduced the swelling degree and solubility of the composite film in water as well as the mechanical properties of the film.However,the antibacterial properties of chitosan film were significantly improved with the addition of active components,particularly with thyme essential oil.The migration rate of essential oil and its components in 95%ethanol was significantly lower than that in water.In comparison,the migration rate of thymol was the fastest,followed by essential oil and caryophyllene,while no migration was observed in linalool.FTIR showed strong hydrogen bond interaction between chitosan and thyme essential oil,thymol and caryophyllene. |
