Preparation Of Cinnamaldehyde-Loaded Shellac-Chitosan Composite Film And Its Application In Beef Preservative

In China,it is an inevitable trend for chilled meat to become the mainstream of meat consumption.However,problems such as short shelf life,surface browning,and loss of juice greatly limit the consumption of chilled meat.Under the promotion of natural and environmentally friendly,efficient and green concepts,it is of great significance to use natural ingredients for preservation of chilled meat.Among the meat preservation methods,coating preservation has the advantages of safety and low cost,and can control the ingredients according to the application scenario to adjust its preservation effect.Natural essential oil active ingredients are highly valued for their broad-spectrum antibacterial properties and safety.However,its instability and impact on food odors limit its application.Chitosan is a natural polymer resin with hydrophobicity,amphiphilicity and weak acidity,which is widely used as a carrier for composite coatings and loaded active ingredients.However,most studies only mix chitosan with film-forming materials to improve the properties of the film,or directly apply the nano-particles of loaded active ingredients to food.The food coating materials that combine the advantages of chitosan and active ingredients still need to be explored.Therefore,this paper first prepared Tween 80-stabilized chitosan nanoparticles by anti-solvent precipitation method,loaded the active ingredient cinnamaldehyde of cinnamon essential oil,and then combined with chitosan coating to explore the effect of chitosan nanoparticles loaded with cinnamaldehyde on chitosan film,and finally evaluated the preservation effect of coating on beef.The results of this paper can provide reference for the storage and preservation of chilled beef.The main research results of this paper are as follows:1.Optimization of the formulation of chitosan-cinnamaldehyde antimicrobial composite film loaded with payload cinnamaldehyde.The effects of Tween 80,chitosan,cinnamaldehyde,and glycerol content were investigated through single-factor experiments and orthogonal experiments to determine the best ratio.The experimental results showed that Tween 80 could improve the dispersion of chitosan particles and reduce the particle size of nanoparticles（<141.7 nm）and negative charge（absolute value<5.0 m V）.The increase in chitosan concentration could reduce the particle size to below 161.0 nm.Both of these factors exhibited an increasing-then-decreasing trend in the mechanical and light barrier properties of the film.The optimal level of single-factor experiment was 10 mg/m L and 7 mg/m L,respectively,with the tensile strength and elongation at break of the film being 11.8 MPa and 27.7%,and 17.0 MPa and 49.3%.The loading of cinnamaldehyde would increase the particle size of nanoparticles to 221.6 nm.The increase in cinnamaldehyde content would first decrease and then increase the tensile strength of the film,while the elongation at break showed a decreasing trend,with the tensile strength and elongation at break being 25.0 MPa and 14.1%at a concentration of 10 mg/m L.The antibacterial test showed that the optimal antibacterial effect was achieved when the cinnamaldehyde concentration was 10 mg/m L.Glycerol had a limited effect on the barrier properties but could increase the flexibility of the film.The performance of the film was significantly slowed down when the glycerol content was higher than 110μL,with the tensile strength and elongation at break of the film being 14.6 MPa and 41.8%.The results of the orthogonal experiment showed that the optimal concentrations or volumes of Tween80,chitosan,cinnamaldehyde,and glycerol in the best formula were 10 mg/m L,7 mg/m L,10 mg/m L,and 120μL,respectively,with the tensile strength and elongation at break of the film being 13.07±0.79 MPa and 53.41±1.34%.2.Preparation and characterization of chitosan-based antimicrobial composite film.The optimized formula is used to prepare the composite film,which is characterized in two dimensions,macroscopic and microscopic.Infrared spectroscopy analysis results show that chitosan and gelatin are cross-linked through electrostatic interaction,while cinnamaldehyde is synthesized through condensation with chitosan,generating substances containing carbon-nitrogen double bonds（C=N）.X-ray diffraction results show that the condensation products of cinnamaldehyde and chitosan are in a hydrated crystalline and amorphous state.The reaction of both substances with chitosan can improve the thermal stability of the film,and scanning electron microscopy images indicate good compatibility between the substances.Gelatin reduces the transparency of the film and changes its color to brown-yellow,but loading cinnamaldehyde restores the film’s smooth transparency.In addition,the addition of both substances can reduce the film’s light transmittance,water vapor transmission rate,and water content to 2 mm-1,4.5 g*h^-1*m^-3,and 25%,respectively.The curling and swelling phenomena of the film under different p H conditions are significantly reduced,indicating improved corrosion resistance and adaptability to a wider range of application scenarios.3.Application of chitosan antimicrobial composite film in beef preservation.The prepared composite film was applied to cooled beef to evaluate its effectiveness in delaying the deterioration of beef quality and extending its shelf life.The addition of cinnamaldehyde effectively inhibited the growth of total bacterial colonies while slowing down the rate of p H and TVB-N changes in beef.On the 10th day,the optimal formulation of cinnamaldehyde/chitosan-gelatin composite film treatment maintained the total bacterial count and p H at 106 CFU/g and 6.2,respectively,while the TVB-N value only reached 19.1mg/100g.The loading of nanoparticles further enhanced the antibacterial effect of cinnamaldehyde and extended the shelf life of beef.Additionally,both gelatin and cinnamaldehyde enhanced the barrier properties of the film.The cinnamaldehyde/chitosan-gelatin coated group kept the beef weight loss rate below 25%within 10 days,delaying the oxidation rate of beef and maintaining its color and sensory performance.Considering multiple indicators of beef freshness,film coating can extend the shelf life of beef by 2-4days.Moreover,the loading of nanoparticles also helps to reduce the impact of cinnamaldehyde on beef odor,which is of great significance for ensuring beef quality and eating experience.