Characterization Of Thymol/Sodium Alginate Composite Film And Its Application On Preservation Of Fresh-Cut Apple

As a kind of natural polysaccharide,sodium alginate has great potential in the study of film,but it has no antibacterial property after film and cannot inhibit the growth and reproduction of microorganisms in food.As a natural antibacterial agent,thymol has strong antibacterial properties.In this paper,using sodium alginate as the substrate,the composite film formed by sodium alginate has better properties after added thymol.The application of fresh-cut apple was studied to explore the practical adaptability of the composite film.The main research results are as follows:(1)Thymol was added to sodium alginate solution to form thymol/sodium alginate composite film.The thickness and color difference of the composite film did not change significantly.With the addition of thymol,when the concentration of thymol was 1 mg/mL,the mechanical properties of composite films have been improved.With the increase of its concentration,the water solubility,swelling degree and water vapor transmittance of the composite film are continuously reduced,and the water vapor transmittance is also continuously reduced,and the antioxidant performance is greatly improved.The composite film had strong inhibition on Escherichia coli and Staphylococcus aureus.(2)The light transmittance analysis showed that the light transmittance of thymol/sodium alginate film was significantly lower than that of sodium alginate film under the wavelength scanning of 200 ~ 800 nm.Fourier infrared scanning analysis(FTIR)showed that the addition of thymol made the absorption peaks of the functional groups O-H and C-O-C of sodium alginate film blue shift and the absorption peaks of the functional groups C-H red shift.The surface roughness of single sodium alginate membrane was observed by Scanning electron microscope(SEM).With the addition of thymol,the surface of the composite film was improved.When the concentration of thymol was 1 mg/mL,the surface of the composite film was relatively smooth and clean.However,when the concentration is 10 mg/mL,cracks will appear on the surface of the composite film.(3)Compared with single sodium alginate film,thymol/sodium alginate composite film can effectively maintain the better color of fresh-cut apple,maintain more SSC,TA and higher ASA.Compared with PE plastic wrap,the weight loss rate of fresh-cut apple was higher in the composite film treatment group.However,it maintained better color and hardness,as well as higher titratable acid and ascorbic acid content,and the bacterial growth and reproduction were effectively inhibited.In summary,thymol effectively improved the mechanical and functional properties of sodium alginate film,and endowed it with better antioxidant and bacteriostatic properties.In the application of fresh-cut apple preservation,the composite film maintained its quality and showed a good antibacterial effect,which extended its shelf life by two days.Thus,the thymol/sodium alginate composite film has a certain potential in fresh-cut fruit preservation.