Study On Screening Of Compound Essential Oil And Preparation Of Antimicrobial Film

People are very concerned about non-synthetic natural preservatives that are able to inhibit food-borne pathogens and extend shelf life of food,as well as their application to degradable packaging films so as to maintain food quality and protect the environment.This paper focuses on the antibacterial effects of plant essential oils.The orthogonal test was used to optimize the preparation process of the antibacterial packaging films.Then the characterization of the films was carried out to detect the antibacterial active of the new packaging.1?The antibacterial activity of seven plant essential oils was initially selected by filter paper method.The results showed that cinnamon oil had the strongest inhibitory effect on all strains,followed by clove oil and thyme essential oil.These three essential oils were further investigated The MIC and MBC values of the three essential oils were determined by solid double dilution method.The MIC values of clove oil,thyme oil and cinnamon oil were 0.25-1,0.5-1 and 0.0625?0.25 ?L/mL respectively,and the MBC values were 0.5-1,1 and 0.0625?0.50 ?L/mL.The combined antibacterial activity of clove oil and cinnamon oil was determined by the checkerboard dilution method The oil combination displayed synergistic effect against Staphylococcus aureus and additive effect against Escherichia coli,Vibrio parahaemolyticus,Salmonella,Aspergillus niger and Penicillium chrysogenum.Using Staphylococcus aureus as the testing bacteria,the ratio of clove oil and cinnamon oil for the best inhibitory effect was found to be 2:8 by filter paper method where the inhibition zone reached 32.13±1.06 mm The MIC values of the composite essential oils with the best ratio against Staphylococcus aureus,Escherichia coli,Vibrio parahaemolyticus,Salmonella,Aspergillus niger and Penicillium chrysogenum were 0.125,0.25,0.125,0.25,0.0625,0.0625 ?L/mL accordingly,meanwhile MBC values were 0.25,0.25,0.125,0.25,0.0625,and 0.0625 ?L/mL.2?The main components of clove oil were determined to be caryophyllene(51.92%)and eugenol(16.78%)under headspace injection conditions,while those under liquid injection conditions were eugenol(47.43%)and 2-methoxy-4-(2-Propyl)acetic acid phenyl ester(26.39%).In contrast,the main components of cinnamon oil were cinnamaldehyde(21.07%)and benzaldehyde(19.50%)under the headspace injection conditions,and were cinnamaldehyde(86.20%)and cinnamyl acetate(4.02%)under liquid injection conditions.The antibacterial effects of clove and cinnamon essential oils and growth of microorganisms were shown affected by the pH value of the medium where the bacteriostatic effect was enhanced generally in the case of more acidic and alkaline conditions.After treatment with different temperatures(40?,60?,80?,100? and 121?)and UV treatment at different times(20 min,40 min,60 min and 80 min),both clove oil and cinnamon oil showed good antimicrobial effects against the six tested microorganisms.3?In the single factor and orthogonal test,the formula of the composite film was optimized with respect to the amounts of added essential oil,polyvinyl alcohol and glycerin.The tensile strength,water vapor transmission,oxygen transmission and inhibition zone were tested Results showed that the formula to obtain the best antimicrobial effect contains the amounts of EOs,polyvinyl alcohol and glycerin at 0.85%,10%,and 0.4%respectively.The composite film prepared under these conditions has an opacity of 3.36,a tensile strength of 47.23 MPa,an elongation at break of 100.27%,inhibition zone of 11.08 mm,water vapor transmission rate of 250.41 g·(m2·day)-1 and oxygen transmission amount of 0.79 cm3·(m2·day)-1.Moreover,FTIR analysis showed that there were interactions between the compound molecules,resulting in a more stable structure with good compatibility.