Preparation Of Clove Essential Oil Composite Antibacterial Film And Its Application In Preservation Of Yellow Peach

Yellow peach,also known as yellow flesh peach,belongs to the peach genus of Rosaceae.It is favored by many consumers because of its crisp pulp,delicious taste and rich nutritional value.However,yellow peach is not resistant to storage at room temperature,and the shelf life is generally 5-7 days.How to prolong the shelf life of yellow peach has become the key to the development of yellow peach industry in China.In this paper,Yanling Jinxiu yellow peach was used as experimental material to isolate and identify the strains causing its corruption at room temperature,and determine the main spoilage bacteria of yellow peach.The plant essential oil with good inhibitory effect on yellow peach spoilage bacteria was selected from four plant essential oils,and added to the chitosan polyvinyl alcohol blend film.The preparation process of the blend film was optimized by single factor test and response surface design,and the best blend film was obtained.The fresh-keeping experiment of yellow peach was carried out to explore its fresh-keeping effect on yellow peach,so as to provide scientific basis and theoretical support for prolonging the fresh-keeping period of yellow peach.The main research results are as follows:(1)Isolation and identification of main spoilage bacteria of yellow peach and their inhibitory effects of four plant essential oilsSeven kinds of molds were isolated and purified from rotten yellow peach,and three of them were found to have the ability of causing rot.morphological identification,rDNA its sequence analysis and phylogenetic tree construction were used to determine that the rotten bacteria of yellow peach were Fusarium tricinctum,Diplodia seriata and Fusarium oxysporum.The bacteriostatic effect of four plant essential oils on three line Fusarium,two spores and Fusarium oxysporum was studied by in vitro bacteriostatic test.The results showed that clove essential oil>Litsea cubeba essential oil>essential oil of Eucalyptus spp>Eucalyptus essential oil.At the same time,the bacteriostatic ability of four essential oils was further studied.Among them,the minimum inhibitory concentration(MIC)of the clove essential oil with the strongest bacteriostasis against three line Fusarium,two spores and Fusarium oxysporum was 1.25,1.25,0.625 μL/mL;The minimum bactericidal concentration(MBC)was 1.25,2.50 and 1.25 μL/mL.(2)preparation and properties of clove essential oil chitosan polyvinyl alcohol antibacterial filmThe antibacterial film of clove essential oil chitosan polyvinyl alcohol was prepared with chitosan and polyvinyl alcohol as the main film-forming substrate,clove essential oil as the antibacterial active substance and glycerol as the plasticizer.The effects of the addition amount of chitosan,polyvinyl alcohol,glycerin and clove essential oil on the mechanical properties,water vapor transmission and water resistance of the composite membrane were investigated by single factor test.Based on the results of single factor test,taking the tensile strength and elongation at break of the composite membrane as the indexes,the response surface methodology was used to determine the optimal parameters:the addition amount of chitosan was 1.56%,the addition amount of polyvinyl alcohol was 10.9%,and the addition amount of glycerin was 1.56%,When the content of clove essential oil is 0.81%,the tensile strength predicted by the software is 25.68 MPa,and the elongation at break is 292.95%.Under this condition,the test was repeated three times.The tensile strength of the composite film was 25.72±0.15 MPa,and the elongation at break was 295.12±4.5%.The structure,morphology and thermal stability of the composite membrane were studied by Fourier transform infrared spectroscopy(FT-IR),scanning electron microscopy(SEM)and thermogravimetric analysis(TGA),and the release of clove essential oil in different food simulants was investigated.The results showed that there was no chemical reaction after the compound clove essential oil was added,and only physical cross-linking hydrogen bonding occurred when the clove essential oil was added to the composite membrane.Proper concentration of clove essential oil can enhance the compactness of the membrane and have good compatibility.When the content of clove essential oil was 0.5%,the thermal stability of the composite membrane increased,but with the increase of clove essential oil,the thermal stability decreased.The experimental results of release rate showed that the release rate of clove essential oil in the composite membrane was significantly different in different food simulants.The release rate was the fastest in 50%ethanol and the slowest in 95%ethanol.(3)application of clove essential oil chitosan polyvinyl alcohol antibacterial film in preservation of yellow peachUnder the optimum film forming conditions,clove essential oil-chitosan polyvinyl alcohol antibacterial film was prepared and applied to the preservation of yellow peach.The changes of appearance,decay index,weight loss rate,hardness,soluble solids,respiratory intensity,titratable acid and malondialdehyde of yellow peach in different treatment groups at room temperature(temperature 23℃-26℃,humidity 70%-80%)and cold storage(temperature 4℃-5℃,humidity 60%-70%)were studied.The results showed that the overall preservation effect of clove oil packed with antimicrobial film was better than that of the chitosan polyvinyl alcohol blend film packaging group and the unpacked blank group,which significantly slowed down the weight loss rate,hardness,soluble solids content,and the rate of titratable acid content,and slowed down the increase rate of respiratory intensity and malondialdehyde content.Under the condition of 11 d storage at room temperature,the weight loss rate was 11.65%,the hardness was 1.56 N,the titratable acid content was 0.14%,the soluble solid content was 11.46%,and the malondialdehyde content was 1.24 μmoL/g;When stored under cold storage for 26 days,the weight loss rate was 3.83%,the hardness was 1.73 N,the content of titratable acid was 0.16%,the content of soluble solid was 10.93%,and the content of malondialdehyde was 1.01μmoL/g。Compared with the blank control group,the storage time of yellow peach was prolonged by 3-4 d at room temperature,and the storage time could be prolonged by 5-10 d under cold storage.