Study On Fresh-keeping Effect Of Compound Natural Plant Antimicrobial Agent On Phoenix Peach Storage At High Temperature

Honey peach(Prunus persica)is a peach plant of Rosaceae.Peach fruit is deeply loved by people for its high nutrition and delicious taste over the world.However,due to t its thin and juicy skin,peaches are susceptible to mechanical damage,water loss and fungal infection,leading to decay and deterioration,causing great economic losses.Therefore,improving the storage quality of peaches after harvest and prolonging the shelf life of fruits are urgent problems to be solved in the process of production and transportation of peaches.In this study,10 kinds of natural plants were screened for in vitro bacteriostasis test,and the natural plants with the best inhibitory effect on the pathogenic fungus Penicillium spp.of peach were screened out.Response surface methodology was used to optimize the extraction process of antimicrobial active substances from burdock.Meanwhile,Fenghuang honey peach was used as experimental material,and different concentrations of burdock extract,antagonistic yeast of Cryptococcus laurentii and sodium alginate were used to prepare biofilm.The effects of physiological indexes on the preservation of honey peach were analyzed.The aim was to explore a green,safe,efficient and pollution-free preservation method for the development of safety and to provide theoretical basis for the development of safe and healthy fresh-keeping products of peach.The main contents of the study are as follows:1.Screening of natural plant antimicrobial agents and study of antimicrobial effect on pathogenic bacteria of honey peach:The antimicrobial activity of 10 natural plants was extracted by ultrasonic method,and the antimicrobial test of Penicillium spp.was carried out.It was found that Arctium lappa had the best antimicrobial effect on Penicillium spp.On the basis of single factor experiment,response surface methodology was used to optimize the extraction process of antimicrobial substances from Arctium lappa.The optimum extraction conditions were determined as follows:ethanol concentration 46%,solid-liquid ratio 15%,ultrasonic time 73 min,and the predicted value of antimicrobial circle was 13.43 mm.The diameter of bacteriostasis circle is 13.3 mm,which is basically consistent with the theoretical predicted value.It shows that the model has good predictive effect,accurate and reliable results,and has good practical application value.2.The effect of burdock extract on the freshness-keeping effect of Fenghuang honey peach at high temperature:0.5%,1%,2%and 4%ethanol extract of burdock and sterile water were used to soak the peach fruit.After natural air-drying,they were stored at high temperature,and physiological indexes were measured daily.The results showed that Arctium lappa extracts at four concentrations could all delay fruit decay,control fruit weight loss,maintain fruit flavor and appearance quality to varying degrees,and the fresh-keeping effect of peach was negatively correlated with the concentration of Arctium lappa extracts.The fruit decay rate and weight loss rate of 0.5%Arctium lappa extracts treatment group were 51%and 4.7%lower than that of control group,respectively,and the content of soluble solids was 21.8%lower than that of control group.The results showed that burdock extract with 0.5%concentration was superior to other treatments in reducing fruit decay rate and maintaining hardness.It could maintain the appearance quality of fruits and improve the fresh-keeping effect of peaches.3.The effect of burdock extract combined with antagonistic bacteria on the storage quality of Phoenix peach at high temperature:The peach was treated with burdock extract and Cryptococcus laurentii alone and in combination,and the physiological indexes were measured daily.The results showed that both single and compound treatments had a certain fresh-keeping effect on honey peach fruit.The physiological and biochemical indexes were better than those of the control group.Compound treatment could significantly reduce the rot rate of honey peach fruit,which was only 10%at the end of storage,while the rot rate of the control group was 70%.The results showed that the combination of burdock extract and Cryptococcus laurentii could significantly reduce the respiratory intensity of fruits,delay fruit decay,reduce the content of malondialdehyde and polyphenol oxidase activity,and improve the storage quality of peaches.4.The effect of biological preservative on storage quality of Fenghuang honey peach at high temperature:Burdock extract and sodium alginate with different proportions were used to prepare biological preservative coating agent.The honey peach was coated and stored at room temperature,and physiological indexes were measured daily.The results showed that coated with sodium alginate and burdock extract at different proportions had certain antiseptic and fresh-keeping effects on peach fruits at room temperature.Among them,coated with sodium alginate and 1%burdock extract could significantly reduce the rot rate of peach fruits.On the 7th day of storage,the decay rate was 40%lower than that of the control group,and the treatment group could inhibit respiration and delay the peak of respiration,maintain fruit firmness and delay the increase of malondialdehyde content.Therefore,sodium alginate combined with 1%burdock extract coating treatment can significantly inhibit fruit decay,maintain fruit quality and prolong fruit shelf life.The main innovations are as follows:Firstly,the antimicrobial biological fresh-keeping material is natural,easy to obtain and had high safety.Natural plant inhibitors with the best bacteriostatic effect on pathogenic bacteria of honey peach were selected from 10 natural plants,and the optimal extraction process of burdock bacteriostatic substances was determined by response surface model.Secondly,the botanical bacteriostasis was innovatively combined with other biological preservation materials(antagonistic bacteria,sodium alginate)to prepare biological preparations.Full validation tests were carried out to find that the combined fresh-keeping treatment was better than the single fresh-keeping treatment,which provided new fresh-keeping methods and ideas for the pretreatment of fruits and vegetables such as peaches before entering the cold chain logistics transportation.In a word,the results of the experiments show that the burdock extract has a significant inhibitory effect on the growth of Penicillium spp.of peach pathogenic fungi;different concentrations of burdock extract have different preservation effects on peaches under high temperature(35<2 degree C),and 0.5%concentration of burdock extract has the best preservation effect;burdock extract and Cryptococcus laurentii yeast are combined to treat peaches.The effect of preservation was better than that of single treatment,and sodium alginate combined with 1%burdock extract could significantly inhibit fruit decay and prolong the shelf life of fruits.