Effect Of Natural Essential Oil Combined With Cold Plasma On Sterilization Efficiency And Flavor Quality Of Salted Duck

Nanjing salted duck,as one of the traditional low-temperature sauced meat products in China,has the characteristics of rich nutrients and high water content,which is suitable for the growth and reproduction of microorganisms.Therefore,the products are prone to taste and deterioration,and the shelf life is short.The traditional high temperature and high pressure sterilization method is very easy to destroy the unique flavor of salted duck.However,in recent years,the irradiation technology still has some problems,such as the change of flavor caused by irradiation dose,low consumer acceptance and so on.As a new non thermal sterilization technology in food field,cold plasma sterilization technology has the advantages of simple and safe operation,high sterilization efficiency,low cost and no pollution to the environment.At present,it has been widely used in food sterilization and preservation.However,plasma treatment can cause lipid oxidation of meat products and reduce the acceptability of products.Therefore,how to shorten the plasma treatment time,reduce lipid oxidation,optimize meat flavor,and improve its sterilization efficiency is one of the difficulties and hotspots in current research.In this study,cold plasma cold sterilization(CPCS)technology was used to treat salted duck,and natural plant essential oil / antioxidant was used to enhance its germicidal efficacy,so as to inhibit the lipid oxidation of the product.At the same time,the effect of natural essential oil combined with CPCS on the volatile flavor of salted duck was analyzed,which provided a theoretical basis for the industrial application of low temperature plasma in sauced meat products.The results and contents are as follows:1.Effects of Cold Plasma Sterilization on Shelf Life and Flavor Quality of Salted DuckDBD cold plasma was used to sterilize prepackaged salted duck breast and duck neck.After the treatment time was selected from the pre experiment,the high-voltage electric field working voltage(55,65,75 k V)was used as the experimental factor.After a single treatment of 2 min and three cycles,the samples were stored at 4 ℃ and 75% relative humidity for 15 days,The changes of physicochemical indexes such as juice loss rate,thiobarbituric acid value(TBARS)and sensory quality were analyzed.The results showed that the bactericidal effect of CPCS on salted duck increased significantly with the increase of treatment voltage(P < 0.05).The bactericidal rates of total bacterial count and Escherichia coli in CPCS treatment group were as high as 97.8% and 99.8%,which could significantly extend the shelf life from 5-6 days to 15 days at most.In addition,CPCS treatment can effectively reduce the juice loss rate and inhibit the rise of total color difference during storage.In CPCS treatment group,the sensory quality of 65 k V treatment group was the best,and the shelf life of products could be extended to 14 days.Therefore,this study provides a theoretical basis and data reference for the application of CPCS technology in the preservation of low-temperature meat products.2.Effect of natural essential oil combined with CPCS on sterilization and preservation of salted duck and regulation of lipid oxidationIn this study,the suitable concentration of compound essential oil was selected from the aspects of bacteriostasis,total phenol content,DPPH radical scavenging rate,and then applied to salted duck samples with CPCS.The effects of essential oil addition on its germicidal efficacy,color difference,lipid oxidation and shelf life were analyzed.The results showed that the addition of essential oil could significantly improve the bactericidal efficacy of CPCS on the total number of microorganisms and Escherichia coli.The treatment group of essential oil combined with CPCS could reduce the coliform flora from 2.65 log(MPN /100 g)to 0.87 log(MPN / 100 g)and the total number of colonies from 4.46 log(CFU / g)to 2.12 log(CFU / g)in the control group,and extend the shelf life of samples from 6 days to 18 days,The shelf life of CPCS group was 5 days longer than that of CPCS group and 9days longer than that of essential oil group.In addition,essential oil combined with CPCS treatment could significantly reduce the lipid oxidation level of the samples during storage.The TBARS value of the control group increased from 1.91 mg / kg to 5.84 mg / kg,while that of the EOS + CPCS treatment group only increased from 1.12 mg / kg to 4.58 mg / kg.Therefore,the addition of essential oil can improve the germicidal efficacy of CPCS,reduce the lipid oxidation of samples,and maintain the sensory quality of samples during storage.3.Effect of natural essential oil combined with CPCS on flavor quality of salted duckElectronic nose,electronic tongue and headspace gas chromatography ion mobility spectroscopy(HS-GC-IMS)were used to analyze the changes and effects of cold plasma treatment,essential oil treatment and essential oil combined with cold plasma treatment on flavor(odor and taste)and volatile flavor of salted duck.The results showed that the electronic nose could accurately distinguish the samples from the control group,the essential oil treatment group and the essential oil + CPCS treatment group,but there was no significant difference between the control group and the CPCS treatment group.The electronic tongue was used to analyze the taste change of each sample.It was found that the addition of essential oil would lead to the change of bitter and astringent taste,while the bitter and astringent signal intensity of the essential oil would decrease after CPCS treatment.A total of 62 volatile compounds were identified by HS-GC-IMS,including 18 aldehydes,18 alcohols,12 ketones,8 esters,2 acids,one pyrazine and one furan.Compared with the control group,CPCS treatment group had more nonanal,n-octanal,propyl butyrate,1-octanol,3-Hexen-1-ol,1-nonanol,2,6-dimethylpyrazine and other substances.The volatile flavor compounds of essential oil treatment group and essential oil + CPCS treatment group were almost the same,but there were significant differences between the two groups compared with the control group,with less aldehydes such as hexanal,2-methylpropionaldehyde and heptanal,and ketones such as acetone,acetylacetone and 2-butanone,indicating that essential oil has certain antioxidant effect and can inhibit lipid oxidation.