Isolation,Identification And Control Of Spoilage Microorganisms From Chaenomeles Speciosa(Sweet) Nakai

Chaenomeles speciosa(Sweet)Nakai is rich in nutrition and functional ingredients,and has unique medicinal and health value.It is popular with consumers and has a bright market prospect.However,there are still some problems in the storage of C.speciosa,such as microbial decay,loss of water,loss of nutritional and functional components,which lead to the decline of nutritional value,edible and medicinal quality.It is of great significance for the storage and preservation of C.speciosa to identify the types of spoilage microorganisms and select suitable antimicrobial agents to control them.In this paper,the tissue isolation method was used to isolate the microorganisms causing decay of C.speciosa.The main microorganisms causing decay of C.speciosa were identified by morphological and molecular biological identification.On this basis,the best combination of antimicrobial agents was determined by screening natural antimicrobial agents.The main findings are as follows:(1)The tissue isolation method was used to isolate the microorganisms causing decay of C.speciosa.Two strains of bacteria and six strains of molds were initially isolated,but no yeasts were isolated.The results of the return test showed that there were two strains of bacteria and three strains of molds causing the decay of C.speciosa.(2)The spoilage microorganisms from C.speciosa were identified by morphological and molecular methods as Bacillus megaterium,Bacillus pseudomycoides,Penicillium crustosum,Cladosporium velox and Penicillium expansum,respectively.(3)Natamycin was a good antimicrobial agent for Penicillium expansum,Cladosporium velox and Penicillium crustosum.It inhibited the mycelia growth of molds,increased the extracellular conductivity,slowed down the pH value decline,and caused obvious nucleic acid leakage.To a certain extent,it inhibited the synthesis of ergosterol.The minimum inhibitory mass fraction of natamycin on all three strains of mold was 0.002‰.(4)Lysozyme was a good bacteriostatic agent for Bacillus megaterium.?-polylysine was a good bacteriostatic agent for Bacillus pseudomycoides.Both of them can inhibit bacteria by enhancing the permeability of bacterial cell wall,leading to the leakage of nucleic acid and alkaline phosphatase.The minimum inhibitory mass fraction of Bacillus megaterium was 0.002%.The minimum inhibitory mass fraction of ?-polylysine against Bacillus pseudomycoides was 0.002%.(5)The optimal combination of antimicrobial agents determined by single factor and response surface test were: natamycin mass fraction 0.032%,?-polylysine mass fraction 0.033%,lysozyme mass fraction 0.041%.The decay rate and mass loss rate of C.speciosa treated with the optimal combination of antimicrobial agents were significantly lower than that of untreated C.speciosa,while the quality indexes such as soluble solid content,Vc content and titratable acid content were significantly higher that of untreated C.speciosa.