| Tremella fuciformis is popular among consumers because of its high nutritional value and unique taste.However,the storage period of fresh Tremella fuciformis is very short and it is highly susceptible to microbial contamination and spoilage,especially Burkholderia gladioli,which is prone to produce the deadly toxin of bongkrekic acid,posing a great threat to food safety and human health.Chitosan is mostly used in synthetic coatings due to its adsorptive and film-forming properties,however,when used alone,chitosan has limited antibacterial and antioxidant capacity.Therefore,the addition of some bioactive substances to chitosan coating could improve its performance.Clove essential oil is a natural plant essential oil that has received much attention for its antioxidant and antibacterial activity.However,its application in the food industry is limited by its hydrophobic and volatile nature.Nanoencapsulation systems are an effective solution to solubility and volatility problems.Therefore,in this paper,optimal nanoemulsion formulations were obtained through screening and incorporated into chitosan coating to obtain composite coating for the control of B.gladioli and to investigate its effect on the freshness of fresh Tremella fuciformis.(1)Preparation and stability study of clove essential oil nanoemulsion(CNE).Clove essential oil was used as the oil phase,the optimum surface/co-surfactant was assessed by stratified volume and the optimum Km value was screened by the area of the pseudo-ternary phase diagram.After screening,Tween 80 and anhydrous ethanol(Km=3:1)were found to be the best formulation.When the mass ratio of clove essential oil to surfactant blend was 1:9,the nanoemulsion droplets were spherical and had the smallest particle size(16.47 nm)as well as good kinetic and thermodynamic stability.(2)Preparation and performance study of chitosan composite coating(CNE-CSC)with clove essential oil nanoemulsion.The functional system CNE was added to the chitosan solution to prepare the composite coating,which exhibited better antioxidant and antibacterial activities.CNE-CSC possessed excellent DPPH·and ABTS·+radical scavenging ability and iron reduction ability.Also,the inhibition experiments showed that CNE-CSC inhibited B.gladioli up to 90%when encapsulated clove essential oil was at a concentration of 1.25 mg/m L,and reduced biofilm production,disrupted cell structure and led to bacterial death.Moreover,the CNE-CSC composite coating was proved to be safe and non-toxic by cytotoxicity and acute toxicity tests.These results show that CNE-CSC had good antioxidant and antibacterial activities and can be used as a safe and ideal composite coating for food preservation.(3)Study on the effect of chitosan composite coating(CNE-CSC)with clove essential oil nanoemulsion on the inhibition and preservation of fresh Tremella fuciformis.The inhibition effect of CNE-CSC on B.gladioli substrates was verified by connecting the Tremella fuciformis inoculation model.Storage experiments revealed that the CNE-CSC composite coating with the addition of clove essential oil nanoemulsion could better maintain the quality of fresh Tremella fuciformis and reduce the microbial population,and had a positive effect on the weight loss,enzyme activity,and sensory quality of fresh Tremella fuciformis,delaying spoilage and deterioration compared with the chitosan coating alone.In conclusion,the new composite coating prepared by incorporating clove essential oil nanoemulsion into chitosan coating could effectively control the contamination of B.gladioli and improve the storage quality of fresh Tremella fuciformis.This clove essential oil nanoemulsion chitosan composite coating is expected to be used as a new green preservative for the antimicrobial preservation of fresh Tremella fuciformis. |
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