Preparation Of Rosemary Essential Oil Chitosan Nanoparticles And Study On Quality Of Chilled Fish

Fresh fish has high water content and rich nutrients,so it is prone to spoilage and deterioration.Use safe,non-toxic,and green chemical preservatives for preservation in advance,and then place the fish in a low-temperature environment of 0 to 4 ?.It is an effective and common means to prevent the rapid growth of microorganisms on the fresh fish surface and prevent the excessive oxidation of unsaturated fatty acids in fish currently.In this paper,the one with the best preservation activity were select from 20 kinds of essential oils.Nano-preservative agents were prepared with plant essential oils as core materials and chitosan as wall materials.The preparation process of rosemary essential oil chitosan nanoparticles(CS-NP-REO)were optimized,taking encapsulation rate as an index,considering the result of single factor test and orthogonal test.Then the antibacterial activity,antioxidant activity and preservation effect on the grass carp of CS-NP-REO were investigated.The major contents and results as follows:1.The preservation effect of 20 kinds of plant essential oils on refrigerated grass fish was determined using the total volatile basic nitrogen(TVB-N)and the total number of colonies(TVC)as the evaluation index.The results showed that peppermint oil,thyme oil and rosemary oil could effectively inhibit the growth of total colonies during storage of refrigerated grass fish at a dose of 0.2%,and the antibacterial effect of rosemary essential oil was the best.The total number of the colonies on the grass fish treated by rosemary essential oil on 7th days of storage was 6.72 ± 0.04 log CFU/g.Citronella oil,thyme oil and rosemary oil can slow the rise in the value of refrigerated grass fish TVB-N,of which the best effect is rosemary essential oil,and the value of the TVB-N of the grass fish stored 7th days was 17.84 ± 1.27 mg/100 g.It could be concluded that rosemary essential oil has a better effect on the preservation of refrigerated grass fish.2.The rosemary essential oil chitosan nanoparticles(CS-NP-REO)were prepared by ion crosslinking method and its process is optimized.Taken encapsulation efficiency as main index,the influencing factors on nanoparticles are discussed,including the concentration of chitosan solution,the concentration of TPP,pH and the concentration of rosemary essential oil.The results showed that when the pH value in the reaction system was 4.0,the chitosan concentration was 2 mg/ml,TPP concentration was 1.5 mg/ml,REO concentration was 2 mg/ml,the volume ratio of CS/TPP/REO solution was 5: 2: 1,the CS-NP-REO showed a good dispersion,with the diameter of about 200 nm,the encapsulation efficiency(EE)of 84.5%,the loading capacity(LC)of 10.56%.3.CS-NP-REO has antibacterial and antioxidant activities.CS-NP-REO has a certain inhibitory effect on Gram-negative bacteria and Gram-positive bacteria.Bacillus subtilis exhibited highly sensibility.Minimum inhibitory concentration is 10.0 mg/mL.Escherichia coli exhibited moderately sensibility.Minimum inhibitory concentration is 20.0 mg/mL.At concentrations of 0.1 to 1.5 mg/mL,the DPPH free radical scavenging rate of CS-NP-REO was 14.3 to 61.5%.4.CS-NP-REO exhibited a good preservation effect during storage of grass carp.Through the comparison of refrigerated grass carp treated by CS-NP-REO,CS-NP and REO,the results can be concluded that CS-NP-REO can protect the fish color,inhibit the growth of bacteria,delaying lipid oxidation.The shelf life of refrigerated fish by CS-NP-REO reached 8 days at 4 and were prolonged 3?-4 days,while better than the separate treatment under the same concentration of chitosan or rosemary essential oil.CS-NP-REO can prolong the shelf life of chilled grass carp.