Study On Preparation Of Fingered Citron Peel Essential Oil Microcapsule And Its Application In Edible Film

At present,the industry of fingered citron is facing problems such as low comprehensive utilization rate of resources,insufficient deep processing and low product conversion rate of its natural products.In this study,the essential oil was extracted from the fingered citron peels and was then embedded into microcapsules by 2-hydroxypropyl-β-cyclodextrin.Finally,the embedded particles were loaded into the sodium alginate edible film applied to the preservation of blueberries.This study aimed to improve the utilization rate and the deep processing level of fingered citron and its essential oil.Meanwhile,this study also provided theoretical data for the application of fingered citron essential oil in fruit preservation.The main research contents and results are as follows:(1)Study on the extraction,composition,and activities of fingered citron peel essential oil(FPEO):The extraction process of FPEO was optimized through single-factor experiment and response surface experiment,with extraction rate as the evaluation index.The result showed that the optimum extracting conditions were:enzymatic hydrolysis p H 5.2,enzyme addition 0.7%,enzymatic temperature 52℃,and enzymatic hydrolysis time 2.1 h.Under the optimum conditions,the extraction rate of FPEO was 3.11%.42 volatile components were identified in FPEO,with linalool acetate(14.72%),d-limonene(14.58%),and linalool(8.89%)ranking among the top three in terms of relative content.In the antioxidant activity study,the results showed that FPEO had favorable ability to remove ABTS+·and DPPH·,with half clearance rates were 5.043 mg/m L and 30.994 mg/m L respectively.In the antibacterial activity study,there was a dose-effect relationship between FPEO concentration and antibacterial activity.Meanwhile the antibacterial activity of FPEO on three pathogenic microorganisms was different:Staphylococcus aureus>Salmonella enteritidis>Bacillus subtilis.(2)Study on the preparation,characterization and stability of FPEO microcapsules:The embedding process of FPEO microcapsules was optimized through single-factor experiment and response surface experiment,with the OD value of inclusion rate and yield as the evaluation index.The result showed that the optimum embedding conditions were:feed ratio9.2:1,inclusion temperature 50℃and inclusion time 1.97 h.Under this conditions,the average inclusion rate of microcapsules was 73.28%,the average yield was 82.05%,and the OD value was 0.9438.In the study of microcapsule characterization,the particles size distribution of microcapsules was relatively uniform,and the average particle diameter was about 241.5 nm.Under SEM,it was observed that the microcapsule particles showed a rhombic shape without pores.The results of SEM,FTIR and TG-DTG-DSC all demonstrated the successful encapsulation of microcapsules.Stability study showed that microencapsulation could effectively reduce the quality loss of FPEO in harsh environment.(3)Study on the preparation of FPEO microcapsule edible film:The film-forming formula was optimized through single-factor experiment and response surface experiment,with the OD value of water vapor permeability(WVP),tensile strength(TS)and elongation at break(E)as the evaluation index.The result showed that the best formula was:sodium alginate content 2.4%,rice bran wax content 0.4%and glycerol content 6.47%.Under this formula,the average WVP of edible film was 0.64 g·mm/(cm~2·d·k Pa),the average TS was144.85 MPa,the average E was 66.68%and the OD value was 0.841.Through appearance comparison and scanning electron microscopy observation,it was found that the larger the molecular weight of edible films,the worse their appearance characteristics.Therefore,the upper limit of the amount of microcapsules added is about 10 g.(4)Preliminary study on the preservation effect of FPEO microcapsule edible film on blueberries:The fresh-keeping ability of edible films for blueberries was preliminarily studied,by determining the five indexes including weight loss rate,rot rate,fruit hardness,anthocyanin content and total phenol content.The results indicated:the treatment of 100mg/m L edible film covering on blueberries could effectively reduce the weight loss by nearly60%.It also could cut down the membrane lipid peroxidation of blueberries and reduce fruit rot by about 76%.Moreover,it also could maintain the hardness and delay the softening of blueberries for about 6 days.Meanwhile,covering treatment could delay the ripening speed of blueberries after harvest in order to decrease the oxidative decomposition of the nutrients.Compared with the blank group,the anthocyanin content and total phenol content of blueberries stored for 15 days were 3.62 times and 1.25 times higher respectively.The high concentration edible film mulching treatment not only effectively extended the shelf life,but also guaranteed the nutritional value and quality of blueberry fruits.