Preparation And Stability Of Grapefruit Essential Oil Microcapsules

Grapefruit essential oil is a natural flavor and fragrance with a unique aroma and is used in the food industry.Because grapefruit essential oil is in contact with the external environment,it is volatile and oxidized and deteriorates,which has certain limitations in production applications.The complex coacervation reaction is a mild and effective embedding method for preparing microcapsules,which can electrostatically polymerize two oppositely-charged water-soluble materials by adjusting the reaction conditions of the system,thereby coating the unstable active materials.At present,microencapsulation is a technical means to be promoted in the food industry and the chemical industry.This study mainly uses the method of complex coacervation,using type A gelatin and sodium alginate as wall materials,microencapsulation of grapefruit essential oil,and preparation of nanocapsules by ultrasound.The optimal process conditions for the preparation of grapefruit essential oil microcapsules and nanocapsules were determined by process optimization.The stability and sustained release properties of the prepared microcapsules were investigated,which provided a theoretical basis for industrial development of essential oil microcapsules.The main research methods and results of the thesis are as follows:The preparation of grapefruit essential oil microcapsules by complex coacervation method is mainly carried out by microcapsule embedding of grapefruit essential oil with type A gelatin and sodium alginate as the wall material,and finally preparing grapefruit with high yield and embedding rate.Essential oil microcapsules.The effects of experimental factors such as the amount of emulsifier added,the total concentration of mixed wall materials,core wall ratio,reaction pH and re-agglomeration reaction time on the microencapsulation rate and yield were investigated.The results of single factor test showed that the embedding rate and yield of microcapsules were 80.5%and 89.49%,respectively,when the total wall material concentration was 1.5%,the core wall ratio was 1:1,the pH was 3.8,and the reaction time was 60 min.Using the Design-Expert 8.1 software,the response surface optimization experiment was carried out with the microcapsule yield as the index.The optimal process conditions were simulated as the total wall material concentration of 1.38%,the core wall ratio of 1.04:1,and the reaction pH value of4.1.The complex coacervation reaction time was 60.03 min,and the yield of microcapsules reached 90.659%.The response surface test equation was obtained:Y=90.42-0.36A+0.88B+1.34C+0.033D+2.30AB-0.53AD-0.79BC-0.62BD+0.54CD-3.04A~2-4.38B~2-2.51C~2-3.49D~2,the regression equation obtained is significant(P=0.0051<0.05),and the misclassification test was not significant(P=0.2007>0.05).It is feasible to fit the relationship between the four factors and the microcapsule yield by equation.The coefficient of determination R~2=0.8106,indicating a good fit between the actual microcapsule yield and the actual value.The experimental results show that the optimized results are ideal.Ultrasound-assisted preparation of grapefruit essential oil nanocapsules,mainly by single factor and orthogonal test,using microcapsule average particle size,PDI and Zeta potential as indicators,to investigate the core wall ratio,ultrasonic time,ultrasonic amplitude and curing agent addition The effect of nano-microcapsules.The results showed that when the pH was 3.8,the ratio of type A gelatin to sodium alginate was 3.5,the core-to-wall ratio was 1:1,the ultrasonic time was 10 min,the ultrasonic amplitude was 10%,and the addition amount of curing agent was compared with the wall material ratio.When the ratio is 1:3,the average particle size of the microcapsules prepared under these conditions is 210.08±10.12 nm,the embedding rate is 65.02%±1.18%,and the PDI is 0.295.The system has good dispersion and good stability.The stability and sustained release properties of microcapsules were studied.The retention rates of essential oils in different periods were determined under different temperature conditions(4℃,25℃,40℃)and different light treatments(natural light and dark treatment).On the research surface,the microcapsule retention rate was the highest at 4℃and protected from light,and the low temperature and dark environment were more conducive to the storage of grapefruit essential oil.At the same time,the microcapsules and nanocapsules were compared to study the sustained release properties and oxidation resistance of microcapsules.Studies have shown that compared with general microcapsules,nano-microcapsules have small particle size,compact structure,low volatilization rate and peroxidation rate.