Study On Preparation Of Peony Seed Oil Microcapsule And Its Properties

Peony seed oil, as a kind of potential nutritional-oil resource, is rich in polyunsaturated fatty acids, such as α- linolenic acid. But peony seed oil is unstable and easy to be oxidized, and the fat-soluble property also limits its application in the food field. Microencapsulation technology can not only prevent peony oil from oxidation, but also change its physical properties. In this paper,gum arabic and β-cyclodextrin were used as wall materials to prepare peony seed oil microcapsule by spray drying method. The aim of this study was to investigate the optimal preparation conditions and evaluate the properties of peony seed oil microencapsule, such as surface morphology, thermal stability and storage stability. The main contents were as follows:(1) Preparation method of microcapsule was investigated and its perfomance was determined by mircoencapsulation efficiency. The optimal preparation condition was determined as follows: gum arabic and β-cyclodextrin ratio 1:2(w/w), core material and wall material ratio 1:2(w/w), emulsion concentration 20%(w/v), inlet-air temperature 180℃, liquid feeding temperature 55℃, liquid feeding rate 20 m L/min. Under the optimal conditions, microencapsulation efficiency of peony seed oil reached 87.21%.(2) Laser Particle Sizer and Scanning Electron Micro scope(SEM)were used to analyze the surface morphology of peony seed oil microcapsule. The analysis results showed good shape, moderate wall thickness in SEM and the paticle size was about 1~10 μm.(3) FT-IR Spectra suggested that peony seed oil had been well protected by wall materials. DSC analysis results confirmed that the thermal stability of peony seed oil was improved after encapsulation.(4) Peroxide value(POV)variation of peony seed oil microcapsule was used to analyze its storage stability, and shelf life of peony seed oil microcapsule was predicted with oxidation kinetics according to Avrami’s and Vant’Hoff equation. The results showed that the shelf life of peony seed oil and its microcapsule were 110 d and 212 d, respectively. Therefore, microencapsulation can greatly reduce oxidation of peony seed oil and significantly improve its shelf life.(5) Fatty acids composition variation of peony seed oil microcapsule was also used to analyze its storage stability. The analysis results indicted that fatty acids composition of peony seed oil microcapsule had no significant change during storage at room temperature for 60 days. Its unsaturated fatty acids still reached 92.24%, α- linolenic acid and linoleic acid were 37.43% and 29.43%, respectively. After storage at 45℃ for 60 days, the unsaturated fatty acids and α-linolenic acid reached 91.10% and 33.75%, respectively, a little lower than microcapsules at 25℃. Therefore,microcapsule of peony seed oil was much more stable at low temperature, though it showed good thermal stability at high temperature. Therefore, high temperature should be avoided in daily life storage.