Preparation And Sustained-Release Properties Of Chitosan-Extruded Starch Doublelayer Microcapsules

Resveratrol,a phenolic stilbenoid compound with powerful antioxidant activity,was used as the core material and encapsulated by starch,chitosan and ?-Amylase as extrusion materials.And the chitosan was employed to coated the microencapsulation to control the sustained release of resveratrol and improve its effectiveness.The research was as follows.Four kinds of microcapsules were prepared with starch(ESR),starch and chitosan(ESCR),starch and amylase(ESRA),starch,chitosan and amylase(ESCRA)as wall materials and resveratrol as core material,respectively.?-Amylase and chitosan as variables,and the resveratrol release of microcapsules was discussed.The effects of the release rate,the antioxidant properties of microcapsules during the release process,the photothermal stability of microcapsules and the changes of particle size before and after immersion were studies.Scanning electron microscopy(SEM),X-ray diffraction(XRD)and Fourier transform infrared spectroscopy(FT-IR)were performed to investigate the properties and characterization of microcapsules before and after release.Double-layer microcapsules were prepared by above-mentioned extruded starch microcapsules that were encapsulated with different concentrations of chitosan acetic acid.The release ability,antioxidant capacity and particle size of resveratrol of different chitosan-extruded starch double-layer microcapsules were determined,and their properties were identified and characterized.The experimental results were as follows:(1)The release rate of resveratrol in four kinds of extruded starch microcapsules was studied at different temperatures.The effects of a-amylase and chitosan on the release of resveratrol in extruded starch microcapsules were analyzed.Temperature had a certain effect on the release of resveratrol.Higher temperature(37?)could promote the hydrolysis of starch,resveratrol releases rapidly and has a high release rate.a-Amylase,the release-promotion reagent,is conducive to promote the gelatinization of starch during extrusion and hydrolysis,destroy microcapsules and facilitate the release of resveratrol.Therefore,ESRA and ESCRA are easy to hydrolyze and have high release rate,while ESR and ESCR have low release rate and long-term effectiveness.Meanwhile,chitosan was benefit to the sustained release of resveratrol.(2)The antioxidant activity of extruded starch microcapsules during resveratrol release was studied.Results showed that the order of antioxidant activity was ESRA >ESCRA > ESR > ESCR according to 25?(the first 4 days)and 37?(the first 24 hours).The release rate of extruded starch microcapsules showed the same trend as the antioxidant activity of microcapsules.The antioxidant ability of ESR and ESCRA was higher thanESRA and ESCRA.Combined with resveratrol release rate and antioxidant activity in extruded starch microcapsules,ESR and ESCR can be used as sustained-release microcapsules with their performance of antioxidant activity.(3)The results showed that the particle size in the chitosan-absent group(ESR,ESCR)was significantly different from the chitosan-present group(ESRA,ESCRA).The particle size gradually decreased after the expansion of ESR and ESCR duing to the lower gelatinization degree and starch crystals.The particle size of ESRA and ESCRA decreased rapidly after 1 hour water immersion,and then changed slightly.(4)The photothermal stability of extruded starch microcapsules was evaluated.The results showed that extruded starch microcapsules had a significant effect on improving the photothermal stability of resveratrol,nevertheless it was difficult to prove that extruded starch microcapsules had a positive effect on the thermal stability of resveratrol.(5)Scanning electron microscopy(SEM),X-ray diffraction(XRD)and Fourier transform infrared spectroscopy(FT-IR)were used to study the properties and characterization of the microcapsules before and after water immersion.(6)Double-layer microcapsules were obtained by the extruded starch microcapsules were further encapsulated different concentration of chitosan solution(0%,0.5%,1%,1.5%,2%)as coating.Resveratrol release rate in different double-layer microcapsules was investigated.Double-layer microcapsules had certain sustained-release ability of resveratrol,and the release rate of resveratrol increased with the increase of chitosan concentration,which is mainly caused by the repulsion between resveratrol and acetic acid molecules.(7)The influence of chitosan solution concentration on the ABTS radical scavenging rate of double-layer microcapsules was checked and there were no significant difference between these microcapsules,and the antioxidant ability of microcapsules at 37? was better than 25?,but it can be predicted that the antioxidant capacity of microcapsules would decrease gradually with the time prolonging at 37?.(8)The particle size of different double-layer microcapsules was analyzed under different soaking time(0 h,1 h,3 h,5 h,1 d,3 d).The results showed that the particle size of microcapsules decreased with the prolongation of immersion time,and the particle size of microcapsules decreased with the increase of chitosan concentration in the same immersion time.Compared with the size change of extruded starch microcapsules,the size change of double-layer microcapsules was smaller,and the size of extruded starchmicrocapsules was smaller than double-layer microcapsules in the same immersoin time.It showed that extruded starch microcapsules were encapsulated by chitosan solution was beneficial to the sustained-release ability of microencapsulated resveratrol.(9)The properties and characterization of chitosan starch microcapsules before and after release were studied by scanning electron microscopy(SEM),X-ray diffraction(XRD)and Fourier transform infrared spectroscopy(FT-IR).Resveratrol release was reflected from the structural properties of microcapsules.Chitosan molecule in chitosan acetic acid solution interacts with starch molecule in microcapsules to form strong hydrogen bond,which weakens the hydrogen bond between starch molecule,reduces the crystallinity of starch and weakens the characteristic diffraction peaks of starch.