| Four kinds of microspheres with sustained release ability of proanthocyanidins were prepared by low temperature extrusion with corn starch,zein and thermostability alpha-amylase to improve the stability and bioavailability of proanthocyanidins.The optimum sustained release conditions of the particles were optimized by single factor test and orthogonal test to control its sustained release ability and enhance the release of proanthocyanidins,and the optimum release parameters of the four particles were obtained.The particle size of the particles during the release process was analyzed to verify relation between the release amount and disintegration of microcapsule,and the apparent structure and crystallization of the particles before and after the release of proanthocyanidins were investigated.The single factor test showed that the initial temperature was positively correlated with the release of procyanidins,and the content of procyanidins in the solution system decreased as the temperature increased.Considering the amount of proanthocyanidins released and the stability of proanthocyanidins,the intermediate temperatures of particle SP and SAP,particle SZP and SZAP orthogonal experiments were selected at 35?and 45?,respectively.The acidic and neutral conditions are not conducive to the release of proanthocyanidins.The release of proanthocyanidins from the four particles reached the highest level at pH 9,and the stability was also acceptable.Therefore,pH of 9.5 was chosen as the intermediate level of pH orthogonal test.The time of 24 hours was chosen as the intermediate level of the release time in the orthogonal experiment according to the release amount of proanthocyanidins water with different temperature and pH.Temperature,solvent pH and release time that had effect on the sustained release ability of the particles were investigated by orthogonal experiments.The optimal release conditions of the four particles were obtained.The optimal release temperatures of the four particles were35?,42?,38?,42?,pH 9 and time 8 h,respectively.Under the optimum conditions,the release rates of proanthocyanidins from four kinds of particles were95.30%,82.27%,90.75%,91.67%,respectively.The stability of proanthocyanidins in alkaline solution was enhanced by embedding.Samples were taken at 6 h intervals at 37?in aqueous solution.ABTS~+clearance rate,reducing sugar content and proanthocyanidins content were determined.The results showed that ABTS~+scavenging rate was closely related to proanthocyanidin content.Under these conditions,the release of proanthocyanidins from SZP and SZAP particles was less than 20%of the added amount,however,they still showed a strong ability to scavenge free radicals.The content of reducing sugar is related to the degree of starch gelatinization and the action of amylase,which affects the release of proanthocyanidins to a certain extent.At the same time,it was proved that a small amount of heat-resistant alpha-amylase in the raw material remained active after extrusion.Simulated gastric fluid,simulated intestinal fluid,simulated colonic fluid were used for in vitro simulated digestion test.Particle SP and SAP showed advantages in proanthocyanidins release.Although the release of proanthocyanidins from microparticles SZP and SZAP is low,it can be proved by experiments that the four microparticles have the same protective effect on proanthocyanidins.The original particle morphology of the four particles is irregular.The addition of thermostability alpha-amylase makes the particle size of SAP and SZAP relatively large.The width of particle size distribution increased gradually following the prolongation of soaking time.Meanwhile,the particle size experienced a process of swelling first and then decreasing during the soaking process.In the whole process of immersion,the particle size of SZP and the change range of d(0.5)are the smallest compared with the other three kinds of particles,which verifies the result that the release rate of proanthocyanidins in SZP is the lowest.The following conclusions are drawn by comparing the physical properties of the particles before and after the release of proanthocyanidins:(1)The particles have desired dispersion with irregular shape,obvious edges,cracks,holes,cracks and corners on the surface,compact and complete honeycomb-like structure in the interior.The irregular particles almost disintegrated after the release of proanthocyanidins.(2)The results of infrared spectroscopy showed that the crystallization of the four kinds of particles was different due to the different constituents,and the crystalline structure of the particles soaked in buffer solution was seriously damaged.(3)The diffraction peak of corn starch crystal in the particles shifts.The particle structure was destroyed and the crystal was lost after soaking with fewer broadened diffraction peaks in the four kinds of diffraction diagrams.(4)Red areas observed in the samples with zein added indicated that the zein was dispersed among starch molecules.Microparticles with water soaking showed dark appearance and weak fluorescence.Disappearance of red color and the generation of cracks in samples with zein addition,especially in the SZAP indicated that the microstructures were destroyed in buffer.Meanwhile,structure of the microcapsules without water soaking were compact and integrate,which could resist the damage of oxygen,light and water molecules.The contact between starch crystals becomes looser after water soaking,which also provided the possibility for the release of proanthocyanidins.Sustained-release microcapsules prepared by extrusion process increased the stability of proanthocyanidins,and the addition of zein can enhance its sustained release performance.The stability of proanthocyanidins was also enhanced by the enzyme to starch.The four kinds of microcapsules improved the stability of proanthocyanidins in alkaline conditions.This study provides a technical for the encapsulation of functional substances with poor stability and the preparation of sustained-release particles. |
PDF Full Text Request