| ?-Carotene is a lipid-soluble carotenoid with a strong tinging strength.As food additives,it has the effect of pigment and nutrition enhancer.There is a considerable interest in?-carotene because not only it has the function of food colorants,but also it is one of the most effective vitamin A precursors,and it has a number of other potential health benefits,e.g.,it has been proposed as a antioxidant,cancer prevention agent,ulcer inhibitor,human immunity improver,and many other physiological functions.Nevertheless,its utilisation is currently limited mostly because of its poor water-solubility,chemical instability and low bioavailability.In addition,?-carotene is also highly prone to chemical degradation during food processing and storage due to various environmental effects,such as heat,light,pH,ionic strength and air.Zein,it has an amphiphilic nature,which attribute to self-assemble property to form nanoparticles which has encapsulated and delivery function.Carboxymethyl chitosan(CMCS),it has been shown that negatively charged CMCS is able to form nanoparticles spontaneously with positively charged ions.Tea polyphenols(TP),it has antioxidative property and the effect of cross-linking.So we utilized these properties of them and applied anti-solvent precipitation technology to construct protein-polysaccharide binary complexes and protein-polysaccharide-polyphenols ternary complexes to realize multiple composite core-shell structure encapsulated ?-carotene based on the zein/?-carotene dispersion,and then formed water-soluble P-carotene nanoparticles delivery systems with high transparency,good uniformity,strong stability and high bioavailability.Used single factor and response surface analysis to optimize the best operation conditions,and studied the antioxidant properties and particle micro-structure of delivery systems,as well as the re-dispersibility and solubility of freeze-dried powders,and in vitro kinetic release test and stability in simulated gastrointestinal tract(SGI)were also studied.In addition,we investigated the influences of environmental stresses on the stability of delivery systems.Main conclusions are as follows:1.The nanoparticles delivery systems prepared by anti-solvent precipitation technology will be strictly affected by the operating conditions(adding speed of anti-solvent,stirring speed,ethanol concentration,volume ratio of solvent to anti-solvent,mixing temperature).The faster of adding anti-solvent,the more uniform of nanoparticles size distribution.There is no big effect of stirring speed during 800-2000 rpm on delivery systems.With the increase of ethanol concentration,the delivery systems showed the trend of better first,and then turned bad.The volume ratio of solvent to anti-solvent has the important effect on nanoparticles supersaturation and formation.When the volume ratio is 2:3,the dispersion presented the most uniform,clear and the particle size is the smallest.In theory,the higher temperature,the higher solubility of ?-carotene.However,?-carotene will occur to isomerizate and zein will occur to denature if the temperature is too high,so we set to 50? of mixing temperature.We selected three main influence factors according to the range analysis of the result of single factor experiment.We designed the response surface experiment with the particle size serves as response value,and then determined the best operating conditions:ethanol concentration of 90%,the volume ratio of solvent to anti-solvent of 2:3,mixing temperature of 50?,nanoparticles of delivery systems prepared under these conditions is 76.42 nm,which is little different from theoretical value.This indicated the preparation conditions optimized by response surface method are reliable.2.According to the second chapter selected the best process,with the particle size,zeta potential,encapsulation efficiency as index,the effects of the ratio of zein to ?-carotene,CMCS and TP concentration on the dispersion were studied.The best dispersion and the highest encapsulation efficiency of ?-carotene prepared with the ratio of ?-carotene to zein of 1:5,CMCS concentration of 0.25 mg/mL,TP concentration of 0.1 mg/mL.Some particles connected to each other,which observed by Scanning Electron Microscopy(SEM),indicating the possible cross-linking between TP and zein-CMCS occurred not only in molecular interior,but also in intermolecular.Simultaneously,the nanoparticles appeared spherical and exhibited smooth surfaces with mean particle size corresponded with the particle size measured by dynamic light scattering.By differential scanning calorimetry,we can know that ?-carotene in an amorphous form,not in a in a crystalline form in the complex nanoparticles,which indicated ?-carotene was encapsulated in the nanoparticles.By Fourier Transform Infrared Spectroscopy(FTIR),we can draw a conclusion that hydrogen bonding,hydrophobic interactions,covalent bond and electrostatic interactions were considered to be the major forces facilitating nanoparticles formation.Zein/?-carotene nanoparticles with CMCS and TP could provide the best controlled release of ?-carotene,after 5 h of incubation,only released 45%of P-carotene.What's more,the zein-CMCS-TP/?-carotene delivery systems presented the best stability in simulated gastrointestinal conditions and showed the good antioxidant property with radical scavenging rate of 65%.Re-dispersibility in distilled water after freeze-drying,the particle yield was 92.7%higher than zein-CMCS/?-carotene nanoparticles and zein/?-carotene.In addition,the powders of zein-CMCS-TP/?-carotene had a fast dissolution rate and the best solubility property.Therefore,we can draw inspiration from this study that zein-CMCS-TP complexes has a potential to be used as a novel stabilizer in colloid delivery systems to encapsulate poor water-soluble bioactive compounds.3.In this chapter,we constructed three kinds of nanoparticles delivery systems with the same wall-materials,and then investigated the effect of environmental stresses on the stability of delivery systems.With the increase of temperature and storage time,zein/?-carotene dispersion has the biggest impact with the more and more color degradation and bigger and bigger particle size.Finally resulted in precipitation.Zein-CMCS/?-carotene dispersion is less affected by temperature.Zein-CMCS-TP/?-carotene dispersion showed the best stability.By the first order kinetics,we can know that zein-CMCS-TP/?-carotene dispersion has the longest half-life at 20?,which is about 38.5 days.With the increase of ionic strength,the color of dispersions all turned turbid and aggregation.Color degraded rapidly at the acidic conditions.The nanoparticles delivery systems can remain stable under neutral and alkaline conditions.Illumination can also accelerate the degradation of ?-carotene,resulted in loss of color.Summing up the above,zein-CMCS-TP complex can serve as effective stabilizer to encapsulate bioactivators. |
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