| Using broken rice as raw material to extract rice starch,the rice starch is efficiently prepared into porous starch(Porous starch,PS)through ultrasound-assisted enzymatic hydrolysis method,and compounds with xanthan gum(Xanthan gum,XG)to form double-walled material as the wall material of microcapsules' application.First,the experiment studied the method of ultrasound-assisted enzymatic preparation of broken rice porous starch,followed embedding the common alcohol-soluble macromolecular functional components curcumin(polyphenols),quercetin(flavonoids)and ?-carotene(lipids Solubility),and characterizing the physical and chemical properties of the prepared microcapsules.On this basis,in vitro gastrointestinal simulated digestion technology is used to analyze the release rule of the functional components that was embedded in the microcapsules.Compared with the traditional microcapsule wall material,the wall material has the advantages of easy access,low price and high embedding rate and strong stability.The main research conclusions of this study are as follows:(1)Ultrasonic-assisted enzymatic preparation of porous starch:Taking the oil absorption rate as the optimization index,the response surface experiment optimization of the ultrasonic-assisted enzymatic preparation process of porous starch was carried out.It was confirmed that the optimal technological conditions of ultrasonic-assisted enzymatic preparation of rice porous starch were:when the ultrasonic time was 25 min,the power was 450 W,the temperature was 40?,pH=4.0,the enzyme ratio was 1:5(?-amylase:glucoamylase),the amount of enzyme added was 1.4%and the enzymolysis time was 14 h.The oil absorption rate of porous starch can reach 105.33%under the preparation conditions of this process.(2)Typical functional component embedding:Embedding functional components(curcumin,quercetin and ?-carotene)with PS,PS and XG compound wall materials(PS/XG),and embedding rate and loading was measured.The results showed that the embedding rate of the three functional components in PS was between 70 and 80%,and the loading was 1.41 to 1.54?g/mg;while in the microcapsules with PS and XG as composite wall materials,the encapsulation of quercetin microcapsules had the highest embedding rate and loading(94.93%and 1.89 ?g/mg,respectively,PS/XG ratio of 10:1),followed by curcumin microcapsules(94.17%and 1.88 ?g/mg,respectively,PS/XG ratio of 10:1),and the value of ?-carotene microcapsules was the smallest(93.70%and 1.87?g/mg,respectively,and PS/XG ratio is 10:1).It showed that a single PS can be used as the wall material of alcohol-soluble macromolecular functional microcapsules,but the loading was relatively lower.The loading capacity of PS/XG double-wall materials was significantly improved,which was more in line with the high embedding rate requirements of microcapsule wall materials.It was speculated that the loading of different functional components may be related to factors such as intermolecular hydrogen bonding,molecular weight,surface area and total pore volume of the wall material,and in addition,the results also indicated that the small molecular weight flavonoid quercetin has the highest affinity between PS and PS/XG wall materials,and was more suitable as a PS/XG embedded core material.(3)Characterization of microcapsule structure:The results of scanning electron microscopy showed that the overall shape characteristics of microcapsules were similar to PS,but the smoothness and three-dimensionality of PS/XG were slightly reduced,and the surface structure was more dense.Zeta potential value indicated that the point value of PS/XG microcapsules was 1.42 to 1.78 times that of PS microcapsules and1.87 to 3.24 times that of functional components,and the smaller the ratio of PS to XG wall material,the greater the absolute value of the microcapsule Zeta potential value.The characteristic peaks of the functional components after embedding in the X-crystal diffraction spectrum disappeared,the infrared spectrum peak migration and widening,and the differential calorimetry scan results confirmed that the original characteristic endothermic peaks disappeared after the functional components were embedded.These results indicated that functional components are successfully embedded to form an inclusion compounds,rather than forming a physical mixture with porous starch,xanthan gum,etc.;the three representative functional components interact with the wall material through hydrogen bonding.The structural characterization showed that the PS/XG composite wall material has higher stability than the single PS wall material,and the smaller the ratio of PS to XG,the higher the stability of the microcapsules,so the ratio of PS to XG can be adjusted to meet the stability requirements of microcapsules.(4)Slow release rule of functional ingredients:DPPH free radical antioxidant was used to find that the antioxidant activity of microcapsules was closely related to the type and loading of functional ingredients.The embedding rate value of microcapsules was match to the embedding rate value determined by direct measurement.Using in vitro gastrointestinal simulated digestion to analyze the release rules and release models of three functional components in PS and PS/XG microcapsules in different ratios,it was found that the release rates of PS embedded curcumin,quercetin and ?-carotene were 1.05?1.46,1.45?1.75,1.25?1.64 times(simulated gastric juice)and 1.12?1.51,1.14?1.63,1.07?1.54 times(simulated intestinal fluid)in PS/XG microcapsules,and the release percentage of functional ingredients in PS/XG microcapsules was negatively correlated with XG content.The release kinetic curve fitting results showed that the functional components were more in line with the first-order and Korsmeyer-Peppas release models in the gastric environment,and the release factor n value was less than 0.50,which belonged to non-Fick diffusion;it was more in line with Higuchi Korsmeyer under intestinal conditions-Peppas model,the release factor n value was greater than 0.64,which belonged to Fick diffusion.These conclusions indicated that the embedding rate value can be determined by the DPPH experiment,and the release rate of functional ingredients in microcapsules can be controlled by reasonably changing the amount of xanthan gum added.The above research showed that the composite of broken rice porous starch and xanthan gum as the wall material of microcapsules has the advantages of high embedding rate,good stability and low cost.The effect of PS/XG composite wall material on embedding macromolecules of flavonoid functional components with smaller molecular weight was better than that of fat-soluble macromolecules with larger molecular weight.Therefore,this composite wall material can be more applied to embed flavonoids with low molecular weight to improve their loading,stability and bioavailability. |
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