| Glucoamylase is a kind of hydrophilic functional components with catalytic effect.Due to its low stability and rapid reaction with the substrate,the temperature rise is large,which affects fermentation and other factors limit its practical application.In recent years,many scholars have done a lot of research on the immobilization of glucoamylase,but the limitation of variability and leakage exists after the immobilization of glucoamylase is usually used.In order to achieve smooth surface and environment stimulation,the encapsulation efficiency of glucoamylase in core material is high,activity is strong and the reaction effect is prolonged in liquid and solid state.It can provide a reference for expanding the application of glucoamylase microcapsules in food fermentation industry,and build a theoretical basis for the subsequent construction of hydrophilic bioactive material loading system.The research work of this subject is mainly divided into four parts:(1)Based on the determination of the W/O/W type-complex coacervation microcapsule technology,the type of wall material and the p H value of the system and the mass ratio of wall material are optimized.Immediately,the influence of factors such as core-wall ratio,total wall material concentration,coagulation time,drying time,and colostrum water-oil ratio on the encapsulation efficiency of glucoamylase microcapsules was explored,and the preparation process of glucoamylase microcapsules was preliminarily formulated.(2)Use the glucoamylase as the core material and the preliminary microencapsulation process as the template,the interaction test of core-wall ratio,total wall material concentration,and coagulation time was designed by response surface method to optimize the preparation process parameters of glucoamylase microcapsules.Then,the encapsulation efficiency,residual activity,loading capacity,water activity and solubility of the glucoamylase microcapsules optimization and non-optimization were determined respectively.(3)Use the Optical microscope,Scanning electron microscope,Differential scanning calorimetry,Fourier transform infrared spectroscopy and Ultraviolet spectrophotometer to characterize and analyze the apparent morphology,thermal properties,chemical components and slow release properties of the microcapsules after double-layer assembly.(4)Study on the stability of glucoamylase capsules: the hydrolysis of the capsule was carried out with soluble starch as substrate.Subsequently,the changes in the enzymatic properties(optimum p H,optimum temperature)of optimization and nonoptimization glucoamylase microencapsulation were compared.In addition,the tolerance of glucoamylase microcapsules to environmental stimuli,such as temperature,p H,ethanol concentration,added salt,and storage time,was also explored.The research results show that:(1)The optimal preparation parameters of glucoamylase microcapsules are: system p H=4.5,wall material mass ratio m(Chitosan):m(Gum Arabic)=1:7,core wall ratio of glucoamylase to outer aqueous shell is 1:1,total wall material concentration is 8%,coagulation time is 20 min,drying time is 7h,and primary emulsion water-oil ratio is 1:2.(2)The glucoamylase microcapsules prepared under the optimal process parameters have an encapsulation efficiency of 85.64±1.60%,a retained enzyme activity rate of 75.52±0.94%,and an enzyme load of 0.0921±0.0021 m L/g.This paper found that the optimization of the preparation parameters changed the distribution of the mixed core material W/O primary emulsion and the wall material,thereby strengthening the glucoamylase microcapsule structure.In addition,the water activity of the optimized glucoamylase microcapsules is only 0.460±0.0031(<0.5),which can be stored stably.However,its solubility is significantly reduced,which indicates that the capsule body will not collapse in a short time after the microcapsule is in contact with the aqueous solution.(3)Glucoamylase microcapsules were characterized by Optical microscope,Scanning electron microscope,Differential scanning calorimetry,Fourier transform infrared spectroscopy and Ultraviolet spectrophotometer.The morphology,thermogravimetric,chemical functional group and long-term application performance in liquid and solid systems were analyzed.It was found that the glucoamylase microcapsules had complete morphology and typical folds on the surface.At the same time,the thermal stability is significantly improved,and no new chemical bonds are formed between the wall material and the core material,indicating that the properties of the glucoamylase have not changed.On the other hand,in the simulated substrate environment,the complex microcapsules has good sustained-release performance,with continuous release for more than 96 h in the liquid state and slow reaction for more than 336 h in the solid state.(4)The optimal reaction p H of the glucoamylase after W/O/W type-complex coacervation and microencapsulation has not changed(the optimal p H is 4.0),but the optimal reaction temperature is quite different.It is worth noting that the microencapsulated glucoamylase has good catalytic performance in high temperature regions.In addition,in different environments,the microcapsule-shaped glucoamylase is more resistant to external factors such as temperature,p H,ethanol,and external salt.At the same time,the storage time of the glucoamylase microcapsules can reach more than 120 d under natural and non-light storage. |
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