| Colostrum is the milk secreted by cows within 48 hours of delivery.It contains immunoglobulin,oligosaccharides,vitamins and other functional active ingredients,which can improve the immune capacity of the body,effectively prevent the invasion of bacteria and viruses,and promote the growth and development of the body.It is known as the most promising non-herbal natural health food in the 21 st century.IgG is the most important immune factor in bovine colostrum,but it is easily affected by the adverse environment such as high temperature,acid,and alkali,can not play its biological activity function.Therefore,this characteristic of IgG limits the large-scale development of colostrum dairy products in the food field.Currently,the bioactive ingredient IgG of functional products of colostrum in the market has low activity,and the form is relatively single,lacking certain functionality.In this thesis,IgG was extracted from bovine colostrum by the ammonium sulfate salting-out method.To explore the stability of IgG under different conditions;Using glycine,maltitol,and inulin as raw materials,the Box-Behnken response surface methodology was used to optimize the formulation of bovine colostrum IgG composite thermal protective agent.Finally,a functional dairy product was developed with bovine colostrum as raw material combined with puffing and freeze-drying technology.The optimum amount of each component in the formula was determined by an orthogonal test,and its quality was determined.This thesis provides a new idea for the development of bovine colostrum functional products,which is of great significance for promoting the research and development of new dairy technology and guaranteeing the development of human health.Mainly completed the following aspects of the content:1.Bovine colostrum was used as experimental raw material,casein was removed by curd enzymatic method,and IgG in bovine colostrum was separated and extracted by ammonium sulfate salting-out method and dialysis method,to explore the stability of bovine colostrum IgG under different conditions.The results showed that bovine colostrum IgG had good stability after being heated at 65 ? for 30 min.When the temperature continued to increase,the retention rate of IgG activity decreased and reached 85 ?.When heated for 3min,IgG was almost completely inactivated.The p H stability of bovine colostrum IgG ranged from p H 4.0 to 10.0,and it was unstable under the condition of over-acid and overalkali.The degree of destruction of IgG activity was greater during pepsin digestion than during trypsin digestion.In the gastrointestinal tract,gastric acid in gastric juice is the most important factor causing IgG denaturation.In the intestinal tract,the content of trypsin is the main factor affecting the denaturation of IgG.2.Based on a single-factor experiment,with IgG activity retention rate as response value,glycine,maltitol,and inulin as response factors,the Box-Behnken response surface method was used to optimize the formulation of IgG thermal protective agent.The structure of bovine colostrum IgG was characterized by Fourier transform infrared spectroscopy and endogenous fluorescence spectroscopy.The results show that the optimal formulation of IgG composite thermal protective agent is: Inulin 14.98%,glycine 0.48%,maltitol 12.50%,the compound thermal protective agent can effectively maintain its activity after heat treatment at 75 ? for5 min,and the IgG activity retention rate can reach 36.59%.Compared with the control group without the compound thermal protective agent,the IgG activity retention rate increased by16.25%.Fourier transform infrared spectroscopy showed that compared with bovine colostrum IgG without the compound thermal protective agent,the ?-folding content and irregular curl content of bovine colostrum IgG with compound thermal protective agent significantly decreased(P<0.05),and the secondary conformation showed a relatively orderly state.The composite thermal protective agent can effectively protect the hydrogen bond that maintains the stability of the IgG structure in bovine colostrum,prevent it from being damaged,and delay its thermal denaturation.Endogenous fluorescence spectra showed that the composite thermal protective agent could reduce the exposure of hydrophobic amino acid residues such as tryptophan,reduce surface hydrophobicity,and make the IgG molecules more compact.Due to the addition of inulin,maltitol,and other functional active substances,the compound thermal protective agent has a good practical application value and provides a certain reference for the research and development of bovine colostrum functional food.3.A new functional dairy product was developed by combining vacuum freeze-drying technology and ice cream puffing technology with bovine colostrum as experimental raw material.Its formula was optimized through an orthogonal experiment,and its quality was evaluated.The results showed that the best formula for bovine colostrum expanded freezedried dairy products was as follows: Bovine colostrum 63%,inulin 14.98%,glycine 0.48%,maltitol 12.50%,composite emulsifying stabilizer 0.4%,whey protein powder 3%,cheese powder 3%,the product prepared by this formula has good flavor,moderate hardness,high sensory score and smooth microstructure surface.The product retained 68.8% of IgG activity when stored at 4 ? for 28 days.The product contains rich immune active substances to meet people's needs for nutrition and health.In addition,the sweetener used in the product is maltitol,which is suitable for people with obesity and hypertension.Therefore,the product has a broad market prospect. |
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