The Preparation Of High Internal Phase Emulsions Stabilized With Whey Protein Isolate Microgels,and Studies On The Stability Enhancesd Of Lactobacillus Plantarum

Whey protein is a protein which is dissolved in whey,and it is a by-product of cheese production.Whey protein isolate(WPI)refer to a whey protein product with a protein content not less than 90%,and is prepared by ultrafiltration techniques,electrodialysis,ion exchange,and so on.Whey protein has a lot of nutritional properties such as maintenance of cardiovascular health,anti-virus,anti-aging,and functional properties such as gel property,emulsifying property,and coating property.Utilizing the emulsifying property of whey protein,a stable oil in water type(O/W type)emulsion system can be prepared,which can be used to change the properties of foods,cosmetics,and so on.At the same time,the emulsion system is also used to the protection of unsaturated fatty acids.Thereby extended the protection of some bioactive substances which are difficult to dissolve in water or unstable in the outside environment,such as carotenoids,fat-soluble vitamins and so onHigh internal phase emulsions(HIPEs)are a general term for ultra-concentrated emulsions,usually with a volume fraction of disperse phase above 74%.At present,research and application of HIPEs mainly focus on physics,chemistry and so on.There are few researches and applications in foods,and the use of emulsions to encapsulate and protect probiotics is relatively rare.Moreover,there are relatively few researches on the encapsulation and protection of probiotics by emulsions.The application of HIPEs stabilized with WPI microgels for the encapsulating of probiotics has not yet been reported.This paper studied the preparation and characterization of whey protein isolate microgels,the preparation and characterization of the HIPEs stabilized with WPI,the optimization and characterization of freeze-dried protective agent of Lactobacillus plantarum,and the application and characterization of the HIPEs stabilized with WPI encapsulated Lactobacillus plantarum.1.Preparation and characterization of WPI microgelsThe WPI microgels were prepared by the method of heat polymerization,and the WPI solution concentration,pH value,heating time,and heating temperature several preparation conditions were studied the influences particle size,Zeta potential and turbidity of the WPI microgels.The effect of storage time on the particle size and Zeta potential of WPI microgels was studied.The WPI microgels were observed by transmission electron microscopy.2.Preparation and characterization of the HIPEs stabilized with WPIA nano-sized WPI microgels was used as the continuous phase of the emulsion,grape seed oil as the dispersed phase,and an O/W type emulsion was prepared using a disperser.The effects of oil phase volume fraction,WPI concentration and pH value of aqueous phase on the type,stability and rheological properties of emulsions and HIPEs were studied.The microstructure of the emulsions were observed by an inverted microscope and a laser scanning confocal microscope.3.Optimization of Lactobacillus plantarum freeze-dried protective agent and and the application and characterization of the HIPEs stabilized with WPI encapsulated Lactobacillus plantarumSelect skimmed milk powder,sugars(glucose,sucrose,trehalose,inulin,fructo-oligosaccharides,xylo-oligosaccharides),alcohols(sorbitol,mannitol),buffer salts(manganese sulfate,Sodium acetate)4 types of 11 kinds of protective agents were subjected to single factor experiments.Three factors that have greater impact were selected:skimmed milk powder,trehalose,and sodium acetate,and three-level response surface optimization was performed.The data was statistically analyzed by Design Expert 8.0.6 software to obtain the optimum freeze-dried protective agents ratio and corrected according to actual conditions:skim milk powder concentration of 15.5 g/100 mL,trehalose concentration of 4.0 g/100 mL,and sodium acetate concentration 0.20 g/100 mL.The validation experiment was repeated three times.The survival rate was 90.64±1.07%,and there was no significant difference from the predicted value of 92.0117%,indicating that the optimized conditions obtained by the model can be used to prepare the Lactobacillus plantarum freeze-dried powder.The Lactobacillus plantarum freeze-dried powder was encapsulated in the emulsion or HIPEs system stabilized by the WPI microgels.The oil phase volume fraction,WPI concentration and pH value of aqueous phase were investigated for pasteurization were studied the effect of the number of viable cells of Lactobacillus plantarum in the system.By extending the storage time,the stability of the encapsulating system and the changes in the number of live Lactobacillus plantarum in the encapsulating system and rheological properties were studied.The microstructure of the emulsion system encapsulating Lactobacillus plantarum was observed by a laser scanning confocal microscope.