Study On The Stabilizing Mechanisms And Applications Of The Emulsions Co-stabilized By Amorphous Taro Starch And Whey Protein Isolation

Starch and protein are food-grade biomacromolecules with wide sources,low prices and eco-friendliness.The emulsion system stabilized by starch and protein has attracted much attention in the fields of food,medicine and cosmetic formulation.Taro starch（TS）has the characteristics of small particle size and high endogenous protein content,which can be developed and utilized as a potential emulsifier.However,natural TS has strong hydrophilicity,so it is not suitable to be directly used as emulsifier,and it needs to be modified.Pasting treatment can make starch particles into amorphous state,and then stabilize the emulsion stabilize the emulsion through steric hindrance and their own gelation.Proteins are amphiphilic compounds and have the advantages of good interfacial activity,can adsorb at the oil-water interface and promote emulsion formation.Therefore,pasting treatment and mixed with protein can be used to improve the emulsifying capacity and emulsifying stability of TS.In this thesis,amorphous TS/WPI mixture was prepared from TS and Whey Protein Isolation（WPI）,and the influence of the existence and content of WPI on the physicochemical characters of TS/WPI mixture was investigated.Then the mixture was used as emulsifier to stabilize the emulsion and the formation mechanism and stability of the emulsion were explored.The high internal phase emulsion gel was prepared by changing the complex ratio of TS and WPI and the solid content,and the in vitro digestion characteristics of emulsion gel and its protection and delivery ofβ-carotene were also investigated.The main results are as follows:（1）Amorphous TS/WPI mixtures with different WPI contents（1,4,7,10 and 13%）were prepared using pasting treatment（90°C,30 min）,and the physicochemical properties of the mixtures were investigated.The results show that in the mixtures system,the interaction between molecules were dominated by hydrogen bonding and hydrophobic interaction.Compared with TS alone,the addition of WPI significantly decreased the paste viscosity,but increased the pasting temperature of TS in a WPI content-dependent effect.More the WPI was added,the lower the apparent viscosity and G’of the amorphous TS/WPI mixture paste.Compared with TS,the gelatinization temperatures（T_o,T_p,and T_c）of the amorphous TS/WPI mixture increased gradually as the WPI content increased,while the gelatinization enthalpy change（ΔH₁）gradually decreased.After the gelatinized samples were stored at 4°C for 28 days,the retrogradation temperature of the samples did not change significantly compared with the corresponding pasting temperature,but their retrogradation enthalpy change（ΔH₂）and the retrogradation rate（R）decreased significantly.Compared with gels made with TS starch alone,TS/WPI mixed gels had increased pore size and decreased pore wall thickness,demonstrating a gradually increasing trend as WPI content increased.（2）Emulsion was prepared with amorphous TS/WPI mixture as emulsifier.The appearance,droplet size,microstructure,rheological properties,and environmental and storage stabilities of the mixture-stabilized emulsions were investigated to determine the emulsion stability and the mechanism of synergistic stabilization of emulsions.The results show that the amorphous TS/WPI mixture showed a higher emulsification stability than TS or WPI alone.As the WPI content increased from 0%to 10%,the droplet size of the emulsion decreased gradually,and its storage modulus G’and freeze-thaw,centrifugal,and storage stabilities increased gradually.The emulsion with a WPI content of 10%had a droplet size of 10.24μm and a creaming index of 0%after 28 days of storage.Confocal laser scanning microscopy revealed that WPI and the TS/WPI complex were mainly distributed at the oil-water interface;TS and a small quantity of WPI filled the droplet interstices as a continuous phase.Except for obvious delamination at pH 5.0,thermal treatment and ionic strength had little influence on the appearance but had different influences on the droplet size and G’value,and the increasing rates of droplet size and G’value under storage varied with various environmental factors.（3）The emulsion gel was constructed by adjusting the solids content of amorphous TS/WPI mixture paste（5%,7%and 9%）and the ratios of TS/WPI（5:0,4:1,3:2,2:3,1:4and 0:5,w/w）at a svolume of oil phase of 75%.The results show that emulsion gel can be formed under the parameters of solid content of 5%,7%and 9%and TS/WPI ratio of 2:3,1:4 and 0:5,and the structural strength,modulus,apparent viscosity and water holding capacity of emulsion gel network increased with the increase of TS content and solids content,and the droplet size shows the opposite trend.At the solid content of 5%and 7%the emulsion gel sample has good thixotropic recovery characteristics.This was attributed to greater TS-WPI interactions.The above emulsion gels loaded withβ-carotene can all be made into emulsion gels with firm network structure.The stability ofβ-carotene in emulsion gel is positively correlated with the solid content and the mixture ratio of TS/WPI,while the release rate of FFA and the bioavailability ofβ-carotene in emulsion gel are negatively correlated with it,indicating that a strong gel network structure can effectively delay the digestion of lipids and the release ofβ-carotene.The above results show that the emulsion gel system stabilized by TS/WPI mixture can be used as a good carrier for embedding and protectingβ-carotene.