Study On Whey-protein-isolate Based Carriers For The Protection Of Multiple Bioactive Components And Their Interactions

Bioactive components such as vitamins,polyphenols and polyunsaturated fatty acids have the effect on regulating physiological functions of human body and can thus prevent some chronic diseases.However,many bioactive components are unstable and very sensitive to environmental conditions.In the process of food production and storage,they are susceptible to degradation due to light,oxygen and temperature,losing biological activity.Meanwhile,poor solubility of hydrophobic and amphiphilic bioactive components makes them difficult to be absorbed in the body,resulting in low bioavailability.The unexpected characters limit their application in food and pharmaceutical industries.Multiple bioactive components may have synergistic or antagonism effects,so different bioactive components can be enhanced in a product with development prospect.Whey protein isolate(WPI)is a kind of edible protein with high nutrition,possessing multiple functional properties such as emulsification and ligand binding.It can be used as an effective carrier for the encapsulation of multiple bioactive components.At present,the protection of bioactive components based on microcapsule technology mainly focused on the study of freshly-prepared carriers.However,bioactive component and its degradation products may affect the composition and structure of the carriers,thus affecting the protection effect for bioactive component in turn.The effect of bioactive components on carrier has the guiding significance for choosing the carrier.In this study,WPI was chosen as a carrier model,hydrophobic ?-tocopherol,amphiphilic naringenin and hydrophilic folic acid were chosen as bioactive component models.The impact of WPI on the storage stability of ?-tocopherol and naringenin and photo-stability of folic acid was studied.In addition,the effect of bioactive components on WPI was also investigated,which were of great importance for selecting the appropriate carrier.The main research contents are as follows:Firstly,WPI-?-tocopherol,WPI-naringenin and WPI-?-tocopherol-naringenin complex nanoparticles were prepared and characterized in term of size distrubution,?-potential,antioxidant activity and encapsulation efficiency.The results showed that effective diameter of nanoparticles was between 125 and 145 nm,and size distribution was uniform.The initial ?-potential was greater than 30 mV.Encapsulation efficiency of ?-tocopherol was larger than 93% and not significantly changed with the increase of WPI concentrations,while encapsulation efficiency of naringenin increased with the protein concentrations.Simultaneous encapsulation of two bioactive compontents did not affect the encapsulation efficiency of ?-tocopherol,but decreased that of naringenin when the protein concentration were 0.50% and 1.00%.The mixture of ?-tocopherol and naringenin produced antagonistic effect,which could be inhibited by 0.50% and 1.00%WPI.Meanwhile,the stability of nanoparticles and bioactive components in different storage temperatures and the effect of the bioactive components on the protein were also studied.During storage at 25? and 45?,effective diameter increased and absolute value of ?-potential decreased.WPI improved the stability of ?-tocopherol during storage at 25? and 45?,addition of naringenin had no influence on the stability of ?-tocopherol.Degradation of bioactive components during storage did not affect protein's structure.Secondly,protective effect of WPI on the folic acid was discussed under ultraviolet irradiation.It is found that WPI and its main components ?-lactoglobulin(?-LG)and ?-lactalbumin(?-LA)can delay the photo-degradation of folic acid by using fluorescence spectrometry,which ranked in the order ?-LG ? WPI > ?-LA in term of effectiveness.The WPI separated from its FA mixture during irradiation was also used to protect folic acid.Results suggest that the protective effect of protein on folic acid became better after irradiation for longer time.Mechanism for improved protection of WPI against the photodecomposition of folic acid was studied.During the vitamin decomposition,WPI's change was characterized in term of composition,structure,interaction with the vitamin or its decomposition products.Folic acid decomposition photosensitized indirect oxidation of WPI,leading to unfolding,degradation in concurrence with oligomerization.The increase in the absorbance and antioxidant activity contributed to the protein improved protection for folic acid.