Effect Of Complexes With Pinctada Martensii Protein Isolates And Three Hydrophilic Polysaccharides Based On Electrostatic Interactions On The In Vitro Simulated Digestion Of Fats

Fat has different influence on body health.Fat can provide essential fatty acids to human body,and promote the absorption of carotenoids and fat-soluble vitamins.However,excessive intake of fat will cause the accumulation and increase of lipid in the body,which will cause a series of diseases.Studies have shown that the structure of food,the compositon and the presence of fat in food have an important impact on the digestion and absorption of fat in the human baody.Therefore,it is a very meaningful research topic in the field of food&nutrition science to Construct a food structrural system to change the existence state of fat in food and then regulate the digestion and absorption of fat in food.Marine protein resources have the characteristic of high protein and low fat,and have been a popular research object for researchers to develop nutritious and healthy food.In this study,an oil-in-water?O/W?emulsion system and a gel system were constructed with Pinctada martensii protein isolates hydrophililc polysaccharide complexes?PPI-HP?and the influence of two food systems on the in vitro simulated digestion of fat was studied.The relationship between PPI-HP and fat digestion behavior was established,which provided a reference for the design and development of nutritional function food.The main research contents and results are as follows.1.The objective of this study was to prepare Pinctada martensii protein isolate?PPI?and PPI-hydrophilic polysaccharide?pectin,kappa-carrageenan and alginate?complexes based on electrostatic interactions and the properties of PPI and complexes were compared.The results show that compared to the solubility of PPI,the solubility of PPI-HP changed in different degrees,and the 10:3 PPI-pectin complex?PPI-P?had the highest solubility?10.02±0.68%?.The emulsion properties of 10:2 and 10:3PPI-A were significantly higher than those of the other PPI-HP.The conjugation of PPI and pectin could obviously reduce the surface hydrophobicity of PPI.The thermal denaturation temperature of PPI-HP was generally higher than that of PPI.PPI and PPI-HP at p H 7.0 formed gel structure in the range of 70-80?,while storage modulus of PPI-HP were lower than that of PPI.FT-IR spectroscopy showed a slight change in the?-sheet and?-helical protein structure in PPI-HP,while the O-H stretching of water and the C-C and C-O stretching and C-H bending of colloidal polysaccharides changed significantly.In summary,the conjugation of PPI and hydrophilic polysaccharides based on electrostatic interactions improve the functional properties to a certain extent.2.Medium chain triglycerides?MCT?and fish oil?FO?were used as model fats.Emulsions were prepared by PPI-P and MCT/FO,and an in vitro digestion model of fat was established.The process of fats digestion was analyzed by calculating the fatty acid release?Na OH titration method?,and the effect of emulsifier?Tween 80?and initial reaction p H on the in vitro simulated digestion of fat was studied.The results show that the digestion rates of MCT/FO emulsions were improved by adding PPI-P and Tween 80.After adding Tween 80,particle sizes of PPI-P-MCT/FO emulsions were decreased to different degrees,their emulsion particles were more uniform,the charge of PPI-P-MCT/FO emulsions decreased and?-potential tended to 0.After adding Tween 80,the digestion rates of PPI-P-MCT/FO emulsions were inhibited to some degrees in the early stage?0-60 min?,and their final Na OH consumption slightly reduced.After changing the p H value of PPI-P-MCT/FO emulsions,particle sizes of p H 5.0 and 6.0 emulsions were generally higher than other p H,the charge dispersion of p H 7.0 and 6.0 emulsions was more uniform while their?-potential tended to 0.The digestion rates of p H 7.0 and 6.0 emulsions were slightly lower than other p H conditions in the early stage of digestion?0-20min?,and their final Na OH consumption slightly reduced.In summary,after adding Tween 80,the particle sizes of PPI-P-MCT/FO emulsions decreased to different degrees,and the?-potential tended to 0,and it can inhibit the digestion rate of the emulsion in the early stage of the reaction to a certain extent.Particle sizes of PPI-P-MCT/FO emulsions at p H5.0-7.0 were generally higher than other p H while?-potential tended to 0.The digestion rates of PPI-P-MCT/FO emulsions at p H 5.0-7.0 were a slightly lower than other p H conditions.3.Medium chain triglycerides?MCT?and fish oil?FO?were used as model fats.the gel system was prepared by PPI-P and MCT/FO,and an in vitro digestion model of fat was established.The effect of moisture content,initial reaction p H and the Ca²⁺concentration on rheological properties,fat distribution and the in vitro simulated digestion of PPI-P-MCT/FO gels were studied.The results show that moisture content had a significant effect on in vitro digestion of PPI-P-MCT/FO gels.During the heat treatment,G'values of PPI-P-MCT/FO gels with low moisture content[1:6,were generally higher than those of samples with high water content,which indicated that three-dimensional network structure was more stable.The low-frequency NMR images of PPI-P-MCT/FO gels with low moisture content showed that the luminosity of samples was generally lower than that of the sample with high moisture content,which indicated that the gel structure could be goodto wrapthe fat.Initial reaction p H and Ca²⁺concentration had little effect on in vitro digestion of PPI-P-MCT/FO gels.Under the condition of neutral or weak acidity(p H 5.0,7.0 and 5%Ca²⁺)can promote the formation of gel structure to a certain extent and slow down the reaction rate of fat digestion.In summary,the PPI-P-MCT/FO gels with low moisture content could form a stable network structures and suppress the digestion rates of fats.The network structures of PPI-P-MCT/FO gels at neutral,slightly acidic environments and moderate Ca²⁺concentration were slightly superior to other conditions and the digestion rates slowed down toa certain extent.