| The research and application of protein-polysaccharide complexes has always been a research hotspot in the food industry.Pea protein is a high-quality protein with low price,high nutritional value and low allergenicity.The development of products based on pea protein is of great significance.Therefore,in this project,the pea protein(PPI)-Acacia(GA)system was used as the research object to characterize the PPI-GA complex and study the emulsification characteristics of the PPI-GA complex,which was further applied to the fish oil microcapsules.In addition,the storage stability and release performance of the microcapsule products were also studied.The main findings are as follows:The phase behavior of the PPI-GA complex formation process was studied,and the interactions between PPI and GA were characterized using fluorescence spectroscopy,Fourier infrared spectroscopy(FTIR),X-ray diffraction(XRD),thermogravimetry(TG)and other technical means.The change of PPI conformation was studied and the results show that at the condition with complex concentration 0.1%and the mass ratio of PPI-GA 1:1,as the pH value decreases,four phase zones appear in the complex solution:co-dissolution zone(pH>4.2)soluble zone(3.5<pH<4.2)incompatible zone(1.6<pH<3.5)soluble zone(pH>1.6),and the turbidity value of the solution reaches the maximum at pH 2.9.The formation of PPI-GA complex is mainly driven by the electrostatic interaction between the amino group in PPI and the carboxyl group in GA.GA changes the tertiary conformation of PPI and shifts the tryptophan residue of PPI.In a more hydrophobic environment,the denaturation temperature of PPI is also changed.By X-ray diffraction combined with AFM image analysis,it can be concluded that PPI and GA interact to form a complex,which changes the?-helical structure of PPI,weakens the electrostatic repulsion between particles,and produces a more stable complex.The effects of pH,heat treatment and salt addition on the PPI-GA composite emulsion were studied.The effect of those factors on the emulsion was evaluated by investigating the emulsification,emulsification stability and the average particle size of the composite emulsion,Zeta potential,emulsification index,and microstructure.The stability of the emulsions was also evaluated during storage and the mechanism was further analysed.Heating can stretch the PPI,exposing more hydrophobic groups,and improve the stability of the emulsion;salt ions weaken the electrostatic repulsion between the complexes,and the complex emulsion exhibits lower storage stability.The application of PPI-GA compound as a wall material in the preparation of fish oil microcapsules was studied.Using orthogonal design to optimize the preparation process of fish oil microcapsules,the optimal preparation process of fish oil microcapsules was obtained as follows:wall material concentration is 5%,PPI:GA is 1:1,homogeneous pressure is 500 MPa,and core-to-wall ratio is 1:2.Under these conditions,the embedding rate of fish oil microcapsules is 78.10%,the water content is low,the DHA retention rate is95.33%,the particle size is mainly distributed within 1.30-39.89?m,and the fluidity is good.Through TG analysis and DSC analysis,it can be concluded that below 189.61°C,the quality of microcapsules hardly change,and the thermal stability is good.Observation and analysis of the microstructure of fish oil microcapsules by SEM shows that the surface of the microcapsules is smooth and flat and presents an irregular sheet structure;CLSM is used to further analyze the microstructure of fish oil microcapsules,and it is concluded that the PPI and GA complexes have formed a relatively tight and continuous structure.The film completely envelops the fish oil.The storage stability and release performance of fish oil microcapsules were studied.The change of POV value of fish oil microcapsules during storage was analyzed by oxidation kinetics of zero-order and first-order reaction equations,and the shelf life of microcapsule products was predicted by the Vant'Hoff empirical formula.The results showed that fish oil microcapsules were stored at 4?,the capsule can be stored stably for 135 days,which significantly improves the shelf life of fish oil.The Avrami's formula was used to study the release performance of fish oil microcapsules under different temperature and humidity environments.The results show that high temperature and high humidity conditions are not conducive to the retention of core material.After the Avrami's formula is fitted,R~2 is greater than 0.95,and the fit is good.The release rate and particle size distribution of the core material of the microcapsule products in the simulated gastric and intestinal juice digestion process were measured to study the release law of the fish oil microcapsules during the digestion process.The results showed that the fish oil microcapsules released only 14.5%fish oil in the simulated gastric juice,and nearly 70%of fish oil is released in simulated intestinal fluid.The release law of microcapsule products during the digestion process was further studied by the method of CLSM combined with fluorescent labeling.Experiments have shown that fish oil microcapsules have good sustained release and enteric solubility,which is beneficial to the digestion and absorption of polyunsaturated fatty acids in fish oil in human body.The application of fish oil microcapsules as food additives in salad dressings was studied.The sensory score was used as an indicator to optimize the salad dressing formula through single factor and orthogonal design.The results showed that the best preparation conditions for salad dressing were fish oil microcapsules at 1%,corn oil at 25%,and egg yolks at 25%.The salad dressing prepared with this formula has stable performance,delicate and shiny state,and a sensory score of 8.92.Through the comparative study with two representative salad dressing products on the market,the results show that the self-made salad dressing showed more yellowish in color,smaller in particle size,unobvious in solid characteristics,and easy to digest and absorb. |
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