Preparation,characterization And Application Of Flavonoid-protein Complex System

Flavanones are important food polyphenolic compounds and are widely found in plant foods.Naringenin,hesperetin and their aglycones in flavanones have received special attention due to their high activity and are often used as an additive in functional foods.Factors such as oxidative degradation of polyphenols and digestive enzymes can significantly reduce the biological activity of polyphenols.It is of great significance to enhance the stability of flavanones in the gastrointestinal tract and achieve targeted delivery to enable flavanones to exert their biological activities.Proteins have amino,carboxyl and hydroxyl groups,which can be combined with polyphenols to improve the gastrointestinal stability and bioavailability of biologically active substances,which is of great significance to the development of healthy food and the enhancement of nutrients.In this paper,four different kinds of flavonoids [including flavanones(naringenin,hesperetin)and flavonols(quercetin,myricetin)] were prepared in a noncovalent manner with whey protein isolate(WPI).The composite system of flavonoidsWPI was characterized and its biological activity was determined by simulating in vitro digestion,and a relatively stable flavonoid-WPI system was screened out for the next test.The relatively stable composite system(flavanone-WPI)was screened for the preparation of microcapsules by spray drying,polyphenols were extracted from pomelo peels,and four different wall materials(whey protein isolate,soybean protein isolate,whey protein isolate-maltodextrin,soybean protein isolate-maltodextrin)were embedded in pomelo peel polyphenol extract(GPE),and the structural characteristics and in vitro digestion characteristics of microcapsules embedded in different wall materials were compared.Microcapsules with good structural and functional properties were screened out,and on this basis,their practical application was studied,and a pomelo polyphenol solid beverage containing milk protein was developed.The main research results are as follows:1.Preparation,characterization and functional analysis of flavonoid-WPI complexes: using naringenin(Nar),hesperetin(Hes),quercetin(Que),and myricetin(Myr)as raw materials,the WPI-flavonoid non-covalent complex system was prepared by non-covalent binding method.The conclusion shows that all four flavonoids bind to WPI,and the main interactions are hydrogen bond,van der Waals force and electrostatic interaction.The surface texture of the flavanone-WPI composite system is dense,flaky and uniform,with relatively few honeycomb structures.The negative potential value of the flavanone-modified WPI in aqueous solution increases,which reduces the isoelectric point of the protein and improves the stability of the complex as a whole.After the non-covalent reaction between WPI and flavonoids,the denaturation temperature of WPI increased,and the thermal stability of the composite system was improved.The total phenolic content and antioxidant analysis of the simulated digestion products in vitro showed that after the combination of WPI and flavanones,the flavanones were minimally affected by the digestive juice and had high antioxidant activity in the simulated digestion stage.2.Protein-polyphenol microencapsulation: characterization,function and in vitro digestion characteristics: The encapsulation of polyphenols in pomelo peel by different wall materials was compared,and four microcapsules(G-WPI,G-SPI,G-WMD,GSMD)structural,functional properties and in vitro digestion properties.Microcapsules embedded with proteoglycan composite wall material have higher stability.The microcapsules prepared from pomelo peel polyphenol extract-whey protein isolatemaltodextrin(MD)have a dense surface texture,the samples are spherical,less agglomerated and irregular in shape,the particle surface is smoother,and the structure is more stable.After GFP is embedded in the WPI-MD composite wall material,the negative potential value increases,which reduces the isoelectric point of the protein;at the same time,after the GPE is embedded in the composite wall material,the thermal stability is higher,which improves the overall performance of the microcapsules.stability.Simulated in vitro digestion of microcapsules found that microencapsulated G-WMD reduced the loss of GPE in the digestive tract and enhanced its antioxidant activity in the intestine.3.Research and development of solid microcapsules containing WPI-Grapefruit peel polyphenols: The microcapsule raw material,which is relatively stable and has biological activity in the intestine in the above test,is used as the main formula of solid beverage,and a product containing GFP and WPI is developed.,MD and other solid beverages with flavoring agents,adjust the bitterness and astringency of pomelo peel polyphenols and improve the added value of pomelo by-products.The sensory evaluation of solid beverages was carried out through sensory evaluation,and the optimal process ratio of solid beverages was obtained by response surface optimization test.The optimal process parameters were: pomelo peel extract 2%,fructooligosaccharide 7.5%,maltodextrin 5%,honey pomelo juice 25%,inulin 5%,whey protein isolate 20%,and the sensory score was 89 points.After brewing,the solid beverage is pale yellow in color,has the fragrance of grapefruit,moderate sweetness and acidity,mellow milk flavor,fast dissolving speed,almost no precipitation,uniform texture,good stability and delicate taste.Solid beverages have high reconstitution properties,which are in line with the characteristics of solid beverages.