Application Of Corn Fiber Gum In Lutein Loaded Nanoemulsions

Lutein is a natural colorant and functional ingredient with many health-promoting bioactivities.It can improve lung aging,protect the retina,prevent body's aging,enhance human immunity and etc.However,its use in food and pharmaceutical fields is limited due to its low water-solubility and chemical instability.Owing to unstable conjugated double bonds in its molecular structure,lutein is prone to degradation exposure to light,oxygen and high temperature.In order to overcome this limitation,corn fiber gum(CFG)was isolated from de-starched and de-oiled corn fiber.The chemical composition,primary structure and emulsifying property of CFG were investigated.In addition,the physicochemical property,stability and in vitro bioaccessibility of lutein loaded emulsions stabilized by CFG were investigated.The results would lay a theoretical foundation for designing stable emulsions for delivering lipophilic compounds,such as lutein.Main results are listed as follows:(1)Two CFG fractions(CFG1 and CFG2)were isolated from de-oiled and de-starched corn fiber by the alkaline hydrogen peroxide method.The yields of CFG1 and CFG2 were 16.6 and 5.7%,respectively.CFG1 contained carbohydrate(88.9%),protein(0.27%),and ferulic acid(0.45%),respectively,and CFG2 contained carbohydrate(85.6%),protein(1.0%),and ferulic acid(1.2%),respectively.The average molecular weights of CFG1 and CFG2 were 319.2 and 382.8 k Da,respectively.CFG1 consisted of Ara,Gal,Glu,Xyl,Man,GalA,and GlcA in molar percentages of 24.4,11.4,3.97,35.9,0.16,19.8 and 4.37%,respectively,and CFG2 consisted of Ara,Gal,Glu,Xyl,Man,GalA,and GlcA in molar percentages of 25.0,11.4,6.58,34.5,1.40,18.1 and 3.02%,respectively.CFG1 and CFG2 showed uneven flaky smooth surface with similar chemical structure.It consisted of a backbone chain of ?-(1,4)-xylopyranose with D-glucuronic acid residues at O-2 position.The ?-L-arabinofuranose residues were existed at the 2 or 3 positions in molecular structure.Thermogravimetric analysis result showed that CFG showed strong thermal stability below 220°C.(2)The antioxidant activities and emulsifying properties of CFG1 and CFG2 were comparatively investigated.Results showed that both CFG1 and CFG2 exhibited significant scavenging DPPH radical capacity.The scavenging rates increased with increasing concentrations in the range of 0-6.0 mg/m L.When the concentration was 6.0 mg/mL,the scavenging rates were reached to 83.1% and 71.8%,respectively,indicating that CFG2 had better antioxidant activity.The surface and interfacial tension values of CFG1(2.0 wt%)were 54.2 and 20.8 mN/m,respectively.The surface and interfacial tension values of CFG2(2.0%)were 50.6 and 17.8 mN/m,respectively.This result indicated that CFG2 exhibited better emulsifying capacity.In addition,viscosity of the CFG2 emulsion was higher than that of CFG1 emulsion at the same concentration.Lutein loaded oil-in-water(O/W)emulsions stabilized by CFG1 and CFG2 were fabricated using high-pressure homogenization.The physicochemical properties and effects of environment conditions on the stability of lutein emulsions were investigated.The results indicated that the CFG2-stabilized emulsions exhibited better emulsion stability than CFG1.Environment pH and temperature had little effect on particle size and ?-potential of CFG1-and CFG2-stabilized emulsions.(3)In vitro lutein bioaccessibilities of the emulsions were evaluated by digestion profiles in stimulated gastrointestinal tract.Results showed that emulsification yields of lutein in CFG1-and CFG2-stabilized emulsions were 90 and 95.48%,respectively.After three weeks of storage,some creaming was observed in the CFG1-stabilized emulsion.However,CFG2-stabilized emulsion maintained good stability with no creaming.Under the conditions of light,oxygen,and high temperature,the amount of lutein retention in CFG-stabilized emulsions were higher than that of GA-stabilized emulsion.Moreover,GFG2 emulsion exhibited better stability than CFG1 emulsion.After digestion,the amount of FFA release in CFG2-and CFG1-stabilized emulsions was 90.9 and 82.7%,respectively.The lutein bioaccessibilities of the emulsions stabilized by CFG2 and CFG1 were increased from 13.8%(corn oil)to 32.37% and 24.85%,respectively.These results suggest that CFG can be used to prepare stable emulsions for delivering lutein or other lipophilic bioactive compounds.