Study On Preparation And Physicochemical Characteristics Of Nanoemulsion-based Lutein Delivery Systems

Lutein is a naturally occurring carotenoid and lipophilic nutrient that has particularly beneficial uses as a natural pigment or antioxidant.The utilization of lutein in the food industry suffers from water insolubility and physicochemical instability.Oil-in-water nanoemulsion can be used for the delivery of bioactive lipophilic components,which have been reported to possess higher kinetic stability,and could improve the stability and bioavailability of nutrients.Therefore,a lutein-enriched nanoemulsion was formed,the preparation conditions were optimized and the storage stability,free radical scavenging activity and simulated digestion characteristics of nanoemulsion were evaluated.The main conclusions were as follows:The present work forms lutein-enriched nanoemulsions stabilized by sodium caseinate（SC）using a high-pressure homogenization process,and the results showed that the mean droplet diameter of the nanoemulsion was largely dependent on the homogenization conditions.Optimum results were obtained for 1.0 wt%SC,100 MPa homogenization pressure,and 7homogenization cycles,which produced a final nanoemulsion with a mean droplet diameter of 234.01±3.40 nm,polydispersity index of 0.123±0.028,zeta potential of-36.56±1.51 mV,encapsulation efficiency of 84.89±0.48%and lutein content of 54.04±2.70μg/mL.Moreover,the nanoemulsion remained physically stable after a 30 d storage period at 4°C,and the rate of chemical degradation of lutein was considerably decreased compared with lutein in an organic solvent system.The influence of environmental conditions on the physicochemical stability of nanoemulsion during storage were investigated.Nanoemulsions with all added CaCl₂ concentrations or adjusted to pH 4.0-5.0 exhibited phase separation,and emulsions with NaCl concentrations at 100-500 mM were unstable with extended storage,and the retention of lutein over the 30d storage period were considerably less than that of the untreated emulsion;the mean droplet diameters of all concentrated nanoemulsions increased significantly,but all represent a greater lutein retention than that of the untreated emulsion,conversely,thermal treatment at 60–100°C for 30 min had little effect on the physicochemical stability of the nanoemulsion.The influence of incorporation into emulsion-based systems on the in vitro digestibility,radical-scavenging capacity,stability and bioaccessibility of lutein were investigated.The radical-scavenging capacity of lutein was improved after incorporation,and lutein kept stable during in-vitro digestion,in addition,in-vitro simulate stomach digestion had little impact on the 1,1’-diphenyl-2-picrylhydrazyl（DPPH?）radical scavenging activity and ORAC of nanoemulsion,in addition,the 2,2’-azino-bis（3-ethylbenzothiazoline-6-sulfonic acid）（ABTS⁺?）radical scavenging activity and oxygen radical absorbance capacity（ORAC）of nanoemulsions were improved after simulate small intestine digestion;the bioavailability of lutein was improved after incorporation into nanoemulsion（81.72%）,in compared with oil suspension（51.48%）.As a result,the nanoemulsion could delivery lutein to intestinal stage and exhibited certain antioxidant activity and higher bioavailability.