Preparation Of Carotenoid Nanoemulsions From Lycium Barbarum L. And Their Bioaccessibility Evaluation

Fruits of Lycium barbarum L.,known as goji berries,is one of the important homologous resources of medicine and food in China.It is rich in carotenoids,especially zeaxanthin dipalmitate(ZDP).Effective intake of ZDP will help prevent chronic eye diseases such as age-related macular degeneration and cataracts.However,Due to the structural barrier of the goji berries and the fat-soluble nature of carotenoids,the absorption efficiency of the carotenoids is poor.In order to solve the problem of low bioaccessibility of goji carotenoids,In this study,the physicochemical properties,stability and bioaccessibility of the enrich oil and oil-in-water nanoemulsion delivery system were studied,which laid a theoretical foundation for the design of stable carotenoid products.This study developed three types goji berry carotenoids enriched oils and nanoemulsions(oil in water,O/W),namely,goji berry carotenoids enriched olive oil(GCOO),goji berry carotenoids enriched linseed oil(GCLO),and goji berry carotenoids enriched soybean oil(GCSO),GCOO nanoemulsion(ON),GCLO nanoemulsion(LN),and GCSO nanoemulsion(SN).The stability of three enrich oils and nanoemulsions at different storage temperatures(4°C,25°C)was investigated.Subsequently,the physical properties of the nanoemulsion before digestion,stomach digestion and intestinal digestion were evaluated by in vitro digestion and the ZDP bioaccessibility was determined at different incubated time of intestinal digestion period(7.5,15,30,45,60,120 min).The specific results are as follows:(1)The composition of carotenoids in GCOO,GCLO and GCSO was consistent with goji berries pulps,the major one being ZDP(85%).The optimized preparation formula and conditions of nanoemulsion are as follows: sucrose ester: monoglyceride 3:2 as emulsifier in2%(w/w),5% enriched oil as oil phase,and high pressure homogenization cycle 3 times under conditions of 75 MPa.(2)ZDP in GCOO,GCLO and GCSO had good retention when stored at 4°C and 25°C,respectively for 30 days.Particle size distribution Z-average and PDI of the three nanoemulsions(ON,LN and SN)were observed relatively stable for 30 days at 4°C and25°C.At 4°C,the ZDP content of the three emulsions decreased slightly as well as the insignificant chromaticity values changes were observed,while the chromaticity values changed greatly with the lower ZDP retention rate considering the higher storage temperature of 25°C,and the stability of chromaticity values and ZDP retention were in order of ON > SN > LN.Consequently,ON and SN were cho SN for the in vitro digestion assay.(3)The particle size of both ON and SN increased significantly after gastric digestion,and the types of particles in the digest after intestinal digestion were various.The bioaccessibility of ZDP of ON and SN during in vitro digestion was investigated by a kinetic approach.The bioaccessibility value increased gradually and then reached a plateau during the in vitro digestion for both tested nanoemulsions,and the bioaccessibility values of ON and SN reached to 49.1%,and 50.94%,respectively,although rate constants of ZDP of ON micellar incorporation was slightly higher than SN.A fraction conversion model could adequately describe the kinetic changes of ZDP bioaccessibility of ON and SN.