Encapsulation,Protection And Delivery Of Pigments From Lycium Barb Arum Based On Food-grade Emulsions

Lycium barbarum,a popular traditional Chinese herbal medicine,is well-known for nourishing the liver and improving eyesight.Carotenoids,enriched in Lycium barbarum.Because of the health care efficacy of carotenoid,so it has become a hot research topic to add carotenoid into the food and beverage.However,there are challenges associated with incorporation of them into many commercial foods due to the poor water-solubility,chemical instability and low bioavailability of carotenoids.This paper used the small molecule surfactant,protein and polysaccharide as the emulsifier to fabricate the carotenoids-loaded emulsions.The influence of food environmental conditions on the emulsion's stability and the property of emulsions in vitro digestion were studied.The results of the current study would have important implications for the design of effective delivery systems to encapsulate carotenoids and other lipophilic bioactive components in food or pharmaceutical applications.This also provides theory basis for practical application of emulsions.The main results are as follows:1.The ratio of mixed surfactants in the system composition had an appreciable impact on droplet size and the small droplet could be formed at Span80:Tween80=1.5:8.5.The surfactant to oil ratio(SOR),organic phase content and stirring speed have important effect on droplet size,particle size distribution index(PDI)and transparency of emulsions.Carotenoids-loaded nanoemulsions with small mean droplet size(d<50 nm)could be obtained after the optimization of preparation conditions.The low temperature storage,neutral condition and antioxidants in food environment could delayed the degradation of carotenoids in the emulsions.The different pH value,salt concentration had no effect on droplet size,but the droplet size increased and the emulsions was cloudy after heating treatment.The initial digestion rate decreased as the SOR increased.The high bioaccessibility could reach up to about 80%at SOR = 2-5.The bioaccessibility was high when droplet size was small or soybean oil as oil phase in vitro intestinal digestion.The fasting state and fed state have little effect on oil hydrolyzation and the bioaccessibility of carotenoids.2.The SPI-stabilized emulsions(about 200-300nm)can be fabricated by high pressure microfluidics.The emulsions was stable after 30 days storage at 4? and pH7.The emulsions were stable at pH 6-7.But there was a large increase in mean droplet size at pH 3-5.5.The SPI-stabilized emulsions exhibited extensive droplets aggregation at salt concentration ?100 mM.The high temperature storage could accelerated the degradation of carotenoids in emulsions.Compared with small molecular emulsifier,the SPI-stabilized emulsions could more effectively inhibited the degradation of carotenoids.The VE and EDTA also had certain inhibitory effect on the degradation of carotenoids.The bioaccessibility of carotenoids gradually improved with bile salt content's increase or the carotenoids content's decrease.The FFAs release rate was slow and bioaccessibility of carotenoids gradually decreased with droplet size increase.It showed that larger lipid drops against of the carotenoids into the mixed micelles.Compared with only simulated digestion in the small intestine,the bioaccessibility was decreased obviously in simulated gastrointestinal digestion.The bioaccessibility were 18.4%and 10.6%with SO and MCT as oil phase,respectively.3.The multilayer emulsions were prepared by electrostatic deposited polysacchride or protein onto the surface of SPI-stabilized droplets.The stability of the emulsions to pH change depends mainly on the characteristics of coating.The droplets stabilized by alginate were relatively stable to droplets aggregation from pH 3 to 7(without salt)and in salt concentration of 0-500mM NaCl(pH 3).The droplets coated by chitosan exhibited good stability at pH3-6(without salt).However,droplets aggregation occurred in emulsions stabilized by chitosan at salt concentration>300 mM(pH5).The droplets stabilized by lactoferrin were stable at pH 3-7,but the emulsions was sensitive to salt concentration(?50 mM,pH5).There was nearly identical degradation profile between primary and alginate-stabilized emulsions during storage at pH 6.0.Carotenoids seemed to be more chemically stable in alginate-stabilized emulsions than primary one at pH3.0.The emulsions stabilized by chitosan had fast degradation rate at pH6.0.However,there were significant differences in carotenoids degradation between the primary and chitosan-stabilized emulsions at pH 3.0,and the retention rates were 33.5%and 42.6%,respectively.Lactoferrin-stabilized emulsions are stable than primary one and the retention rate after 15 days storage at 37 ? was 73.4±1.5%(pH6)and 47.1±1.6%(pH3),respectively.In addition,there was no appreciable difference in the digestive extent of lipids between primary emulsions and alginate-stabilized emulsions,but the FFAs released rate of alginate-coated droplets was faster.Chitosan is capable of reducing the digestibility of emulsified lipids(87.9%).The extent of released carotenoids in the emulsions was in the order of AL-SPI-E>SPI-E? LF-SPI-E>Cs-SPI-E and the bioaccessibility were 11.3±0.35%,10.6±1.03%,10.5±0.8%and 4.46±0.36%,respectively.4.After ultrasound treatment,the surface hydrophobicity of lactoferrin increased slightly,and heating treatment can significantly increase its surface hydrophobicity(from 115 to 293).Ultrasound and heating could destructed disulfide bond in protein molecules to release free sulfhydryl group.Ultrasound and heating increased lactoferrin tryptophan microenvironment polarity and the intrinsic fluorescence intensity.The treatment decreased in the ?-helix proportion and an increase in P-sheets content,which revealed that the secondary structure of lactoferrin have changed after ultrasonic treatment.There almost no effect on primary structure of protein.Ultrasound and heating treatment could decreased iron-bingding capacity of lactoferrin.When the emulsions was prepared,the initial pH value of lactoferrin solution had a great effect on the stability of the emulsions.The small droplet size of emulsions(185 nm)could be produced at pH3,but the emulsions exhibited some aggregation at pH7.The emulsions have droplet aggregation at pH7-9 due to decreasing electrostatic repulsion.The emulsions was stable with different concentration of NaCl(0-250mM)at pH 3 and pH 5.However,after heating the emulsions have obvious droplets flocculation at pH5 under the salt concentration of 100-250 mM.Compared with LF-SPI emulsions,the multilayer emulsions have better chemical stability than monolayer lactoferrin emulsions at pH5 due to its thicker interface layer.5.The aggregation of lactoferrin depended on temperature,pH and concentration.The heat-induced aggregation happened easily at 65 ? and pH value near the isoelectric point.Different particle size of aggregation had different properties.Compared with natural lactoferrin,intrinsic fluorescence intensity of aggregation was reduced.The surface hydrophobicity enhanced obviously,and it was inversely proportional to the particle size,which the smallest particle size of aggregate G have highest surface hydrophobicity(about 1300).Free sulfhydryl group increased significantly after heating,but the iron-bingding capacity of lactoferrin was decreased(about 15-30%),and the degree of protein aggregation higher,the iron-bingding capacity lower.Aggregates have good physical stability and there had no obvious change in particle size at pH3-10 or NaCl 0-500 mM.The droplet size of emulsions that aggregation as emulsifier increased gradually with oil phase content increased.The chemical stability of emulsions with different particle size aggregate as emulsifier was almost same.