Preparation Of Carotenoid Nanoemulsions From Red Grapefruit And Their Bioaccessibility Evaluation

Red grapefruit(Citrus paradisi Macf.),rich in ?-carotene and lycopene,is a good source of carotenoid supplement.Red grapefruit carotenoid supplement development has broad commercial prospects and research values according to its rich nutrition and unique flavor.However,there are conjugated double bonds in carotenoids structure,which are unstable during processing and storage.It is difficult for carotenoid micellization from food matrices due to its strong hydrophobicity,and subsequent relatively low bioaccessibility and bioavailability.Hence,the aim of the present work was to study and compare the physicochemical characteristics of nanoemulsions formulated with soybean oil,linseed oil or olive oil,containing red grapefruit pulp carotenoid by homogenization respectively.Afterwards,the protection of ?-carotene and lycopene encapsulated with nanoemulsions formulated with different oils(at 4 °C and 25 °C)was observed.Finally,their behavior during in vitro digestion conditions was investigated by conducting a kinetic study in the intestinal phase in order to monitor the influences of carotenoid molecular structure and nanoparticle size on bioaccessibility of ?-carotene and lycopene.This work evidences the potential of nanoemulsions to protect lipophilic bioactive compounds with a high bioaccessibility.The main results are as follows:(1)Carotenoids of red grapefruit pulp are composed of beta-carotene and lycopene,in ratio of 1:2.37.CSO,CLO and COO all enriched carotenoids with beta-carotene: lycopene(1:1.15,w/v).Sucrose ester : monoacylglycerol(3:2,w/v)was used as emulsifier,with the amount of 2%(w/v).The oil phase was set at 5%(w/v)to prepare low fat oil-in-water emulsions.The large particle size emulsion(about 250 nm)and small particle size emulsion(about 150 nm)were gained under high pressure homogenization of 25 MPa,4 cycles,and75 MPa,4 cycles,respectively.(2)Nanoemulsions presented relatively good stability during storage at 4 °C and 25 °C,respectively.Small particle emulsions have good particle size stability,meanwhile large particle emulsions have good stability of carotenoid retention during storage.(3)The effect of particle size on the biological proximity of carotenoids in nanoemulsions is as follows: With the increase of intestine digestion time in vitro,the biological proximity of ?-carotene and lycopene in nanoemulsions first increased and then stabilized.And the ?-carotene biological proximity is higher than lycopene.The biological proximity of ?-carotene and lycopene in small particle size CSO nanoemulsion is higher than that of other nanoemulsions,and the final biological proximity is 65.01% and 44.92%.Therefore,the particle size of the emulsion and the carotenoid structure have an effect on its biological proximity.The kinetic analysis showed that the Boltzmann model and the Dose Resp model can better fit the changes in the biological proximity of ?-carotene and lycopene in the nanoemulsion during in vitro digestion.