Process Optimization And Bioavailability Of Lycopene Nanostructured Lipid Carriers

Lycopene has a variety of physiological functions,while cis-configuration of lycopene has a higher physiological activity.However,due to the strong hydrophobic structure,lycopene is insoluble in water,which greatly limits its application in food systems.In this paper,a high-cis configuration of lycopene,a liquid lipid rich in omega-3 polyunsaturated fatty acids,a natural surfactant and antioxidant were used to prepare stable and more functional high cis proportion lycopene nanostructured lipid carriers(cis-Lyco-NLC),which improved the water dispersibility of lycopene.We studied the storage stability,bioavailability and sensory acceptance of cis-Lyco-NLC products,and aimed to provide ideas and methods for expanding the application of carotenoids in water-soluble foods.Firstly,the isomerized lycopene as a raw material was used to filtrate solid lipids,liquid lipids,surfactants and antioxidants in the composition of cis-Lyco-NLC.The optimal solid and liquid lipid conditions were selected as glyceryl monostearate and peony seed oil by measuring particle size,encapsulation efficiency and lycopene loading of the cis-Lyco-NLC.Sodium caseinate was selected as the optimum surfactant by the accelerated storage test.Alpha-tocopherol was selected as the most suitable antioxidant by the accelerated oxidation test.The preferred composition of cis-Lyco-NLC was that the isomerized lycopene content was 0.3 g/100 mL(69.82% of the cis configuration),mass ratio of glyceryl monostearate and peony seed oil was 1:4,lipid concentration was 7.5 g/100 mL,sodium caseinate concentration was 3.5 g/100 mL,antioxidant alpha-tocopherol was 0.01 g/100 mL.Preparation process by high pressure homogenization: firstly,high cis proportion lycopene,glyceryl monostearate,peony seed oil,?-tocopherol mixed with water phase(sodium caseinate aqueous solution at 75°C)at 85°C.secondly,a pre-emulsion was prepared by high-speed shearing(16000 r/min).finally,the cis-Lyco-NLC product was obtained after high pressure homogenization(1000 bar,3 cycles).The encapsulation efficiency of cis-Lyco-NLC was as high as 99.76±0.14%,the concentration of lycopene(88.16% of the cis configuration)was(2.79±0.11)mg/mL,and the product diluted by any multiple had good stability.Secondly,the structure of cis-Lyco-NLC was characterized by fourier transform infrared spectroscopy(FTIR),differential scanning calorimetry(DSC),X-ray diffraction(XRD).The results showed that the characteristic absorption peak of lycopene was not observed in the FTIR spectrum of cis-Lyco-NLC,and the XRD pattern of cis-Lyco-NLC also did not appear the diffraction peak of lycopene crystal,while cis-Lyco-NLC,blank-NLC and glyceryl monostearate had a similar endothermic melting curve.Combined with the characterization results of FTIR,XRD and DSC,it showed that lycopene in a molecular form was dispersed in the imperfect lattice of the nanostructured lipid carriers.Thirdly,the physicochemical stability of cis-Lyco-NLC during storage was studied by using the particle size,PDI and lycopene retention rate as indicators.The results of cis-Lyco-NLC storage for 35 days at 4°C showed that the particle size distribution was between 185 nm and 199 nm,the PDI value was less than 0.25,and the retention rate of lycopene was 89.3%.The cis-configuration of lycopene in the product accounted for 84.66%,of which the proportion of 5-Z isomer was 22.71%,the proportion of 13-Z isomer was 13.05%,and the proportion of 9-Z isomer was 19.35%.The prepared cis-Lyco-NLC had good physical and chemical stability,and the lycopene cis isomer had a high proportion.Fourthly,the digestion and absorption characteristics and bioavailability of nanostructured lipid carriers prepared from high-cis configuration of lycopene and all-trans lycopene was evaluated by in vitro digestion model.Changes in potential and particle size of cis-Lyco-NLC and Lyco-NLC during digestion showed that the nanostructured lipid carriers could maintain good stability in simulated oral and simulated gastric digestion.However,after entering the simulated small intestine digestion stage,the oil droplets were digested,the lipid carriers were destroyed,the lycopene was released and formed micelles with bile salts and phospholipids.The results of simulated digestion showed that the release rates of free fatty acids in cis-Lyco-NLC and Lyco-NLC were 65.7% and 64.4%,and the bioavailability of lycopene was 31.65±2.48% and 21.54±2.55%,respectively.which indicated that increasing the proportion of cis isomers of lycopene could increase the bioavailability of lycopene.Finally,sensory evaluation between the cis-Lyco-NLC products prepared in this study and samples prepared previously in the laboratory(all-trans lycopene as raw material,Tween 80 as surfactant,glyceryl monostearate and medium chain triglyceride as solid and liquid lipid combinations)was studied.The results showed that the overall quality of the products prepared in this study was significantly better than the products made in the early stage of the laboratory.