| The current research showed that 9-cis-β-carotene may be more active than all trans-β-carotene.β-carotene in normal food raw materials is almost all trans isomer,only in Dunaliella salina,the 9-cis-β-carotene can be accounted for nearly 40%,but Dunaliella salina is expensive,this might go against to make it applied in a large production scale.Therefore,it’s necessary to find a isomerization method using all trans-β-carotene as raw material to prepare high cis-isomers ratio,especially high 9-cis-isomer ratio β-carotene efficiently.In addition,the limitation of the structure of β-carotene makes it has poor solubility in water,poor stability and low bioavailability.The author tried to overcome the application problem effectively by prepareing β-carotene-nanostructured lipid carriers(β-C-NLC) so as to apply it to water-based food.The preparing technique of high 9-cis-isomer ratio β-carotene was studied. Using β-carotene(all-trans isomer ratio is 96%,9-cis isomer ratio is 0.15%) producted by chemical synthesis as material,preliminary isomerizaton was conducted by normal solvent refluxing.The isomerization products were analyzed with HPLC-APCI-MS and it showed that they were 15-cis-,13-cis-,9,13-cis-,all-trans-,and 9-cis-β-carotene,confirming that the measure was effective.Based on the comparison of isomerization technologys including normal solvent refluxing,high temperature and short time solvent refluxing, solvent refluxing with nano catalyst made by iodine doped Ti O2, the author optimized the technology of solvent refluxing with nano catalyst made by iodine doped Ti O2 via single factor experiments and orthogonal methods and the optimized reaction conditions were as follows: β-carotene was dissolved in ethyl acetate,concentration of β-carotene was 1 mg/m L,reaction temperature was 75°C,reaction time was 90 min, catalyst dosage was 1.2 mg/mg(based on β-carotene).The product contains 25.31% of 9-cis-β-carotene and 47.41% of cis-isomers in total.The degradation rate of β-carotene during reaction was 12.6%.the method is applicable for preparing high 9-cis-isomer ratio β-carotene.This processing techonology has the characteristics of simpleness and low costs.The effect of storage conditions on the stability of isomerization products was studied.The results showed that storage in dark and at low temperature,filled by nitrogen and adding a certain amout of antioxidants can greatly reduce oxidation degradation of high 9-cis-isomer ratio β-carotene, then enhancing the stability of the products.β-carotene-nanostructured lipid carriers were successfully prepared by an optimized high-pressure homogenization method.To achieve the balance between the efficacy and economy of the homogenization process,the heated lipid phase(distilled monoglyceride and medium chain triglycerides) mixed with water phase(Tween 80 as surfactant) and the mixture was sheared under 16000 rpm for 2 min,three cycles on 500 bar,lipid concentration as 10%(w/v), surfactant concentration as 1.6%(w/v), ratio of solid lipid to liquid lipid as 3:1(w/w) were chosen to be the optimal parameters.The results indicated that the optimal formulation of β-C-NLC had entrapment efficiency(EE) of 95.64%,partical size of 191 nm, polydispersity index(PDI) of 0.2 and the concentration of β-carotene in β-C-NLC of 2.9 mg/g,Transmission electron microscopy(TEM) revealed that the β-C-NLC exhibited a spherical shape.The influence of storage conditions on the stability of β-C-NLC was studied. The results indicated that storage in dark and at 4°C,filled by nitrogen and p H 3.5-7.5 can greatly reduce oxidation degradation of β-carotene.Furthermore the partical size changed a little, thereby improving the stability of β-C-NLC. |
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