Study On Stability And In Vitro Digestion Characteristics Of Two Oil Bodies Emulsion And Curcumin-carrying Emulsions

Oil-in-water emulsion delivery systems can be used for nutrient delivery.Curcumin has the potential to resist chronic diseases,but its low bioavailability and its low solubility and high melting point limit its application as a nutraceutical ingredient in the food industry.The rich protein content of the membrane surface of the oil body can be regarded as a natural and effective emulsifier,and based on the structure and composition of the oil body,it can be used as an oil in the emulsion.In this study,the soybean and rapeseed oil bodies were used as natural oil phases containing emulsifiers to prepare oil-in-water emulsions and the delivery of curcumin was studied.The stability of soybean and rapeseed oil body emulsions under different conditions was studied.And in vitro digestion characteristics,provide a theoretical basis for better use of natural oil bodies and curcumin.Using soybean and rapeseed as raw materials,the oil body is obtained by the method of centrifugal separation after alkali dissolution.The dry protein content of soybean and rapeseed oil bodies were 12.86% and 7.9%,respectively.The isoelectric points of soybean and rapeseed oil body proteins are pH 4.8 and 6.5,respectively.With the increase of shear rate,soybean and rapeseed oil bodies show shear thinning.In the measured frequency range,the G’（dynamic elastic modulus）value of soybean and rapeseed oil bodies is greater than the G "（dynamic viscosity modulus）value and the G’and G" values of soybean oil bodies are significantly higher than that of rapeseed The corresponding value of oil body（P<0.05）.Soybean oil has a stronger solid phase and resists coalescence between droplets.Soybean and rapeseed oil bodies are dispersed in the water phase at the same concentration.The particle size of soybean oil body is significantly smaller than that of rapeseed oil body（0.48 μm<1.59 μm）.Observed by optical microscope and laser confocal microscope,the soybean and rapeseed oil bodies are spherical and uniformly dispersed.They are composed of red triglycerides and green surface proteins embedded in the outer layer.The soybean and rapeseed oil bodies are used to prepare an emulsion.As the oil body concentration increases,the particle size of the soybean and rapeseed oil body emulsions decreases.Soybean oil body emulsion can be well maintained and stable in 300 mmol/L-500 mmol/L CaCl₂ and NaCl solutions.Rapeseed oil body emulsion is destabilized in the same concentration of CaCl₂ solution and aggregated and layered in the same concentration range The NaCl solution can be better maintained stable.When the environmental pH value changes,the soybean and rapeseed oil emulsions have the largest particle size（26.7 μm,6.8 μm）at pH 4 and 6 respectively.The soybean oil body emulsion has good stability when the heating temperature and time are 25 ℃-95 ℃,0 min-90 min respectively,while the rapeseed oil body emulsion shows obvious aggregation and delamination when it is heated above 85 ℃.The in-vitro digestion model was established by simulating in vivo digestion environment and ingredients to digest soybean and rapeseed oil body emulsion.The particle size of the two oil body emulsions increased first and then decreased during the digestion of the stomach.The particle size value continued to decrease during digestion of the small intestine and corresponded to the change in the Zeta-potential value of the oil body emulsion during the digestion stage of the stomach and intestine.According to SDS-PAGE（polyacrylamide gel electrophoresis）,after digestion by the stomach,the soybean oil body emulsion has more protein bands on the surface of the droplet than the rapeseed oil body emulsion.The release of free fatty acids in soybean and rapeseed oil emulsions in the small intestine was 55.3 μmol/mL and 31.75 μmol/mL,respectively.The microstructural changes of each sample in the digestion stage of the stomach and small intestine under the laser confocal microscope correspond to the particle size and potential results.The above research shows that the emulsion prepared by soybean oil body has better stability and digestion characteristics under different conditions.The soybean oil body and curcumin are used to prepare a curcumin emulsion carried by the soybean oil body.This emulsion has no delamination when the concentration of CaCl₂ and NaCl solution is 0 mmol/L-500 mmol/L,heating temperature and time are 25 ℃-95 ℃,0 min-90 min,and it is better to maintain its own stability.The change trend of the particle size and potential of this emulsion is the same as that of the corresponding index of soybean oil emulsion.According to SDS-PAGE,there are still a lot of protein bands in the emulsion after stomach digestion,and continue to protect the internal curcumin.After intestinal digestion of the emulsion,the free fatty acid release amount was 59.6 μmol/mL,and the curcumin release rate reached 54%.