Structuring Mechanism Of Stearic Acid Derivatives On Sunflower Seed Oil

The oleogel formed by the structuring of vegetable oils under the action of gelators can reduce the application of trans-and saturated fatty acids.It can also be used as the carrier of hydrophobic nutraceuticals with wide potential applications in food industry.The mechanism of gelators structuring vegetable oils is a hotspot of food research.In this study,the capacity of stearic acid derivatives structuring sunflower seed oil were evaluated.The effects of gelator concentration and storage temperature on the textural,rheological,thermodynamic properties and lutein protection were systematically investigated.Based on the experimental results,molecular simulation methods were applied to clarify the cross-scale relationship,“Gelator structure-Assembly behavior-Oleogel properties”,which could clarify the structuring mechanism of stearic acid derivatives at the molecular level.The obtained results are as following:?1?A method for preparation of food-grade lutein ester-loaded oleogels was established by extracting lutein ester from marigold flower with the edible vegetable oil as solvent and then structuring with monoglyceride stearate.Compared with soybean oil,canola oil and corn oil,sunflower oil showed the highest extraction efficiency at 60?.The lutein ester-loaded sunflower seed oil obtained could be structured by monoglyceride stearate to form oleogels.The textural and rheological properties of oleogels were positively related to the gelator concentration,and negatively related to the storage temperature.Their gelation temperatures were only affected by the gelator concentration.The oleogels could effectively improve the stability of lutein ester against UV radiation,and the protective effect was positively correlated to the gelator concentration.This preparation method of lutein ester-loaded oleogels is simple and safe,which can provide a reference for the development of other hydrophobic nutraceuticals.?2?The feasibility of the mixture of monoglyceride stearate?MG?and stigmasterol?ST?structuring sunflower seed oil was evaluated.Then,the effects of gelator composition,concentration and storage temperature on the textural,rheological and thermal properties of the oleogels were systematically investigated.Their lutein protective effects were also compared.It was found that the MG/ST ratio had significant influence on the critical concentration of the oleogel.When the gelator concentration was more than 4%,the oleogel could be formed at all the tested ratios.At the storage temperature of 5°C,the hardness,viscosity and chewiness values of the MG or ST oleogels were higher than those of the MG-ST oleogels.But when the temperature rose?20°C?,these textural properties of the MG-ST oleogels were much higher.In the rheological assay,all the oleogels exhibited the shear-thinning behavior with similar rheological properties.Their gelation temperatures depended on the composition and concentration of the MG-ST mixture,instead of the storage temperature.The oleogel with the MG/ST ratio of 2:8 possessed the highest gelation temperature?80°C?.The gelation temperature of the MG-ST oleogel declined with the decrease of the ST concentration.It was found that the obtained oleogel could significantly improve the stability of lutein under UV radiation.The oleogel with the MG/ST ratio of 8:2 showed the highest lutein protection effect.The obtained results are helpful to develop the new edible oleogels and promote the application of lutein in foods.?3?The structuring effects of stearic acid?SA?,2-hydroxyethyl stearate?HES?,12-hydroxy stearic acid?HSA?,methyl stearate?MS?,sorbitan monostearate?SS?on sunflower seed oil were systematically investigated.The structuring mechanism was revealed based on experimental and molecular simulation methods.SA,HSA and HES were able to structure sunflower seed oil,among which the structuring ability of HES was reported for the first time.The oleogel formed with HSA?HSAO?exhibited the highest textural properties?such as hardness,fracturability,adhesiveness and chewiness?,followed by the oleogels formed with HES?HESO?and SA?SAO?.The texture properties of SAO and HESO increased with the increasing gelator content,and reduced with the increase of storage temperature.But the texture properties of HSAO were positively correlated with both the gelator content and storage temperature.The rheology analysis suggested that all the oleogels belonged to the pseudoplastic gel,and their G'_LVR followed this order:HSAO>SAO>HESO.Their gelation temperatures were only related to the concentration of monostearin.The high mechanical and lutein protection performance of HSAO could be attributed to its high solid fat content and degree of crystallinity.The MD simulation indicated that the lowest E_interaction and R_g were found in the HSA dimer.The results of the SA and HES dimers were similar but much higher than those of the HSA dimer.The IGM analysis also confirmed that these dimers were maintained by hydrogen bonding,and HSA had the most compact crystal structure.The molecular simulation result could explain the structuring performance of stearic acid derivatives.