Study On The Characteristic And Mechanism Of Oleogel Based On ?-sitosterol And Stearic Acid

The most commonly used methods to convert liquid oils to traditional plastic fats is transesterification or hydrogenation.However,these traditional processing methods produce trans fatty acids and saturated fatty acids that are harmful to health.As people pay more attention on healthy diet,there is increasing interest in the searching for alternative methods to reduce harmful saturated fatty acids and trans fatty acids in fats and oils and to increase the content of unsaturated fatty acids in plastic fats.Addition of edible gelators to liquid vegetable oils to convert them to hard oleogels with properties similar to hard fats has attracted much attention in the recent years.In this study,?-sitosterol(Sit)and Stearic acid,which have shown many potential health benefits such as cholesterol-lowering effect and anti-cancer activity were chosen as gelators to make oleogel and oleogel-based emulsion from edible oils.Modern analysis techniques were used to study the microstructure,thermal properties,oil bingding capacity,and rheological as well as other properties of the prepared oleogels.On the other hand,the changes in structure and properties of the oleogel in aqueous phase were investigated.Furthermore,enrichment of oleogel and oleogel-based emulsions with?-carotene(BC)was studied.The contents of the present research work can be concluded as follows:Ability of ?-sitosterol and stearic acid as single gelator or in mixture to convert liquid oils to oleogels was studied.The obtained oleogels were charcterized by different methods to study their properties.It was found that the hydroxyl group on the benzene ring of ?-sitosterol molecule is an electron-donating group that can interact with stearic acid or an electron-with drawing group in the oil phase to form an intermolecular hydrogen bond,which interacts with the gelators-vegetable oil provide active sites.However,?-sitosterol alone could not convert liquid oil to gel and showed a fiber-like crystallization behavior and three-dimensional network structure in vegetable oil.On the other hand,stearic acid alone could convert liquid vegetable oil c to gel with good stability.The microstructerof stearic acid in vegetable oil showed a needle-like and lamellar coexing crystal structure.?-Sitosterol and stearic acid was mixed at varying ratios and concentrations,which added into sunflower oil to prepare edible oleogel.Oleogel was characterized by optical microscope,fourier transform infrared spectrometer(FTIR),differential scanning calorimeter(DSC)and texture analyzer.The results showed that the intermolecular interaction of stearic acid and ?-sitosterol in vegetable oils created a new aggregate structure.The oil binding capability,melting temperature,and firmness of oleogel increased as the stearic acid amount increased in the gelator mixture.On the other hand,the effect of gelators mixture concentration on the oleogel properties was studied.The results showed that the content of solid matter and the saturation of the system increased,and the gel properties(such as oil binding capability,firmness and rheological properties)of the oleogel improved as the gelator concentration increased.The effect of the oil type on the packing pattern and properties of the oleogel was investigated.It was found that the oil type influenced the color,appearance,and microscopic structure of the oleogel.Flaxseed oil resulted in oleogel system with higher hardness,oil binding capacity,storage modulus(G'),and loss modulus(G'').The effect of water addition on microstructure and texture of the oleogel system was studied.The results showed that when the water was added into the oleogel system,the aqueous phase was uniformly dispersed in the grease gel system after homogenization and refrigeration.More dense vesicles appeared in the microstructure as water content increased.In addition,the dispersion of gel-aggregates and water droplets was more intensive,and the arrangement of the spatial network structures of grease gels disturbed to varying degrees.The gel components interacted with water molecules and the interaction of gelator molecules in the oil phase decreased.Also,the system saturation decreased and the texture bcame softer.On the other hand,the ?-sitosterol-stearic acid based oleogel can be used for preparing a stable water-in-oil emulsion(i.e.,Oleogel-based emulsions).Enrichment of ?-sitosterol-stearic acid based oleogel and emulsion with?-carotene was studied.It was found that high temperature can accelerate the oxidation of ?-carotene.When the heating temperature was lower than 40 °C,the self-assembled crystal structure in theoleogel and oleogel-based emulsion system could protect ?-carotene.However,the crystal structure collapsed and the protective effect was lost as the heating temperature increased.On the other hand,it was found that UV light has a significant destructive effect on ?-caroteneand the self-assembly structure can enhance the stability of ?-carotene to light damage,but could not completely prevent the degradation.The release studies of ?-carotene showed that?-sitosterol-stearic acid oleogel and oleogel-based emulsion have a positive effects on?-carotene releasing rate.