The Research On Vegetable Oil Organogels With Oryzanol And Phytosterols

Edible oil organogels are formed upon self assembly of surfactant-like small molecules (gelator) into crystalline fibers, which eventually lead to gelation of oil. An edible oil organogel can be defined as an edible oil entrapped within a thermo-reversible, three-dimensional gel network. The unique physical, functional, and nutritional properties of these organogels has caught the eye of the food and pharmaceutical and daily chemical industries. In this paper, we prepared oil organogels by adding gelators-the mixtures of ?-oryzanol and ?-sitosterol into vegetable oil, and then discussed a series of properties of these organogels.Vegetable oil organogels can be obtained after sequentially stirring, heating and cooling the mixtures of vegetable oil and a certain amount of ?-oryzanol and ?-sitosterol (3:2 w/w). This research first investigated the influence of oil type to the formation of organogels and the relationship between structurant concentrations andorganogels thermal properties. Oil type affected the forming time of gels greatly (sunflower oil gels was 14min, and castor oil was more than 24h).As the structurant concentrations increased (8%,12%,16%)the melting points increased(50,60,70? proportionally. After comparison and analysis, we could conclude that the vegetable oil with lower viscosity and higher unsaturation would form gels easily.Then by fitting the isothermal crystallization curves of different gels and Avrami model, we could find that the crystal nucleation of the mixtures of ?-oryzanol and ?-sitosterol solidifying different vegetable oil resulted two modes of instantaneous nucleation (n=1) and sporadic nucleation (n=2), and crystal growth mode was 1-D growth.We prepared sunflower oil organogel by adding a certain concentration of ?-oryzanol and ?-sitosterol into the base oil-first-degree filter pressed sunflower oil, and explored the effects of different preparation conditions on the firmness and microstructure of sunflower oil organogel. On the basis of single factor experiment, the optimal preparation conditions of 6%(w/w) ?-oryzanol and ?-sitosterol organogels made with sunflower oil were determined by orthogonal experiment. The results showed that the cooling temperature affected the firmness of sunflower oil organogel significantly, followed by ?-oryzanol and ?-sitosterol weight ratio, heating time and heating temperature; the optimal preparation conditions of 6%(w/w) ?-oryzanol and ?-sitosterol organogels made with sunflower oil were obtained as follows:heating temperature 140 ?, heating time 50min,cooling temperature 5? and ?-oryzanol and ?-sitosterol weight ratio 60:40. Under the optimal conditions, the firmness of 6%(w/w) ?-oryzanol and ?-sitosterol organogels made with sunflower oil reached 479.61±9.18 g.By the contrast of organogel hardness, Storage modulus, loss modulus and microstructure of 8% sunflower oil organogels prepared with different preparations, we could find that these organogel properties were all affected by ?-oryzanol and ?-sitosterol weight ratio, heating time, heating temperature and cooling temperature. In detail, compared with other oil organogels of different ?-oryzanol and ?-sitosterol weight ratio, the sunflower oil organogel with 60:40 ?-oryzanol and ?-sitosterol weight ratio behaved greater harness, Storage modulus and loss modulus,and steady three-dimensional gel network. With the increase of heating temperature and heating time, sunflower oil gel hardness, elastic modulus and the viscous modulus increased firstly and then remained constant, and gel network formed gradually and then kept stable. When the cooling temperature was too low (-5?), gel hardness, storage modulus and loss modulus were lower; with the increase of cooling temperature, gel hardness, Storage modulus and loss modulus reached maximum at 10?, but these values all drsreased when cooling temperature continued to rise, and the three-dimensional network structure disappeared at higher temperature. By analyzing rheological properties of sunflower oil gel, we could find that with the increase of shear rate, sunflower oil gel'apparent viscosity decreased gradually and showed pseudoplastic fluid properties. Through the study of thermodynamic model of organogels, it was concluded that the self-assembly process of three-dimensional network structure formation in oil-based systems was driven by change in enthalpy.The oil binding capacity of sunflower oil organogels decreased over time under the condition of two kinds of storage (4 ? and 25 ?), and oil binding capacities were more than 90% within 9 weeks, while the capacity of binding oil of gels at 4 ? was stronger. Compared with the organogels storaged at room temperature (25?),the gels storage at low temperature (4?) behaved higher hardness and viscosity, and good oxidation stability.