| Oleogels are considered as a viable alternative to traditional plastic fat since they include a significant amount of unsaturated healthy fat,and its preparation are mainly affected by the base oil and the type of gelators.In this paper,the effects of different gelators(12-hydroxystearic acid,sunflower wax,beeswax,monoglyceride,sodium stearoyl lactylate,stigmasterol,cinnamic acid and diosgenin)on the preparation and properties of rapeseed oil based oleogels were systematically studied with double low rapeseed oil as the base oil,and then,exploring the effect of stigmasterol concentration on rapeseed oil-based oleogels.On this basis,the water-in-oil(W/O)gel emulsion was prepared by replacing the oil phase with part of the water phase,and the formation mechanism and stability reasons of gel emulsion prepared under different proportions were studied.Finally,the simulated digestion performance of rapeseed oil-based gel emulsion prepared from stigmasterol was evaluated in vitro.The details and conclusions of the study were as follows:Firstly,the effects of different gelators on the structure and properties of rapeseed oilbased oleogels were systematically compared,and the optimal gelators was selected to prepare rapeseed oil-based oleogels,and the preparation method of oleogel was established.The results indicate that,the oil binding capacity(OBC)of the oleogels prepared by the gelator except for diosgenin and cinnamic acid at the concentration of 6%,could reach more than 94%;the G′ value of 12-hydroxystearic oleogel was large and the structure was not easily altered by external forces,and the oleogel formed by stigmasterol had the best thermal stability(phase transition temperature 93.4oC);12-hydroxystearic acid formed a dense fibrous network structure in rapeseed oil,dousterol and diosgenin formed rod-like crystals in the oil,while cinnamic acid showed sparse lamellar crystals,the other gelators were internally crystallised with small particles;Stigmasterol could formed rod-like crystal structure through intermolecular hydrogen bond force,which was not easy to be destroyed.Compared with the oleogels prepared by several other gelators,the OBC value was 99.74% with stigmasterol oleogels,system has high better rheological property,phase transition temperature of 93.4oC,the rheological properties of the stigmasterol system were better,phase transition temperature of 93.4oC,and the intermolecular hydrogen bond made the gel system difficult to be destroyed at high temperature.Therefore,stigmasterol as a gelator to prepare oleogel was the preferred choice for grease gel system.Secondly,the mechanism of the formation of rapeseed oil-based was investigated by examing the effect of stigmasterol concentration on the macroscopic properties and microstructure of the oleogel.The results showed that at a gel formation temperature of 5oC,a critical concentration of 2% stigmasterol was able to form a gel oil with rapeseed oil;the oil holding rate analysis found that the OBC value of stigmasterol oleogel increased with increasing concentration at 2%-6% stigmasterol concentration,the OBC reaching a maximum of 99.74%,but at 7% of stigmasterol,the self-assembly structure reached the saturation point,the OBC rise was not obvious;the analysis of rheological properties found that the stigmasterol oleogel was a shear thinning pseudoplastic fluid,and the G′ of the oleogel did not change with the frequency of scanning increases,showing the characteristics of strong gel,and the thermal stability was better(the critical phase transition temperature of 6%stigmasterol oleogel was 98.3oC,and 7% stigmasterol oleogel did not undergo gel to sol conversion process even at 100oC).The stigmasterol formed a rod-like crystal structure mainly through intermolecular hydrogen bonding and self-assembly,which bound the rapeseed oil in its three-dimensional structure.Therefore,the preparation process of stigmasterol oleogel was a physical change,and the gel structure was relatively stable,which did not produce excess trans fatty acids and saturated fatty acids,and could better retain the nutrients of double low rapeseed oil.Furthermore,based on the hydrophobic properties of stigmasterol,a method for preparing rapeseed oil-based gel emulsion with stigmasterol and PGPR under different ratio conditions was established and optimized.The results showed that with the increase of stigmasterol concentration,the gel emulsion network structure became more compact and the system stability was better.The gel emulsion prepared by 2%PGPR and stigmasterol was stabilized by the mechanism of continuous phase network structure stabilization.The pickering interface stability and continuous phase network stability were used to improve the network strength and stability of the gel emulsion system prepared by 3%PGPR and stigmasterol.The gel emulsion prepared by 6%PGPR and stigmasterol was stabilized by pickering interface stabilization mechanism.Compared with the gel emulsions prepared by 2,6%PGPR and stigmasterol,the gel emulsions stabilized by pickering interface and crystallization network with 3%PGPR and stigmasterol had higher rheological strength,viscosity recovery up to71.53%,the peak melting temperature of the gel emulsion could reach 111.1oC,and it had good thermal stability;the gel emulsion could keep its gel shape when storaged at high temperature,and the change in particle size was minimal;when oxidation was accelerated,the retarding effect on oil oxidation was more noticeable.Finally,the impact of stigmasterol content on the digestibility of grease gel system was examined.Compared to the control emulsions,fat digestion was inhibited in the stigmasterol gel emulsion,with an increase in the concentration of stigmasterol leading to an increased inhibition effect.The FFA release rate of 4% stigmasterol gel emulsion was 44.1(±0.18)%and 6% stigmasterol oleogel was 11.43(±0.76)%,which was much lower than that of control Tween 85(94.56(±0.93)%)and PGPR(63.02(±1.46)%)emulsion.After treatment,the characteristic peaks of hydrogen bonding in the digest’s infrared spectrum widened and shifted to the low frequency region(red shift),and bile salt absorption peaks appeared in the range of1170-1000 cm-1,the stigmasterol crystals and bile salt particles were observed in the lower precipitate of the digest.This further suggested that stigmasterol adsorbed bile salt and precipitated them,thus inhibiting the digestion of gel emulsion lipid.The rapeseed oil-based gel system constructed from stigmasterol has the advantages of low trans-fatty acid,low saturated fatty acid and low calorie,and difficult to be digested in the simulated intestinal system,which has the potential to replace hydrogenated solid fat. |
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