| Walnut oil is rich in nutritional value,which not only contains essential fatty acids such as linoleic acid and linolenic acid,but also contains vitamin E,sterol,squalene and so on.At present,most researches on walnut oil have focused on the basic composition and oxidative stability.There is no report on the preparation feasibility and gel properties of walnut oleogels.Therefore,in this paper,walnut oil was used as the base oil to prepare walnut oleogels using small molecule gelling agents such as glyceryl monostearate.On this basis,the type of gelling agent,the preparation process of oleogels and the influence of walnut oil matrix on the structure and properties of oleogels were studied,and the formation mechanism of walnut oleogels was initially explored.At the same time,the effect of adding water and nutrients on the characteristics of walnut oleogels were further studied.The storage stability,thermal stability,oxidation and digestion stability of walnut oleogels were studied with ?-carotene as a marker.The main research contents and results are as follows:(1)Walnut oleogels were prepared using three gelling systems such as glyceryl monostearate,sitosterol/oryzanol,sitosterol/lecithin,and their texture characteristics,rheology,oil retention,intermolecular forces,crystal properties and colors were measured.The internal intermolecular forces and crystal self-assembling structures of oleogels prepared using different gelling agents were different.The walnut oleogels prepared by the oryzanol/sitosterol gel system had the highest oil retention of 96.13%,but the hardness and apparent viscosity were too large and the spreadability was poor.The oleogels prepared using sitosterol/lecithin gel had the lowest oil retention and gel strength,the hardness was only 19.2 g,and the system had poor stability.Walnut oleogel using glyceryl monostearate has good texture and oil-holding property,and is suitable for spreading solid fat.(2)The effects of the amount of gelling agent,heating temperature,heating time and cooling temperature on the structural properties of walnut oleogels were studied.The results showed that with the increasing amount of the gelling agent,the internal self-assembly structure of the walnut oleogels became denser,and the hardness,strength,apparent viscosity and the oil holding ability of the oleogels gradually increased.With the increase of cooling temperature,the oleogels hardness and oil holding capacity both increased first and then decreased the heating temperature and heating time during the preparation of oleogels had no significant effect on its apparent viscosity.At the same time,the preparation conditions didn't change the shear thinning phenomenon of the oleogels.(3)The effects of the physicochemical properties of walnut oil on the structure properties of its oleogels were studied.The results showed that different oil extraction processes and refining would change the physical and chemical properties of walnut oil.Compared with walnut oil prepared using cold pressing and solvent extraction,hot pressed walnut oil had more phospholipid content and higher viscosity.Hot pressed oil had the highest acid value and peroxide value,which were 0.48 mg KOH/g and 2.16 mmol/kg respectively.The acid value and total phenol content of hot pressed walnut oil were reduced after refining.The physical and chemical properties of walnut oil were different,and the structural properties of the oleogels prepared by them were also different.Correlation analysis showed that the hardness of walnut oleogels was significantly negatively related to the peroxide value and anisidine value of walnut oil.The cohesion and oil retention of oleogels were significantly negatively related to the peroxide value and total polarity of the oil matrix.In summary,the physical and chemical properties of walnut oil would affect the structural characteristics of the oleogels to a certain extent.(4)The effects of adding water and nutrients on the oleogels structure of walnut oil were studied.The results showed that the hardness and oil retention of the gel system were reduced after adding nutrients,and different nutrients had different effects on them.The addition of nutrients reduces the strength of the gel system,but did not change the solid-like properties of the gel system.The swelling phenomenon occurred in the walnut oleogels system after adding water,and its swelling index was affected by the addition of the gelling agent and the amount of water.When the amount of gelling agent was 8% and 12%,the amount of water added has no significant effect on the hardness of the oleogels system,when the amount of gelling agent was 16%,the hardness of the oleogels system decreased first and then increased with the increase of the amount of water added,when the amount of water added was 40%,the minimum oleogel hardness was 35.3 g.Rheological analysis showed that the storage modulus and loss modulus of the oleogels system were affected by the oscillation frequency after adding water.In summary,the system was no longer stable and behaves as a "weak-gel" state.(5)The storage stability of walnut oleogels was studied,and its thermal stability,oxidative stability and digestive stability were studied with ?-carotene as a marker.The results showed that the hardness and oil-holding properties of the oleogels gradually decreased with the prolonged storage period.After storing at 4 ? for 40 d,the oil gel hardness was 78.04 g and the oil retention was 80.93%,significantly higher than the index under 25? storage conditions.Under high temperature environment,the internal self-assembly structure of the oleogels would slow down the degradation of ?-carrot.During the accelerated oxidation process,the peroxide value and anisidine value of the oleogel were significantly lower than those of walnut oil.In vitro simulated digestion experiments showed that the digestive decomposition rate of monoglyceride walnut oleogelswere higher than that of walnut oil matrix.When the digestion time was 160 min,the fatty acid release rate of oleogels containing 16% monoglyceride was 78.04%,?-carotene release rate was 69.55%,nutrient release is more complete.and it was easier to release nutrients. |
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