Effect Of Soybean Oil On The Gel Properties And Microstructure Of The Soy Protein

Protein and fat as the main macromolecules of food, the relationship between them has a vital role for the study of food processing technologies and the development of soybean product. In the soy processing process, heating is the most commonly used, and heating is the main factor induced protein denaturation. Soybean oil added to the soy protein, the quality of the thermal gel would change. In order to understand the improvement of protein adding soybean oil, this issue studyed the soy protein adding soybean oil, and heating it, analysising the features and micro-structure of the gel, through the instrument of analyzer, colorimeter, rheometer, infrared spectroscopy, UV spectrum.The results show that:As the temperature rised, the heating time longer, the increase of soybean protein isolate(SPI), the hardness and spring of gel increase; With the increase of glucose lactone (GDL), the gel hardness increased, but the spring is lower. With the addition of soybean oil, the synergy between soybean oil and gel conditions reduces the protein gel strength, but the elasticity first increases and then decreases. After reaching saturation in a combination of soybean oil(12%) and soy protein continue to add soybean oil, hardness and elasticity are reduced.As the temperature increased, ΔE, ΔL*, Δa*, Δb*reduced; With the heating time longer, SPI increased, soybean oil increased, as the synergy between soybean oil and heating time, soybean oil and SPI, ΔE, ΔL*,Δa*, Δb*increased. With the the GDL amount of0.02mol, ΔE, ΔL*, Δa, Δb*increased with soybean oil increases. The GDL is more, the effect of synergy between soybean oil and GDL decline, chroma small changes. GDL is more than0.02mol, there were negativethe of Δa*, Δb*; GDL is more then0.04mol, there were negativethe of AL*. Other conditions, ΔL*, Δa*, Δb*are positive, showing lighter, reddish, yellowish.Rheological analysis,①With the addition of soybean oil, linoleic acid, the strain valueincrease, adding oleic acid and a mixed system, the strain valuedecline②Rrequency sweep:the storage modulus(G□)also increases with the increase of oleic acid and soybean oil; the modulus (G")increase linearly with the amount of oil, the most significant increased is linoleic acid. The ratio between G□and G" is greater than1. Adding oil increased the elasticity of the gel, but the solid nature of the dominant position reduced with adding oil. Oleic acid, soybean oil increasing protein flexibility, and linoleic acid in turn hinder the protein gel.③Temperature sweep:G□increased of adding soybean oil,and G□is the largest with12%oil. The protein gel of adding oleic acid, linoleic acid and mixed system, the warming trend of G□is rapid. Thermostat stage of G□adding soybean oil was significantly greater than the other case, adding the oleic acid and oil of the storage modulus G□is closest, followed by a mixed system, The acid protein storage modulus G□is less than the blank protein gel.IR spectra of protein gel after regreasing added grease, the peak of2980-2850cm-1,1745cm-1,1140cm-1,1170cm-1,1070cm-1were changed.Addition of soybean oil, soy protein isolate amide I band from1600-1700cm-1of the secondary structure of a-helix, β-sheet content significantly reduce, P-turn, random coil to improve the contrary. The soybean oil content of12%, protein gel a-helix, P-sheet reduce the most significant, β-turn, random coil to increase the maximum, the content of soybean oil affect the soy protein structure played a key role. The effect of the secondary structure of the SPI adding Oleic acid:content of α-helix, β-turn is the most significant,the effect of linoleic acid low than oleic.UV spectra of protein as follows:①<270nm, there is a greater absorption, but no significant absorption peak at the far ultraviolet region;(2)Only linoleic acid absorption values greater than the blank value at the280nm and290nm.DSC curve of SPI offset to the left crest added soybean oil, the peak temperature is less the blank. And peak increased with soybean oil increased, soy protein denaturation enthalpy values were decline.