Thermal-Oxidation Stability of Soybean Germ Phytosterols in Different Lipid Matrixes.

The stability of soybean germ phytosterols (SGPs) in different lipid matrixes, including soybean germ oil, olive oil, and lard, was studied at 120, 150, and 180 °C. Results on the loss rate demonstrated that SGPs were most stable in olive oil, followed by soybean germ oil, and lard in a decreasing order. It is most likely that unsaturated fatty acids could oxidize first, compete with consumption of oxygen, and then spare phytosterols from oxidation. The oxidation products of SGPS in non-oil and oil systems were also quantified. The results demonstrated that at relatively lower temperatures (120 and 150 °C), SGPs' oxidation products were produced the most in the non-oil system, followed by lard, soybean germ oil, and olive oil. This was consistent with the loss rate pattern of SGPs. At a relatively higher temperature of 180 °C, the formation of SGPs' oxidation products in soybean germ oil was quantitatively the same as that in lard, implying that the temperature became a dominative factor rather than the content of unsaturated fatty acids of lipid matrixes in the oxidation of SGPs.

Calculation Model of Shale Reserves Considering the Adsorption Layer Based on Molecular Simulation.

In this paper, molecular simulation methods are used to construct nanopore models of organic matter, montmorillonite, and quartz. The occurrence state of CH4 molecules in shale nanopores was simulated, and the distribution characteristics of CH4 molecules at different temperatures, pressures, and pore widths were obtained. The thickness and density of the adsorption layer of CH4 molecules at different temperatures and pressures were studied. On the basis of these, a calculation model of shale gas reserves considering adsorption is proposed. The results show that CH4 molecules in shale nanopores present a nonuniform distribution. Two obvious wave peaks form in the space close to the surfaces of the shale nanopore, and the wave peaks increase with the increase of pressure. As the pressure increases, a second peak appears and gradually becomes larger. The adsorption layer formed on the surface of the medium has a certain thickness and density, which are affected by pressure and temperature. In the calculation example, the difference between the calculation results of the shale gas reserve calculation models considering and not considering the adsorption layer is about 26%. The higher the proportion of adsorbed gas, the greater the calculation error, which is related to pressure and adsorption capacity.

The characterization of soybean germ oil and the antioxidative activity of its phytosterols.

The aim of this study was to characterize the composition of soybean germ and its oil from Northeast (NE-SG) and Shandong Province (SD-SG) of China with a focus on the composition of fatty acids and phytosterols as well as physicochemical properties. The results show that the average contents of water, protein, crude fat, crude fiber and ash of NE-SG and SD-SG were 8.23 ± 0.11%, 40.47 ± 0.10%, 11.65 ± 0.14%, 6.20 ± 0.09% and 4.79 ± 0.14%, respectively. The major fatty acids of the two soybean germ oils were linoleic acid (NE-SGO, 55.45%; SD-SGO, 52.15%), alpha-linolenic acid (NE-SGO, 16.21%; SD-SGO, 18.50%), palmitic acid (NE-SGO, 12.59%; SD-SGO, 11.40%) and oleic acid (NE-SGO, 9.87%; SD-SGO, 10.96%). The soybean germs were rich in phytosterols (NE-SGO, 3168 mg/100 g oil; SD-SGO, 3010 mg/100 g oil) consisting of ß-sitosterol, Δ7-stigmastenol, campesterol, stigmastanol, and citrostadienol. The antioxidant ability of soybean germ phytosterols was evaluated using DPPH˙ and OH˙ radical scavenging assays, ß-carotene protection assay and a heating oil system. The results demonstrated that soybean germ phytosterols had better antioxidant ability in oil systems than in non-oil systems. The antioxidant ability of these phytosterols was temperature- and time-dependent since it was more effective at lower temperatures (60 °C) with longer times as compared to higher temperatures (120 °C and 180 °C) with shorter times. These results prove that soybean germ phytosterols could be used as antioxidants in preventing lipid oxidation in foods stored at a low temperature for a long time.