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•Thermal decomposition and combustion of stearic acid were conducted and simulated.•Three flame propagation stages of stearic acid combustion were divided in detail.•Initial ...decomposition and main products of stearic acid combustion were depicted.•Effects of density, temperature, and oxygen content on the combustion were probed.•Combustion mechanism of stearic acid was established by combined flame propagation.
To better look into the thermal decomposition and combustion progress of stearic acid (C18H36O2), the experimental tests and Reaction Force Field (ReaxFF) molecular dynamics simulation were conducted. Also, an investigation into the flame propagation characteristics and the reaction mechanisms of stearic acid was explored under different conditions. The thermal decomposition activation energy of stearic acid obtained by the TG tests was 105.01 kJ/mol. This is consistent with the initial decomposition stage reaction activation energy calculated to be 94.273 kJ/mol in the simulation. The flame propagation process of stearic acid combustion was explored and involved three stages: the flame growth stage, the stable flame stage, and the flame decay stage. The flame growth stage was subdivided into the flame growth inside the tube, upper the tube, and mushroom-shaped cloud. Besides, the flame growth stage could correspond to three flame propagation velocity peaks. Furthermore, the simplified reaction mechanism scheme for stearic acid radicals could explain the macro flame propagation behaviours. The main reaction pathway through which the C18H36O2 molecules were decomposed into C2H4 and C2H3, C2H5, and other free radicals was found to correspond to the initial flame growth stage, and the flame decay stage was dominated by the generation of final reaction products (H2O, CO2, and CO2, etc.). Concerning the overall reaction mechanism, the unburned stearic acid was continuously ignited, and the combustion products were continuously generated at the same time, thereby corresponding to the stable flame propagation stage. According to the flame propagation process and the simulation results, combustion reaction mechanisms of stearic acid were constructed.
Chain length and degree of saturation plays an important role for the characteristics of various products derived from fatty acids, such as fuels, cosmetics, and food additives. The seeds of ...Theobroma cacao are the source of cocoa butter, a natural lipid of high interest for the food and cosmetics industry. Cocoa butter is rich in saturated fatty acids that are stored in the form of triacylglycerides (TAGs). One of the major TAG species of cocoa butter, consisting of two stearic acid molecules and one oleic acid molecule (stearic acid‐oleic acid‐stearic acid, sn‐SOS), is particularly rare in nature as the saturated fatty acid stearic acid is typically found only in low abundance. Demand for cocoa butter is increasing, yet T. cacao can only be cultivated in some parts of the tropics. Alternative means of production of cocoa butter lipids (CBLs) are, therefore, sought after. Yeasts also store fatty acids in the form of TAGs, but these are typically not rich in saturated fatty acids. To make yeast an attractive host for microbial production of CBLs, its fatty acid composition needs to be optimized. We engineered Saccharomyces cerevisiae yeast strains toward a modified fatty acid synthesis. Analysis of the fatty acid profile of the modified strains showed that the fatty acid content as well as the titers of saturated fatty acids and the titers of TAGs were increased. The relative content of potential CBLs in the TAG pool reached up to 22% in our engineered strains, which is a 5.8‐fold increase over the wild‐type. SOS content reached a level of 9.8% in our engineered strains, which is a 48‐fold increase over the wild type.
Microbial production of cocoa butter requires modification of fatty acid chain length and saturation of the host organism Saccharomyces cerevisiae. Altering the activity of the fatty acid biosynthetic and modifying enzymes Ole1p, Acc1p, and Elo1p changes the fatty acid composition favorably. The modifications lead to an increased content of saturated fatty acids and an increased production of cocoa butter lipids.
•Stearic acid addition increased the yield of isolated materials from HAMS.•Pasted Gamma irradiated HAMS produced type I ALCs.•Un-irradiated HAMS produced type II ALCs.•ALCs produced were at ...nanoscale.
This study determines the effects of stearic acid and gamma irradiation, alone and in combination, on properties of amylose-lipid nanomaterials from pasted high amylose maize starch (HAMS) with and without alpha amylase hydrolysis. HAMS was incorporated with stearic acid (0, 1.5% and 5%, w/w), irradiated at 0, 30 and 60 kGy and pasted under pressure in a rheometer. Isolated materials after thermostable alpha amylase or hot water washing were freeze-dried and characterised using differential scanning calorimetry (DSC), X-ray diffraction (XRD), Atomic Force Microscopy (AFM) and Transmission Electron Microscopy (TEM). The isolated materials contain amylose-lipid complexes (ALCs) as determined by DSC and XRD. Pasting of gamma irradiated HAMS produced type I ALCs, whereas that for un-irradiated HAMS produced type II ALCs. The ALCs occurred at nanoscale with sizes ranging from 10 to 110 nm as observed with AFM and TEM. Tailor-made ALCs nanomaterials can be produced from HAMS (with and without added stearic acid).
BACKGROUND: High stearic acid (STA) soybean oil is a trans-free, oxidatively stable, non-LDL-cholesterol-raising oil that can be used to replace trans fatty acids (TFAs) in solid fat applications. ...OBJECTIVE: The objective was to assess the cardiovascular health effects of dietary STA compared with those of trans, other saturated, and unsaturated fatty acids. DESIGN: We reviewed epidemiologic and clinical studies that evaluated the relation between STA and cardiovascular disease (CVD) risk factors, including plasma lipids and lipoproteins, hemostatic variables, and inflammatory markers. RESULTS: In comparison with other saturated fatty acids, STA lowered LDL cholesterol, was neutral with respect to HDL cholesterol, and directionally lowered the ratio of total to HDL cholesterol. STA tended to raise LDL cholesterol, lower HDL cholesterol, and increase the ratio of total to HDL cholesterol in comparison with unsaturated fatty acids. In 2 of 4 studies, high-STA diets increased lipoprotein(a) in comparison with diets high in saturated fatty acids. Three studies showed increased plasma fibrinogen when dietary STA exceeded 9% of energy (the current 90th percentile of intake is 3.5%). Replacing industrial TFAs with STA might increase STA intake from 3.0% (current) to almost equal to4% of energy and from 4% to 5% of energy at the 90th percentile. One-to-one substitution of STA for TFAs showed a decrease or no effect on LDL cholesterol, an increase or no effect on HDL cholesterol, and a decrease in the ratio of total to HDL cholesterol. CONCLUSIONS: TFA intake should be reduced as much as possible because of its adverse effects on lipids and lipoproteins. The replacement of TFA with STA compared with other saturated fatty acids in foods that require solid fats beneficially affects LDL cholesterol, the primary target for CVD risk reduction; unsaturated fats are preferred for liquid fat applications. Research is needed to evaluate the effects of STA on emerging CVD risk markers such as fibrinogen and to understand the responses in different populations.
•Oxidation performance of stearic acid coated aluminum dust.•Influence of stearic acid coating on MEC of aluminum dust.•Effect of stearic acid coating on explosion characteristics of aluminum ...dust.•Analysis of explosion products of stearic acid coated aluminum dust.•Physical model of stearic acid coated aluminum dust explosion.
To explore the effect of stearic acid coating on the explosion characteristics of aluminum dust, the flame propagation characteristics, minimum explosion concentration and explosion overpressure characteristics of aluminum (Al) and stearic acid coated aluminum dust (SA-Al) were studied by using the synchronous thermal analyzer, the improved Hartmann tube explosion test device, and 20 L explosion test device. Then micro morphology and composition of the explosion products were determined by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), and a physical model of stearic acid coated aluminum dust explosion was established. The results showed that the combustion intensity and flame propagation velocity of SA-Al dust cloud in the semi-closed pipe were lower than that of Al dust cloud, and the flame propagation was weak in the initial stage of explosion. The minimum explosion concentration (MEC), the optimal explosion concentration, the maximum explosion pressure (Pmax) and the maximum explosion pressure rise rate ((dP/dt)max) of SA-Al dust cloud were greater than that of Al dust cloud, and its products contained the incomplete combustion products AlO2, indicating that the stearic acid coating could abate the explosion sensitivity of Al dust cloud, and weaken the degree of oxidation of Al dust. In case of explosion, stearic acid coating could significantly enhance the explosion hazard of Al dust, resulting in a higher explosion risk.
A simple method, involving etching with copper(II) chloride and immersion in stearic acid, a low-surface-energy material, is used to fabricate a super-hydrophobic surface on magnesium alloy. ...Specimens modified by stearic acid show super-hydrophobicity, with the contact angle reaching 154°. SEM images show petal-shaped ridges, which form a three-dimensional porous structure containing voids that can trap air to form air cushions. These air cushions can prevent droplets from infiltrating the surface, thus leading to the super-hydrophobicity of the coating. Impedance and polarization analyses conducted in 3.5% NaCl aqueous solution show that electrochemical properties of the treated Mg alloy are significantly improved compared with the bare alloy, thereby enhancing its corrosion resistance. The super-hydrophobic surface also exhibits an excellent long-term durability in 3.5% NaCl aqueous solution.
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•A simple method is used to fabricate a super-hydrophobic surface on magnesium alloy.•The petal-shaped microstructure played critical role in super-hydrophobicity.•The super-hydrophobic film exhibited good corrosion-resistance ability.•The super-hydrophobic film is well bonded with the substrate.
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•Trace level cadmium was preconcentrated by DSPE prior to ICP-OES measurement.•Stearic acid coated Fe3O4 MNPs were used as adsorbent in the extraction procedure.•Univariate and ...multivariate optimizations were applied to determine optimum values.•LOD/LOQ for sunflower/olive and hazelnut oils were 0.14/0.46 μg/kg and 0.38/1.28 μg/kg, respectively.•Recovery results for the selected edible oils were found in the range of 85.0–126%.
In this study, a new and efficient sample pretreatment method called as dispersive solid phase extraction (DSPE) was proposed for the extraction and preconcentration of cadmium from edible oil samples and combined with inductively coupled plasma-optical emission spectrometry (ICP OES) for analyte determination at trace levels. Stearic acid coated-Fe3O4 magnetic nanoparticle (SA-MNP) was selected as the best adsorbent for the preconcentration of analyte. Under the optimum experimental conditions, analytical performance of DSPE-ICP OES system for the analyte was evaluated in terms of limit of detection (LOD), limit of quantification (LOQ) and dynamic range. LOD/LOQ values for sunflower oil/olive oil and hazelnut oil matrices were determined as 0.14/0.46 μg/kg and 0.38/1.28 μg/kg, respectively. In order to test the accuracy and applicability of DSPE-ICP OES method, recovery studies were performed in edible oils (sunflower oil, olive oil and hazelnut oil). The recovery results for sunflower oil, olive oil and hazelnut oil samples were calculated as 92.6–114.9 %, 85.0–104.3 % and 92.1–126.0 %, respectively.
Biodegradable plastics are actively studied to address the environmental issues caused by petroleum-based plastics. Sodium-alginate-based biodegradable materials containing crosslinking agents and ...stearic acid have been developed. A sodium alginate-based bag was fabricated by immersing a film composed of sodium alginate and stearic acid into a calcium lactic acid solution, to induce transformation through calcium bonding. These bags exhibited variations in tensile strength (TS), breaking height (E), moisture absorption, swelling, and contact angle depending on the percentage of stearic acid (1, 3, 5, 8, and 10 %); additionally, stearic acid showed a rough surface in morphological measurements. The rough surface facilitated effective integration with stearic acid, ultimately improving hydrophobicity. This was confirmed by a water absorption experiment. In addition, the combination of stearic acid and sodium alginate resulted in an increased breaking height, demonstrating comparable performance to conventional plastic bag. The interaction between sodium alginate and stearic acid shows that the generated biodegradable bags exhibit physical properties similar to those of the conventional plastic bags.
Abstract
Safe building structures cannot be achieved without reliable waterproofing engineering. To address the susceptibility of concrete materials to water leakage, a low‐viscosity stearic acid ...emulsion has been developed as a waterproofing agent for mortar. By introducing lauric acid, the formation of stearic acid crystals in water could be effectively prevented, resulting in a stearic acid emulsion with a viscosity of only 24 mPa·s. It is found that the best overall performance was achieved when the ratio (R) of lauric acid to stearic acid was 2/3. This emulsion has the least effect on mortar fluidity and setting time. The as‐prepared modified mortar possessed the highest compressive strength (127% of the blank) and the lowest water absorption at 48 h (37% of the blank). X‐ray diffraction (XRD), Fourier‐transform infrared spectroscopy (FTIR), energy‐dispersive x‐ray spectroscopy (EDS), scanning electron microscopy (SEM), dynamic light scattering (DLS) particle size analysis, and water contact angle measurements were used to investigate the mechanism of stearic acid emulsion's modification. It is determined that the stearic acid emulsions successfully modified the internal and external hydrophobicity of the mortar by chemical action with calcium hydroxide.
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