A mathematical technique for approximating the values of melting points of diacylglycerols

A method of correlating the values of melting points of diacylglycerols (DAG) with the values of the melting points of the two fatty acids constituting the DAG as its acyl radicals was studied by making use of the least squares method. The method was applied to the set of values of melting points of the β crystal form of DAG with acyl radicals comprising decanoyl, lauroyl, myristoyl, palmitoyl, stearoyl, and oleoyl. The melting point of the β crystal form of DAG is approximated by the prediction equations in which the values of the melting points of the two fatty acids are contained as variables. Furthermore, the prediction equations indirectly contain a variable parameter that reflects the physical effect due to the free hydroxyl group in the molecule of DAG. The best‐fit equations can finally be fixed by varying the parameter while satisfying the criterion of least squares. The least squares method with concomitant variable parameter enables us to estimate the melting points of possible molecular species of DAG comprising the acyl radicals above, and will certainly be helpful for designing oleo materials including DAG for industrial use.     

Measurement of the melting points of oligomers obtained in the manufacture of poly(ethylene terephthalate)

The melting points (T_m) were measured for oligomers obtained by a direct continuous esterification process between terephthalic acid and ethylene glycol. Multiple regression analyses of data were carried out, and an equation was obtained for predicting melting points with correlation coefficient of ～0.99.     

How can we genetically engineer oilseed crops to produce high levels of medium‐chain fatty acids?

The end products of fatty acid synthase activities are usually 16‐ and 18‐carbon fatty acids. There are however, several plant species that store 8‐ to 14‐carbon (medium‐chain) fatty acids in their oil seeds. Among the medium‐chain fatty acids (MCFA), caprylic (8:0) and capric (10:0) are minor components of coconut oil, which are used in many industrial, nutritional and pharmaceutical products. Engineering crop plants such as Brassica could provide an economical source of these oils. During the last decade many laboratories have identified, cloned and characterized both the biosynthetic and catabolic enzymes regulating the composition and levels of these unusual fatty acids in seed oil. Among the biosynthetic enzymes thioesterases (TE), β‐ketoacyl‐ACP synthases (KAS) and acyltransferases are best characterized. In fact several independent investigators have shown that combined expression of the medium‐chain specific enzymes, specifically, TE, KAS and lysophosphatidic acid acyltransferase (LPAAT) results in the production of significant levels of MCFA in seed that otherwise do not accumulate any medium‐chain fatty acid. However, any additional increase in the levels of MCFA in transgenic seeds will require further detailed studies, such as possible induction of the medium‐chain specific enzymes in β‐oxidation and the glyoxylate pathways. To examine such a possibility, a number of genes involved in the β‐oxidation cycle among them a novel enzyme now designated as ACX3, a medium‐chain specific acyl‐CoA‐oxidase, has also been cloned. This article is an attempt to summarize our current knowledge and the present status of engineering oilseed crops for production of medium‐chain fatty acids.     

基于混合遗传算法的人工神经网络模型及其对有机化合物熔点的预测

为了避免BP神经网络在训练过程中收敛于局部极小的缺陷,采用自适应交叉变异、最优保存的混合遗传算法对BP网络的权值和阈值进行优化,从而提出一种新的基于混合遗传算法的神经网络模型.该算法首先对一给定的网络结构,采用混合自适应交叉变异和最优保存策略,取各自的长处,用尽可能少的搜索代数找到问题的最优解,从而既防止算法陷入局部最优,又保证算法有较好的平均适应值和最佳的适应值个体.采用上述优化策略的人工神经网络可明显改善收敛的稳定性和收敛速度,并确保网络收敛于全局极小点.人工神经网络运用于物性数据的预测是一个具有潜力和有待开发的领域.运用该模型,根据有机化合物的分子量、临界密度、正常沸点和偶极矩,对其熔点进行预测.预测结果表明：提出的混合遗传算法神经网络优于其他算法神经网络,而且预测结果优于文献上已有的Joback方程和许氏方程的计算值.     

A mathematical method to estimate the equilibrium melting temperature from growth rate data

The regime transitions analysis is subject to all the limitations of the ordinary least squares method which is generally applied to the linearized form of the Lauritzen-Hoffman equation. Therefore, polymers growth rate has to be measured in a sufficiently wide temperature range to ensure a reliable kinetic analysis based on the secondary nucleation theory. Furthermore, an accurate value of the equilibrium melting temperature has to be used in order to achieve trustworthy thermodynamics outcomes, although this quantity may be affected by a high uncertainty. Here a method is proposed in order to verify directly from growth rate data the use of the most reliable value of the equilibrium melting temperature. The method is based on the comparison between the derivatives of the growth rate functions calculated by the Lauritzen-Hoffman equation using the outcomes of the regime analysis.     

Determination of In-Shell Peanut Oil and Fatty Acid Composition Using Near-Infrared Reflectance Spectroscopy

NIR reflectance spectroscopy was used to analyze the total oil and fatty acid concentration of Virginia and Valencia types of in-shell peanuts rapidly and nondestructively. NIR absorbance spectra were collected in the wavelength range from 400 to 2,500 nm using a NIR instrument. Average total oil concentrations of all samples were determined by a standard Soxtec extraction method. Fatty acids were converted to the corresponding methyl esters and measured using gas chromatography. Partial least squares analysis was performed on the calibration set, and models were developed for predicting total oil and fatty acids. The best model was selected based on coefficient of determination (R ²), standard error of prediction, and residual percent deviation (RPD) values. Virginia-type in-shell peanuts had RPD values of >5.0 for both absorbance and reflectance models, indicating that the method could be used for quality control and analysis. Valencia peanuts had an RPD value of 3.01, which indicates that the model is good for initial screening purposes. For both types of peanuts, fatty acid prediction gave RPD values of <5 for all the models, indicating they could be used for initial screening purposes.     

Isothermal crystallization and melting behavior of polypropylene with lanthanum complex of cyclodextrin derivative as a β‐nucleating agent

A novel highly active β‐nucleating agent, β‐cyclodextrin complex with lanthanum (β‐CD‐MAH‐La), was introduced to isotactic polypropylene (iPP). Its influence on isothermal crystallization and melting behavior of iPP was investigated by differential scanning calorimeter (DSC), wide‐angle X‐ray diffraction (WAXD), and polarized light microscopy (PLM). WAXD results demonstrated that β‐CD‐MAH‐La was an effective β‐nucleating agent, with β‐crystal content of iPP being strongly influenced by the content of β‐CD‐MAH‐La and the isothermal crystallization temperature. The isothermal crystallization kinetics of pure iPP and iPP/β‐CD‐MAH‐La was described appropriately by Avrami equation, and results revealed that β‐CD‐MAH‐La promoted heterogeneous nucleation and accelerated the crystallization of iPP. In addition, the equilibrium melting temperature (T) of samples was determined using linear and nonlinear Hoffman‐Weeks procedure. Finally, the Lauritzen‐Hoffman secondary nucleation theory was applied to calculate the nucleation parameter (K_g) and the fold surface energy (σ_e), the value of which verify that the addition of β‐CD‐MAH‐La reduced the creation of new surface for β‐crystal and then led to faster crystallization rate. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Pristanic acid is activator of peroxisome proliferator activated receptor alpha

lsoprenoid phytanic acid (3,7,11,15‐tetramethylhexadecanoic acid) is degraded in peroxisomes by α‐oxidation to pristanic acid (2,6,10,14‐tetramethylpentadecanoic acid) and then via β‐oxidation. Branched‐chain phytanic acid is an activator of the peroxisome proliferator activated receptor α (PPAR ) which in liver cells regulates expression of genes encoding peroxisomal and mitochondrial β‐oxidative enzymes as well as cytosolic/nuclear liver‐type fatty acid binding protein (L‐FABP). In this report we address the question whether pristanic acid also acts as activator of PPARα and thus mediates the expression of its catabolizing enzymes. In a first in vivo approach we fed pristanic acid for 14 days to wildtype mice and to mice lacking sterol carrier protein 2/sterol carrier protein x which Ieads to a phenotype having high concentrations of branched‐chain fatty acids. In either genotype, feeding pristanic acid was associated with a strong induction of peroxisomal β‐oxidation enzymes tested (acyl‐CoA oxidase, bifunctional enzyme, thiolase) as well as of L‐FABP. The link between pristanic acid and protein expression observed was established by carrying out assays for transactivation of PPARα in transfected HepG2 cells. In comparison to hypolipidemic drugs and to straight‐chain fatty acids known to be PPARα agonists, branched‐chain phytanic and pristanic acids were substantially stronger activators, pristanic acid being even superior to phytanic acid.     

Pro- and Antioxidative Effect of α-Tocopherol on Edible Oils, Triglycerides and Fatty Acids

Using advanced electron paramagnetic resonance techniques (EPR), oxidation of crude vegetable oils and their components (fatty acids and triglycerides) by radicals generated from hydrogen peroxide was investigated. The correlation rotational times were determined allowing us to characterize radicals formed during edible oils oxidation. Additionally ¹H- and ¹⁴N-hyperfine coupling constants differentiate the fatty acids dependently on their unsaturation. The acids with a higher number of unsaturated bonds exhibit higher A_N values of PBN/·lipid adduct. The waste oil with high free fatty acids content underwent the oxidation reaction more efficiently, however due to saturation and the high content of the fatty acids the carbon-centered radicals formed (upon hydrogen peroxide radicals) and their PBN (N-tert-butyl-α-phenylnitrone) adducts were less stable. The antioxidant effect was dependent on the amount of α-tocopherol added. In small amounts of up to 0.35 mg/1 g of fatty acid or triglyceride, it inhibited the creation of PBN/·lipid adducts while with higher amounts it intensified adduct formation. The α-tocopherol (AT) addition influence was also studied as spin scavenging dependence and indicated that any addition of the antioxidant in the investigated samples led to free radical scavenging and the effect increased with the increase in AT content.     

Oxidation at elevated temperatures: competition between α‐tocopherol and unsaturated triacylglycerols

The competitive oxidation between α‐tocopherol and unsaturated fatty acyls at thermoxidation conditions (180 and 240 °C) was evaluated using purified triacylglycerols from nine fats and oils (refined coconut, palm, tallow, olive, high oleic sunflower, sunflower, corn, soybean, and flaxseed oil). α‐Tocopherol degraded faster in less unsaturated lipids and a linear correlation between the iodine value (x) and the residual tocopherol content (y) was obtained after 2 h of heating at 240 °C (y = 3.72x + 137.5, R² = 0.9463). The formation of polar oxidation products was established and the results were explained by a non‐selective oxidation of unsaturated fatty acyls and α‐tocopherol by highly reactive alkoxyl and hydroxyl radicals generated by decomposition of hydroperoxides.     

Correlation between the ash composition and melting temperature of waste incineration residue

The correlation between the ash composition of various incinerated waste residues and their melting temperatures was examined by using their chemical composition parameters. There was a low correlation between the melting temperatures and the acidic oxide content in the ashes. However, the composition parameters derived from the basic oxides showed a good correlation with the ash melting temperature. The composition parameter, P₇, which is defined as the ratio of basic oxides (CaO+MgO+K₂O+Na₂O) to acidic oxides (SiO₂+Al₂O₃+Fe₂O₃), showed a strong correlation with the ash melting temperature. By fitting the composition parameter to the experimental data, the correlation equation for the half fluid temperature (HFT) was found to be HFT=426.77P ₇ ² ?736.76P₇+1592.3 with a correlation coefficient of 0.91. The correlation equation could be used to predict the melting temperatures of various waste incineration residues. The relative error between the measured and predicted melting temperature was approximately 5%. Overall, these parameters and correlation equations can be used to predict and reduce the melting temperature of incineration residues.     

Effect of amide distribution in polyamide isomers on their melting points

A new insight has been obtained relating the different structures of linear aliphatic homopolyamides to their melting points. A new equation is derived for structures based on monomers with an even number of methylene units. In this equation, the amide distribution along the polymer chain is defined by a newly introduced parameter K which indicates the lowest number of methylene units between adjacent amide groups. For K ≥ 4 a generic empirical relation is defined, describing the observed melting points of these polyamides. The trend in H‐bond densities in the melt obtained by modeling corresponds well with the trend in observed melting points. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45837.     

Optimization of the production of β‐carotene from molasses by Blakeslea trispora: a statistical approach

The effect of pretreatment of molasses, nitrogen sources, natural oils, fatty acids, antioxidant, precursors, and mixtures of the above substances on β‐carotene production by Blakeslea trispora in shake flask culture was investigated. Also, a central composite design was employed to determine the maximum β‐carotene concentration at optimum values for the process variables (linoleic acid, kerosene, antioxidant). The highest concentration of the carotenoid pigment was obtained in molasses solution treated with invertase. Corn steep liquor and yeast extract at concentrations of 5.0% and 0.5% (w/v), respectively, increased slightly the concentration of β‐carotene, while the natural oils, fatty acids, and precursors (except kerosene) did not improve the production of pigment when they were added separately to the medium. On the other hand, the mixture of linoleic acid, kerosene and antioxidant increased significantly the concentration of β‐carotene. The fit of the model was found to be good. Linoleic acid, kerosene and antioxidant had a strong linear effect on β‐carotene concentration. The concentration of β‐carotene was significantly affected by linoleic acid–antioxidant and kerosene–antioxidant interactions as well as by the negative quadratic effects of these variables. The interaction between linoleic acid–kerosene had no significant linear effect. Maximum β‐carotene concentration (790.0 mg dm^?3) was obtained in culture grown in molasses solution supplemented with linoleic acid (30.74 g dm^?3), kerosene (27.79 g dm^?3) and antioxidant (10.22 g dm^?3). © 2002 Society of Chemical Industry     

Enhanced crystallization of the γ‐form of propylene–ethylene copolymer in its miscible blends with propylene homopolymer

BACKGROUND: How to promote the formation of the γ‐form in a certain propylene‐ethylene copolymer (PPR) under atmospheric conditions is significant for theoretical considerations and practical applications. Taking the epitaxial relationship between the α‐form and γ‐form into account, it is expected that incorporation of some extrinsic α‐crystals, developed by propylene homopolymer (PPH), can enhance the crystallization of the γ‐form of the PPR component in PPR/PPH blends. RESULTS: The PPH component in the blends first crystallizes from the melt, and its melting point and crystal growth rate decrease with increasing PPR fraction. On the other hand, first‐formed α‐crystals of the PPH component can induce the lateral growth of PPR chains on themselves, indicated by sheaf‐like crystal morphology and positive birefringence, which is in turn responsible for enhanced crystallization of the γ‐form of the PPR component. CONCLUSION: Crystalline/crystalline PPH/PPR blends are miscible and the crystallization of the γ‐form of the PPR component is largely enhanced due to the heterogeneous nucleation from the α‐crystals first developed by the PPH component. Our findings could provide an effective way in practice to obtain isotactic polypropylene copolymers rich in γ‐form. Copyright © 2009 Society of Chemical Industry     

液相扩散系数与浓度的新关联方程和实验考察

用液相扩散新型金属膜池考察了含有长链分子的五个二元体系在25℃时不同浓度的扩散系数,得出了扩散系数与浓度的经验关联多项式的参数拟合值.推导了二元液相扩散系数与浓度的新关联方程:D_(AB)η/V=(D°_(BA)η_A/V_A)~(φA)(D°_(AB)η_B/V_B)~(φB)β用上列方程及其他用于比较的方程对23种体系(207点)进行了预估计算,其总平均百分偏差如下:结果表明,在无拟合参数的方程中,本文所提方程(22)的总平均百分偏差为最小.     

A comparison between semiempirical equations to predict the solubility of pharmaceutical compounds in supercritical carbon dioxide

The aim of this work is to determine, depending on the operation conditions, which semiempirical equation provides the best fit to solubility data of pharmaceutical compounds in supercritical CO₂. Solubility data from 27 different pharmaceutical solutes were collected from literature and the different density-based models (Chrastil, Adachi-Lu, del Valle-Aguilera, Sparks, Kumar-Johnston, Bartle, Méndez Santiago-Teja) together with the Yu's model and Gordillo's model were employed. The results showed that, in general, Sparks’ equation provides the best fit to the solubility data for this kind of solids in supercritical CO₂. However, at certain specific conditions, the best correlation is obtained using Gordillo's equation. By means of a brief comparison with Peng-Robinson equation of state, semiempirical equations present a more accuracy prediction compared to cubic equations of state, and present no drawbacks such as properties estimation and computational difficulties.     

Fatty acid composition of fats of differing melting points extracted from ram subcutaneous tissue

The observation that the subcutaneous fat of pasture-fed Southdown rams consists of two distinct regions is reported. Fatty acid composition of fat from the outer and inner regions of subcutaneous tissue taken from the rib region of eight Southdown rams fed pasture were determined. Relative to the harder inner regions (mean melting point 43.1°C), the softer outer regions (mean melting point 31.8°C) were shown to contain more 9∶0-, 15∶0-, 17∶0-, 17∶1-, 18∶1-cis and total 18∶1 fatty acids; less 14∶0-, 16∶0-, 18∶0- and 18∶1-trans fatty acids; and a greater variety and a greater concentration of branched-chain components. Proportions of medium chain-length fatty acids other than 9∶0, did not differ between the layers. The fatty acid contents of serial samples taken at 1-mm intervals through these tissues were determined. Changes in concentrations of components among samples were gradual through the tissues. There was no clear connective tissue sheet, as has been reported for pigs. The inner region of the tissues contains apparently nonrandom fluctuating changes in fatty acid composition.     

Phase behavior of homologous series of monoesters of polyols

Phase behavior of anhydrous monopalmitates and stearates and of most laurates, myristates and behenates of ethylene glycol, erythritol, xylitol, sorbitol, and mannitol has been studied. The compounds, substantially free of diesters, are mostly not isomerically pure but are predominantly primary esters. Also studied were the (nonisomeric) palmitate and stearate of pentaerythritol (Pe) and the oleate of erythritol. Mesomorphism, absent in anhydrous monoglycerides unless of short chain length and symmetrical, is a prominent feature of the members of the present group of compounds containing at least three unesterified hydroxyls. In general, crystal melting points rise with length of polyol, and mesomorphic melting points rise faster. Crystal melting points rise with acyl chain length while mesomorphic melting points run through a maximum. Heats of fusion are of the order 40 cal/g for crystal melting and 0.5 cal/g for melting of mesomorphic states. In the range explored, mesomorphic values fall with both polyol length and acyl length. At higher acyl chain length, notably with behenates, there are new features of mesomorphic behavior. Crystalline phase, from solvent, melts to a neat or lamellar phase, which in turn melts to liquid with subsequent appearance of higher melting middle or cylindrical phase. Polymorphism is general among the crystal states and tends to be complex. In a brief study of solvent crystallized 50–50 binary mixes of xylitol stearate with other xylitol esters and other stearates, considerable evidence of solid solution in Form I crystals (of xylitol stearate type) was observed with very modest eutectic lowering of crystal melting point. Mesomorphic points were almost linearly intermediate between those of components. Of particular interest were mixtures of xylitol stearate and 1-monostearin (50–50 and 25–75), for which mesomorphic melting points were realized, and for which an extrapolation to 100% monostearin leads to a hypothetical mesomorphic melting point far below any monoglyceride crystalline melting point. A brief examination of an aqueous xylitol palmitate system explored to a maximum temperature of 165 C shows extensive occurrence of aqueous mesomorphic state somewhat after the manner of monoglyceride systems. Mesomorphic melting level rises rapidly from the value for anhydrous ester.     

Viscosities of fatty acids, triglycerides, and their binary mixtures

Viscosity data have been obtained as a function of temperature for seven fatty acids (pelargonic, capric, lauric, myristic, palmitic, stearic, and oleic) and four triglycerides (tricaprilin, tripalmitin, tristearin, and triolein) and their binary mixtures at temperatures from above their melting points to 90°C. The viscosity measurements were performed by using Cannon Fenske glass capillary kinematic viscometers. Modified versions of the Andrade equation were used to correlate the kinematic viscosities of pure fatty acids and pure triglycerides. The MacAllister method was used for their binary mixtures. The correlation constants are valuable for designing or evaluating chemical process equipment, such as heat exchangers, reactors, distillation columns, and process piping.     

MODELLING ADSORPTION EQUILIBRIUM MOISTURE CHARACTERISTICS OF ROUGH RICE

Equilibrium Moisture Content (EMC) data for medium rough rice grain, Lido variety were obtained by equilibrating rice samples at different Equilibrium Relative Humidities (ERH) and Temperatures. The employed models to fit the data were GAB, modified Chung-Pfost, modified Halsey, Modified Henderson, and modified Oswin. The data were evaluated using the standard error of moisture content, mean relative standard error (%P) of the model and the correlation coefficient r². The GAB model by indirect regression described the EMC the best, however its parameters lacked of physical meaning. The modified Chung-Pfost and modified Henderson equations presented a similar fit of the EMCERH relationships. The modified Chung-Pfost equation had lower residual values than the modified Henderson equation and was considered the best model to explain the EMC-ERH relationships.