The positional and fatty acid selectivity of oat seed lipase in aqueous emulsions

The positional and fatty acid selectivities of oat (Avena sativa L.) seed lipase (triacylglycerol hydrolase EC 3.1.1.3) were examined. Pure triacylglycerols were used as substrates. The products of lipolysis were examined by thin-layer chromatography and gas-liquid chromatography. Only symmetrical triacylglycerols were used as substrates; thus potential complications arising from stereobias were avoided. Controls were carried out with a lipase specific for primary positions. The lipase from oat seeds catalyzed the hydrolysis of both primary and secondary esters. When the lipase was tested upon mixtures of homoacid triacylglycerols (triacylglycerols composed of the same three fatty acids), the lipase acted most rapidly upon those containing oleate, elaidate, linoleate and linolenate. Strong intermolecular selectivity against homoacid triacylglycerols containing palmitate, petroselinate and stearate was observed. Comparison of assays performed at 26°C with those performed at 45°C showed that selectivity was temperature-independent. When mixed-acid triacylglycerols containing both oleate and stearate were treated with lipase, intramolecular selectivity was observed, with oleate hydrolysis predominating. From this work and earlier work, it can be concluded that the selectivity exhibited by the oat seed lipase is similar to that of the lipase fromGeotrichum candidum, except that the oat seed lipase attacks elaidate, a fatty acyl group with atrans double bond, whereas theG. candidum lipase strongly discriminates against elaidate.     

The use of lipase (acetone powder) from Vernonia galamensis in the fatty acid analysis of seed oils

Examined in this study is a potential application of Vernonia galamensis lipase (acetone powder) in enzyme-catalyzed hydrolysis of seed oils, most especially of those containing reactive functionalities which are easily affected under drastic hydrolytic and methylating/transesterification conditions during fatty acid analysis. Eight seed oils from V. galamensis, Ximenia kaffra, castor, corn, soyabean, palm kernel, sunflower and olive were hydrolyzed by lipase (acetone powder) followed by methylation using diazomethane in ethyl ether. Results obtained showed that the lipolytic hydrolysis of triglycerides by V. galamensis lipase (acetone powder) was probably nonspecific and did not result in isomerization and as such hydrolyzed the triglycerides of the seed oil in a fashion that the resulting fatty acids were unaltered during hydrolysis. The fatty acids obtained were representative of the parent seed oils. Values reported for the various seed oils were similar to those of previous studies.     

Effect of roasting on the physico-chemical properties,fatty acids,polyphenols and mineral contents of tobacco (Nicotiana tabacum L.) seed and oils

The physico-chemical properties, phytochemicals, mineral contents of tobacco (Nicotiana tabacum L.) seeds grown at Samsun province in Turkey were evaluated. The oil contents of tobacco seeds ranged from 20.6% (control) to 29.0% (microwave-roasted). L*, a* and b* values of tobacco seeds ranged from 32.38 to 35.61; from 6.32 to 6.78; from 13.72 to 14.27, respectively. Total phenolic contents of tobacco seed extract and oils were reported between 31.02 (oven-roasted) and 34.42 mg GAE/100 g (microwave-roasted) to 4.60 (microwave-roasted) and 6.45 mg GAE/100 g (oven-roasted), respectively. Total flavonoid values of raw and roasted tobacco seed extract and oils were determined between 26.62 (oven) and 67.10 mg/100 g (control) to 21.57 (control) and 44.71 mg/100 g (microwave-roasted), respectively. Gallic acid, 3,4-dihydroxybenzoic acid and catechin are the predominant phenolic components of raw and roasted tobacco seed oils. The amounts of oleic and linoleic acid in raw and roasted tobacco seed oils ranged from 10.23% (oven-roasted) to 12.48% (control) and 73.72% (control) to 76.63% (oven-roasted), respectively. The abundant elements found in seeds were K, P, Ca, Mg, S and Fe. The mineral amounts of the roasted seeds were found higher than that of the control. The highest increase was detected in oven roasted tobacco seeds.     

Grafting of itaconic acid onto LDPE by the reactive extrusion: Effect of neutralizing agents

Grafting of itaconic acid (IA) onto low‐density polyethylene (LDPE) was performed by reactive extrusion where the initiator was dicumyl peroxide, and the neutralizing agents (NAs) were zinc oxides and hydroxides as well as magnesium oxides and hydroxides. The carboxyl groups were neutralized in molten LDPE directly in the course of acid grafting, and in prefabricated functionalized polyethylene (LDPE‐g‐IA). It was found that neutralizing agents introduced into the initial reaction mixture increase the yield of LDPE‐g‐IA while the carboxyl groups were neutralized partially or totally through chemical reactions. The physical structure of LDPE‐g‐IA did not in fact suffer any substantial changes. From the standpoint of neutralization activity, the NAs studied could be arranged as follows: Zn(OH)₂ > ZnO > Mg(OH)₂ > MgO. NA, added into the initial reaction mixture improved the grafting efficiency of IA onto LDPE. In case of the one‐step process (neutralization simultaneously with grafting), the neutralizing effect appears stronger than that in the two‐step process (neutralization of prepared LDPE‐g‐IA). This means that neutralization of carboxyl groups in IA was less effective when NA was introduced into LDPE‐g‐IA than for the case of the initial reactive mixture. Chemical neutralization of grafted IA results in products of improved resistance to thermal oxidation and thermal stability of melt. This result is of practical importance to the opportunities for widening the application range for PE modified by grafting IA, while preparing polymer blends to be compounded, processed, and used at elevated temperatures. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 828–836, 2003     

Oxidation of linoleic acid in emulsions: Effect of substrate, emulsifier, and sugar concentration

Linoleic acid oxidation in oil-in-water emulsions stabilized by a nonionic surfactant (Tween-20) was studied. The emulsion composition was varied at a constant oil droplet size. Lipid oxidation was measured as a function of time in the presence of a catalyst (FeSO₄ corbic acid) by two methods: gas chromatographic determination of residual substrate and ultraviolet-visible spectrophotometric determination of conjugated dienes. Rate of oxidation was influenced by the emulsion composition (relative concentrations of substrate and emulsifier) and especially by the partition of the emulsifier between the interface and water phase. Concentrations of emulsifier exceeding the critical micelle concentration protected the fatty acid against oxidation. Excess surfactant formed micelles and mixed micelles with linoleic acid, which retarded oxidation by diluting the substrate or perhaps by replacing linoleic acid at the interface, making it less accessible to radical attack. The addition of sucrose also had a protective effect, but only up to a certain concentration, indicating the effect may involve factors other than viscosity.     

Production of structured triacylglycerols in an immobilised lipase packed‐bed reactor: batch mode operation

Structured triacylglycerols with caprylic acid at the sn‐1 and sn‐3 positions of the glycerol backbone and eicosapentaenoic acid (EPA) at the position sn‐2 were synthesised by acidolysis of a commercially available EPA‐rich oil (EPAX4510, Pronova Biocare) and caprylic acid catalysed by the 1,3‐specific immobilised lipase Lipozyme IM. The reaction was carried out in an immobilised lipase packed‐bed reactor by recirculating the reaction mixture through the bed. The exchange equilibrium constants between caprylic acid and the native fatty acids of EPAX4510 were determined. The n‐3 polyunsaturated fatty acids (PUFAs), EPA and docosohexaenoic acid (DHA), were the most easily displaced by the caprylic acid. The exchange equilibrium constants were 3.68 and 3.06 for EPA and DHA, respectively. The influence of the flow rate of the reaction mixture through the packed‐bed and the substrate concentration in the reaction rate were studied. For flow rates between 74 and 196 cm³ h^?1 (bed of 6.6 mm internal diameter and 0.46 porosity) and triacylglycerol concentrations between 0.036 and 0.108 M , the data fitted well to an empirical kinetic model which allowed representative values of the apparent kinetic constant to be obtained. Hence, the average reaction rates and kinetic constants of exchange of caprylic acid and native fatty acids of EPAX4510 could be calculated. In the conditions indicated, the parameter (lipase mass × time/triacylglycerol mass, m_Lt/V[TG]₀) constituted the intensive variable of the process for use in predicting the composition of structured triacylglycerols at different reaction times. At equilibrium, the structured triacylglycerol produced had the following composition: caprylic acid 59.5%, EPA 9.6%, DHA 2.2% and oleic acid 11.8%. Copyright © 2004 Society of Chemical Industry     

Catalytic oxidation of Fe(II) by activated carbon in the presence of oxygen.: Effect of the surface oxidation degree on the catalytic activity

The catalytic oxidation of Fe(II) species in aqueous solution by activated carbons with different degrees of surface oxidation is described. The parent activated carbon was oxidized with aqueous solutions of nitric acid or hydrogen peroxide, and submitted to thermal treatment at 373, 523 and 773 K. The activated carbons prepared were characterized by N₂ adsorption and temperature-programmed desorption, and their catalytic behavior was determined by measuring the oxidation rate of Fe(II) to Fe(III) and the generation of hydrogen peroxide. Catalytic activity is a function of the nature of oxygen surface groups generated by oxidation.     

Esterification of palm fatty acid distillate (PFAD) in supercritical methanol: Effect of hydrolysis on reaction reactivity

This study demonstrated the potential use of local palm fatty acid distillate (PFAD) as alternative feedstock for fatty acid methyl esters (FAMEs) production and the possibility to replace the conventional acid-catalyzed esterification process (with H₂SO₄), which was industrially proven to suffer by several corrosion and environmental problems, with non-catalytic process in supercritical methanol. At 300 °C with the PFAD to methanol molar ratio of 1:6 and the reaction time of 30 min, the esterification of PFAD in supercritical methanol gave FAMEs production yield of 95%. Compared with transesterification of purified palm oil (PPO) in supercritical methanol, the production of FAMEs reached the maximum yield of only 80% at 300 °C with higher requirement for methanol (1:45 PPO to methanol molar ratio). Compared with the conventional acid-catalyzed esterification of PFAD, only 75% FAMEs yield was obtained in 5 h. The presence of water in the feed (between 0 and 30% v/v) was found to lower the yield of FAMEs production from PFAD significantly. This negative effect was proven to be due to the further hydrolysis of FAMEs, which nevertheless can be minimized when high content of methanol was used.     

New green coatings made from fatty acid dispersions: improvement in barrier properties of biodegradable thermoplasticized-starch substrate

This work was aimed at developing new coatings on biodegradable substrates for possible use in food packaging. In order to study barrier properties of these coatings made from fatty acid dispersions, oxygen permeability, water vapor permeability and also contact angle measurements were carried out. The coatings made from a fatty acid exhibited good barrier properties towards oxygen gas. Moreover, these coatings presented a higher contact angle value than the one obtained directly for the substrate without coating; this can be likely due to the hydrophobic nature of fatty acid and the recrystallization of fatty acid during the drying process.     

Vernolic and cyclopropenoid fatty acids in Plectranthus mollis,syn. Plectranthus incanus,link seed oil: A rich source of oil

Plectranthus mollis, syn. Plectranthus incanus Link seed oil contains the following acids: palmitic (7.2%), stearic (13.6%), oleic (21.7%), linoleic (46.5%), malvalic (2.3%), sterculic (3.2), and vernolic (6.1%).     

Tissue testing for phosphorus in dried tops and seed: Effect of fertilizer type,plant species,and time of sampling within a year and in different years

The apparent relationship between yield and phosphorus (P) concentration in dried whole tops or seed was studied in field experiments. Yield and P concentration in tissue were measured at the time of sampling for several harvests within each year to estimate the current P status of the plants. For each sampling time, there were close relationships between yield and P concentration in tissue that gave a good indication of the current P status of the plants. For the same site and plant species, the relationship did not differ for different fertilizer types (superphosphate or rock phosphate) or method of applying the fertilizer. However, the relationship did differ for different harvests within and between years, and differed for different plant species.Tissue test for P values are sometimes used to predict future plant yields. In the experiments, the P concentrations measured in tissue harvested earlier during the growth of the annual plants were related to subsequent plant yields measured later on within each year. The relationship between future plant yields and tissue test for P values differed for different P fertilizer types and for different sampling times, both within and between years. It also differed for different plant species.     

Cyclopropenoic fatty acids in gymnosperms: The seed oil of Welwitschia

The seed oil of the gymnosperm Welwitschia mirabilis was found to contain malvalic acid, a cyclopropenoic fatty acid. This is in sharp contrast to most other gymnosperms, which contain Δ5cis-fatty acids as well as the normal set of fatty acids. The importance of this finding in relation to questions of the evolution of the Gymnospermae and Angiospermae, the two main branches of higher plants, is briefly discussed.     

Processing‐induced degradation of nanoclay organic modifier in melt‐mixed PET/PE blends during twin screw extrusion at industrial scale: Effect on morphology and mechanical behavior

Immiscible PET/PE blends (80/20 wt %) were prepared on an industrial twin‐screw extruder with and without different types of commercially available montmorillonites (Cloisite® C15A, C10A, and 30B), containing organic surfactants differing by their polarities and their thermal stability). XRD and TEM observations evidence an intercalated structure, C15A leading to a better dispersion compared to C30B and C10A. The size of the PE dispersed phase decreases upon addition of organoclays (OMMT), suggesting an efficient compatibilization. The most efficient compatibilizing effect is observed in the case of C15A (smallest droplet size and narrowest size distribution). Nevertheless, elongation at break in tension and impact strength of PET/PE blends drastically decrease upon addition of OMMT, whatever the organoclay added, due to a possible degradation of the clay surfactant during melt compounding, which counteracts the nanofiller compatibilization effect. Furthermore, similar PET/PE/OMMT blends prepared at a lab scale using a microcompounder are ductile contrary to those compounded in the industrial extruder, which show a brittle behavior. This difference was ascribed to the extrusion residence time (much higher in an industrial extruder than in a lab micro‐compounder), which appeared to be a key parameter in controlling the clay surfactant degradation and thus the end‐use properties of such immiscible blends. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39712.     

Catalytic oxidation of Fe(II) by activated carbon in the presence of oxygen.: Effect of the surface oxidation degree on the catalytic activity

The catalytic oxidation of Fe(II) species in aqueous solution by activated carbons with different degrees of surface oxidation is described. The parent activated carbon was oxidized with aqueous solutions of nitric acid or hydrogen peroxide, and submitted to thermal treatment at 373, 523 and 773 K. The activated carbons prepared were characterized by N₂ adsorption and temperature-programmed desorption, and their catalytic behavior was determined by measuring the oxidation rate of Fe(II) to Fe(III) and the generation of hydrogen peroxide. Catalytic activity is a function of the nature of oxygen surface groups generated by oxidation.     

Effect of temperature on linolenic acid loss and 18:3 Δ9-cis, Δ12-cis, Δ15-trans formation in soybean oil

Oil was extracted from soybeans, degummed, alkalirefined and bleached. The oil was heated at 160, 180, 200, 220 and 240°C for up to 156 h. Fatty acid methyl esters were prepared by boron trifluoride-catalyzed transesterification. Gas-liquid chromatography with a cyanopropyl CPSil88 column was used to separate and quantitate fatty acid methyl esters. Fatty acids were identified by comparison of retention times with standards and were calculated as area % and mg/g oil based on 17:0 internal standard. The rates of 18:3ω3 loss and 18:3 Δ9-cis, Δ12-cis, Δ15-trans (18:3c,c,t) formation were determined, and the activation energies were calculated from Arrhenius plots. Freshly prepared soy oil had 10.1% 18:3ω3 and no detectable 18:3c,c,t. Loss of 18:3ω3 followed apparent first-order kinetics. The first-order rate constants ranged from .0018±.00014 min⁻¹ at 160°C to .083±.0033 min⁻¹ at 240°C. The formation of 18:3c,c,t did not follow simple kinetics, and initial rates were estimated. The initial rates (mg per g oil per h) of 18:3c,c,t formation ranged from 0.0031±0.0006 at 160°C to 2.4±.24 at 240°C. The Arrhenius activation energy for 18:3ω3 loss was 82.1±7.2 kJ mol⁻¹. The apparent Arrhenius activation energy for 18:3c,c,t formation was 146.0±13.0 kJ mol⁻¹. The results indicate that small differences in heating temperature can have a profound affect on 18:3c,c,t formation. Selection of appropriate deodorization conditions could limit the amount of 18:3c,c,t produced.