The Experts below are selected from a list of 264 Experts worldwide ranked by ideXlab platform
James G. Goodwin - One of the best experts on this subject based on the ideXlab platform.
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Reaction Kinetics and Mechanisms for Hydrolysis and Transesterification of Triglycerides on Tungstated Zirconia
Topics in Catalysis, 2010Co-Authors: Kanokwan Ngaosuwan, Xunhua Mo, James G. Goodwin, Piyasan PraserthdamAbstract:Hydrolysis and transesterification are two reactions which can occur during the synthesis of biodiesel. An Investigation of the mechanistic pathways in hydrolysis and transesterification were carried out at a relatively high temperature (100–130 °C) and moderate pressures (120–180 psi) with tricaprylin and water for hydrolysis or methanol for transesterification using a tungstated zirconia catalyst in a batch reactor. It was found that upon increasing the concentration of TCp, the reaction rates for both hydrolysis and transesterification increased at all conditions. In contrast, water inhibited the reaction rate of hydrolysis by poisoning the active sites. For transesterification, the apparent reaction order of methanol evolved from positive to negative as the concentration of methanol relative to TCp increased. Using a reaction model discrimination procedure, it was found that hydrolysis on WZ could be successfully described by an Eley–Rideal single site mechanism with adsorbed TCp reacting with bulk phase water. The mechanistic pathway for transesterification also seems to follow a similar mechanism, identical to the one previously proposed for transesterification on a solid acid catalyst (SiO_2-supported Nafion-SAC-13) at lower temperature (60 °C).
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Reaction Kinetics and Mechanisms for Hydrolysis and Transesterification of Triglycerides on Tungstated Zirconia
Topics in Catalysis, 2010Co-Authors: Kanokwan Ngaosuwan, James G. Goodwin, Piyasan PraserthdamAbstract:Hydrolysis and transesterification are two reactions which can occur during the synthesis of biodiesel. An Investigation of the mechanistic pathways in hydrolysis and transesterification were carried out at a relatively high temperature (100–130 °C) and moderate pressures (120–180 psi) with tricaprylin and water for hydrolysis or methanol for transesterification using a tungstated zirconia catalyst in a batch reactor. It was found that upon increasing the concentration of TCp, the reaction rates for both hydrolysis and transesterification increased at all conditions. In contrast, water inhibited the reaction rate of hydrolysis by poisoning the active sites. For transesterification, the apparent reaction order of methanol evolved from positive to negative as the concentration of methanol relative to TCp increased. Using a reaction model discrimination procedure, it was found that hydrolysis on WZ could be successfully described by an Eley–Rideal single site mechanism with adsorbed TCp reacting with bulk phase water. The mechanistic pathway for transesterification also seems to follow a similar mechanism, identical to the one previously proposed for transesterification on a solid acid catalyst (SiO2-supported Nafion-SAC-13) at lower temperature (60 °C).
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simultaneous free fatty acid esterification and triglyceride transesterification using a solid acid catalyst with in situ removal of water and unreacted methanol
Industrial & Engineering Chemistry Research, 2009Co-Authors: Kaewta Suwannakarn, Kanokwan Ngaosuwan, Edgar Lotero, James G. GoodwinAbstract:Waste greases used in biodiesel production contain high concentrations of free fatty acids (FFAs). To efficiently utilize these low-cost feedstocks for biodiesel synthesis, a preliminary acid-catalyzed esterification pretreatment is necessary to reduce their FFA contents. In this study, the use of a three-phase reaction has been investigated for the simultaneous esterification of FFAs and transesterification of triglycerides (TGs) using model mixtures of TGs and FFAs [0−25 wt % lauric acid (HLa) in tricaprylin (TCp)] to simulate waste grease and to permit easy distinction between the reactions. Trans/esterification with methanol was carried out using a commercial tungstated zirconia (WZ) solid catalyst in a well-stirred semibatch reactor at 130 °C operating at atmospheric pressure. Methanol was continuously charged to the reactor. Unreacted methanol and water produced during the reaction were continuously removed by vaporization, thereby favoring esterification. Esterification occurred 4 times faster than...
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esterification and transesterification using modified zirconia catalysts
Applied Catalysis A-general, 2008Co-Authors: Dora E Lopez, James G. Goodwin, David A Bruce, Satoshi FurutaAbstract:Abstract In this paper, modified zirconias (WZ, SZ, and TiZ) have been extensively compared under the same reaction conditions as catalysts for both the transesterification of triglycerides (TGs) and the esterification of carboxylic acids (free fatty acids, FFAs) with ethanol. In addition, for the first time, the catalyzed rate of hydrolysis/esterification + transesterification of triglycerides has been quantified and compared to that of the rate of simultaneous esterification of FFAs present in the same reaction mixture. Tricaprylin and caprylic acid were used as representative compounds for the comparison of the catalyst for transesterification and esterification since they give reaction rates related to those of larger TGs and FFAs typically present in vegetable oils and animal fats. For the measurement of the kinetics for the simultaneous reaction of a TG-FFA mixture, the reaction of tricaprylin and oleic acid with ethanol was studied using the most promising of the Zr-based catalysts, WZ. Reaction was carried out in a well-mixed batch reactor under mild conditions (75–120 °C). TiZ, while more active than WZ for transesterification, had by far the lowest activity for esterification. SZ, while the most active catalyst (on a weight basis) for both transesterification and esterification reactions, exhibited significant sulfur loss, which greatly reduced its long term activity. As expected, esterification occurred at a much faster rate than transesterification. However, under simultaneous reaction conditions, by virtue of the water being produced in esterification and hydrolysis of the TG taking place, the conversion of the triglycerides to ester products was greatly increased. The resulting caprylic acid from hydrolysis did not accumulate in the reaction mixture due to its rapid esterification to ethyl caprylate. The activity results for WZ indicate how biodiesel can be efficiently produced from free-fatty-acid-containing feedstocks using a solid-acid-catalyzed pre-esterification step, and how a significant fraction of the triglycerides can also be converted at the same time assisted by initial hydrolysis with byproduct water from esterification.
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activation and deactivation characteristics of sulfonated carbon catalysts
Journal of Catalysis, 2008Co-Authors: Xunhua Mo, James G. Goodwin, Dora E Lopez, Kaewta Suwannakarn, Edgar Lotero, Changqing LuAbstract:Abstract Recently, there have been reports in the literature on sulfonated carbon catalysts prepared from sugars exhibiting interesting acid catalytic properties. However, to date, little has been reported about their activation/deactivation characteristics. For this paper, the activation/deactivation behaviors of such sulfonated carbon catalysts were investigated through the esterification of free fatty acids (acetic acid and caprylic acid) and transesterification of triglycerides (triacetin, tricaprylin and soybean oil) with methanol. The catalytic properties of the sulfonated catalysts were compared with those of Nafion ® SAC-13 and sulfuric acid, other similar Bronsted acid catalysts. For the liquid-phase esterification of acetic acid and transesterification of triacetin with methanol, the sulfonated carbon catalysts exhibited catalytic site activities comparable to those for sulfuric acid, along with higher (by weight) specific catalytic activities but lower initial TOFs compared with Nafion ® SAC-13. Catalyst swelling was critical for catalytic activity of the sulfonated carbon catalysts. Poor swelling in the gas phase of the catalysts led to the appearance of an induction period and inferior catalytic performance in the gas-phase esterification of acetic acid. In the liquid-phase esterification of acetic acid, catalytic activity decreased during the initial reaction batch cycles but reached a plateau after several catalytic cycles at 60 °C. Elemental analysis, 1 H NMR results of the liquid reaction mixtures after reaction, and the decreased activity of the catalysts after extensive solvent washing suggest that the initial catalyst deactivation was caused by the leaching of polycyclic aromatic hydrocarbons containing SO 3 H groups. Cycling experiments involving large triglycerides actually showed a cumulative effect of slower catalyst swelling in the less-polar reaction mixtures moderated by deactivation of the catalyst due to leaching, resulting in increased activity in the early cycles followed by a loss of activity in later cycles.
Benilde Saramago - One of the best experts on this subject based on the ideXlab platform.
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Static and Dynamic Wetting Behavior of Triglycerides on Solid Surfaces.
Journal of colloid and interface science, 2000Co-Authors: Marie-caroline Michalski, Benilde SaramagoAbstract:Abstract Triglyceride wetting properties on solid surfaces of different hydro-phobicities were investigated using three different methods, namely, the sessile drop method for static contact angle measurements, the Wilhelmy method for dynamic contact angle measurements, and the captive bubble method to investigate thin triglyceride film stability. For solid surfaces having a surface free energy higher than the surface tension of triglycerides (tributyrin, tricaprylin, and triolein), a qualitative correlation was observed between wetting and solid/triglyceride relative hydrophobicities. On surfaces presenting extreme hydrophobic or hydrophilic properties, medium-chain triglycerides had a behavior similar to that of long-chain unsaturated ones. On a high-energy surface (glass), tricaprylin showed an autophobic effect subsequent to molecular adsorption in trident conformation on the solid, observed with the three methods. Thin triglyceride films between an air bubble and a solid surface were stable for a short time, for solids with a surface free energy larger than the triglyceride surface tension. If the solid surface had a lower surface free energy, the thin film collapsed after a time interval which increased with triglyceride viscosity.
Gino Ciafardini - One of the best experts on this subject based on the ideXlab platform.
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Distribution of dimorphic yeast species in commercial extra virgin olive oil.
Food microbiology, 2010Co-Authors: B. A. Zullo, G. Cioccia, Gino CiafardiniAbstract:Recent microbiological research has demonstrated the presence of a rich microflora mainly composed of yeasts in the suspended fraction of freshly produced olive oil. Some of the yeasts are considered useful as they improve the organoleptic characteristics of the oil during preservation, whereas others are considered harmful as they can damage the quality of the oil through the hydrolysis of the triglycerides. However, some dimorphic species can also be found among the unwanted yeasts present in the oil, considered to be opportunistic pathogens to man as they have often been isolated from immunocompromised hospital patients. Present research demonstrates the presence of dimorphic yeast forms in 26% of the commercial extra virgin olive oil originating from different geographical areas, where the dimorphic yeasts are represented by 3-99.5% of the total yeasts. The classified isolates belonged to the opportunistic pathogen species Candida parapsilosis and Candida guilliermondii, while among the dimorphic yeasts considered not pathogenic to man, the Candida diddensiae species was highlighted for the first time in olive oil. The majority of the studied yeast strains resulted lipase positive, and can consequently negatively influence the oil quality through the hydrolysis of the triglycerides. Furthermore, all the strains showed a high level of affinity with some organic solvents and a differing production of biofilm in "vitro" corresponded to a greater or lesser hydrophobia of their cells. Laboratory trials indicated that the dimorphic yeasts studied are sensitive towards some components of the oil among which oleic acid, linoleic acid and triolein, whereas a less inhibiting effect was observed with Tricaprilin or when the total polyphenols extracted from the oil were used. The observations carried out on a scanning electron microscope (SEM), demonstrated the production of long un-branched pseudohyphae in all the tested dimorphic yeasts when cultivated on nutrient-deficient substrates.
Sebastien Marze - One of the best experts on this subject based on the ideXlab platform.
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Studying the real-time interplay between triglyceride digestion and lipophilic micronutrient bioaccessibility using droplet microfluidics. 2 application to various oils and (pro)vitamins
Food Chemistry, 2019Co-Authors: Hoang Thanh Nguyen, Mélanie Marquis, Marc Anton, Sebastien MarzeAbstract:The kinetics of micellar solubilization of lipophilic micronutrients (bioaccessibility) in relation with triglyceride digestion remains poorly known. To study this interplay in real-time, a droplet microfluidic method was designed and used as reported in the first part of this article series. In this second part, the interplay between the micellar solubilization of (pro)vitamins (beta-carotene or retinyl palmitate) and the digestion of triglyceride oils (tricaprylin TC, or high-oleic sunflower seed oil HOSO, or fish oil FO) during simulated gastrointestinal digestion was investigated. The relation between the release of both micronutrients and of triglyceride lipolytic products was found to be non-linear. The kinetics of beta-carotene was found to follow the kinetics of lipolytic products, depending on the oil type (TC > HOSO > FO). The effect of the gastric phase on the intestinal phase was also found to follow this order, mostly due to partial lipolysis during the gastric phase.
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Refining in silico simulation to study digestion parameters affecting the bioaccessibility of lipophilic nutrients and micronutrients
Food and Function, 2015Co-Authors: Sebastien MarzeAbstract:Despite the considerable number of in vivo and in vitro studies on the digestive fate of lipophilic nutrients, micronutrients, and bioactives, the effects of the structure and composition of foods on the physico-chemical mechanisms of luminal digestion are still poorly understood. Studying them is indeed complex because the number of parameters is high and many of them are interdependent. To solve this problem, an in silico simulation based on a multi-agent system was recently proposed to study the intestinal bioaccessibility of lipophilic nutrients and micronutrients from a single oil droplet. The roles of lipolysis and solubilization in bile salt were included. The effects of several food and digestion parameters were in line with those reported in the experimental literature. The goal of the research reported in this new article was to include more digestion parameters in the simulation in order to make it more realistic against complex cases. This was done in one specific digestion condition reflecting in vitro experiments, using droplets of tricaprylin or triolein containing vitamin A. The structure and principles of the original model were kept, with independent local modifications in order to study each factor separately. First, a gastric step was added where lipolysis took place, and only a marginal effect on the following intestinal step was found. Then, the chemical form of vitamin A, either non-hydrolyzed retinyl ester or retinyl ester instantly hydrolyzed into retinol, was investigated by considering different localizations in the droplet, resulting in a higher bioaccessibility for the retinol. The case of a mixture of tricaprylin and triolein indicated an influence of the oil phase viscosity. The consideration of mixed micelles compared to simple bile salt micelles was also investigated, and resulted in a higher vitamin A bioaccessibility, especially with triolein. Finally, a full model including the most influential parameters was tested to simulate the digestion of triglyceride-limonene mixtures, giving bioaccessibility trends in very good agreement with the literature.
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In vitro digestion of emulsions: mechanistic and experimental models
Soft Matter, 2012Co-Authors: Sebastien Marze, Maela ChoimetAbstract:Digestion is a complex combination of physical, chemical and biological processes. In order to investigate the impact of food structure on the digestion of lipids, we work on a controllable triglyceride-based system: emulsion. In this study, the emulsion was composed of a single triglyceride (tricaprylin or triolein), decanal as a model lipophilic micronutrient, and a single emulsifier (beta-lactoglobulin or sodium oleate) at different concentrations. We investigated the effects of these parameters on an in vitro intestinal static digestion, which was monitored using classic physicochemical methods: fatty acid titration, lipids extraction/chromatography and sizing. To interpret the results, we developed several mechanistic models based on mass transfer kinetics, which enable a direct comparison and identification of the factors influencing the digestion. These factors are the molar mass of the lipids, the initial interfacial area (droplet size) and dispersed volume fraction, the interfacial tension and dilatational viscoelasticity. We also developed an experimental digestion model based on a single droplet using tensiometry. This technique was able to monitor the kinetics of lipolysis and micellar solubilization simultaneously. All methods confirmed the result from our previous study that the type of triglyceride is the major parameter influencing the digestion. Moreover, the mechanistic and experimental models proved that digestion was usually faster for beta-lactoglobulin emulsions/droplets compared to the sodium oleate ones. There was no clear effect of the emulsifier concentration.
Casimir C. Akoh - One of the best experts on this subject based on the ideXlab platform.
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esterification and hydrolytic activities of candida rugosa lipase isoform 1 lip1 immobilized on celite 545 duolite a7 and sephadex g 25
Journal of Agricultural and Food Chemistry, 2008Co-Authors: Stephen E Lumor, Casimir C. AkohAbstract:The esterification and hydrolytic activities of free and immobilized Candida rugosa lipase isoform 1 (LIP1) were investigated. Esterification activity was determined by reacting caprylic acid with glycerol in the presence of molecular sieves (30%, w/w), and the volume of 1.0 M NaOH consumed by the reaction products upon titration was used to calculate esterification activity. Caprylic acid was also reacted with cottonseed oil, and the amount of caprylic acid incorporated after 12 h of reaction was determined. Results indicated that LIP1 had little esterification activity, which was not significantly improved upon immobilization. Hydrolytic activity was determined by incubating tricaprylin emulsion (15%, w/w) with the respective lipases for 60 min, and the reaction products were titrated against 0.5 M NaOH. LIP1 showed hydrolytic activity comparable to Lipozyme RM IM. The hydrolytic activity improved significantly upon immobilization. Immobilization on Celite 545 produced the highest increase in hydrolytic activity.
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characterization of enzymatically synthesized structured lipids containing eicosapentaenoic docosahexaenoic and caprylic acids
Journal of the American Oil Chemists' Society, 1998Co-Authors: Casimir C. AkohAbstract:Structured lipids (SL) containing n-3 polyunsaturated (eicosapentaenoic or docosahexaenoic) and mediumchain (caprylic) fatty acids were synthesized in gram quantities and characterized. Tricaprylin was mixed with n-3-rich polyunsaturated fatty acids in a 1:2 molar ratio and transesterified by incubating at 55°C in hexane with SP 435 lipase (10% by wt of total substrates) in a 125-mL Erlenmeyer flask as the bioreactor. After several batches of reaction, the products were pooled and hexane was evaporated. Short-path distillation was used for purification of synthesized SL. The distillation conditions were 1.1 Torr and 170°C at a feed flow rate of 3 mL/min. Up to 240 g of SL was isolated and deacidified by alkaline extraction or ethanol-water solvents. The fatty acid profile, free fatty acid value, saponification number, iodine value, peroxide value, thiobarbituric acid, and conjugated diene contents were determined. Oxidation stability, with α-tocopherol as antioxidant, and the oxidative stability index were also determined.
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enzymatic synthesis of position specific low calorie structured lipids
Journal of the American Oil Chemists' Society, 1997Co-Authors: Casimir C. AkohAbstract:An immobilized sn-1,3-specific lipase from Rhizomucor miehei (IM 60) was used to catalyze the interesterification of tristearin (C18:0) and tricaprin (C10:0) to produce low-calorie structured lipids (SL). Acceptable product yields were obtained from a 1:1 mole ratio of both triacylglycerols with 10% (w/w of reactants) of IM 60 in 3 mL hexane. The SL molecular species, based on total carbon number, were 44.2% C41 and 40.5% C49, with 3.8 and 11.5% unreacted tristearin C57 and tricaprin C27, respectively, remaining in the product mixture. The best yield of C41 species (44.3%) was obtained with zero added water. Tricaprylin (C8:0) was also successfully interesterified with tristearin in good yields at 1:1 mole ratio. Products were analyzed by reverse-phase high-performance liquid chromatography with an evaporative light-scattering detector. Reaction parameters, such as substrate mole ratio, enzyme load, time course, added water, reaction media, and enzyme reuse, were also investigated. Hydrolysis by pancreatic lipase revealed the specific fatty acids present at the sn-1,3 positions of SL.
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immobilized lipase catalyzed production of structured lipids with eicosapentaenoic acid at specific positions
Journal of the American Oil Chemists' Society, 1996Co-Authors: Casimir C. AkohAbstract:Structured lipids (SL) were synthesized by the interesterification reaction between medium-chain triacylglycerols and eicosapentaenoic acid (EPA) ethyl ester. The products were partially purified, and the fatty acid at thesn-2 position was determined after pancreatic lipase-catalyzed hydrolysis. The effect of additives (water and glycerol) on the rate of reaction was also investigated. Mol% EPA incorporated into the triacylglycerols was increased by adding water when trilaurin and tricaprylin were the substrates and IM 60 was the biocatalyst. With SP 435, EPA incorporation was always less with additional water than without water. The addition of glycerol (0.005 g or 0.01 g) improved interesterification catalyzed by IM 60 to some degree, but an excess amount (0.02 g) inhibited the reaction. The reaction with glycerol showed no significant difference with SP 435. After scale-up and fractionation by column chromatography, we could recover approximately 0.3–0.4 g of product/g of reaction products. After hydrolysis by pancreatic lipase, we can conclude that IM 60 has a high specificity forsn-1,3 positions. With SP 435 lipase, 34.8–39.3 mol% of EPA was found at thesn-2 position of the recovered SL.
