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Ki-teak Lee - One of the best experts on this subject based on the ideXlab platform.

  • enzymatic interesterification of palm stearin with cinnamomum camphora seed oil to produce zero trans medium chain triacylglycerols enriched plastic fat
    Journal of Food Science, 2012
    Co-Authors: Liang Tang, Xuemei Zhu, Liping Luo, Lin Lei, Zeyuan Deng, Ki-teak Lee
    Abstract:

    It is known that Cinnamomum camphora seed oil (CCSO) is rich in medium-chain fatty acids (MCFAs) or medium-chain triacylglycerols (MCTs). The purpose of the present study was to produce zero-trans MCTs-enriched plastic fat from a lipid mixture (500 g) of palm stearin (PS) and CCSO at 3 weight ratios (PS:CCSO 60:40, 70:30, 80:20, wt/wt) by using lipase (Lipozyme TL IM, 10% of total substrate) as a catalyst at 65 °C for 8 h. The major fatty acids of the products were palmitic acid (C16:0, 42.68% to 53.42%), oleic acid (C18:1, 22.41% to 23.46%), and MCFAs (8.67% to 18.73%). Alpha-tocopherol (0.48 to 2.51 mg/100 g), γ-tocopherol (1.70 to 3.88 mg/100 g), and δ-tocopherol (2.08 to 3.95 mg/100 g) were detected in the interesterified products. The physical properties including solid fat content (SFC), slip melting point (SMP), and Crystal Polymorphism of the products were evaluated for possible application in shortening or margarine. Results showed that the SFCs of interesterified products at 25 °C were 9% (60:40, PS:CCSO), 18.50% (70:30, PS:CCSO), and 29.2% (80:20, PS:CCSO), respectively. The β' Crystal form was found in most of the interesterified products. Furthermore, no trans fatty acids were detected in the products. Such zero-trans MCT-enriched fats may have a potential functionality for shortenings and margarines which may become a new type of nutritional plastic fat for daily diet.

  • preparation of interesterified plastic fats from fats and oils free of trans fatty acid
    Journal of Agricultural and Food Chemistry, 2008
    Co-Authors: Jeung-hee Lee, David S Himmelsbach, Ki-teak Lee
    Abstract:

    Interesterified plastic fats were produced with trans-free substrates of fully hydrogenated soybean oil, extra virgin olive oil, and palm stearin in a weight ratio of 10:20:70, 10:40:50, and 10:50:40, respectively, by lipase catalysis. The major fatty acids of the products were palmitic (32.2−47.4%), stearic (12.0−12.4%), and oleic acid (33.6−49.5%). After storage at 5 °C (refrigerator temperature) or 24 °C (room temperature) for 16 h, the physical properties were evaluated for solid fat content, texture, melting, and Crystallization behavior, viscoelastic properties, Crystal Polymorphism, and Crystal microstructure. The interesterified fats contained desirable Crystal polymorphs (β′ form) as determined by X-ray diffraction spectroscopy. They exhibited a wide plastic range of solid fat content of 52−58% at 10 °C and 15% at 40 °C. The physical properties were influenced by the ratio of palm stearin and olive oil. Harder and more brittle texture, Crystallization and melting at higher temperature, higher sol...

  • Preparation of interesterified plastic fats from fats and oils free of trans fatty acid
    Journal of Agricultural and Food Chemistry, 2008
    Co-Authors: Hee Lee Jeung, David S Himmelsbach, Ki-teak Lee
    Abstract:

    Interesterified plastic fats were produced with trans-free substrates of fully hydrogenated soybean oil, extra virgin olive oil, and palm stearin in a weight ratio of 10:20:70, 10:40:50, and 10:50:40, respectively, by lipase catalysis. The major fatty acids of the products were palmitic (32.2-47.4%), stearic (12.0-12.4%), and oleic acid (33.6-49.5%). After storage at 5 degrees C (refrigerator temperature) or 24 degrees C (room temperature) for 16 h, the physical properties were evaluated for solid fat content, texture, melting, and Crystallization behavior, viscoelastic properties, Crystal Polymorphism, and Crystal microstructure. The interesterified fats contained desirable Crystal polymorphs (beta' form) as determined by X-ray diffraction spectroscopy. They exhibited a wide plastic range of solid fat content of 52-58% at 10 degrees C and 15% at 40 degrees C. The physical properties were influenced by the ratio of palm stearin and olive oil. Harder and more brittle texture, Crystallization and melting at higher temperature, higher solid fat contents, and more elastic (G') or viscous (G') characteristics were observed in the produced fats containing a higher content of palm stearin and lower content of olive oil. The produced fats stored at 5 degrees C consisted mostly of beta' form Crystal together with a small content of beta form, while those at 24 degrees C had only beta' form. The produced fat with a higher amount of palm stearin appeared to have more beta' form Crystal and small size Crystal clusters. Thus, the physical properties of the produced plastic fats may be desirable for use in a bakery product.

  • Physical properties of trans-free bakery shortening produced by lipase-catalyzed interesterification
    JAOCS Journal of the American Oil Chemists' Society, 2008
    Co-Authors: Jeung-hee Lee, Ki-teak Lee
    Abstract:

    Abstract  Lipase-catalyzed interesterified solid fat was produced with fully hydrogenated soybean oil (FHSBO), and rapeseed oil (RSO) and palm stearin (PS) in a weight ratio of 15:20:65, 15:40:45 and 15:50:35. The interesterified fats contained palmitic (27.8–44.6%), stearic (15.6–16.2%), oleic (27.5–36.5%) and linoleic acids (8.0–13.5%). After interesterification of the blends, the physical properties of the products changed and showed lower melting points and solid fat contents, different melting and Crystallization behaviors as well as the formation of more stable Crystals. The produced interesterified fats (FHSBO:RSO:PS 15:20:65, 15:40:45 and 15:50:35 blends) contained desirable Crystal Polymorphism (β′ form) as determined by X-ray diffraction spectroscopy, a long plastic range with solid fat content of 51–63% at 10 °C to 4–12% at 40 °C, and melting points of 39 (15:50:35), 42 (15:50:45) and 45 °C (15:20:65). However, a reduction in tocopherols (α and γ) content and a reduced oxidative stability were observed in the interesterified fats. The physical properties of the interesterifed fats were influenced by the amount of PS, resulting in more hardness and higher solid fat contents for 15:20:65 than 15:40:45 and 15:50:35 blends. The present study suggested that the produced interesterified fats containing trans-free fatty acids could be used as alternatives to hydrogenated types of bakery shortenings.

Adam J Matzger - One of the best experts on this subject based on the ideXlab platform.

  • survey and analysis of Crystal Polymorphism in organic structures
    IUCrJ, 2018
    Co-Authors: Kortney M Kersten, Ramanpreet Kaur, Adam J Matzger
    Abstract:

    With the intention of producing the most comprehensive treatment of the prevalence of Crystal Polymorphism among structurally characterized materials, all polymorphic compounds flagged as such within the Cambridge Structural Database (CSD) are analysed and a list of Crystallographically characterized organic polymorphic compounds is assembled. Classifying these structures into subclasses of anhydrates, salts, hydrates, non-hydrated solvates and coCrystals reveals that there are significant variations in Polymorphism prevalence as a function of Crystal type, a fact which has not previously been recognized in the literature. It is also shown that, as a percentage, polymorphic entries are decreasing temporally within the CSD, with the notable exception of coCrystals, which continue to rise at a rate that is a constant fraction of the overall entries. Some phenomena identified that require additional scrutiny include the relative prevalence of temperature-induced phase transitions among organic salts and the paucity of Polymorphism in Crystals with three or more chemical components.

  • Towards Exhaustive and Automated High-Throughput Screening for Crystalline Polymorphs
    2016
    Co-Authors: Laura Y. Pfund, Adam J Matzger
    Abstract:

    ABSTRACT: Methods capable of exhaustively screening for Crystal Polymorphism remain an elusive goal in solid-state chemistry. Particularly promising among the new generation of approaches is polymer-induced heteronucleation (PIHn), a tool utilizing hundreds of unique polymers for granting kinetic access to polymorphs. Here PIHn is redeployed in a high density format in which 288 distinct polymers, each acting as a heteronucleant, are arrayed on one substrate. This format allows determining the outcome of thousands of Crystallizations in an automated fashion with only a few milligrams of sample. This technology enables the study of a broader range of targets, including preclinical candidates, facilitating determination of Polymorphism propensity much earlier in the drug development process. Here the efficacy of this approach is demonstrated using four pharmaceutically relevant compounds: acetaminophen, tolfenamic acid, ROY, and curcumin

  • Towards Exhaustive and Automated High-Throughput Screening for Crystalline Polymorphs
    2015
    Co-Authors: Laura Y. Pfund, Adam J Matzger
    Abstract:

    Methods capable of exhaustively screening for Crystal Polymorphism remain an elusive goal in solid-state chemistry. Particularly promising among the new generation of approaches is polymer-induced heteronucleation (PIHn), a tool utilizing hundreds of unique polymers for granting kinetic access to polymorphs. Here PIHn is redeployed in a high density format in which 288 distinct polymers, each acting as a heteronucleant, are arrayed on one substrate. This format allows determining the outcome of thousands of Crystallizations in an automated fashion with only a few milligrams of sample. This technology enables the study of a broader range of targets, including preclinical candidates, facilitating determination of Polymorphism propensity much earlier in the drug development process. Here the efficacy of this approach is demonstrated using four pharmaceutically relevant compounds: acetaminophen, tolfenamic acid, ROY, and curcumin

  • Crystal Polymorphism in a carbamazepine derivative oxcarbazepine
    Journal of Pharmaceutical Sciences, 2010
    Co-Authors: Katie M Lutker, Adam J Matzger
    Abstract:

    Although Crystal Polymorphism of carbamazepine (CBZ), an anticonvulsant used to treat epilepsy, has been known for decades, the phenomenon has only recently been noted for its keto-derivative oxcarbazepine (OCB). Here it is demonstrated that OCB possesses at least three anhydrous polymorphs. Although all forms are morphologically similar, making differentiation between Crystal modifications by optical microscopy difficult, powder X-ray diffraction, Raman spectroscopy, and thermomicroscopy show distinctive differences. These techniques provide an efficient method of distinguishing between the three polymorphs. The Crystal structure of form II of OCB is reported for the first time and the structure of form I has been redetermined at low temperature. Remarkably, both the molecular conformation and Crystal packing of form II are in excellent agreement with the blind prediction made in 2007.

  • Crystalline polymorph selection and discovery with polymer heteronuclei
    Journal of the American Chemical Society, 2005
    Co-Authors: Christopher P Price, And Adam L Grzesiak, Adam J Matzger
    Abstract:

    The discovery and selective production of Crystalline polymorphs, an outstanding problem in solid-state chemistry, is of great importance industrially in, for example, the manufacture of pharmaceuticals and pigments. Despite considerable efforts, no reliable method exists to produce all of the stable polymorphs of a given compound. Herein, we report methodology to control the phenomenon of Crystal Polymorphism through the use of diverse libraries of polymer heteronuclei including both commercially available polymers and combinatorially synthesized cross-linked polymers. This new approach for exploring polymorph space offers the advantage of high throughput Crystallization to discover multiple polymorphs combined with the ability to selectively produce a given form from a single solvent and temperature condition by simply varying the nature of the polymer substrate. This technique is successfully demonstrated on the pharmaceuticals acetaminophen, sulfamethoxazole, and carbamazepine and on the pharmaceutical intermediate 5-methyl-2-[(2-nitrophenyl)amino]-3-thiophenecarbonitrile (ROY). High throughput screening, accomplished by optical microscopy and Raman spectroscopy, identified the selective production of the two stable polymorphs of acetaminophen and all six stable forms of ROY. Furthermore, one new form of carbamazepine and two new forms of sulfamethoxazole were discovered; in these cases, single Crystals were obtained enabling the structural characterization of two new tetramorphic systems.

Bernhard Wunderlich - One of the best experts on this subject based on the ideXlab platform.

Maria Laura Lorenzo - One of the best experts on this subject based on the ideXlab platform.

  • Influence of chain structure on Crystal Polymorphism of poly(lactic acid). Part 2. Effect of molecular mass on the Crystal growth rate and semiCrystalline morphology
    Colloid and Polymer Science, 2015
    Co-Authors: Maria Laura Lorenzo, Paolo Rubino, Romain Luijkx, Marion Hélou, Barbara Immirzi, René Androsch
    Abstract:

    The influence of molecular parameters on the Crystallization kinetics and α/α ′-Crystal Polymorphism of poly(lactic acid) (PLA) was analyzed. Previous studies indicated that the content of l - and d -lactic acid affects both the Crystallization rate and the formation of α- and α′- Crystals of PLA. This preliminary investigation has now been completed by analysis of the influence of the chain length on the growth rate of the α- and α′-polymorphs. A series of linear PLA grades with molecular masses ranging from 60 to almost 600 kDa, and containing up to 3 wt.% d -lactic acid was investigated. Independent of the copolymer composition, an increase of the molecular mass leads to a lower maximum Crystallization rate but does not affect the α/α′-Crystal Polymorphism of PLA upon melt Crystallization, at least for the analyzed range of molecular mass and d -lactic acid content. Lower molecular mass causes an initial growth of hedritic superstructures, which gradually transform into spherulites. The d -lactic acid content also affects the morphology, as hedrites are observed also at higher molecular mass. Highly irregular and fibrillar structures grow in PLA grades with low stereoregularity and high molecular mass.

  • Influence of chain structure on Crystal Polymorphism of poly(lactic acid). Part 1: effect of optical purity of the monomer
    Colloid and Polymer Science, 2014
    Co-Authors: Maria Laura Lorenzo, Paolo Rubino, Romain Luijkx, Marion Hélou
    Abstract:

    The influence of chain structure on Crystal Polymorphism of poly(lactic acid) (PLA) with high l -lactic acid content (97.8–100 %) is detailed in this contribution. Upon usual processing conditions of PLA, only α and α′ Crystals grow, which makes these two polymorphs of major interest for research. The two Crystal modifications have similar chain packing, which complicates their quantitative analysis by diffraction methods. The two Crystal modifications are instead easily identified by analysis of the Crystallization kinetics, which varies not only with temperature, but also with Crystal Polymorphism. The dependence of the rate of ordering on temperature shows two distinct maxima around 105–110 and 120–125 °C, which are related to growth of α′ and α Crystals, respectively. Addition of d -lactic acid co-units leads to a decrease of the overall Crystallization rate of PLA, as well as of the rate of spherulite growth ( G ) of both the Crystal modifications. The relative Crystallization rates of α and α′ forms are highly affected by stereoregularity, especially in the PLA grades that have a high Crystallization rate. A high d -lactic acid content results not only in an overall slower Crystal growth, but also in a varied temperature range where each of the two Crystal modifications prevail, with a shift to lower temperatures of both the maxima of the G vs. temperature plots, indicating that inclusion of d -lactic acid units in the PLA chain affects Crystallization rate of both α and α′ Crystal modifications.

  • Crystal Polymorphism of poly l lactic acid and its influence on thermal properties
    Thermochimica Acta, 2011
    Co-Authors: Maria Laura Lorenzo, Mariacristina Cocca, Mario Malinconico
    Abstract:

    Abstract The influence of Crystal Polymorphism on the thermal properties of poly( l -lactic acid) (PLLA) is discussed in this contribution. Crystallization of PLLA at high temperatures yields the stable α form, whereas at low temperatures the metastable α′ modification develops, which is characterized by slightly larger lattice dimensions compared to the α counterpart, and by some degree of conformational disorder. Quantitative analysis with conventional and temperature-modulated calorimetry revealed a three-phase structure of PLLA composed of a Crystal phase and two amorphous fractions with different mobility, for all the analyzed thermal histories. A higher coupling of the amorphous chain segments with the Crystal phase was found in the presence of α Crystals, probably due to the slightly larger lattice dimensions and the looser arrangements of PLLA chains in the α′ structure. Some peculiarities in the thermal behavior were rationalized, like an unusual frequency-dependence of the reversing apparent heat capacity upon the solid–solid transition from the α′ to the α Crystals. Devitrification of the rigid amorphous segments seems also to be differently affected by the coupled Crystal structure for the two analyzed Crystal modifications of PLLA.

  • influence of Crystal Polymorphism on mechanical and barrier properties of poly l lactic acid
    European Polymer Journal, 2011
    Co-Authors: Mariacristina Cocca, Maria Laura Lorenzo, Mario Malinconico, Vincenzo Frezza
    Abstract:

    Abstract The effect of Crystal Polymorphism on barrier and mechanical properties of PLLA is detailed in this contribution. PLLA films containing different amounts of α and α′ Crystal forms were prepared by annealing quenched PLLA at different temperatures. The polymorphic structure of the films was analyzed by X-ray diffraction. Mechanical properties and permeability to water vapor were investigated as a function of degree of Crystallinity (wC) and related to Crystal Polymorphism developed during annealing. The polymorphic structure of PLLA significantly affects mechanical and barrier properties. The α Crystal modification provides a better barrier to water vapor and a higher Young’s modulus, compared to films containing the α′ modification, but a lower elongation at break. The varied barrier and mechanical properties were correlated to the different packing of PLLA chains in the two analyzed polymorphs. The conformational disorder of the α′ form makes this structure a mesophase (condis Crystal), with remarkable effects on material properties.

  • influence of Crystal Polymorphism on the three phase structure and on the thermal properties of isotactic poly 1 butene
    Macromolecules, 2009
    Co-Authors: Maria Laura Lorenzo, Maria Cristina Righetti, Bernhard Wunderlich
    Abstract:

    The influence of Crystal Polymorphism on the three-phase structure of isotactic poly(1-butene) (PB-1) is discussed. Crystallization of PB-1 from the melt yields the tetragonal phase, known as form ...

Alan Aspuruguzik - One of the best experts on this subject based on the ideXlab platform.

  • diffusion monte carlo study of para diiodobenzene Polymorphism revisited
    Journal of Chemical Theory and Computation, 2015
    Co-Authors: Kenta Hongo, Mark A Watson, Toshiaki Iitaka, Alan Aspuruguzik, Ryo Maezono
    Abstract:

    We revisit our investigation of the diffusion Monte Carlo (DMC) simulation of para-diiodobenzene (p-DIB) molecular Crystal Polymorphism. [See J. Phys. Chem. Lett. 2010, 1, 1789–1794.] We perform, for the first time, a rigorous study of finite-size effects and choice of nodal surface on the prediction of polymorph stability in molecular Crystals using fixed-node DMC. Our calculations are the largest that are currently feasible using the resources of the K-computer and provide insights into the formidable challenge of predicting such properties from first principles. In particular, we show that finite-size effects can influence the trial nodal surface of a small (1 × 1 × 1) simulation cell considerably. Therefore, we repeated our DMC simulations with a 1 × 3 × 3 simulation cell, which is the largest such calculation to date. We used a density functional theory (DFT) nodal surface generated with the PBE functional, and we accumulated statistical samples with ∼6.4 × 105 core hours for each polymorph. Our fina...

  • understanding Polymorphism in organic semiconductor thin films through nanoconfinement
    Journal of the American Chemical Society, 2014
    Co-Authors: Ying Diao, Alan Aspuruguzik, Kristina M. Lenn, Wen-ya Lee, Yisha Mao, Yeongin Kim, Julia A. Reinspach, Steve Park, Martin A Bloodforsythe, Gi Xue
    Abstract:

    Understanding Crystal Polymorphism is a long-standing challenge relevant to many fields, such as pharmaceuticals, organic semiconductors, pigments, food, and explosives. Controlling Polymorphism of organic semiconductors (OSCs) in thin films is particularly important given that such films form the active layer in most organic electronics devices and that dramatic changes in the electronic properties can be induced even by small changes in the molecular packing. However, there are very few polymorphic OSCs for which the structure–property relationships have been elucidated so far. The major challenges lie in the transient nature of metastable forms and the preparation of phase-pure, highly Crystalline thin films for resolving the Crystal structures and evaluating the charge transport properties. Here we demonstrate that the nanoconfinement effect combined with the flow-enhanced Crystal engineering technique is a powerful and likely material-agnostic method to identify existing polymorphs in OSC materials a...

  • a benchmark quantum monte carlo study of molecular Crystal Polymorphism a challenging case for density functional theory
    2012
    Co-Authors: Mark A Watson, Kenta Hongo, Toshiaki Iitaka, Alan Aspuruguzik
    Abstract:

    E-mail:mark.watson@cantab.netWe have applied the diffusion Monte Carlo method todetermine the relative stabilities of the two polymorphs ofthepara-diiodobenzeneorganicmolecularCrystal. Ourresultpredicts the α phase to be more stable than the β phaseat zero temperature (with a 2% statistical uncertainty) inagreementwithexperiment. Weusedtheresulttobenchmarkeight commonly-used local, semi-local and hybrid densityfunctionals. Thesemi-localandhybridfunctionalsincorrectlypredicttheβphasetobethemoststableusingtheexperimentalCrystalstructures,whiletheadditionofanempiricaldispersioncorrectionwasfoundtostronglyover-compensatethiserror.Thelocalfunctionalsarethemostconsistent,butthisisalmostcertainlyduetofortuitouserrorcancellation.Weconcludethatthereisarealneedforefficient,accuratemany-bodymethods,orimproveddensity-functionals,whichcanaccuratelycaptureelectron correlation and dispersion interactions in molecularCrystals.©2012AmericanChemicalSociety

  • failure of conventional density functionals for the prediction of molecular Crystal Polymorphism a quantum monte carlo study
    Journal of Physical Chemistry Letters, 2010
    Co-Authors: Kenta Hongo, Mark A Watson, Toshiaki Iitaka, Roel S Sanchezcarrera, Alan Aspuruguzik
    Abstract:

    We have applied the diffusion Monte Carlo method, for the first time, to an organic molecular Crystal (para-diiodobenzene) in order to determine the relative stability of its two well-known polymor...