Lipase-Catalyzed Synthesis of Cocoa Butter Equivalent from Palm Olein and Saturated Fatty Acid Distillate from Palm Oil Physical Refinery

Cocoa butter equivalent was prepared by enzymatic acidolysis reaction of substrate consisting of refined palm olein oil and palmitic?Cstearic fatty acid mixture. The reactions were performed in a batch reactor at a temperature of 60?°C in an orbital shaker operated at 160?RPM. Different mass ratios of substrates were explored and the compositions of the five major triacylglycerol (TAG) of the structured lipids were identified and quantified using cocoa butter-certified reference material IRMM-801. The reaction resulted in production of cococa butter equivent with TAG compostion (POP 26.6 %, POS 42.1, POO 7.5, SOS 18.0 %, and SOO 5.8 %) and melting temperature between 34.7 and 39.6?°C which is close to that of the cocoa butter. The result of this research demonstrated the potential use of saturated fatty acid distillate (palmitic and stearic fatty acids) obtained from palm oil physical refining process into a value-added product.     

Effect of enzymatic interesterification on melting point of palm olein

Immobilized PS-C ‘Amano’ II lipase was used to catalyze the interesterification of palm olein (POo) with 30, 50, and 70% stearic acid in n-hexane at 60°C. The catalytic performance of the immobilized lipase was evaluated by determining the composition change of fatty acyl groups and triacylglycerol (TAG) by gas liquid chromatography and high-performance liquid chromatography, respectively. The interesterification process resulted in the formation of new TAGs, mainly tripalmitin and dipalmitostearin, both of which were absent in the original oil. These changes in TAG composition resulted in an increase in slip melting point, from the original 25.5°C to 36.3, 37.0, and 40.0°C in the modified POo with 30, 50, and 70% stearic acid, respectively. All the reactions attained steady state in about 6 h. This type of work will find great applications in food industries, such as confectionery.     

Determination of the triglyceride composition of avocado oil by high-performance liquid chromatography using a light-scattering detector.

The triglyceride composition of avocado oil was determined by high-performance liquid chromatography using a light-scattering detector. Two avocado varieties, Fuerte and Hass, were analysed, and the qualitative composition of each was found to be similar, though quantitative differences were detected. The triglyceride composition was predicted using a system of equations based on the relationship between log k' and the molecular variables equivalent carbon number, chain length and number of double bonds for each of the fatty acids in the glycerides. A total of 24 molecular species of triglycerides were identified. The chromatographic system used successfully separated the critical pairs OOO-LOS, PaPaO-LnPP and PaOO-LOP (O = olein; L = linolein; S = stearin; Pa = palmitolein; Ln = linolenin; P = palmitin). Detector response was found to have a linear relationship with the amount of sample injected over the injection range 10-70 micrograms.     

Equilibrium melting points of the low-melting and high-melting crystalline forms of trans-1, 4-polyisoprene

Equilibrium melting points in trans-1,4-polyisoprene were calculated from plots of crystallization temperature versus the experimentally measured melting points. The melting points were found to be 78 ± 1.7°C for the low-melting crystalline form and 87 ± 1.3°C for the high-melting form. Within the experimental error, melting points were independent of molecular weight above a number-average weight of 33,000.     

Study of crystallization kinetics of trans-1,4-polyisoprene

The concentrations and the growth rates of high- and low-melting type spherulites of trans-1,4-polyisoprene were measured in the temperature range 39–49°C. It was shown that above about 40°C., the crystallization rate of trans-1,4-polyisoprene is determined primarily by the radial growth rate of high-melting form (HMF) spherulites, whereas the predominance of the low-melting form (LMF) crystals below 40°C. can be attributed to the high rate of formation of LMF primary nuclei at lower crystallization temperatures. Temperature-independent rate parameters were calculated from optical and dilatometric measurements and were found to be in good agreement. Both the change in nucleation habit and spherulite growth rate with temperature can be explained on the basis of a lower end surface free energy of LMF crystals of trans-1,4-polyisoprene compared to that of the HMF crystals.     

Molecular-topological structure of γ-irradiated polytetrafluoroethylene

The molecular-topological structure of polytetrafluoroethylene (PTFE) has been studied in the range of ?100 to +450°C by thermomechanical spectrometry. Revealed in this temperature range is a fourblock topological structure composed of one amorphous (T _g = 16°C) and three crystalline (low-melting (T _m = 315°C), intermediate (T _m ¹ = 355°C), and high-melting (T _m ² = 388°C)) polymorphs. At a dose of 1 kGy, the long-range orientation of chains in the intermediate and high-melting crystalline blocks of PTFE is replaced by short-range orientation of the cluster association structure. At doses of 100?C500 kGy, the latter structure transitions to the amorphous state and the irradiated samples acquire a semicrystalline structure of the two-block type. The molecular-mass distribution function of interjunction chains of the pseudo-network of the amorphous block is bimodal in character and its maxima are noticeable shifted toward lower masses with an increase in the radiation dose. As the dose increases, the crystallinity decreases and the molecular mobility of amorphized chains is enhanced. As a result, both the glass transition and the molecular flow onset temperatures of the polymer are reduced.     

Phase diagram of a tetrapropylammonium bromide-water system according to DTA data

The phase diagram of a tetrapropylammonium bromide-water binary system is studied by means of differential thermal analysis. Three tetrapropylammonium bromide hydrates are identified that include one stable compound of 1: 4 composition (bromide: water; mp, ?32.6°C) and two metastable hydrates of 1: 6 (mp, ?70.4°C) and 1: 24 compositions (mp, ?57.0°C).     

Improvement of Highly Thermostable Xylanases Production by Talaromyces thermophilus for the Agro-industrials Residue Hydrolysis

A newly isolated thermophilic fungal strain from Tunisian soil samples was identified as Talaromyces thermophilus and was selected for its ability to produce extracellular hemicellulases when grown on various lignocellulosic substrates. Following the optimization of carbon source, nitrogen source, and initial pH of the growth medium in submerged liquid cultures, yields as high as 10.00?±?0.15 and 0.21?±?0.02 U/ml were obtained for xylanase and β-xylosidase, respectively. In fact, wheat bran was found to be a good inducer of hemicellulase enzymes, mainly β-xylosidase. The optimal temperature and pH of the xylanase activity were 75°C and 8.0, respectively. This enzyme exhibited a remarkable stability and retained 100% of its original activity at 50°C for 7 days at pH?7.0–8.0. The half-lives of the enzyme were 4 h at 80°C, 2 h at 90°C, and 1 h at 100°C. T. thermophilus could therefore be considered as a satisfactory and promising producer of thermostable xylanases. Crude enzyme of T. thermophilus rich in xylanase and β-xylosidase was established for the hydrolysis of lignocellulosic materials as wheat bran.     

Analysis of dual melting behavior in cold-crystallized poly(ether diphenyl ether metaketone)

By focusing on cold-crystallized poly(ether diphenyl ether metaketone) (PEKm), a more in-depth understanding of the nature of the crystalline morphology has been gained, which may lead to thorough mechanisms for interpreting the observed thermal behavior in PEKm. Apparently, cold-crystallized PEKm containing initially only a single P1 crystal can exhibit dual melting peaks (300 and 320 °C), with the second high-melting peak corresponding to the P2 crystal that was subsequently formed via P1 melting/repacking during the scan. However, dual morphism (preexisting P1 and P2 crystals) could be intentionally introduced into PEKm if it was cold-crystallized at temperature schemes of decreasing order. The P1 and P2 crystals possess the same unit cells (orthorhombic) and thus they differ only in the lamellae populations. The dual lamellar morphism in this PEKm sample also exhibited similar dual melting peaks during scanning, which correspond to melting of the individual P1 and P2 in a sequential order. This study has thus provided important clues in and shed new light on the interpretation of multiple melting with respect to polymorphism in polymers. Relationships between the low-melting and high-melting lamellae in cold-crystallized polyketone polymer have been thoroughly explored. Received: 9 January 2001/Accepted: 3 February 2001     

New data on phase diagram and clathrate formation in the system water–isopropyl alcohol

The phase diagram of the binary system isopropyl alcohol–water was investigated by means of differential thermal analysis and powder X-ray diffraction. Two incongruently melting polyhydrates with the compositions close to the molar ratio of isopropanol to water 1:5 were found. The melting point of one of the polyhydrates is ?49.6 °C, the melting point of the second one is within the range ?38.8 to ?30.6 °C. Assumptions concerning the structure of each compound were made on the basis of powder X-ray diffraction data.     

Chemical,thermal and rheological properties and stability of sapucaia (<Emphasis Type="Italic">Lecythis pisonis</Emphasis>) nut oils

Sapucaia (Lecythis pisonis) is a tree that grows in Colombia, Venezuela and the Guyanas and is widely distributed in Brazil. This work presents a study of sapucaia nut oils (SO) that were obtained by Bligh and Dyer (LP1) and Soxhlet (LP2) methods and were evaluated for their fatty acid composition, rheological and thermal properties, total phenolic compounds (TPC), antioxidant properties and oxidative stability using Rancimat and ATR-FTIR spectroscopy. The analyses showed that the method of extraction impacts the fatty acid profiles of SO. Oil extracts present considerable TPC content and antioxidant properties. Thermal analysis revealed three degradation steps for SO in the air atmosphere, starting at around 130 °C, being thermally stable up to 300 °C (with a ~ 5% mass loss) and reaching total degradation near 620 °C. Thermal analysis under N₂ produced two degradation steps, initiating at around 130 °C and finishing at 500 °C. Rancimat also confirmed the high thermal stability of SO, with induction periods of 13.28 h (LP1) and 7.18 h (LP2). The DSC parameters of SO were similar among each other. Crystallization (? 8.04 to ? 73.93 °C) and melting (? 31.34 to 8.28 °C) phases occurred over a large temperature range. SO presented FTIR spectral features with characteristic bands for vegetable oils. Ostwald–de Waele and Herschel–Bulkley rheological models indicated major pseudoplastic behavior for SO, with a predominant viscous component. These results reinforce that SO are appropriate for human consumption and open up new possibilities for their industrial exploitation, such as for food and the cosmetic, pharmaceutical and biodiesel industries.     

Potential Biodegradable Implants from ϵ-Caprolactone and D,L-Lactide Copolymers: Synthesis,Properties, and In Vivo Degradation

Random copolymers of ?-caprolactone (CL) and D, L-lactide (DLLA) were synthesized by ring-opening polymerization using stannous octoate as catalyst. The effect of polymerization conditions, such as feeding dose, reaction temperature, polymerization time, and catalyst content on the properties of the copolymers was evaluated to prepare suitable copolymers with controlled properties for biodegradable implant applications. The results showed that the polymerization conditions influenced the thermal and mechanical properties of the copolymers strongly and controllable and tunable properties of random copolymers could be obtained by adjusting the copolymer compositions. The optimum reaction conditions to prepare the CL-DLLA copolymers for implant applications are 30–87 mol.% DLLA content in feeding dose, 110°C reaction temperature, and 24 h polymerization time. The results of in vivo implantation revealed the excellent degradability of CL-DLLA copolymers. Copolymers of CL and DLLA with different compositions and properties would be suitable for the application of biodegradable implants.     

TG–DSC–FTIR–MS study of gaseous compounds evolved during thermal decomposition of styrene-butadiene rubber

The thermal decomposition behavior of styrene-butadiene rubber was studied using a system equipped with thermogravimetric analysis, differential thermal analysis, Fourier transform infrared spectroscopy, and mass spectroscopy. Two different experiments were conducted. From these experiments, thermogravimetric analysis results indicated a mass loss of 58 % in the temperature range of ~290–480 °C and a mass loss of 39 % in the temperature range beyond 600 °C. Scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy confirmed the presence of oxides, even at 1,000 °C, accounting for the Zn, Mg, Al, Si, and Ca in the original sample.     

Heating effect on the DSC melting curve of flaxseed oil

Flaxseed oil is rich in the alpha-linolenic acid. The effect of heating on the thermal properties of flaxseed oil extracted from flax seeds has been investigated. The flaxseed oils were heated at a certain temperature (75, 105, and 135 °C, respectively) for 48 h. The melting curve (from ?75 to 100 °C) of flaxseed oil was determined by differential scanning calorimetry (DSC) at intervals of 4 h. Three DSC parameters of exothermic event and endothermic event, namely, peak temperature (T _peak), enthalpy, and temperature range were determined. The initial flaxseed oil exhibited an exothermic peak, two endothermic peaks, and two endothermic shoulders between ?68 and ?5 °C in the melting profile. Heating temperature had a significant influence on the oxidative deterioration of flaxseed oil. The melting curve and parameters of flaxseed oil were almost not changed when flaxseed oil was heated at 75 °C. However, the endothermic peaks of melting curve decreased dramatically with the increasing of heating time when heating temperature was above 105 °C. There is almost no change of melting heat flow of flaxseed oil when heating time exceeded 32 h at 135 °C. The preliminary results suggest that the DSC melting profile can be used as a fast and direct way to assess the deterioration degree of flaxseed oil.     

The differences in thermal profiles between normal and leukemic cells exposed to anticancer drug evaluated by differential scanning calorimetry

Chronic lymphocytic leukemia (CLL) is a heterogenous disease with an imbalance between apoptosis and cell proliferation. Therefore, the main goal in CLL therapy is to induce apoptosis and effectively support this process in transformed B lymphocytes. In the current study, we have compared differential scanning calorimetry (DSC) profiles of nuclei isolated from CLL cells and normal mononuclear cells exposed to cladribine or fludarabine combined with mafosfamide (CM; FM), and additionally to CM combined with monoclonal antibody—rituximab (RCM) for 48 h, as well as in culture medium only (controls). Under current study, the mononuclear cells from peripheral blood (PBMCs) of healthy individuals have been included. The obtained results have shown the presence of thermal transition at 95 ± 5 °C in most of nuclear preparations (92.2 %) isolated from blood of CLL patients. This thermal characteristic parameter was changed after drug exposure, however, to a different extent. These thermal changes were accompanied by the decrease of cell viability, an elevation of apoptosis rate and the changes in expression/proteolysis of poly(ADP-ribose)polymerase-1—main marker of apoptosis. Importantly, in DSC profiles of nuclear preparations of PBMCs from blood of healthy donors exposed to investigated drug combinations and control CLL cells, the lack of such changes was observed. Our results confirmed that DSC technique complemented with other biological approaches could be helpful in tailoring therapy for CLL patients.     

Association of polyacrylonitrile prepared by low-temperature,solution polymerization with an organometallic catalyst

The weight-average molecular weights of polymers of acrylonitrile prepared by a free-radical initiator and an organometallic catalyst have been determined by lightscattering measurements in N,N-dimethylformamide, dimethyl sulfoxide, and dimethylacetamide at 25°C. and in dimethyl sulfoxide at 140°C. The apparent molecular weights of the polymers prepared with the NaAlEt₃S(i-Pr) catalyst in DMF at ?78°C. (referred to as high-melting polymers) changed from 54,800, 82,700, and 480,000 when measured in DMF at 25°C. to 36,000, 41,600, and 225,000 when measured in DMSO at 140°C., whereas the molecular weights of the free-radical polymers remained unchanged. Furthermore, from results obtained in DMSO at 140°C., The intrinsic viscosity–molecular-weight relationships were found to be identical for the high-melting and the free-radical polymer and in substantial agreement with an equation reported by Cleland and Stockmayer. The apparent decrease in molecular weight of the high-melting polymer from 25 to 140°C. indicates rather clearly that the high-melting polymers are associated in DMF at 25°C. The “aggregates,” even though present only at low concentrations, raised the weight-average molecular weight markedly but affected the number-average molecular weight only slightly, thus giving a high M?_w/M?_n ratio. It appears likely that when temperature and solvent are such that association does not occur, linear PAN's will have approximately the same intrinsic viscosity–molecular weight relationship (subject of course to slight change by polydispersity). The often reported abnormal molecular weight of samples prepared by solution polymerization especially at low temperatures, may be attributed to branching, or to an association, as reported here. The nature of association of PAN in dilute solution is also discussed.     

Coefficient of thermal expansion evolution for cryogenic preconditioned hybrid carbon fiber/glass fiber-reinforced polymeric composite materials

Polymeric matrix composites are susceptible to degradation and material properties changes if subjected to low-temperature environmental conditions. This paper attempts to present a study on effective coefficient of thermal expansion for various hybrid carbon fibers/glass fibers polymeric composite structures previously subjected to low-temperature environmental conditioning. The hybrid composite architectures were made from various layers of glass mat and/or glass woven embedded along with layers of unidirectional carbon fibers into a polymeric matrix. The samples were preconditioned to a low-temperature environment at a constant temperature of ?35 °C for 1-week long, 24 h/day. The instantaneous CTE and thermal strain fields were recorded with a DIL 402 PC/1 dilatometer from Netzsch GmbH (Germany) by setting a monotonically linear rise of temperature from 20 to 250 °C, at a rate of 1 °C min^?1. The experimentally retrieved data were compared with the values obtained by running a micromechanical-based approach simulation on a representative volume element.     

Effect of water release on thermal properties of polyaniline

Conducting polyaniline (PANI) was studied by thermal expansion measurement, thermogravimetric analysis and by electrical conductivity measurement. Relative elongation and coefficient of thermal expansion (CTE) were determined from room temperature to 60 °C. Various temperature profiles were used. During heating, the treatment of samples at a constant temperature higher than the room temperature, or evacuation, water was released from the samples. Water release was detected by mass and thermogravimetric analysis. Water release was connected with shrinkage of the PANI samples and apparent negative CTE in the first thermal cycle. In the following thermal cycles, it increased and reached a positive value. CTE of PANI attained values in the range of ?30 × 10^?6 K^?1 up to 20 × 10^?6 K^?1 in dependence on water content in the sample before measurement and on experimental conditions of measurement. Irreversible shrinkage of the polymer was the largest in the first thermal cycle. Water release exhibited a strong time and temperature dependence, and it was only partially reversible. The electrical conductivity was measured by a four-point van der Pauw method. Relative electrical conductivity decreased with amounts of water release. Relative decrease of electrical conductivity reached as far as 20% after evacuation 7 h at the room temperature.     

Effect of pyrolysis conditions on the properties of carbonaceous nanofibers obtained from freeze-dried cellulose nanofibers

Carbonaceous nanofibers (CsNFs) were produced by pyrolysis of cellulose nanofibers synthesised from wood pulp using a top-down approach. The effects of heat treatment conditions on the thermal, morphological, crystal and chemical properties of the CsNFs were investigated using TGA, SEM, XRD and FT-IR, respectively. The results showed that heat treatment conditions around the thermal decomposition temperature of cellulose greatly influence the morphology of resulting materials. Slow heating rates (1 °C/min) between 240 and 400 °C as well as prolonged isothermal heat treatment (17 h) at 240 °C were necessary to avoid destruction of the original fibrous morphology in carbonized nanofibers. On the other hand, such heat treatment had little effect on micron sized fibers. The optimized heat treatment conditions led to the release of oxygen and hydrogen from cellulose before thermal breakdown of glycosidic rings, which in turn prevented depolymerization and tar formation, resulting in the preservation of the fibrous morphology.     

Polysulfone–polydimethylsiloxane block copolymers

Alternating block copolymers have been synthesized from dihydroxyl-terminated polysulfone and bis(dimethylamine)-terminated polydimethylsiloxane oligomers. The products are soluble, amorphous, and transparent, and display excellent thermal and hydrolytic stability. Elastomeric and rigid compositions can be prepared by varying oligomer molecular weight. Copolymers made with oligomers of ≥ 5000 molecular weight are two-microphase systems which display glass transition temperatures at ?120°C and at +160°C, and therefore have a wide useful temperature range.