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Rheological Tests (rheological + test)
Selected AbstractsPhotoinitiating polymerization to prepare biocompatible chitosan hydrogelsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2008Xiaohong Hu Abstract Chitosan hydrogels were prepared from water soluble chitosan derivatives (chitosan-MA-LA, CML) by photoinitiating polymerization under the existence of Irgacure2959 and the irradiation of UV light. The CML was obtained by amidation of the amine groups of chitosan with lactic acid and methacrylic acid. Gelation time of the hydrogel could be adjusted within a range of 5,50 min, and controlled by factors such as the degree of MA substitution, initiator concentration, existence of oxygen, and salt. The dry hydrogel adsorbed tens to hundred times of water, forming a highly hydrated gel. The swelling ratio was smaller at the higher degree of MA substitution, higher pH, and higher salt concentration. Rheological test showed that the hydrogel is elastomeric in the measuring frequency range, with a storage modulus and loss modulus of 0.8,7 kPa and 10,100 Pa, respectively. In vitro culture of chondrocytes demonstrated that the cells could normally proliferate in the extractant of the hydrogels, showing no cytotoxicity at lower initiator concentration. By contrast, the extractant of the hydrogel made by the redox initiating system, i.e., ammonium persulfate (APS) and N,N,N,,N,-tetramethylethylenediamine (TEMED), showed apparent cytotoxicity. Thus, the chitosan hydrogels initiated by the Irgacure2959 have better comprehensive properties, in particular better biocompatibility, and are more suitable for biomedical applications. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Processability and mechanical properties of commercial PVC plastisols containing low-environmental-impact plasticizersJOURNAL OF VINYL & ADDITIVE TECHNOLOGY, Issue 3 2009Paola Persico Preliminary results are presented concerning the use of less-toxic plasticizers such as dioctyl adipate (DOA) and acetyl tributyl citrate (ATBC) in plastisol formulations for rotational molding technology. The DOA and ATBC plasticizers have been studied by comparing the effects of their content, molecular architecture, and polarity on the rheological behavior of liquid plastic systems and on the mechanical properties of the ultimate products prepared with PVCs having different particle sizes and molecular-weight distributions. Rheological tests have confirmed the differences in solvent power of the diethylhexyl phthalate (DOP), DOA, and ATBC plasticizers. The glass transition temperatures measured on rotomolded samples have shown that the use of ATBC leads to a more nearly rigid system as a consequence of the branched structure and polarity of this plasticizer when compared with DOA. Mechanical tests carried out on final products after natural and forced environmental aging revealed a slight decrease in their performance. J. VINYL ADDIT. TECHNOL., 2009. © 2009 Society of Plastics Engineers [source] Influence of co-monomer structure on properties of co-polyamide packaging filmsPACKAGING TECHNOLOGY AND SCIENCE, Issue 1 2002P. Scarfato Abstract In this work a series of co-polyamides were prepared by random polymerization of ,-caprolactam in presence of four different co-monomers at a percentage of 5% w/w, with the aim of verifying their suitability as film-forming materials. The effects of structural changes induced in the ,-caprolactam homopolymer by co-monomers were evaluated in both molten and solid states. Rheological tests in shear and elongational flow were performed to evaluate the processability of co-polyamides. Cast films were obtained and their thermal, mechanical and transport properties were evaluated to establish the performances of the co-polyamides in view of packaging applications. The results indicate that co-polyamide films having a partially aromatic structure display the best mechanical performances and show a significant improvement in barrier properties to gases compared to the homopolymer. Copyright © 2002 John Wiley & Sons, Ltd. [source] Porcine Plasma Proteins as a Surimi Protease Inhibitor: Effects on Actomyosin GelationJOURNAL OF FOOD SCIENCE, Issue 4 2000W. Visessanguan ABSTRACT Effect of porcine plasma proteins (PPP) on thermal gelation of actomyosin in the presence and absence of fish proteinase was studied using a dynamic rheological test. Substantial decreases in development rate and magnitude of gel modulus were observed by the addition of proteinase to actomyosin gels. PPP was effective in protecting a myosin-heavy chain from proteolytic degradation, however, PPP itself interfered with the formation of actomyosin gel. Lower gel modulus was observed with actomyosin gels developed with higher concentrations of PPP added. Overall, PPP reversed the loss of gel modulus by the proteinase, however, the recovered gel modulus was only as high as those containing PPP only. These results implicated that, although PPP may revert autolytic activity in surimi, it interfaces with actomyosin gelation. [source] Synthesis of new superhydrophobic nanosilica and investigation of their performance in reinforcement of polysiloxanePOLYMER COMPOSITES, Issue 9 2010XianLi Fang We reported a new facile method to synthesize superhydrophobic nanosilica using glycidoxypropyltrimethoxysilane and dodecylamine as treatment agents. Also, we systemically investigate their performance in reinforcement of poly(dimethylsiloxane) (PDMS) rubber. Fourier transform infrared spectrum, contact angle (CA) and thermogravimetric analysis (TGA) measurements were used to characterize the modified nanosilica. Results show that the inherent hydrophilicity of parent nanosilica surface can be greatly altered through this modification method. The CA of as-prepared superhydrophobic nanosilica can reach 160.2°. The properties of as-prepared modified nanosilica-filled PDMS composites were systemically investigated by dynamic rheological test, scanning electron microscopy, TGA, dynamic mechanical analysis. These as-prepared superhydrophobic nanosilica exhibit uniform dispersion in the PDMS matrix, and their composites also show good mechanical properties and distinct advantage on thermal stability compared with those of the pure silica-filled PDMS composites. Also described is the probable mechanism for the reinforcement of as-prepared superhydrophobic nanosilica-filled PDMS. POLYM. COMPOS., 31:1628,1636, 2010. © 2009 Society of Plastics Engineers [source] A very promising new glucolipidic surfactant: LipowheatTMINTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 6 2005A. Djedour Synopsis LipowheatTM is an entirely biodegradable 100% natural active ingredient, extracted from non-transgenic wheat. Thanks to its very interesting properties, it can integrate the composition of most cosmetic and pharmaceutical products. The aim of this work was first to realize a large range of stable simple or multiple emulsions, in order to determine and evaluate the ability of a new glucolipidic surfactant LipowheatTM to form and stabilize emulsions. The rheological properties of these emulsions were tested during a 30-day storage period at three different storage conditions (cold, room temperature and at 40°C). In addition to dynamic and static rheological tests, droplet size distribution of the cream was also determined. Furthermore, a stable simple emulsion was selected to realize percutaneous absorption and evaluate the properties of LipowheatTM. Résumé Ce travail a pour objectif de mettre à jour et d'évaluer les propriètés émulsionnantes d'un nouveau tensioactif de nature glucolipidique, connu jusqu'alors pour ses propriétés actives en cosmétologie: le LipowheatTM. Cette étude comporte plusieurs parties distinctes: 1) Formulation d'émulsions simples L/H et/ou H/L et multiples H/L/H stabilisèes par du LipowheatTM, avec des huiles variant par leur origine (naturelle ou synthétique) ainsi que par leur polarité. 2) Caractérisation rhéologique, granulométrique, et conductimétrique de ces émulsions après les avoir soumises pendant 30 jours à des conditions de vieillissement accéléré (conservation à température ambiante, à +4°C et +40°C) et ce, afin d'en retenir les plus stables pour la suite de l'étude. 3) Enfin, dans une dernière phase, les propriètés de ces crèmes dans le domaine de la libération dermopharmaceutique seront évaluées lors d'études in vitro. [source] Rheological, textural and melting properties of commercial samples of some of the different types of pasteurized processed cheeseINTERNATIONAL JOURNAL OF DAIRY TECHNOLOGY, Issue 2 2007YANJIE LU The detailed rheological and textural properties of commercially available samples of the three major categories of pasteurized processed cheese in the USA, that is, pasteurized process American cheese (PPA), pasteurized process cheese product (PPP) and pasteurized process cheese food (PPF), were analysed. All samples had similar pH values, ranging from 5.65 to 5.87, but most were ,5.7. Even within each of the categories considerable differences were observed in textural and melting behaviour. The samples with the lowest melt and the lowest loss tangent parameter from the rheological tests were two PPF and one PPA samples. These two PPF samples also had the highest hardness and adhesiveness force. Significant correlations were observed between several textural, rheological and melting properties. [source] Statistical evaluation of different technological and rheological tests of Polish wheat varieties for bread volume predictionINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 1 2004Iwona Konopka Summary Forty-two Polish wheat flour were used to establish correlation coefficients between protein content, Zeleny test, falling number value, amylograph viscosity, farinograph water absorption, bread volume and rheological properties of dough, as shown by use of a extrusion chamber and alveograph. The equations expressing the changes of bread volume and flour water absorption as a function of significantly correlated parameters were calculated. The correlations and their significance depended on wheat quality and the alveographic parameters were significantly correlated with the dough extrusion parameters. The dough extrusion parameters were significantly correlated only with the water absorption of soft wheats. The dough rheological tests were correlated to a greater extent with the values of the Zeleny test than to the protein content. The prediction of the bread volume as a function of flour quality parameters and dough rheological properties was best done by grouping wheat varieties into specific qualitative classes. [source] Compatibilization and development of layered silicate nanocomposites based of unsatured polyester resin and customized intercalation agentJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010Luigi Torre Abstract In this study a procedure for the preparation of compatibilized nanoclays was used to produce effective nanocomposites based on unsatured polyester (UP) resin. A compatibilization procedure of the filler with a selected surfactant has been developed and optimized, the effect of organic modifiers on the synthesized nanocomposites properties was studied. Moreover, polyester/clay nanocomposites were prepared. In particular, samples were prepared using two different mixing methods. The properties and formation processes of the nanocomposites obtained using the two methods were compared. X-ray diffraction studies revealed the formation of intercalated/exfoliated nanocomposites structures. The effect of processing parameters, used for both the compatibilization procedure and the preparation of nanocomposites, was studied. Dynamic mechanical, thermal analysis, and rheological tests were performed to investigate the formation mechanism of UP/montmorillonite nanocomposite. In particular, mechanical properties of nanocomposites were studied using dynamic mechanical analysis and tensile tests. Mechanical, rheological, and thermal characterization have confirmed the validity of the used approach to compatibilize the nanoclay and to produce nanocomposites. Tensile strength and Young's modulus were modified by the loading of the organoclays. Furthermore, the rheology of the nanocomposite formulation provided processing information, while mechanical and dynamic mechanical characterization was performed on the nanocomposites produced with the newly compatibilized formulation. The results have shown that nanocomposites with better mechanical properties can be obtained through the selection of an appropriate compatibilization process. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] EFFECT OF COMPOSITION OF GLUTHNIN SUBFRACTIONS ON RHEOLOGICAL PROPERTIES OF WHEATJOURNAL OF FOOD BIOCHEMISTRY, Issue 4 2000S. JOOD ABSTRACT Gluten extracted from defatted flours of cv. Aubaine (extra-strong), Hereward (strong) and Riband (weak) was separated into five different fractions (R2 to R6) by sequential centrifugation and addition of sodium chloride. A seven-minute mixing time was used to carry out fractionation on the basis of depolymerization of glutenin macropolymers (GMP). Depolymerization of GMP occurred at much higher rates in dough of the weak cultivar compared to the strong and extra-strong cultivars. Polypeptide compositions of different ghttenin fractions were determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis under reduced and non-reduced conditions, followed by densitometric scanning of stained patterns. The amount of HMW-glutenin subunits decreased and LMW-glutenin subunits increased correspondingly in each cultivar with the fractionation from R2 to R6. The rheological behavior of the fractions was analyzed by small deformation rheological tests (strain sweep and frequency tests). The high molecular weight fraction (R2) from extra-strong wheat had a higher vahte of G' and a lower tan , value as compared to strong and weak bread-making wheats. The moduli of HMW glutenin fractions (R2 and R3) were frequency independent and promoted the network properties, whereas moduli of LMW glutenin fractions were frequency dependent and gave rise to a plasticizing effect. Therefore, it was concluded from the present studies that HMW-glutenin subunits are not the only factors governing good bread-making quality but their proportions in relation to low molecular weight glutenin subunits is equally important in sinking a balance between viscous and elastic properties essential for bread making performance. [source] RHEOLOGICAL PROPERTIES OF MOZZARELLA CHEESE DETERMINED BY CREEP/RECOVERY TESTS: EFFECT OF SAMPLING DIRECTION, TEST TEMPERATURE AND RIPENING TIMEJOURNAL OF TEXTURE STUDIES, Issue 3 2009MARÍA LAURA OLIVARES ABSTRACT The viscoelastic properties of mozzarella cheese using a creep/recovery test considering different sampling directions (parallel and perpendicular to protein fiber orientation), test temperatures (20, 30 and 40C) and ripening times (1, 8, 15, 29 and 36 days) were studied. Creep data were interpreted by a Burger model of four parameters. A semiempirical approach was proposed to obtain the contribution of each main compliance to the total deformation of the system. Creep tests at different temperatures allowed gaining a better understanding of changes that occur in the cheese matrix during heating and ripening. Sampling direction did not affect any of the parameters studied. Finally, it was clearly observed that cheese matrix behaves as a quite different physicochemical system depending on temperature. Therefore, it is recommended to carry out the rheological tests at different temperatures to evaluate appropriately the viscoelastic properties of mozzarella cheese. PRACTICAL APPLICATIONS Mozzarella cheese must have certain characteristics to be used on pizzas and on other prepared foods that use the cheese in melted state. The protein chains in the mozzarella curds coalesce into large strands that are oriented in the direction of stretching. For this reason, mozzarella cheese has an anisotropic structure. Therefore, it is relevant to determine the effect of protein fiber orientation on the rheological properties. Valuable information may be obtained through the creep/recovery test of mozzarella cheese samples to study its rheological properties and to explain molecular mechanisms that occur during ripening or melting processes considering sampling direction. [source] RHEOLOGY AND TEXTURE OF SET YOGURT AS AFFECTED BY INULIN ADDITIONJOURNAL OF TEXTURE STUDIES, Issue 6 2008TATDAO PASEEPHOL ABSTRACT The effect of inulin addition on rheology and texture of nonfat yogurt (NFY) was studied by the large (texture analyzer) and small (dynamic oscillatory rheometry) deformation tests. Skim milks (12% solids) were supplemented with three commercial chicory inulins with different chain lengths at 4% level and inoculated with mixed cultures of Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus thermophilus. Textural and rheological tests were conducted after an overnight storage at 4C and during a shelf life of 28 days. A good correlation was observed between the two tests. During storage, all inulin-containing yogurts in comparison with the control NFY were characterized by lower values of firmness, apparent viscosity, yield stress, complex viscosity, storage modulus and loss modulus. NFYs supplemented with long-chain inulin demonstrated a rheological behavior closer to that of control full-fat yogurt. PRACTICAL APPLICATIONS The use of inulin and oligofructose in the food industry has grown recently because of their interesting nutritional and technological properties. In the work presented here, three commercial inulin products with different chemical composition and functions were added to yogurt milk, and changes in rheological properties of yogurt were investigated in comparison with nonsupplemented control yogurts. According to the manufacturer's specifications, Raftiline HP and Raftiline GR are suitable for fat replacement because of the presence of long-chain inulins, while Raftilose P95, being rich in mono- and disaccharides, is highly recommended for sugar replacement. The knowledge obtained from this study may be applied for the development of nonfat yogurts to satisfy the nutritional expectations of ever-increasing health conscious consumers and at the same time to match the sensory and textural characteristics of full-fat yogurt. [source] RHEOLOGICAL CHARACTERIZATION OF WET FOOD FOAMSJOURNAL OF TEXTURE STUDIES, Issue 2 2007B. EDGAR CHÁVEZ-MONTES ABSTRACT Incorporating air bubbles into foods is a technical challenge, and in all cases, the fabrication of a foam goes through a "wet foam" stage, where bubbles are diluted in the food matrix and require stabilization. Sometimes, the end product is itself a wet foam, and a popular example is ice cream. This article describes a study of structural aspects of wet foams, where the continuous phase is a fluid, by means of dynamic rheological tests. The effects of formulation and processing conditions on aerated food foams are studied, and an example is presented for ice cream mix. The incorporation of gas bubbles at volume fractions of 50% or less modifies moderately the bulk rheological properties, and their effect can be predicted by the foam limit case. The continuous phase dominates to a great part the bulk's rheological behavior, and in the case of food systems, it stems from the presence of polysaccharide thickeners. PRACTICAL APPLICATIONS This work presents an alternative approach to study the rheological properties of short life and difficult-to-sample products, such as wet food foams, in a rheo-reactor. Through the analysis of mechanical properties in oscillatory regime, the structure and stability of wet food foams can be characterized immediately after being fabricated in situ. This work presents new insights on the foaming step of ice cream mix (decoupled from the freezing step), and shows how the mechanical properties are affected by the incorporation ofbubbles, by process conditions and by the presence of thickeners and emulsifiers. This work can be a valuable guide to decide on optimal process and formulation to fabricate wet food foams (e.g., ice cream, aerated desserts) with specific mechanical properties and stability. [source] Quantification of monomeric and polymeric wheat proteins and the relationship of protein fractions to wheat quality,JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 10 2003Jerry Suchy Abstract Wheat protein composition is important for understanding the biochemical basis of wheat quality. The objective of this study was to design a simple protein fractionation protocol with low cross-contamination and to show that these protein fractions were associated with wheat quality. The protocol consists of three sequential extractions from 100 mg of flour with 7.5% propan-1-ol and 0.3 M sodium iodide (monomeric-rich protein), 50% propan-1-ol (soluble glutenin-rich protein) and 40% propan-1-ol and 0.2% dithiothreitol (insoluble glutenin-rich protein). Nitrogen content of protein solubility groups was determined from dry residues using an automated combustion nitrogen analyser. About 90% of the total protein in the flour was solubilised. Cross-contamination of protein fractions was evaluated by SDS-PAGE, SE-HPLC and RP-HPLC. Variation in nitrogen content of the protein solubility fractions was lowest for monomeric-rich protein (<2%) and insoluble glutenin-rich protein (<4%). Three wheats with similar high-molecular-weight (HMW) glutenin subunit composition, Alpha 16, Glenlea and Roblin, varied significantly (P , 0.05) in the proportion of monomeric-rich and insoluble glutenin-rich protein in the flour. Dough rheological properties were directly related to the proportion of insoluble glutenin-rich protein and inversely related to the proportion of monomeric-rich protein. The protocol was validated using an expanded set of 11 wheats which also showed that inter-cultivar differences in the proportion of monomeric-rich, insoluble glutenin-rich protein and glutenin-to-gliadin ratio in the flour governed dough rheological properties such as mixograph, farinograph and microextension tests. The protocol has merit for quality screening in wheat-breeding programmes when the sample size is too small or when time constraints limit the ability to perform traditional rheological tests. For the Department of Agriculture and Agri-Food, Government of Canada, Copyright © Minister of Public Works and Government Services Canada 2003. Published for SCI by John Wiley & Sons, Ltd. [source] Preparation and characterization of polypropylene/solid-state organomodified montmorillonite nanocompositesPOLYMER COMPOSITES, Issue 4 2008Sun Yu-hai A novel organomodified montmorillonite prepared by solid-state method and its nanocomposites with polypropylene were studied. The interaction between modifying agent and montmorillonite was investigated by X-ray diffraction (XRD) analysis, contact angle determination, and Fourier-transform infrared spectroscopy. The results showed that the modifying agent behaves as an effective intercalating agent, enlarging the interlayer spacing of montmorillonite and making montmorillonite more hydrophobic. Polypropylene/solid-state organomodified montmorillonite composites were prepared by melt-mixing method. The dispersion of the silicates was investigated by XRD analysis and transmission electron microscopy. It was found that the nanocomposites are formed with solid-state organomodified montmorillonite and polypropylene. The thermogravimetric analysis and differential scanning calorimetry results showed that the organoclay could enhance the thermal stability and decrease the relative crystallinity of polypropylene. Mechanical and rheological tests indicated that the organoclay improves the mechanical properties but has no obvious effect on rheological properties of polypropylene. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers [source] | |||||||||||||