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  • 1
    Electronic Resource
    Electronic Resource
    FLOW CURVES, STRESS RELAXATION AND CREEP MEASUREMENTS OF STARCH GELS (2001)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of texture studies 32 (2001), S. 0 
    Details
    ISSN: 1745-4603
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Flow curves, stress relaxation, and creep compliance were measured for various types of corn starch gel that underwent different degrees of modification. The four starches were native corn starch, medium hydroxypropylated distarch phosphate, highly hydroxypropylated distarch phosphate, and distarch phosphate. All the starches exhibited pseudo-yield stress behavior at low shear rates and shear-thinning at higher shear rates. Stress relaxation data at different strains indicated strain-softening phenomenon for all starches. Higher degrees of cross-linking decreased the half relaxation time due to the addition of rigid filler into the matrix. Increasing the concentration increased the relaxation modulus for all starches. Creep compliance and recovery measurements were conducted over the range of 3.2 Pa-320 Pa. In the linear viscoelastic region, the compliance data were not dependent on the magnitude of stress applied. As concentration increases, higher stress magnitude leads to nonlinear behavior. The creep compliance data were fitted into the Ninomiya and Ferry relation from dynamic viscoelastic data and the Maxwell-Voigt model. Ninomiya and Ferry overpredicted the relaxation data while the Maxwell-Voigt model fitted the data reasonably well.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1745-4603.2001.tb01047.x
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  • 2
    Electronic Resource
    Electronic Resource
    DEVELOPMENT OF DYNAMIC MODULUS AND CELL OPENING OF DOUGH DURING BAKING (2005)
    Oxford, UK and Malden, USA : Blackwell Science Inc
    Journal of texture studies 36 (2005), S. 0 
    Details
    ISSN: 1745-4603
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: The dynamic shear modulus (elastic and viscous modulus) development of dough during baking was studied. Flooded parallel plate geometry was used to monitor the rheological changes of commercially available canned doughs (bread dough, bun dough and biscuit dough). The normal force exerted on the upper plate by the expanding dough was measured to study the cell-opening event. The dough-baking process was simulated in a rheometer oven. The morphology of baked dough was studied using a scanning electron microscope to elucidate the effect of ingredients and process parameters on the properties of the final baked product. Three stages of modulus development were observed during the baking process: bubble growth and packing, rapid expansion/starch gelatinization and final curing. The cell opening coincided with the sudden rise in modulus caused by starch gelatinization. The rate at which starch gelatinization takes place controls the temperature of the cell opening. The type and concentration of various ingredients have a greater effect on the modulus and on the cell opening than the heating rates. Frequency dependence was observed during baking, but the effect on modulus development diminished at higher frequencies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1745-4603.2005.00003.x
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Synthesis and characterization of anhydride-functional polycaprolactone (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 35 (1997), S. 1139-1148 
    Details
    ISSN: 0887-624X
    Keywords: polycaprolactone ; chemical grafting ; anhydride-functional polymer ; FTIR ; 1H-NMR ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Polycaprolactone-graft-maleic anhydride (PCL-g-MA) copolymer was prepared by grafting maleic anhydride onto PCL in a batch mixer and in an extruder using dicumyl peroxide as the initiator. The graft content was determined with the volumetric method by converting the anhydride functions to acid groups and then titrating with ethanolic potassium hydroxide. The grafted polymer was extracted with xylene to remove any unreacted monomer before the estimation step. The effect of temperature and the various concentrations of the initiator and monomer used for the grafting reaction were investigated. The presence of residual initiator in the reaction product was checked using thin-layer chromatography. Molecular weight determination was carried out for the pure and grafted polymer using gel permeation chromatography to determine if chain scission was present. Results indicate that maleic anhydride is grafted onto PCL using free radical initiators. The grafting reaction was confirmed by FTIR and NMR techniques. FTIR spectra showed absorption bands around 1785 and 1858 cm-1. NMR spectra gave signals for methine proton at 3.47 ppm. For a given peroxide level, a higher temperature or residence (reaction) time gave higher percentage of grafted MA. There was an optimum temperature and initiator concentration after which the percentage of MA grafted on PCL decreased. The number-average molecular weight, tensile strength, and the percent elongation of PCL-g-MA were comparable to those of PCL before grafting. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1139-1148, 1997
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 4
    Electronic Resource
    Electronic Resource
    Properties of blends of starch and synthetic polymers containing anhydride groups (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 52 (1994), S. 617-628 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Corn starch was blended with styrene maleic anhydride copolymer (SMA), ethylene-propylene-g-maleic anhydride copolymer (EPMA), and corresponding nonfunctional polystyrene and ethylene propylene copolymers. The concentration of starch in the blend was varied between 50 and 80% by weight. The torque generated during blending is reported increasing starch content for starch/SMA blends: the reverse was true for starch/EPMA blends. The torque was higher for the blends of the anhydride functional polymers compared to the blends of corresponding nonfunctional polymers. Water absorption of the blends increased with an increase in the starch content. Starch/SMA blends made at higher mixer speed or time were more water sensitive. Blends containing EPMA absorbed less water than SMA blends containing the same weight fraction of starch. Tensile strengths of blends containing functional groups were superior compared to the blends made from nonfunctional polymers. When the starch contents increased from 60 to 70%, the tensile strength remained unchanged for SMA blend but increased for EPMA blend. All samples supported the growth of microorganisms, which increased with increasing starch content. © 1994 John Wiley & Sons, Inc.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070520505
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  • 5
    Electronic Resource
    Electronic Resource
    Properties of blends of starch and synthetic polymers containing anhydride groups. II. Effect of amylopectin to amylose ratio in starch (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 57 (1995), S. 539-554 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Corn starch with different amylopectin to amylose ratios was blended with styrene maleic anhydride copolymer (SMA) and ethylene-propylene-g-maleic anhydride copolymer (EPMA). The starch had an amylose content of approximately 0, 50, and 70%. The concentration of starch in the blend was kept constant at 60% by weight. The samples were melt blended in a corotating twin screw extruder. Scanning electron micrographs showed that the amount of starch granules remaining in the samples varied with the torque. Optical micrograph showed that starch/EPMA blends formed a cocontinuous phase in all blends irrespective of starch variety. For starch/SMA blends, the starch granules remained dispersed in the SMA phase. The torque during blending, tensile strength, water absorption, storage and loss modulus, and data on biodegradability of the blends are presented. Tensile strength and water absorption correlated well with the torque generated during blending: the higher the torque, the lower the tensile strength and the higher the water absorption. The tensile strength of blends containing SMA decreased when the humidity increased. Fractured surfaces of starch/SMA blends exhibited brittle failure; for the ductile starch/EPMA blends, shear tearing appeared to be the major failure mechanism. For blends containing EPMA, the percentage elongation increased with increased humidity. Dynamic mechanical analysis of the blends showed two sharp peaks for tan δ vs. temperature plot for starch/EPMA plots, but showed a single peak for starch/SMA blends. Starch/EPMA blends had a higher percentage of water aborption that became constant after 20 days. Using the ASTM test method D5902, the starch content in the samples was found to degrade. © 1995 John Wiley & Sons, Inc.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1995.070570504
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