Dynamic rheology of wheat flour dough. I. Non‐linear viscoelastic behaviour

Controlled stress rheometry was used to investigate the effects of starch and gluten fractions on the non‐linearity of wheat flour dough. Flour–water dough showed non‐linear viscoelastic behaviour over all stress values in a cyclic stress sweep. The amplitude‐dependent behaviour of the starch and amplitude‐independent nature of the gluten revealed that starch is responsible for the non‐linearity of the flour–water dough system. Adding starch to gluten caused a substantial narrowing of its linear viscoelastic range. © 2002 Society of Chemical Industry     

Dynamic rheological properties and bread‐making qualities of wheat gluten: effects of urea and dithiothreitol

Controlled stress rheometry differentiated glutens from the cultivars under study into ‘extra‐strong’, strong and weak on the basis of their elastic and viscous moduli measured in the linear domain. The mechanical spectra of different glutens revealed no qualitative differences, but exhibited large quantitative differences in the magnitude of the dynamic measurements, ie elastic modulus, G′, viscous modulus, G″, and loss tangent, tanδ. Both covalent and non‐covalent interactions appeared to contribute to these differences. However, disulfide cross‐links proved to be especially important determinants of differences in the elastic characteristics of the glutens. The present study indicated that dynamic rheological parameters of glutens were related to their bread‐making performance, as evidenced by the significant correlations between the dynamic moduli of the glutens and loaf volume. Copyright © 2004 Society of Chemical Industry     

Physicochemical,Morphological, Thermal and Pasting Properties of Starches Isolated from Rice Cultivars Grown in India

Physicochemical, morphological, thermal, and pasting properties of starches, isolated from basmati (HBC-19 and Bas-370) and non-basmati (Jaya, a coarse cultivar; P-44 and HKR-120, the medium cultivars and Sharbati, fine cultivar) rice cultivars grown in India were studied. The amylose content of starches from different cultivars ranged from 2.25 (Jaya) to 22.21 g/100 g of starch (HBC-19). Jaya, HKR-120, and P-44 cultivars showed soft gel consistency as 84, 73, and 69 mm, respectively, whereas Sharbati, Bas-370 and HBC-19 cultivars showed medium gel consistency as 54, 53, and 58 mm, respectively. Swelling power (at 95°C) indicated a significant positive correlation with amylopectin content (r = 0.828, p < 0.05) and gel consistency (r = 0.983, p < 0.01). Turbidity had a highly significant positive correlation with solubility (r = 0.919, p < 0.01) and amylose content (r = 0.945, p < 0.01). Starch form Jaya cultivar showed the presence of smallest size granules (2.4–5.7 μm) with an average size of 3.96 μm, whereas Bas-370 showed the presence of largest size granules (3.3–6.7 μm) with an average size of 5.0 μm. The transition temperatures, enthalpy of gelatinization (ΔH_gel), peak height index (PHI) and gelatinization range were determined using differential scanning calorimetry (DSC). The starch from Sharbati cultivar showed highest onset temperature (T_o), peak temperature (T_p), conclusion temperature (T_c), enthalpy of gelatinization and peak height index (PHI) of 68.8°C, 73.2°C, 79.0°C, 11.56 J/g and 2.63 respectively. Pasting temperature of rice starches varied from 68.9°C (Jaya) to 74.5°C (Sharbati). The peak viscosities observed were in the range of 2223 to 3297 cP, lowest for HBC-19 starch and highest for Jaya starch.     

Tribological Investigation of AZ91/SiC Magnesium Hybrid Composite under Dry,Oil and Nanofluids Lubricating Conditions

Silicon - In present research AZ91D/SiC composites were developed using advanced vacuum assisted stir casting process. The tribological properties of AZ91D/SiC composites under dry, oil and...     

Synthesis and characterization of luminescent Eu(HMAP)3·2H2O and Tb(HMAP)3·2H2O complexes

The novel complexes Eu(HMAP)₃·2H₂O and Tb(HMAP)₃·2H₂O (where HMAP = 2′-hydroxy-4′-methoxyacetophenone) are synthesized and characterized by infra red spectroscopy, ¹H NMR spectroscopy, TGA/DTA, SEM and elemental analysis. The qualitative analysis of the complexes to detect the presence of rare earth (Eu, Tb), have been performed by energy dispersive analysis (EDX). The Eu(HMAP)₃·2H₂O on excitation at 354 nm emits bright red luminescence with main peak at 612 nm and Tb(HMAP)₃·2H₂O on excitation at 354 nm emits bright green luminescence with main peak at 547 nm. The luminescence intensity of Eu(HMAP)₃·2H₂O is higher than Tb(HMAP)₃·2H₂O. These complexes emitting red and green luminescence might be used to make the electroluminescent (EL) devices for display applications.     

Color tunable nanocrystalline SrGd2Al2O7:Tb3+ phosphor for solid state lighting

Color tunable Tb³⁺ doped SrGd₂Al₂O₇ nanophosphor is synthesized employing a facile and economic urea assisted solution combustion approach. XRD studies confirm the crystallization of single phased SrGd_2(1-x)Tb_2xAl₂O₇ nanophosphor in tetragonal lattice with I4/mmm (139) space group. Rietveld refinement is performed over SrGd_1.9Tb_0.1Al₂O₇ sample to execute qualitative as well as quantitative phase analysis. TEM analysis confirms the more or less spherical shaped phosphors in nano domain with average particle size ranging 45–80?nm. Photoluminescent investigation reveals that this nanophosphor can be successfully excited by ultraviolet light yielding significant luminescent properties arising due to radiative transitions from ⁵D_3,4 levels to ⁷F_j levels. Dipole-dipole interactions are solely responsible for the energy transfer causing concentration quenching. Concentration controlled luminescent tendency can be employed to induce chromaticity from blue to green region. Findings of the study proclaim the application of this nanophosphor as one of the green component of tricolor based ultraviolet excited white LEDs.     

Dynamic rheology of wheat flour dough. II. Assessment of dough strength and bread‐making quality

Controlled stress rheometry revealed that differences in wheat flour dough strengths could be observed by means of dynamic rheological measurements in the region of higher stress amplitude (ie >100 Pa). At lower stress amplitude (τ_o) the values of elastic modulus G′ for weak doughs were higher than those for strong doughs, but they decreased substantially beyond 100 Pa stress amplitude (τ_o), such that the G′ values for strong doughs crossed over the G′ values for weak doughs. Beyond a critical value of stress amplitude (ie 100 Pa), true differences in dough strengths could be seen on the basis of their elastic characteristics, because at large deformations protein–protein interactions played a more dominant role in the rheological behaviour of flour doughs. Dynamic rheological analysis demonstrated a very weak inverse relationship (R² = 0.16) between the G′ values of flour doughs and loaf volume data for 12 wheat cultivars of diverse bread‐making performance. However, the G′ values of glutens showed significant positive relationships with bread‐making performance, explaining 73% of the variation in loaf volume. © 2002 Society of Chemical Industry