Abdellatif A. Mohamed

Effect of okra gum on the pasting, thermal, and viscous properties of rice and sorghum starches.

The effect of okra gum (OE) on the physical properties of rice and sorghum starches was investigated using rapid visco-analyzer (RVA), Brookfield viscometer, differential scanning Calorimetry (DSC), and light microscopy. Starch was replaced with 5, 10, 15% OE weight basis (g/100 g). In the presence of OE, the peak and final viscosity as well as the setback of both starches were reduced. However, the difference between the theoretical and the measured setback was more than just can be attributed to the omitted starch. The DSC data of the blends showed higher peak temperature compared to the control, indicating slower starch gelatinization in the presence of OE. Brookfield profiles demonstrated increase in shear stress at higher shear rate confirming pseudoplasticity of the system (n<1). Over all, it can be assumed that OE has influenced the properties of the starches, particularly, by decreasing viscosity, setback, and pseudoplasticity of the starch gels.

Elimination of interference from water in KBr disk FT-IR spectra of solid biomaterials by chemometrics solved with kinetic modeling

Infrared analysis of proteins and polysaccharides by the well known KBr disk technique is notoriously frustrated and defeated by absorbed water interference in the important amide and hydroxyl regions of spectra. This interference has too often been overlooked or ignored even when the resulting distortion is critical or even fatal, as in quantitative analyses of protein secondary structure, because the water has been impossible to measure or eliminate. Therefore, a new chemometric method was devised that corrects spectra of materials in KBr disks by mathematically eliminating the water interference. A new concept termed the Beer-Lambert law absorbance ratio (R-matrix) model was augmented with water concentration ratios computed via an exponential decay kinetic model of the water absorption process in KBr, which rendered the otherwise indeterminate system of linear equations determinate and thus possible to solve in a formal analytic manner. Consequently, the heretofore baffling KBr water elimination problem is now solved once and for all. Using the new formal solution, efforts to eliminate water interference from KBr disks in research will be defeated no longer. Resulting spectra of protein were much more accurate than attenuated total reflection (ATR) spectra corrected using the well-accepted Advanced ATR Correction Algorithm.

Black cumin-fortified flat bread: formulation, processing, and quality

Black cumin (BC) (Nigella sativa) defatted meal was added at 5, 10, and 15% to whole wheat flour (WWF) in flat bread formulation so that to deliver daily intake of zinc, potassium, phosphorous, iron, and copper as well as high protein content. BC is known for its anticancer activities, immune stimulation, anti-inflammation, anti-hypertensive, anti-microbial, anti-parasitic, antioxidant and hypoglycemic. Although the water holding capacity of BC was twice as much as WWF, BC has minimal effect on the water absorption of WWF. The farinograph mixing tolerance index of the WWF dough has increased up to 133%, whereas dough stability has decreased by 41%. The extensibility of the control dough was not significantly (P?0.05) affected by BC, but the resistance to extension was reduced. The higher amylograph gelatinisation temperature indicates delay on starch granule swelling, but the peak viscosity dropped as a function of BC content, while the final viscosity was unchanged. By consuming one piece of this bread, ...

Identification and Measurement of Intermolecular Interaction in Polyester/Polystyrene Blends by FTIR-Photoacoustic Spectrometry

Fourier transform infrared photoacoustic spectrometry was used to reveal and identify n–π type intermolecular interaction formed in plastic comprising binary blends of polystyrene and a biodegradable polymer, either polylactic acid, polycaprolactone or poly(tetramethyleneadipate-co-terephthalate). This was the first reported direct and definitive experimental evidence of n–π type bond formation in thermoplastic blends of these polyesters with polystyrene. Also, an infrared method was devised that permits quantitative measurement of the degree of interaction between the two polymers at various concentrations in the blends. The method employs spectral deconvolution by least squares curve fitting of the polymer carbonyl band into its underlying peaks. In a new algorithm the method compares deconvoluted Gaussian/Lorentzian peaks of the polymer blends with deconvoluted peaks in the neat polymers and computes both the magnitude and direction of change in the n–π bond formation with change in polymer concentration. The results indicated that the degree of interaction was dependent on the type and concentration of the biodegradable polymer in the blend. These findings are supported by differential scanning calorimetry and thermogravimetric analyses. Unlike conventional spectral deconvolution methods, this technique with its new algorithm approximates infrared absorptivities of all the underlying peaks, and is thus a superior method that should be applicable to multicomponent polymer blends in general.

Gelatinisation kinetics of corn and chickpea starches using DSC, RVA and dynamic rheometry

The gelatinisation kinetics (non-isothermal) of corn and chickpea starches at different heating rates were calculated using differential scanning calorimetry (DSC), rapid visco analyser (RVA), and oscillatory dynamic rheometry. The data obtained from the DSC thermogram and the RVA profiles were fitted to Kissingers and Ozawas methods. Starch gelatinisation was characterised by two phases, where the first corresponded to the unfolding of amorphous region of the starch granule and the other represented the melting crystalline part. The temperature that separates the unfolding and melting of the granule parts, the breaking temperature, was recorded. Higher activation energy (Ea) was calculated for the DSC data versus the RVA. The Ea values calculated by Kissingers method indicated that one can use either DSC or RVA to get a comparable Ea for both starches, whereas Ozawas method showed comparable results for chickpea starch and less comparable for corn starch. The Ea of corn starch as calculated by dynami...

Effect of urea and sodium chloride on the pasting properties and gelatinisation kinetics of corn starch

The effect of urea and sodium chloride (NaCl) on the pasting properties and gelatinisation kinetic of corn starch was determined using rapid visco-analyser. Starch slurry (3 g in 25 g H2O) was heated at 3, 5, 7, 10, 15, and 20 °C/min. Peak viscosity, setback, and pasting temperature were recorded at all heating rates as well as the swelling power. The pasting temperature was used for activation energy (Ea) calculation according to the Kissinger plot and Ozawa model. The peak viscosity significantly (P≤0.05) increased in presence of urea and NaCl at all heating rates compared to the control, while the setback dropped in NaCl and increased in urea. This indicates better amylose-amylose interaction prevention by NaCl. The pasting temperature exhibited higher values in NaCl and lower in urea. This signifies action of urea on the hydrogen bonding between starch molecules in the amorphous region of the granule (dominated by amylose). The protective action of NaCl is obvious on the high pasting temperature of co...

Enthalpic Relaxation of Vital and Protease-Treated Wheat Gluten

Commercially available vital wheat gluten was purified with α-amylase and treated with protease in a one-step process. The supernatant of the protease-treated gluten was freeze dried, quench cooled, and aged for 2 weeks and analyzed using differential scanning calorimetry, sodium dodecyl sulfate poly-acrylamide gel electrophoresis, reverse phase high performance liquid chromatography, size exclusion high performance liquid chromatography, capillary zone electrophoresis, and dynamic mechanical analysis. The differential scanning calorimetry profile of the aged (un-purified or un-modified) gluten sample exhibited enthalpic relaxation beneath its glass transition (Tg) indicating molecular relaxation. Samples treated with 0.006 g protease/g gluten showed Tg at 49.11°C with ΔCp = 0.12 (J/°C g). Higher protease levels and longer aging time caused high Tg temperature, ΔCp, and ΔH of enthalpic relaxation. The size exclusion high performance liquid chromatography profile of the protease-treated gluten clearly showed differences in molecular size between the supernatant and the precipitate, while reverse phase high performance liquid chromatography profiles signified more hydrophilic gluten molecules than the control. The small difference in gluten molecular size after protease treatments (0.024 g protease versus 0.032 g) appeared to have a significant effect on the enthalpic relaxation, where the two treatments showed different degrees of enthalpic relation. The capillary zone electrophoresis data confirmed the insignificant difference between 0.024 and 0.032 g protease/g gluten regarding the size to charge ratio. The molecular interactions for protease-treated gluten were much weaker than vital gluten, as indicated by much weaker network and sensitivity to temperature, especially above Tg. The weaker network was evidenced by higher G″ versus G′, which explained the fluid like behavior of the protease-treated gluten.

Functional flaxseed in baking

The use of flaxseed as a functional food has gained in popularity in recent years. It has been grown since ancient times for food and other uses. Flaxseed is an excellent source of nutrients including protein, soluble and insoluble dietary fibre as well as omega-3 fatty acids. The flaxseed can be used as a whole or it can be incorporated in other foods including bakery products. The flaxseed proteins can enhance the biological parameters of bread and unleavened flat bread (chapattis). The addition of flaxseed to wheat flour can also contribute towards several health benefits and can serve as a low-cost treatment for many diseases, e.g. diabetes, hypercholesterolemia and cardiovascular complications. The current review will focus on the health benefits of flaxseed and the potential of these seeds to be incorporated into breads and chapattis which are staple foods for a large segment of the population.

Specific Mechanical Energy and Thermal Degradation of Poly(lactic acid) and Poly(caprolactone)/Date Pits Composites

The compatibility of date pits (DP) with polylactic acid (PLA) or polycaprolactone (PCL) is investigated. Composites were prepared by compounding PLA or PCL with date pits at 10, 20, 30, and 40% wt/wt and extruded. Wheat vital gluten (VG) was also used as a filler and in combination with DP. The specific mechanical energy (SME) was calculated and the composites thermal properties were tested using DSC (peak temperature, enthalpic relaxation, and glass transition) and TGA (degradation temperature and mechanism and degradation kinetics). Because DP is hard filler, the SME of PCL-DP composites increased as the amount of filler increased. At 40% fill, the SME decreased due to the lubricating effect of oil found naturally in DP. As illustrated by lower SME, PLA composites exhibited softer texture because PLA is harder than DP. The DSC melting peak temperature of both polymers has increased at higher DP; however, PLA exhibited enthalpic relation between 66 and 68°C. The TGA profile of the composites displayed two distinct peaks versus one peak for the pure polymer. The degradation kinetics showed multistep process for the composites and one-step process for the pure polymer. The utilization of date pits as a hard filler in developing biodegradable plastics is good for the environment and a value added for the date industry.

Amidolysis of Oxirane: Effect of Protein Type, Oils, and ZnCl2 on the Rheological Properties of Cross-Linked Protein and Oxirane

Amidolysis of oxirane group of epoxidized sesame, sunflower, and cottonseed oils was achieved by reaction with primary amide of millet and gluten proteins. Gluten is a coproduct of wheat starch industry and available commercially. Millet is a major part of the staple food of the semiarid region of the tropics. Gluten is a mixture of glutenins and gliadins rich in glutamine residues; however, millet is rich in glutamine and leucine. We have taken advantage of the available primary amide of glutamine for cross-linking with the oxirane of sunflower, sesame, and cottonseed oils under controlled conditions to give a resin of amidohydroxy of gluten and millet proteins. Cross-linking gave a resin with a wide range of textural properties. The texture of the resin was dependent on the source of the oxirane, the amide group, and the amount of the catalyst (ZnCl2). The thermal properties, textural, solubility, and rheological properties were determined as well as the reaction time. The data showed direct relationships between the ZnCl2, nature of oil, and protein type and the properties of the final resin. Consistently, the results pointed to similarity among the outcome of the reactions between sesame and sunflower oils. Depending on the amount of ZnCl2, the texture of the resin can range from viscose to rubbery. The reaction time was influenced by oxirane source, protein type, and catalyst and ranged from 30 min to 4 hr.