Rheological and textural properties of tef [Eragrostis tef (Zucc.) Trotter] grain flour gels

Interest in tef [Eragrostis tef (Zucc.)Trotter] grain in food applications has increased in recent years because of its nutritional merits and the absence of gluten. With the objective of evaluating the suitability of tef for making gel type food products, gel viscoelastic properties of three varieties of tef (one brown and two white) at different concentrations (6, 8, 10, 12 & 14% w/w) were evaluated at 25 °C and 90 °C. The texture and color evolution for 16% (w/w) gels were evaluated. Proximate compositions of the flours were quantified. Rice, refined and whole wheat flours were analyzed as reference. The minimum flour concentration required for gel formation from the three tef varieties was 6–8%, similar to wheat flour. All tef flour suspensions pre-heated to 95 °C led to gels with a solid-like behavior (G′ > G″), both at 25 °C and 90 °C, with higher consistency than wheat gels at the same concentration. The dependence of viscoelastic moduli with concentration fulfilled the power law. The Avrami model was successfully fitted to the textural evolution of tef gels. Important differences were observed among tef and rice and wheat flours, probably contributed by their differences in protein, starch, lipid and fiber constituents. Gelling properties characterized suggest that tef flours would be suitable ingredients in gel food formulations.     

Impact of re-grinding on hydration properties and surface composition of wheat flour

The combination of two analytical methodologies (water vapor sorption isotherm by using the DVS and chemical surface composition by using the XPS) has been used to enhance the understanding of the impact of re-grinding on the wheat flour hydration mechanism. A controlled atmosphere microbalance was used to construct water sorption isotherms at 25 °C of different samples of wheat flours obtained by successive re-grinding of native wheat flour.     

Effects of thermal and moisture transport properties of T-shirts on wearer’s comfort sensations

Little work has been done in the past on how clothing thermal and moisture transport properties affect human comfort sensations during different periods of an exercise. In this work, by correlating the thermal and moisture transport properties of T-shirt fabrics and garments with the comfort sensations during different stages of exercises, we found that thickness, thermal insulation and warm/cool feeling of the T-shirt fabrics are important to warmth sensation, skin wetness sensation and overall comfort throughout the entire period of exercise and immediately after the exercise. Water vapor transmission properties of T-shirt fabrics or garments are not important to comfort sensations at the start of the exercise, but become an important factor to comfort sensations in the middle of the exercise up to the resting period after the running exercise, probably due to the fact that sweating occurs during these periods. Fabric water absorption and air permeability are not significant factors at the start and during the exercise, but are important after exercise, probably because these properties determine how quickly the skin can be dried after sweating.     

Effect of particle size,shape and surface roughness on bulk and shear properties of rice flour

The present study was conducted to compare the flowability of basmati and non-basmati rice flour with commercially available rice flour. Dynamic and shear properties were characterized on the basis of particle size, shape and surface roughness (measured by Atomic Force Microscope) depending upon the processing conditions. In contrast to commercial rice flour having less particle size (65.3 μm), the particle sizes (171.1–171.9 μm) of both the samples were not significantly different. However, the flowability of the non-basmati rice flour was significantly affected by its particle shape (0.487), surface roughness (124.23 nm) and compressibility (25.32%), making it more cohesive than basmati rice flour but less cohesive than commercial rice flour (1.34 kPa). Also, basic flow energy was significantly higher in both commercial rice flour and non-basmati flour, thus required more energy (197.42 mJ and 147.54 mJ, respectively) to flow than basmati rice flour (130.15 mJ). Overall, flowability was analysed by applying three different pressures (3, 6 and 9 kPa) and among which commercial rice flour was found less flowable (2.26 at 9 kPa) followed by non-basmati rice flour (2.33 at 9 kPa) and basmati (3.35 at 9 kPa) causing bulk handling difficult.     

Effects of potato/wheat flours ratio on mixing properties of dough and quality of noodles

The effects of potato flour/wheat flour (PF/WF) ratio on the mixing properties of dough and the quality of noodles were investigated. Substitution of wheat flour with potato flour caused the increases in the water absorption and the protein weakening value (C1-C2) of formulated flours, as well as the decrease in the corresponding dough mixing parameters including dough development time (DDT), dough stable time (DST), initial mixing time (C2), maximum torque during heating (C3), minimum torque of hot paste (C4) and the amount of retrogradation (C5-C4), indicating that the addition of PF weakened dough strength but improved degradation resistance. The textural, cooking, sensory characteristics and microstructure of noodle samples were evaluated. The results indicate that adhesiveness, springiness, broken ratio and cooking lose increased progressively with increasing PF content while the score of sensory evaluation continued to decrease. However, hardness, cooking yield and optimum cooked time for the samples of PF content range from 10% to 20% showed a distinctive variation. Environmental scanning electron microscopy (ESEM) confirmed changes in noodle microstructure as PF addition affected gluten network development. In general, noodles with PF content below 40% were acceptable.     

Thermal and rheological properties of brown flour from Indica rice

The thermal, paste and rheological properties of brown flours from four Indica rice subspecies with different amylose content were examined using Differential scanning calorimetry (DSC), Brabender Viscometer and rheometer. Peak, final and setback viscosities (p < 0.05) increased with increasing amylose content from Brabender micro Visco-Amylo-Graph (MVA), but the phase transition temperatures of brown rice flour from DSC (p < 0.05) decreased with increasing amylose content. Rheological properties were determined by steady shear, small amplitude oscillatory shear (SAOS) and thixotropic experiments. SAOS results showed a gel-like viscoelastic behavior with G′ higher than G″. Steady-shear results showed that the brown rice flour exhibited a non-Newtonian shear-thinning behavior and the flow curves can be well described by the Herschel-Bulkley model. The upward-downward rheograms showed that brown rice flour gel, except IR-1, had a hysteresis loop, indicating a strong thixotropic behavior.     

Thermal,rheological properties and microstructure of hydrated gluten as influenced by antifreeze protein from oat (Avena sativa L.)

This study examined the thermal, rheological properties and microstructure of hydrated gluten as influenced by oat antifreeze protein (AsAFP). The thermal properties of fresh hydrated gluten, including the melting temperature, freezing temperature, freezable water content and glass transition temperature, were determined. For hydrated gluten samples after freeze-thaw treatment, the change in melting performance and freezable water content were analyzed. The results showed that the addition of AsAFP increased the glass transition temperature and decrease the melting enthalpy and freezable water content of fresh hydrated gluten. The supplementation of AsAFP also influenced the melting performance of hydrated gluten after freeze-thaw treatment. The rheological properties showed that the addition of AsAFP inhibited the deterioration of the rheological properties of hydrated gluten. The secondary structure of the gluten proteins changed significantly, α-helix decreased and β-sheet increased. The microstructure of the hydrated gluten demonstrated that supplementation with AsAFP may protect the gluten matrix from disruption during freeze-thaw cycles.     

Moisture sorption isotherms, heat of sorption and properties of sorbed water of raw bamboo (Dendrocalamus longispathus) shoots

Moisture sorption isotherms of raw bamboo shoot were determined by static gravimetric technique based on isopiestic transfer of water vapor at 20, 30 and 35 °C. Inorganic saturated salt solutions in the range of 11.2-97.2% were used to create the required controlled humidity environment in a closed chamber. In the study, the sorption isotherms obtained were of sigmoid shape and of BET II type classification. Out of three sorption models i.e., BET, Caurie and GAB, fitted to the experimental data, Caurie model was found superior in interpreting the moisture sorption characteristics of bamboo shoot at three temperatures. The monolayer moisture content M_m as estimated by the best fitted Caurie's model for the sorption processes were 6.012%, 5.801%, 5.014%, and 5.987%, 5.816%, 4.998% (dry basis) at 20, 30, and 35 °C, respectively. The isosteric heats of sorption for both the adsorption and desorption process of bamboo shoots were found to increase with decrease in moisture content suggesting endothermic reaction at lower moisture content and it approached the value of heat of vaporization of free water at higher moisture content.     

Production of African breadfruit (Treculia africana) and soybean (Glycine max) seed based food formulations, 2: Effects of germination and fermentation on microbiological and physical properties

The effects of germination (G) and naturally fermented (F)on the bacterial flora, viscosities and moisture sorptionisotherms of soybean (S) and African breadfruit (B) seed based food products were investigated. Bacillus,Enterobacter, Enterobacteriaceae, Proteus, Serratia andStaphylococcus species dominated in the nonfermentedproducts. Lactobacillus, Leuconostoc, Pediococcusand yeast species dominated in the fermented products whosegruels also inhibited growth of coagulase positive Staphylococcus aureus in challenge tests. Germination andfermentation resulted in significant (p < 0.05) decreasesin cooked paste viscosities which is advantageous inincreasing nutrient density. The monolayer moisture contents (g H₂O/g solid) and surface areas for monolayer adsorption (m²/g solid) derived from BETmodel were 0.0422 and 148.1 (GFSB); 0.0428 and 150.4 (NGFSB); 0.0436 and 153.3 (NGNFSB); 0.0531 and 186.6 (GNFSB), respectively.     

Characteristics, composition and thermal stability of Acacia senegal (L.) Willd. seed oil

The chemical composition, main physicochemical properties and thermal stability of oil extracted from Acacia senegal seeds were evaluated. The oil, moisture and the ash contents of the seeds were 9.80%, 6.92% and 3.82%, respectively. Physicochemical properties of the oil were iodine value, 106.56 g/100 g of oil; saponification value, 190.23 mg KOH/g of oil; refractive index (25 °C), 1.471; unsaponifiable matter, 0.93%; acidity, 6.41% and peroxide value, 5.43 meq. O₂/kg of oil. The main fatty acids in the oil were oleic acid (43.62%) followed by linoleic acid (30.66%) and palmitic acid (11.04%). The triacylglycerols (TAGs) with equivalent carbon number ECN 44 (34.90%) were dominant, followed by TAGs ECN 46 (28.19%), TAGs ECN 42 (16.48%) and TAGs ECN 48 (11.23%). The thermal stability analysed in a normal oxidizing atmosphere showed that the oil decomposition began at 268.6 °C and ended at 618.5 °C, with two stages of decomposition at 401.5 °C and 576.3 °C. According to these results, A. senegal seed oil has physicochemical properties, fatty acids composition and thermal characteristics that may become interesting for specific applications in several segments of food and non-food industries.     

Some physical properties of rough rice (Oryza Sativa L.) grain

Designing the equipment for processing, sorting, sizing and other post-harvesting equipment of agricultural products requires information about their physical properties. In this study, various physical properties of rough rice cultivars were determined at a moisture content of 10% (wet basis). In the case of Sorkheh cultivar, the average thousand grain weight, equivalent diameter, surface area, volume, sphericity, aspect ratio, true density, bulk density and porosity were 21.64 g, 3.35 mm, 31.76 mm², 20.27 mm³, 39.71%, 0.28, 1269.1 kg/m³, 544.34 kg/m³, and 56.98%, respectively. The corresponding values were 20.52 g, 3.4 mm, 32.58 mm², 21.06 mm³, 39.88%, 0.29, 1193.38 kg/m³, 471.21 kg/m³, and 60.37% for Sazandegi cultivar. For Sorkheh cultivar, the average static coefficient of friction varied from 0.2899 on glass to 0.4349 on plywood, while for Sazandegi cultivar the corresponding value varied from 0.2186 to 0.4279 on the same surfaces. Angle of repose values for Sorkheh and Sazandegi cultivars were 37.66° and 35.83°, respectively. Linear model for describing the mass of rough rice grain was investigated. Mass was estimated with single variable of kernel length with a determination coefficient as 0.862 for Sorkheh cultivar whereas for Sazandegi cultivar was as 0.860.     

Moisture desorption–adsorption isotherms and isosteric heats of sorption of Tunisian olive leaves (Olea europaea L.)

Moisture sorption isotherms are valuable tool for prediction of the stability and shelf-life of agricultural products. The aims of this work were to determine sorption isotherms of four varieties of olive leaves and to compare the experimental and calculated results by using models available in the literature. The equilibrium moisture contents of olive leaves were measured using the static gravimetric method, at water activities and temperatures ranging from 0.058 to 0.898 and from 30 to 50 °C, respectively. Seven models were applied for analysing the experimental data: Guggenheim-Anderson-de Boer, modified Oswin, Henderson-Thompson, White and Eiring, Peleg, Smith and Caurie models. The desorption and adsorption data were best fitted by the Peleg model. Thus, this model can be used for the estimation of the equilibrium moisture contents of olive leaves in the investigated ranges of temperature and water activity. The net isosteric heats of desorption and adsorption of olive leaves were calculated by applying the Clausius–Clapeyron equation to the sorption isotherms and an expression for predicting these thermodynamic properties was developed.     

Compositional,functional and storage properties of flours from raw and heat processed African breadfruit (Treculia africana Decne) seeds

African breadfruit (Treculia africana Decne) seeds were either boiled or roasted and then milled into flour. Chemical composition, functional properties and storage characteristics of raw and treated flours and the effect of partial proteolysis on selected functional properties of the raw flour were determined. Raw flour contained 20.1% crude protein, 2.5% total ash and 13.7% fat. Heat processing significantly (p<0.05) improved in vitro protein digestibility, and water and fat absorption capacities but decreased bulk density, nitrogen solubility, emulsion and foaming properties, trypsin inhibitor, and phytic acid and polyphenol contents of the samples. Boiling proved more effective than roasting for improving protein digestibility, emulsion capacity and foam stability and reducing antinutritional factor levels. Partial proteolysis increased nitrogen solubility, bulk density and water and fat absorption capacities but decreased foam capacity at hydrolysis levels greater than 35%. Fatty acid and peroxide values of the samples increased during storage. Compared to raw samples, heat processed samples had significantly (p<0.05) lower and more acceptable peroxide values and free fatty acid contents and higher and more stable water (3.0 g/g sample) and fat (2.4 g/g sample) absorption capacities.     

Effect of extrusion cooking on chemical structure,morphology, crystallinity and thermal properties of sorghum flour extrudates

The effect of feed moisture content (10, 14 and 18%) and die temperature (110 and 160 °C) on functional properties, specific mechanical energy (SME), morphology, thermal properties, X-ray diffraction pattern (XRD), Fourier transform infrared spectroscopy (FTIR) and amylose-lipid complex formation of extruded sorghum flour was investigated. Results showed that the extrusion cooking significantly changed the functional properties of extruded sorghum flour. Increasing feed moisture increased the peak gelatinization temperature (T_p), the degree of gelatinization (%) and starch crystallinity (%) while it decreased the gelatinization temperature ranges (T_c - T₀), starch gelatinization enthalpy (ΔH_G) and amylose-lipid complex (%) formation. With increasing die temperature, the degree of gelatinization and amylose-lipid complex formation increased and the starch T_p, T_c-T₀, ΔH_G and crystallinity decreased. The FTIR spectra also showed that the extrusion cooking did not create new functional groups or eliminate them in sorghum protein, whereas the sorghum extrudate protein had random coil conformation.     

Comparative study on the effects of buckwheat by roasting: Antioxidant properties,nutrients, pasting,and thermal properties

The increasing need to prolong the shelf life of buckwheat has prompted the use of roasting techniques in buckwheat processing. For effective roasting, the responses of common buckwheat (CB) and tartary buckwheat (TB) to the process should be explored. Herein, the antioxidant properties, nutrients, pasting, and thermal properties of raw and roasted buckwheat flours (roasted at 200 °C for 50 s) from two CB and three TB varieties were investigated. Results showed that roasting considerably reduced the total flavonoid content (TFC) and total phenolic content (TPC) of TB. The TPC of CB was significantly improved by roasting, whereas the TFC significantly decreased. The total antioxidant capacities were consistent with the TPCs. Additionally, the colour deepened as the amount of antioxidant compounds increased. Unexpectedly, roasting enhanced the protein and fat contents of CB and decreased those of TB. Roasting improved the nutritional quality and antioxidant capacity of CB, and opposite results were obtained in TB. In conclusion, CB was more suitable to the development of roasted specialty products with nutritional applications than TB. We suggest that differences among varieties should be considered first in the buckwheat roasting process.     

Preparation and properties of flours and protein concentrates from raw, fermented and germinated fluted pumpkin (Telfairia occidentalis Hook) seeds

In vitro protein digestibility, chemical composition and selected functional properties of flours and protein concentrates prepared from raw, fermented and germinated fluted pumpkin (Telfairia occidentalis Hook) seeds were studied. Protein concentrates prepared by an alkaline extraction process had increased crude protein contents (61.5–70.8%) compared to flour samples (46.4–52.7%). The yields of protein concentrates ranged from 24.5% to 29.4% while values for protein recoveries varied between 64.8% and 65.2%. Protein concentrates also had increased foam volume and decreased foam stability (100% decrease over a 2 h period), compared to flour samples. Fermentation and germination were observed to significantly (p<0.05) lower polyphenol and phytic acid contents, but increased protein digestibility of fluted pumpkin seed flours and concentrates. Both raw flour and concentrate were significantly (p<0.05) higher in water absorption capacity than germinated or fermented flours and concentrates. Protein concentrates had comparatively better fat absorption properties than the flour samples. Hence protein concentrates may prove to have useful applications in ground meat formulations.     

Chemical,sensory and rheological properties of porridges from processed sorghum (Sorghum bicolor,bambara groundnut (Vigna subterranea L. Verdc) and sweet potato (Ipomoea batatas) flours

The chemical, sensory and rheological properties of porridges made from blends of sprouted sorghum, bambara groundnuts and fermented sweet potatoes were examined. Sorghum and bambara groundnuts were sprouted for 48 h while sweet potatoes were fermented for the same period. Blends were formulated from the processed ingredients in the ratio of 60:40:0, 57:42:1, 55:44:1 and 52:46:2 (protein basis) of sorghum, bambara groundnuts and sweet potatoes. Porridges were prepared from the composite flours and the traditional sorghum complementary food. Standard assay methods were used to evaluate the flours for nutrient composition. The porridges were also tested for sensory properties and viscosity. Processing increased the levels of most of the nutrients evaluated. Relative to the sorghum traditional complementary food, thecomposite flours had higher levels of lipids, protein, ash, crude fiber and minerals (p<0.05). The porridges from the composite flours were generally liked slightly by the panelists and were about seven times less viscous than the porridge from the traditional sorghum complementary food. Use of the composite flours, particularly the 52:46:2 blend, as a traditional complementary food should be encouraged in Nigeria especially with the increasing cost of commercial complementary foods.     

Effect of gliadin/glutenin ratio on pasting,thermal, and structural properties of wheat starch

Gluten-starch interactions are of specific importance during the processing of cereal-based products. However, the mechanisms for gluten-starch interactions have not been illuminated. The effects of various gliadin/glutenin (gli-glu) ratios (0:10, 3:7, 5:5, 7:3, and 10:0) on the pasting, thermal, and structural properties of wheat gluten-starch mixtures were investigated. The peak, through, and final viscosities were obviously decreased, and the setback value initially increased and then decreased with increasing gli-glu ratios during the rapid viscosity analysis (RVA). Differential scanning calorimetry showed that the enthalpy changes increased with increasing gli-glu ratios. Thermogravimetric analysis showed a slight increase in the degradation temperature of the mixtures as the gli-glu ratio increased, although it was still lower than that of wheat flour. However, there was no significant difference in the weight loss among different gli-glu ratios. Rheometer-Fourier transform infrared (FTIR) spectroscopy showed that the C-6 peak at 996 cm⁻¹ for all the samples was displaced or disappeared due to the hydrogen bond fracture caused by water molecules entering the starch granules. It was also found that the absorption peak in amide II of gli-starch was more obvious than that of glu-starch. The CLSM obviously described the change structure of mixtures with different gli-glu ratio during starch gelatinizaton. By studying the changes in gluten protein components and how they affected the thermal and structural properties of starch, a simple model was proposed to describe the gelatinization process of the mixtures with different ratios of gli-glu and briefly describe the interactions between starch and wheat gluten components. Optimization of the proportion of protein components in wheat flour will enable greater control over the structural characteristics and elasticity of wheat food products.     

Selected nutritional,physical and sensory characteristics of pan and flat breads prepared from composite flours containing fababean

Composite flour blends containing wheat (W), fababean (F), cottonseed and sesame flours were formulated to provide the FAO/WHO/UNU protein requirements for the 2–5 year old child, and evaluated in pan and flat bread applications. Water absorption of composite flour doughs was up to 35% greater than the control but gluten strength and slurry viscosities were markedly reduced. Loaf volume and specific volume of pan breads prepared from composite flours were 25–60% less than that of the control bread but flat breads tolerated the protein supplements extremely well. The W/F flat bread, containing 27% of fababean flour, received acceptable taste, texture and colour scores and was only slightly inferior to the control in puffing and layer separation. Additions of cottonseed or sesame flours to the W/F blend failed to improve sensory properties of the flat breads.     

Temperature during grain ripening affects the ratio of type-II/type-I protein body and starch pasting properties of rice (Oryza sativa L.)

The starch and protein properties of rice grain are important factors for sake brewing and these properties are reported to be influenced by temperatures during grain ripening. Amylose content, nitrogen content, protein composition, pasting properties measured by a Rapid Visco Analyser (RVA), and their relationship to temperatures during ripening were investigated in a rice cultivar, Yamadanishiki, which was grown under various conditions in the same experimental field. The average temperature after heading was significantly correlated with amylose content and RVA properties, but not with nitrogen content. Under high temperatures during ripening, a decrease in prolamin, which accumulated in type I protein body (PB-I), and an increase in glutelin, which deposits in type II PB (PB-II), were recognized. The ratio of PB-II/PB-I and RVA pasting temperatures were distinctly increased as the temperature became higher. High temperatures during grain ripening would lead to difficulties in digesting steamed rice grains by Aspergillus oryzae, together with ease in digesting rice protein. The average temperature of 11–20 days after heading showed a higher correlation coefficient than that of 1–10 or 21–30 days, implying that temperatures during the middle stage of grain development would be important in determining the rice component that relates to brewing properties.