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Wheat starch is the most common type of starch in Iran as well as many other parts of the world with enormous applications in food and non-food products. To improve its physicochemical properties or create new functionalities, starch can be modified by changing its molecular structure. Amongst different methods for starch modification, physical methods have received more attention recently. Pre-gelatinization of starch is a physical method to modify the properties of native starch. The main aim of this research was to study the physicochemical properties of pre-gelatinized wheat starch produced using a small scale industrial twin drum drier. The results indicated that drum drying destroyed native starch granules, degraded molecular structure and reduced the degree of crystallinity of starch. Pre-gelatinized starch (PGS) showed cold water viscosity at 25 ºC, while native wheat starch was not able to increase the viscosity under this condition. It also increased water absorption and swelling of the starch compared to its native counterpart. Pre-gelatinized wheat starch can be used as a thickening agent in instant food products to eliminate heating stage in their production or in manufacturing of the products sensitive to high temperature.

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Production of part-baked bread is a successful method to postpone bread staling that has been applied widely for production of loaves. In this research, production and some physical characteristics of part-baked flat bread (Barbari) including hardness, volume, color, weight loss, and microstructure were studied during the storage of the samples at ambient (25ºC) and freezing (-18ºC) temperatures. The part-baked bread had higher moisture content than the control and full-baked breads. However, it had a shelf-life of 72 hours, which was shorter than the control at ambient temperature. Full-baking could level out the effects of staling and, hence, the quality of the full-baked bread was similar to that of the fresh bread. For the frozen samples, the optimum storage time was two months. The undesirable effects of frozen storage were more significant for the part-baked bread. Moreover, full-baking could compensate some of the adverse effects of freezing and the resultant bread had superior quality compared with the control.

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  Rheological study of date syrup, date concentrate and date liquid sugar can improve their industrial applications specially for sugar (sucrose) substitution. In this research the rheological behavor of date syrup, date concentrate, date liquid sugar and sucrose solutions was investigated using a Brookfield Viscometer at 50, 55, 60 and 65 °Brix, 25 °C and shear rate of 80-480 s^-1 .The variables were product type and concentration. Moreover, for textural evaluation a texture analyser was used to examine date syrup, date concentrate and date liquid sugar at 50, 60 and 70 °Brix. The results showed that the Power law model was suitable to the rheological behavior of all samples and all concentrations. In date syrup by increasing concentration from 50 to 65 °Brix, consistency coefficient (K) increased, flow behavior index (n) decreased and the sample became more shear thinning. However, all other samples were Newtonian. Therefore a similar flow type behavior for these three samples is expected in food processings. Among all tested concentrations, the date syrup sample with a Brix of 65 had the highest consistency coefficients.  This indcates using date syroup in food formulations, usage level of hydrocolloids can be reduced. These findings were confirmed by texture data.

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Snacks are amongst popular foods, therefore improving the quality of the snacks is of great importance. Half-products are a kind of cereal based snacks that are sold in the form of dried pellets and then deep-fried for a few minutes by the consumer to form puffed crispy edible snacks. The main aim of this study was to determine the sufficient pellet moisture content in order to reach an appropriate snack quality.  Pellets were produced using a single screw extruder by mixing wheat flour and starch to reach moisture content of 7.5%. The moisture content of the pellets was then adjusted on 5, 10, 12, 14 and 16%. Pellets were deep-fried at 185 °C to reach their maximum volume and then their physical and sensory characteristics were studied. Increasing the moisture content from 5 to 16% reduced the density, increased lightness, reduced redness and yellowness of the snacks. The fracture force to break of snacks reduced with increasing the moisture up to 10% but it reduced with further increase in pellet moisture content. Increasing pellet moisture up to 14% improved the sensory characteristics of the snacks while further increase in the moisture content reduced these properties. Adjustment of the pellet moisture content is a practical solution in the industry to improve the quality of the snacks. The most appropriate moisture content of the pellet was in the range of 10-12%. At higher or lower moisture levels, the sensory characteristics of product were affected, negatively.

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The main purpose of this study was to use wheat germ in production of milk dessert. Therefore, wheat germ was first heated at 150 °C for 15 min, then milled to obtain particle sizes of 125, 210 and 354 micrometers. Samples were made with 10% sugar, 2% gelatin and 88% low-fat milk (1.5% fat) and different levels of wheat germ (2.5, 5, 7.5 and 10%, w/w). Different characteristics of the fresh product and after storage for 15 days at 4 °C were determined. The results showed that with increasing the amount of wheat germ, dry materials of the samples increased while the pH decreased. Changes in the particle size of the samples had no effect on the dry materials. Textural evaluations showed that with increasing the germ level, particle size and storage time, hardness, cohesiveness, chewiness and gumminess, increased while elasticity decreased. Studying the internal structure of the desserts using scanning electron microscopy showed that the uniformity of the samples increased with increasing the germ content in dessert formulation. Moreover, with increasing the percentage and particle size of the germ, the darkness, redness and yellowness of the desserts increased. The results showed that the syneresis of desserts reduced with increasing the level of the germ, however, changes in particle size of the germ had no effect on this parameter. Sensory evaluation results concluded that the samples were prepared with maximum amount of 7.5% germ with particle size of 125 micrometer were the most acceptable samples.

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In biscuit production, sucrose is one of the major ingredients. Addition of sucrose is not only for the sweet taste it provides, but also for its positive effects on physical properties of the product. Since sucrose consumption is growing worldwide, finding an alternative sugar source other than sugar beet and sugar cane as the main sources of sucrose is necessary. In this research, sucrose was replaced with 0, 20, 40, 60, 80 and 100% (weight basis) of date syrup and date liquid sugar and the effects on rheological properties of biscuit dough were studied. The results from farinograph showed that the dough consistency and elasticity reduced with increasing the sucrose replacement level. However, no significant difference between the samples made with date liquid sugar and date syrup was not observed. The results of Texture Analyser showed that with reducing the sucrose content dough consistency, energy required for compression, springiness and cohesiveness reduced while adhesiveness increased. The values obtained for energy, consistency and adhesiveness of the samples containing date liquid sugar were higher than those of date syrup, while springiness was lower.  Based on the results the maximum percentage of the sucrose replacement with date liquid sugar was 60% and with date syrup was 40%. At higher percentages the quality of the dough reduced considerably.   

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Wheat germ, a highly nutritive part of wheat kernels, is separated during milling as a by-product. In this study, wheat germ was used to supplement cakes. Different levels of the germ (0, 5, 10, 15 and 20%) at different particles sizes (280, 585, 890 and 1,195 µm) were added to a cake recipe. The results showed that with increasing the germ level and particle size, batter consistency and density of the cakes increased significantly, while the height of the cakes decreased. With increasing the germ level and its particle size, the crumb became slightly yellow while the crust color and the textural parameters (TPA test) remained unaffected. Determination of the sensory attributes of the samples showed that the particle size was negatively correlated with the crumb color and texture of the cakes, while other sensory parameters remained unaffected. In general, 15% of germ was the highest level and 280 µm was the most suitable particle size (as recognized by the panelists) for the production of an appropriate germ cake.

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 Increasing the nutritional value of bread is important since the enriched product can be used for special target groups such as developing countries or special diets. Wheat germ, a highly nutritive part of wheat kernel, is a by-product of milling factories and has the potential to be used for food supplementation. The main aim of this research was to supplement flat bread (Barbari) with wheat germ and to study the quality and staling of the resultant bread. Therefore, processed (heated at 150°C for 45 minutes) and raw wheat germs were added at the rates of 0, 5, 10 and 15% (w/w) in bread recipe, as separate treatments. Using a Farinograph, it was found that the dough made with raw germ had less water absorption, lower consistency, and shorter stability time. Modeling of the data showed that increasing the germ level had negative correlation with bread volume and softness. Such effects were enhanced when raw germ was used. It was found that addition of germ could not delay bread staling; however, it had positive effects on its taste and general acceptability, particularly when 15% processed germ was used.

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The Chaboche kinematic hardening model is generally used for modeling the plastic behaviour of material under quasi-static cyclic and monotonic loadings. This model is independent of strain rate and its constants are normally determined through quasi-static tests. Therefore, it cannot predict material behavior under high strain rate condition. On the other hand, the dynamic behaviour of materials even in some cyclic loadings is usually strain rate sensitive. In this investigation, the constants of Chaboche model are identified at various strain rates through quasi-static and dynamic tests and using these constants the effect of strain rate is incorporated in the Chaboche model. Moreover, the stress-strain diagrams at different strain rates are predicted using artificial neural network (ANN) and the results are compared with the experimental data. The results from the strain rate dependent Chaboche model shows reasonable agreement with the experimental data and the prediction from ANN. It is also shown in this work that the constants of Chaboche plasticity model are strain rate dependent and if the neural network is trained properly, it can be used for interpolating between the experimental data

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Due to the positive effects of fiber on human health, production and distribution of high fiber containing foods is on the increase. Amongst different foods, bread is a suitable option to convey fiber in human diets. Flat breads which are very common in Asian countries, are mainly produced from white flour and hence are low in fiber. The main objectives followed in this study were to produce high fiber Barbari bread (a popular flat bread) using wheat bran, while minimizing the adverse effects of inclusion of bran in the bread recipe. To achieve this, wheat bran of different levels (0-20%, w/w flour basis) and particle sizes (170, 280, 425 and 750 mm) were added to Barbari bread recipe. Using Brabender Farinograph, it was found that with increase in bran level and its particle size, the water absorption of the dough increased. Color determination results showed that the bread crust color became darker as the level of the bran and its particle size increased. The results of determination of the bread texture using Texture Profile Analyser, showed that the bread became harder and less cohesive with increase of the fiber in the dough and for each bran particle size. According to the panelists, barbari breads constituted the most appropriate breads with up to 15% bran with particle sizes of shorter than 280 mm. In total, it was concluded that by a control of the level and particle size of the bran, it is possible to increase the fiber content of the bread without any significant adverse effects on the quality.

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In this study, the effects of moisture content and corn variety on the physicochemical properties of popcorn were investigated and modeled using response surface methodology. Each of the two corn varieties (Hybrid corn KSC 600 PC and American) was prepared with a range of moisture (six moisture levels ranging from 10 to 20%) and popped by a hot air popper. Variety and moisture content affected the density, air bubble diameter as determined from electron micrographs, textural hardness and color parameters. The lowest densities for American and hybrid corns were obtained at moisture contents of 14 and 18%, respectively. As water content deviated from the optimum levels the popcorn density significantly decreased. For both corn varieties, with increasing water content, the lightness of the samples increased while b (yellowness-blueness) values decreased. For American popcorn no significant impact of the moisture content on the hardness was observed, however in hybrid corn, hardness of popcorns significantly decreased with increasing water content, and the lowest density and hardness were observed at moisture content of 18%. Experimental models are presented for the prediction of density, color parameters, air bubble diameter and hardness of popcorns at different moisture contents for American and hybrid corns.

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Rice bran is a major by-product of the rice milling process that contains high amounts of fiber, proteins, fats, vitamins, minerals as well as antioxidants and hence can be utilized in enriching food products. The main aim followed in this study was to determine the effects of rice bran of variable particle sizes (53, 125 and 210 µm) and its quantity (0, 5, 10, 15 and 20%) on the quality of batter and on sponge cake. Increasing bran quantity and particle size increased batter density and consistency. Using a higher quantity of bran with larger particle sizes increased cake density and weight of the cakes (after being baked) while decreasing the cake volume. Textural properties of the samples as determined instrumentally showed that maximum compressive force and the firmness increased, while cohesiveness and springiness decreased with increase in the contents of bran and increase in its particle size. Cake crust color became darker, more reddish and less yellowish with inclusion of rice bran. Increasing the levels of rice bran, negatively affected taste, crust and crumb color as confirmed by the sensory panel. Overall, it was found that addition of 10% rice bran with particle size of 125 µm resulted in the most desirable cake quality.

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Residual stresses of those which remain in the material even after removing the entire external load. Residual stresses may be compressive or tensile depending on the type of the external loads. Compressive residual stresses improve the mechanical properties particularly the fatigue life of material. Compressive residual stresses can be induced by different techniques. Due to its easiness and low cost, deep rolling is one of the widely used techniques in industry to create compressive residual tresses. Deep rolling process is numerically simulated in this work and the effects of some important rolling parameters such as ball diameter, feed rate, penetration depth, and number of passes on the distribution of residual stress are investigated. Chaboche cyclic plasticity model is used in the simulations. The constants of the Chaboche model are calculated from the strain control cyclic tests on Al 7075. The results are validated using the experimental and numerical results reported in the literature. The results indicate that the depth and magnitude of the compressive residual stress increase with the ball diameter increase, depth of penetration and number of passes. Also, the value of residual stress and its uniformity decrease by increasing the feed rate. In addition, Chaboche cyclic plasticity model can simulate material behavior in a low cycle loading such as deep rolling and using finite element method instead of experimental methods for measuring residual stresses reduces cost and time of solution and reveals more depth of residual stress distribution.

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In this research, seeds of Iranian carob trees grown wild in Kazeroon city (Fars Province) were used to extract Iranian locust bean gum as a seed galactomannan. Chemical composition, solubility, and rheological properties of crude and purified gums were investigated and compared with a commercial (Sigma) locust bean gum (LBG) sample. Chemical composition of the purified Iranian LBG was similar to the commercial LBG, however, the protein content of Iranian crude LBG was higher. Solubility data showed that the Iranian crude LBG was partially cold-water soluble (~ 55% at 25°C) and needed heating to reach a higher solubility value (~ 71% at 80 °C). Rheological properties of the solutions of the three LBG samples were investigated as a function of concentration and temperature (5-60 °C) at shear rate range of 0.5-200 s^-1. All three samples showed shear thinning behavior and Power law model was used to fit the experimental data. The Iranian LBG (crude and pure) was able to thicken aqueous solutions; however, its viscosity level was lower than that of the commercial LBG. Study of rheological properties of the three LBG samples at different pH levels (2.5-10) showed that they were significantly affected by pH. The intrinsic viscosities of the Iranian crude and purified LBG and commercial LBG were 3.95, 9.05, and 9.48 dL g^-1, respectively.

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In the present paper, to determine the pressure-dependent yield surface of polypropylene/nanoclay nanocomposites, the extended Drucker-Prager yield criterion is used and its parameters are derived by a combined experimental/numerical/optimization approach. In this method, the difference between the experimental and numerical results obtained from three-point bending test is minimized. In order to alleviate the burdensome numerical simulation, a surrogate model based on Kriging method is used to estimate the cost function. The optimum of this function is obtained by maximizing expected improvement method. Afterward, the results are verified by tension and compression tests. The results show that this method can substitute the complicated experimental tests which are normally employed to identify the extended Drucker-Prager parameters. Also, this method can be used to determine the mechanical properties of thermoplastic material such as tensile and compressive yield stresses and elastic modulus using only a three-point bending test. In addition, it is found that the volumetric change of thermoplastic during plastic deformation is significant and the non-associative, compared with the associative, plastic flow assumption is more proper for this material for the extended Drucker-Prager criterion.

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There is some evidence on the effects of organic acids on the functional properties of native starches. However, there is little information on such effects on modified starches. The main objective of this study was to determine the effects of L-ascorbic acid (150 mg kg^-1, as the permitted level in bakery products) on functional properties of cross-linked wheat starch. Once the starch was treated with L-ascorbic acid, some spots and cracks appeared on the surface of the starch granules, as observed under a scanning electron microscope. Besides, the water solubility increased while water absorption decreased, but intrinsic viscosity of the samples, as determined by a U-tube viscometer, remained unchanged. Also, gelatinization temperature and enthalpy of gelatinization, measured by differential scanning calorimetery, as well as the hardness and elasticity of the starch gels decreased, while adhesiveness and cohesiveness of the gels remained unaffected. In general, it was concluded that the ascorbic acid had some degradation effect on cross-linked wheat starch molecules that could further affect its functional properties.

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Promotion of the dietary fiber of foods can enhance human health by reducing the risk of many serious diseases. Cakes are among the highly consumed foods but sadly of low fiber content. Therefore, increasing the fiber content in them is of great importance, and this was the aim followed in this study. Wheat flour was partially replaced at 0, 10, 20 and 30% (w/w) with corn Resistant Starch (RS), as a source of dietary fiber, and used in the production of sponge cake. Obtained results indicated that batter consistency increased while its density reduced with an increase in the level of RS. Increasing the level of RS caused an increase in cake density but a decrease in volume. Cakes became softer but their cohesiveness, springiness and chewiness reduced. They also became whiter, less reddish and less yellowish. Addition of less than 30% RS had no significant effect on the sensory attributes of the cakes. In total, it was concluded that a maximum level of RS in the sponge cake recipe to produce an acceptable product amounted to 20%.

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Wheat gluten is one of the most important plant proteins of fairly low price consisting of glutenins and  gliadins. The hydrophobic nature and low water solubility of gluten has limited its applications in many food and non-food products. In order to improve the applications of gluten, it was first fractionated into its main components; gliadins and gluteneins and then they were acetylated using acetic anhydride. In the next stage, the rhelogical properties of these proteins at different pH values (3, 6 and 9) were compared with their corresponding controls. The pH had a great impact on the degree of acetylation. Glutenin had the highest, while gliadin had the lowest degree of acetylation at different pH values. Moreover, all these proteins were de-aceytelated at pH 3. Hardness, gumminess, chewiness and elasticity of the acetylated gluten and glutenin decreased significantly at pH 3.

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 Despite the numerous health effects of the dietary fibers, the amount of the fiber in the diet is generally lower than the recommended value. Therefore, increasing the fiber content of the foods particularly those of high consumption can compensate for the shortage of the fiber in the diet. However, it seems a difficult task since increasing the fiber content can have adverse effects on product acceptability. The main objective of this study was to include oat fiber in the cake recipe and to determine the physical and sensory properties of the resultant product. Therefore, oat fiber at different levels of 0, 5, 10, 15, 20, and 30% (w/w, flour basis) were added in the cake recipe. Increasing the level of oat fiber resulted in the increase in batter density and consistency and cake volume. In addition, cake crust and crumb became darker. Cake hardness and gumminess increased, while cohesiveness and springiness decreased as determined using a texture analyzer. Cakes containing no more than 20% oat fiber had acceptable sensory characteristics. In total, it was concluded that addition of maximum 20% oat fiber to cake can result in a product of acceptable sensory characteristics.