Influence of pre-treatment in citric acid solution on physical and mechanical properties of thermally compressed oil palm board
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Summary Cowpeas were cooked in water made hard (or soft) by the separate addition of similar concentrations of certain salts (CaCl 2 , MgCl 2 , or NaHCO 3 ). The beans were also cooked in hard tap water and in double distilled water before and after soaking in water. Hard water caused a significant decrease in softness, led to reduced water absorption, and also decreased solids loss in the cooked product, but it increased the cooking time and discolouration of the beans. Hard water also gave rise to a significant ( P <0.05) increase in mineral content, but it had less effect on the proximate composition of the cooked products.
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Significant differences in the exudation and accumulation of citric acid in common bean genotypes were observed in response to Al toxicity stress by hydroponic cultural experiments. Secreted citric acid increased with increasing external concentrations of Al3+ which ranged from 0 to 50 mumol.L-1, while ranged from 50 to 80 mumol.L-1, secreted citric acid decreased with increasing external concentrations of Al3+. Among different genotypic common beans, citric acid secreted in G19842 was the largest, while Al uptake per unit dry weight in G19842 was the least. No difference in the accumulation of citric acid in leaves was found among different genotypic common beans, while the size of the content of citric acid in roots was G19842 > AFR > ZPV > G5273. The amount of citric acid exuded was smaller induced by phosphorus deficiency than that induced by Al toxicity stress. Exposure to 50 mumol.L-1 LaCl3 could not induce the exudation of citric acid, and it implied that the exudation and accumulation of citric acid in common bean was an important physiological response of resistance to Al toxicity stress.
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A modified first-order reaction model composed of an initial linear phase followed by a diffusion-controlled phase closely predicted water absorption and swelling in several varieties of fresh and stored beans. Dehulling resulted in increased rates of water absorption, but equilibrium values for both water absorption and swelling were reduced as a result of elimination of the water held between the seed coat and the cotyledons as well as between the cotyledons. Swelling of de-hulled seeds was reduced initially, since the seed coat swells faster than the cotyledons in the initial stages of water uptake. Addition of carbonate salt to the soaking solution generally reduced water absorption and swelling. the hard-to-cook defect was manifested by reductions in the rates of water uptake and diminished effects of dehulling and salt soaking on water absorption and swelling. Water absorption was significantly and negatively correlated with cooked bean hardness.
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Abstract Synthesis of acrylamide (AA) hydrogel from an aqueous solution has been performed with radiation processing technology using a Co‐60 gamma source. The influence of time, concentration, dose, and dose rate on swelling and water absorption properties of the hydrogel treated in different conditions such as oven‐dry (OD), room‐dry (RD), and nondry (ND) has been investigated. Swelling and hydration increase rapidly with time for first 48 hr, then become nearly constant in the range 48–336 hr. The samples prepared at lower concentrations and doses exhibit higher values of hydration and swelling but they represent a fall of these values at lower dose rate. These occur mainly as a result of the increase of crosslinking density in the hydrogel by gamma ray irradiation. Furthermore, OD samples have higher swelling and hydration values as compared with RD and ND samples. All these effects of physical parameters and the drying conditions on hydration and swelling of hydrogel are discussed.
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The isothermal kinetics curves of the swelling of a poly(acrylic acid) hydrogel in distilled water and physiological solution at temperatures ranging from 20 to 40 ?C were determined. The possibility of applying both the Fick?s kinetics model and kinetics model of the first order chemical reaction to the swelling kinetics of the PAA hydrogel in distilled water and physiological solution were examined. It was found that the possibilities of applying these models were limited. The new model of the kinetics of swelling in distilled water and physiological solution was established. The kinetic parameters (Ea, ln A) for the swelling in distilled water and physiological solution were determined. The decrease of the equilibrium degree of swelling and the saturation swelling rate of the swelling of the PAA hydrogel in physiological solution compared to swelling in distilled water could be explained by the decreased differences in the ionic osmotic pressures between the hydrogel and the swelling medium. The increase of the initial swelling rate in the physiological solution might be caused by an increased density of charges at the network and by an increased affinity of the network towards the water molecules. The increase of the activation energy of the swelling of the PAA hydrogel in the physiological solution is a consequence of its additional "ionic crosslinking".
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Citric acid is the main tricarboxylic acid present in citrus fruits such as lemons, lime, oranges, grapefruit, grapes, etc. These fruits contain sufficient citric acid. The properties of citric acid make it an important additive for application in various industries such as the food, pharmaceuticals, disinfection, and cleaning industries. The aim of this experimental study is to produce citric acid from orange and grape juices. The chemical route for the synthesis of citric acid from citrus juices involves three steps: (i) Neutralization to adjust pH to 9-10 with 2.5 M NaOH solution, (ii) Addition of CaCl2 solution, and (iii) Acidification with H2SO4 solution to produce citric acid. Juice containing citric acid is neutralized with NaOH solution to obtain trisodium citrate. Then, trisodium citrate is added with CaCl2 solution to produce calcium citrate. Finally, calcium citrate is acidified with H2SO4 solution to collect crystals of citric acid. In this study, the fruits were crushed, juice filtered, neutralized, added CaCl2 solution, and acidified to obtain citric acid. The experiments were carried out by varying different volumes of 2.5 M NaOH solution during neutralization, concentrations of CaCl2 solution, and volume of H2SO4 solution. The percentage of citric acid yield collected from grape juice varied from 44.1 to 79.53%. Similarly, the percentage yield of citric acid was calculated to be from 60.1 to 96.3%. It was found that the percentage of citric acid yield increased with increasing pH and decreased with increasing CaCl2 concentration. Thus, it could be concluded that the orange juice yielded more citric acid than grape juice.
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In this paper,by means of confined free swelling test and confined swelling test under loads,redbed mudstone of Shaximiao group in the Middle Jurassic in Chongqing area is present to study its swelling characteristics under confined free and loading conditions,and swelling under different water injections as well.Results reveal that three phases are present in the confined free swelling of mudstone,fast swelling deformation and high swelling increasment in the first phase and increasing swelling velocity in the second phase.95 percent swelling occurs in the former two phases.It is found that vertical loads greatly restrain the confined swelling of mudstone.The confined loading swelling ratios decrease sharply with the increasing vertical loads.Moreover,the amount of water has no obvious effect on swelling characteristic of red bed mudstone within a short time under confined without load,but it plays a controlling role on the stable swelling capacities,swelling processes and characteristics as time lapsing.
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Woven roving jute fiber-reinforced unsaturated polyester composites were subjected to water absorption tests in order to study the effects of water ageing on the mechanical properties. Composite specimens were immersed in distilled water and salt water up to 2736 h. The water absorption of specimens reached to an equilibrium level after an immersion time of 300 h. It was observed that tensile, flexural, and interlaminar shear strengths (ILSSs) of jute/polyester composites decreased depending on the immersion time. The ILSS values of the composites were reduced by more than 53% for both the distilled water and the salt water after an immersion time of 2736 h.
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Citrus fruits contain sufficient citric acid, which is the main tricarboxylic acid. The properties of citric acid make it an important additive in various process industries. This experimental study aims to produce citric acid from orange and grape juices. The chemical route for the synthesis of citric acid from citrus juices involves three steps: (i) neutralization to adjust pH (9-11) with a 2.8 M NaOH solution, (ii) addition of CaCl2 solution (40.3-41.1% w/v), and (iii) acidification with an H2SO4 solution (1.5-2.3 M) to produce citric acid. In this study, the fruits were peeled, crushed, filtered, neutralized, added CaCl2 solution, and acidified to obtain citric acid. The experiments were carried out by varying the final pH of the solution and the concentrations of CaCl2 and H2SO4 solutions, maintaining the total volume constant. A maximum citric acid yield of 91.1% and 79.8% were achieved from orange and grapefruits, respectively, at the optimum final pH of the solution and the concentrations of CaCl2 and H2SO4 solutions at 10, 40.7% w/v, and 1.9 M, respectively. Finally, the purified citric acid crystals were characterized using FTIR and XRD. Thus, it could be concluded that orange fruit would be a promising source for citric acid production than grape.
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