Copyright (c) 2009 All rights reserved. http://works.bepress.com/el_sayed_abdel_rahman Recent documents in Dr. Eng. El-Sayed Ali Abdel-Rahman en-us Sun, 15 Nov 2009 23:21:34 PST 3600 http://works.bepress.com/el_sayed_abdel_rahman/4 http://works.bepress.com/el_sayed_abdel_rahman/4 Sat, 14 Nov 2009 01:26:40 PST In the present study, the sensitivity and accuracy of the common methods of dextran determination were investigated. Concentrations and progressions of dextran during different sugar production processes and industrial periods were determined and for the first time an evaluation of sugar and molasses quality was provided based on the measurement results. Regarding the dextran determination, the results had shown a significant effect of dextran concentration and molecular fractions on the Haze and Robert's methods. The data demonstrate that the Robert's method was more accurate for different dextran molecular mass fractions than Haze method. Furthermore, the Haze method was too inaccurate to be genuinely useful as a dextran analysis method especially considering low dextran molecular mass fractions. The isolation and identification of Leuconostoc mesenteroides as an important source of dextran in sugar beet factories was performed. It was observed, that the microorganisms grow during the storage of sugar beet and also during the extraction process. The mean counts of colonies were reduced after washing process from 2.5*103 cfu/g of the sugar beet sample to 6*102 cfu/g of cossettes samples. However, the number of microorganisms increased in raw juice after extraction process to reach almost 4*106. In addition, these numbers depend on the degree of deterioration of the sugar beets. Dextran content increased during the extraction process by 4 % to 20 % for fresh and deteriorated sugar beet, respectively. In contrast, the lime-carbon dioxide juice purification reduced the dextran content in raw juice by 40 % to 60 %. The obtained results from Egyptian sugar beet factories showed a correlation between the increase of sugar loss and the presence of dextran during different industrial periods as well as during the production process itself.. As a main focus in this work the negative effects of the presence of dextran during (isothermal) crystallization were investigated. The growth rate of sucrose crystals and the quality of the sugar production in pure sucrose solution at different temperatures were studied. To elucidate the influence of dextran on the growth rate of sucrose crystals, different molecular mass fractions of dextran from 40,000 g/mol (T40) to 2,000,000 g/mol (T2000) were admixed in different concentrations to pure sucrose solution. The most pronounced effect of dextran was found with T2000 at 60°C. On the other hand, negligible influences of dextran T40 and T500 were observed at the same temperature and supersaturation. The high adsorption ability and the increase of solution viscosity particularly caused by high molecular fractions of dextran were identified as the main reasons for the reduction of crystal growth rate. The application of lower temperatures during crystallization enhances the problems deriving from dextran. Regarding the final crystallization steps (e.g. after product crystallization), levels of dextrans and impurities are enhanced and the mentioned problems will be amplified in these production steps. From the morphological studies, it was found that the presence of dextran in sugar mother liquor leads to elongation of the sucrose crystal shape (elongated along the c-axis). In particular, the lower molecular mass fractions of dextran are involved in this effect. A scanning electron microscope (SEM) was utilized for the evaluation of crystal surfaces and crystal morphology. The surface topography of sucrose crystals was affected by the presence of higher dextran molecular mass fractions (T2000), which causes gaps, rough areas and strong adsorption of micro-particles (micro-crystals) on the crystal surface. Again, the described influences are enhanced by the application of lower temperatures. In addition, in this work it could be confirmed that there is a correlation between the dextran content in syrup and quality of sugar produced, in particular the turbidity of the sugar. So, a relation which has already been described in recent literature for organic macromolecules in general could be specified for dextran molecular fractions. El-Sayed Ali Abdel-Rahman Food Process Engineering http://works.bepress.com/el_sayed_abdel_rahman/3 http://works.bepress.com/el_sayed_abdel_rahman/3 Sat, 14 Nov 2009 00:41:49 PST The quality of sugar production in sugar beet factories depends on many parameters, in particular on the properties of sugar syrup (thick juice). The aim of this study is to investigate negative effects of dextran presence during the crystallization process on growth rate of sucrose crystals in pure sucrose solution at different temperatures. To elucidate the influence of dextran presence on the growth rate of sucrose crystals, different molecular weight fractions of dextran from 40,000 g/mol (T40) to 2,000,000 g/mol (T2000) were admixed in different concentrations to pure sucrose solution. The most pronounced effect of dextran was found with T2000 at concentrations of 1500 and 5000 ppm at 60 °C. On contrary, negligible influence of dextran T40 and T500 was observed at the same temperature and supersaturation. From the results it could be shown that a decrease of crystallization rate of up to 50% with dextran admixture, compared to crystallization rate with pure sucrose solution, could be obtained. Such a negative influence extends crystallization time in the sugar house and thus increases the production costs. El-Sayed Ali Abdel-Rahman Food Process Engineering email: elsayed30@hotmail.com http://works.bepress.com/el_sayed_abdel_rahman/2 http://works.bepress.com/el_sayed_abdel_rahman/2 Mon, 06 Oct 2008 12:37:34 PDT This study was conducted to assess in detail the possible effects of some technological processes such as soaking, germination, cooking, soaking + cooking, and germination + cooking on the lipid composition of mung bean seeds of Giza 1 variety. TLC analysis of mung bean lipids showed that the phospholipids and triglycerides recorded the highest percentage among lipid fractions (32.26 and 30.10%), while the 1,3 diglycerides constituted the least percentage (2.80%) in mung bean seeds. The soaking, germination and cooking processes caused a decrease in the phospholipids, triglycerides and hydrocarbons accompanied with an increase in monoglycerides, 1,2-(2,3)-diglycerides, sterols and free fatty acids. Eleven fractions were separated from phospholipids class of the studied samples; seven of these fractions were identified. The major component of phospholipids was phosphatidyl choline, amounting to 21.30, 17.84, 16.21, 13.87, 13.20 and 11.47% of the total phospholipids in raw, soaked, germinated, raw-cooked, soaked-cooked and germinated-cooked mung bean seeds, respectively. Gas liquid chromatography of the total lipids of mung bean seeds showed that the unsaturated fatty acids represented 69.58, 64.35, 63.3, 63.16, 61.84 and 61.12%, while the levels of saturated fatty acids were low being 30.37, 34.05, 35.66, 34.64, 37.93 and 38.75% of the total fatty acids in raw, soaked, germinated, raw-cooked, soaked-cooked and germinated-cooked, respectively. The total essential fatty acids (linoleic and linolenic) represented the highest proportion of fatty acids (50.10% of the total fatty acids). El-Sayed Ali Abdel-Rahman Food Technology http://works.bepress.com/el_sayed_abdel_rahman/1 http://works.bepress.com/el_sayed_abdel_rahman/1 Mon, 06 Oct 2008 12:37:29 PDT The starch yields from both whole (MSI1) and decorticated mung bean seeds (MSI2) were 26.00 and 30.50% on total seed basis and 64.40 and 75.55% of total starch. Chemical analysis of the starch isolates i.e. MSI1 and MSI2 showed that they contained 9.00 and 8.90% moisture, 0.76 and 0.80% protein, 0.05 and 0.09% oil and 0.20 and 0.13% ash , respectively. The results also indicated that the purity of starch isolates was high. Microscopic examination (400X) showed that most mung bean starch granules had irregular shapes, which varied from oval, round to bean-shaped. Mung bean starch granule size varied from 7.65-33.15 µm with mean value at 20.40 µm. Studying the physico-chemical properties of mung bean starch indicated that the gelatinization temperature range was 65-69-75°C at initial, midpoint and final gelatinization of starch granules. Mung bean starch had a considerably lower degree of syneresis than other legume starches. Moreover, gel consistency decreased as starch concentration was increased. Viscosity of mung bean starch was high indicating that it had higher resistance to swelling and rupture than did cereal starches. The results indicated that the swelling power and solubility of the starch increased with increasing temperature. In addition, the solubility percentage increased, but non-linearly, with increasing swelling power. El-Sayed Ali Abdel-Rahman Separation and purification processes for food production