zahra emam-djomeh | University of Tehran (original) (raw)

Papers by zahra emam-djomeh

The pomegranate juice with high nutritional value has turbid appearance that makes it difficult t... more The pomegranate juice with high nutritional value has turbid appearance that makes it difficult to preserve and concentrate. Microfiltration is useful process which can clarify it. One of the most important problems in this process is fouling phenomenon which affected by several parameters. The effects of fluid velocity, transmembrane pressure, membrane type and its pore size on membrane fouling were studied. The results showed that the membrane fouling increased with increase in the fluid velocity and transmembrane pressure. Also, more hydrophilic property and pore size resulted more membrane fouling due to greater flux which move more particles to membrane surface. Scanning electron microscopy (SEM) images support these results. Keywords: Clarification, Fouling, Membrane, Pomegranate juice

Journal of Applied Research and Technology, 2012

Physical aging of semicrystalline polyethylene terephthalate was studied using differential scann... more Physical aging of semicrystalline polyethylene terephthalate was studied using differential scanning calorimetry(DSC). PET samples with crystallinity content of 0.28 were aged at two different temperatures, 25 and 45°C. Thesamples were stored for several days and periodically tested using DSC method. The glass transition temperature forthe samples aged at 25°C was about 73-74°C, and the position and intensity of endothermic peaks wereapproximately constant. Higher glass transition of the samples aged at 45°C, 73-86°C, was attributed to the enthalpyrelaxation process of amorphous regions of semicrystalline PET. For the samples aged at 45°C, the endothermicpeaks shifted to higher temperatures with increasing aging time. The position of the endothermic peaks determined bythe temperature of the maximum, Tmax, tended to increase with aging time for samples aged at 45°C, and theintensity of the peaks continuously increased with time; however, the results showed that the aging of PET sampl...

e-Polymers, 2008

The migration of di-(2-ethylhexyl) adipate (DEHA), di-(2-ethylhexyl) phthalate (DEHP) and ethylen... more The migration of di-(2-ethylhexyl) adipate (DEHA), di-(2-ethylhexyl) phthalate (DEHP) and ethylene glycol from PET bottles into the Iranian yogurt drink was studied. According to European Commission regulations acetic acid (3% w/v) was chosen as stimulant. The acetic acid samples were stored at 4, 25 and 45 °C for four months and analyzed periodically by gas chromatography. Differential scanning calorimetry (DSC) was used to investigate if contact with the food stimulant could affect the PET material. It was concluded that the storage temperature had a great effect on the migration of DEHP, DEHA and ethylene glycol. Also increasing storage time resulted in higher concentrations of migrating substances. The concentrations of migrating substances did not exceed their specific migration limit (EEC regulations). Determination of glass transition (Tg) and crystallinity of PET bottles using DSC method showed that the variations in the migration rate of selected contaminants during the tim...

World Journal of Microbiology and Biotechnology, 2010

Journal of Food Science and Technology, 2011

Pomegranate juice's valuable nutritional components may be reduced during its processing or stora... more Pomegranate juice's valuable nutritional components may be reduced during its processing or storage. This work examined the effect of frozen storage at −25°C on some chemical characteristics of pomegranate juice. Total anthocyanin content of pomegranate juice, which was measured using the pH differential method, decreased by 11% after 20 days of frozen storage. Phenolic components, measured using a Folin and Ciocalteu assay by means of a UV-vis spectrophotometer, decreased by 29% after 20 days of frozen storage. Antioxidant activity, measured based on the radical scavenging properties of the juice using the 2,2-diphenyl-1-picrylhydrazyl method, decreased by 50% after 20 days of frozen storage. Pomegranate juice has 5 major anthocyanins, including Cyanidin 3-glucoside, Cyanidin 3,5-diglucoside, Delphinidin 3-glucoside, Pelargonidin 3-glucoside and Pelargonidin 3,5-diglucoside are 5 major anthocyanins of pomegranate juice. They were measured using the LC-MS method and results showed that Pelargonidin 3,5-diglucoside had the greatest decrease. Also, the LC-MS method showed that ellagic acid decreased by 15%.

International journal of Advanced Biological and Biomedical Research, 2013

The pomegranate seeds of four Iranian commercial varieties (Abanmahi (AB), Malas (MS), Pust Sefi... more The pomegranate seeds of four Iranian commercial varieties (Abanmahi (AB), Malas (MS), Pust Sefid (PS) and Shahvar (SH)) were evaluated in terms of some quality properties including protein, oil, dietary fiber, mineral contents and fatty acid composition. Physicochemical properties and antioxidant activity of pomegranate seed oils (PSOs) were also determined. The oil antioxidant activity was measured by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity. Results showed that PS had the highest oil (16.9%) and crude fiber (42.4%), and nutritional value (460.7Kcal/100g) among selected varieties. PS had the highest level of phosphorus (2766.3 mg/kg) and magnesium (2052.0mg/kg), while the highest calcium (675.3mg/kg) and potassium (3724.6mg/kg) were related to SH. The main fatty acid identified by gas chromatography was punicic acid ranged from 72.07% for SH to 73.31% for MS (p<0.05). The ratios of polyunsaturated/saturated and unsaturated/saturated fatty acids of PSOs ...

Carbohydrate Polymers, 2014

Chitosan-nanocellulose biocomposites were prepared from chitosan having molecular weight of 600-8... more Chitosan-nanocellulose biocomposites were prepared from chitosan having molecular weight of 600-800 kDa, nanocellulose with 20-50 nm diameters and various levels of 30, 60 and 90% (v/w CHT) for glycerol. Agitation and sonication were used to facilitate even dispersion of particles in the polymer matrix. The nanocomposites were examined by differential scanning calorimetry, X-ray diffraction and agar disc diffusion tests; finally, the film was applied on the surface of ground meat to evaluate its performance in real terms. Chitosan-nanocellulose nanocomposites showed high T g range of 115-124 • C and were able to keep their solid state until the temperature (T m) range of 97-99 • C. XRD photographs revealed that nanocellulose peak completely disappeared after their addition to chitosan context. Agar disc diffusion method proved that the nancomposite had inhibitory effects against both gram-positive (S. aureus) and gram-negative (E. coli and S. enteritidis) bacteria through its contact area. Application of chitosan-nanocellulose nanocomposite on the ground meat decreased lactic acid bacteria population compared with nylon packaged samples up to 1.3 and 3.1 logarithmic cycles at 3 and 25 • C after 6 days of storage, respectively.

In this research, natural canthaxanthin as one of the most important carotenoids was extracted fr... more In this research, natural canthaxanthin as one of the most important carotenoids was extracted from Dietzia natronolimnaea HS-1. The changes of canthaxanthin enriched in oilin- water emulsions with vegetable oil (5 mg/ 100 mL), Arabic gum (5 mg/100 mL), and potassium sorbate (0.5 g/100 mL) was investigated. The effects of different pH (3, 5 and 7), as well as, time treatment (3, 18 and 33 days) in the environmental temperature (24°C) on the degradation were studied by response surface methodology (RSM). The Hunter values (L*, a*, and b*) and the concentration of canthaxanthin (C, mg/L) illustrated more degradation of this pigment at low pHs (pH≤ 4) by passing the time (days≥10) with R² 97.00%, 91.31%, 97.60%, and 99.54% for C, L*, a*, and b* respectively. The predicted model were found to be significant (p<0.05).

Journal of Dairy Science, 2006

The effect of the concentration of starter inoculated to milk on the composition, free tyrosine-t... more The effect of the concentration of starter inoculated to milk on the composition, free tyrosine-tryptophan content, microstructure, opacity, and fracture stress of Iranian White cheese (IWC) was studied during 50 d of ripening in brine. Three treatments of cheese were made using 1-fold (IWC1S), 2-fold (IWC2S), and 4-fold (IWC4S) concentrations of a direct-to-vat mesophilic mixed culture containing Lactococcus lactis ssp. cremoris and Lactococcus lactis ssp. lactis as starter. As ripening progressed, moisture and protein contents of the treatments continuously decreased, whereas their total ash, salt, and salt in moisture contents increased. Fat content and pH of cheeses remained stable during ripening. The pH of cheese milk at the time of renneting, which decreased by increasing the concentration of starter (6.57, 6.49, and 6.29 for IWC1S, IWC2S, and IWC4S, respectively), significantly affected most of the chemical characteristics and opacity of cheese. Lower pH values at renneting decreased moisture and ash contents, whereas cheese protein content increased. The concentration of free tyrosine-tryptophan in curd increased at first 29 d but decreased between d 29 and 49 of aging. The changes observed in cheese whiteness followed the changes in moisture content of the treatments. As the concentration of starter inoculated to milk increased, the value of fracture stress at a given ripening time significantly decreased, leading to a less resistant body against applied stress. A similar trend was also observed for fracture strain during cheese ripening. The micrographs taken by scanning electron microscopy provided a meaningful explanation for decrease in the value of fracture stress. As the cheese ripening progressed or the concentration of starter increased, the surface area occupied by the protein fraction in cheese microstructure decreased, leading the way to lower the force-bearing component in cheese texture.

International Journal of Biological Macromolecules, 2015

The effect of high-shear homogenization on the rheological and particle size characteristics of t... more The effect of high-shear homogenization on the rheological and particle size characteristics of three species of gum tragacanth (GT) was detected. Dispersions were subjected to 0-20 min treatment. Static light scattering techniques and rheological tests were used to study the effect of treatment. The results showed that the process caused a decrease in particle size parameters for all three species, but interestingly, the apparent viscosities increased. The highest increase of apparent viscosity was found for solutions containing Astragalus gossypinus, which possessed the highest insoluble fraction. The viscoelastic behaviors of dispersions were also significantly influenced by the process. Homogenization caused an increase in both G and G , in all three species. The alterations seem to be highly dependent on GT species and structure. The results could be of high importance in the industry, since the process will lead to textural modifications of food products containing GT.

Journal of Dispersion Science and Technology, 2014

The accuracy of the Content should not be relied upon and should be independently verified with p... more The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden.

International Journal of Food Properties, 2013

The mechanical characteristics (rupture force, maximal deformation, and rupture energy) of red an... more The mechanical characteristics (rupture force, maximal deformation, and rupture energy) of red and green lentils under compression loading were determined as a function of moisture content ranging from 9.5 to 21.1% (w.b.). Scanning electron microscopy, laser diffraction particle size analysis, and instrumental texture evaluation were successfully applied to relate the microstructure and texture of different lentil seed varieties. Results demonstrated that all of the mechanical parameters of the green lentils, which have smaller starch granules, were significantly (p < 0.05) higher than those of the red lentils. At a loading rate of 4 mm min −1 , the force required for initiating seed rupture decreased with an increase in moisture content, for vertical and horizontal orientations (p < 0.05). The scanning electron microscopy observations also revealed that seeds were more flexible in a horizontal orientation.

International Journal of Biological Macromolecules, 2013

Doogh is a fermented dairy drink which is highly consumed by Iranian people. Stability of this he... more Doogh is a fermented dairy drink which is highly consumed by Iranian people. Stability of this healthy drink was investigated in terms of sedimentation rate, viscosity, density and particle size characteristics including surface-weighted mean diameter (D 32), Span and particle uniformity. Eight treatments were performed as randomized complete block design (RCBD) with three replications. Three types of pectin (high methoxyl pectin (HMP), grapefruit-seed extract pectin (GSEP) and amidated pectin (Ceamsa pectin (CSP)) at a constant concentration (0.35%w/w), three levels of salt (0.50, 0.75 and 1.00%w/w) and two dry matter contents (DMCs, 4 and 5% w/w) were used to produce the Dooghs. The results showed that the maximum stability and viscosity, and the minimum D 32 were obtained by application of CSP, GSEP and HMP, respectively (p < 0.05). Pectin type had no significant difference on the density values of Dooghs. The lowest sedimentation rate, viscosity, density and D 32 were achieved in the minimum concentrations of salt and dry matter. The ANOVA analysis also revealed that the interaction of pectin type, salt concentration and DMC had a significant effect on the Span and particle uniformity. A maximum physical stability was found for the prepared samples with 0.35%w/w CSP, 0.5%w/w salt and 4%w/w dry matter. Evaluation of sensory attributes also confirmed that this formulation had the highest overall acceptability value.

Dairy Science & Technology, 2012

The main aim of the present study was to optimize the hydrolysis conditions of whey protein isola... more The main aim of the present study was to optimize the hydrolysis conditions of whey protein isolate digested by a protease preparation from Aspergilus oryzae through response surface method (RSM) in order to achieve the maximum angiotensin I-converting enzyme (ACE)-inhibitory activity and antioxidant properties. The effects of hydrolysis conditions including time (2, 13, 24, 35, and 46 h), temperature (40, 45, 50, 55, and 60°C) and pH (6, 6.5, 7, 7.5, and 8) were investigated on the bioactivity of whey protein hydrolysates. Each process parameter emerged to have a dual effect on bioactivity; that is, increase in all variables promoted bioactive peptide generation through facilitating enzyme access to the primary protein sequence by partial unfolding of the compact globular assemblies of whey proteins. However, prolonged digestion at high temperatures and alkaline pH were concomitant with decreased bioactivity which are attributed to hydrolysate aggregation and splitting of bioactive peptides into biologically inactive counterparts, respectively. Nonetheless, some discrepancies were observed between the trend of ACEinhibitory activity and that of antioxidant activity changes which was explained in light of their general characteristics. RSM efficiently identified the critical levels of each variable to obtain maximum bioactivity. It was shown that hydrolysate prepared at 56.54°C and pH 6.04 resulting from digestion for 3.89 h exerted 74% ACE-inhibitory activity, 666.31 μM trolox equivalent/mg antioxidant activity, and 14.03% hydrolysis degree.

Advances in Water Resources, 1998

Artificial neural network (ANN) is considered to be a powerful tool for solving groundwater probl... more Artificial neural network (ANN) is considered to be a powerful tool for solving groundwater problems which require a large number of flow and contaminant transport (GFCT) simulations. Often, GFCT models are nonlinear, and they are difficult to solve using traditional numerical methods to simulate specific input-output responses. In order to avoid these difficulties, ANN may be used to simulate the GFCT responses explicitly. In this manuscript, recent research related to the application of ANN in simulating GFCT responses is critically reviewed, and six research areas are identified. In order to study these areas, a one-dimensional unsaturated flow and transport scenario was developed, and ANN was used to simulate the effects of specific GFCT parameters on overall results. Using these results, ANN concepts related to architecture, sampling, training, and multiple function approximations are studied, and ANN training using back-propagation algorithm (BPA) and genetic algorithm (GA) are compared. These results are summarized, and appropriate conclusions are made.

Iranian Journal of Chemistry & Chemical Engineering-international English Edition, Sep 1, 2012

The effect of oleic acid (5 and 10% v/v) and xanthan gum (0.5 and 1% wt) on partitioning and rete... more The effect of oleic acid (5 and 10% v/v) and xanthan gum (0.5 and 1% wt) on partitioning and retention of ethyl acetate and diacetyl from two matrices with a different composition was investigated by applying static head space gas chromatography. Two matrices with different composition have been developed: one containing carbohydrates (xanthan gum) and in the second one, called complex matrix, lipid (oleic acid) was added. The roles of Xanthan Gum (XG) and lipid (oleic acid) on the retention of aroma compounds were pointed out. Changes in the composition of matrices exhibited a considerable effect on the air/liquid partition coefficient (K a/l) values at equilibrium. The kinetic study of the release from both matrices had shown a decrease of the initial rate of release (R i) by reference with water. The rheological properties of all matrices were investigated and the flow behavior of all matrices was successfully modeled with power law and cross models. Power law model was found as the better model to describe the flow behavior of dispersions.

Iranian Journal of Chemistry & Chemical Engineering-international English Edition, Jun 1, 2012

Various scaling methods such as relative viscosity, Peclet and Reynolds scaling were used to find... more Various scaling methods such as relative viscosity, Peclet and Reynolds scaling were used to find the best scaling law. Scaling and modeling of the flow curves of various model emulsions consist of Tragacanth Gum (TG) (0.5, 1 % wt), Oleic acid (5, 10% v/v) and WPI (2, 4 % wt) were investigated and the best models were selected. As these emulsions are non-Newtonian, they do not obey the usual, simple scaling laws. When the apparent viscosity is reduced to relative viscosity of the medium at zero shear rate, a distinct reduced flow curve is obtained, regardless of TG, oleic acid and WPI concentrations. This will lead to a technique of simplifying complex non-Newtonian flow curves and therefore predicting the rheological flow curves and fluid mechanics when different modifiers are added to food emulsions. The flow behavior of all samples was successfully modeled with Cross, power law and Ellis models and power law model was found as the better model to describe the flow behavior of dispersions. Results showed that both G' and G'' increased with TG, oleic acid and WPI concentrations with pronounce effect of TG content.

European Food Research and Technology, 2009

This paper reports on the diversity and dynamics of the dominant microbial populations during 23 ... more This paper reports on the diversity and dynamics of the dominant microbial populations during 23 manufacturing and ripening of Lighvan, a traditional, starter-free Iranian cheese made from raw ewe's and 24 goat's milk, as determined by culturing and PCR-DGGE. Similar dominant populations, composed of Lactococcus lactis and Lactobacillus spp. strains, were found by both techniques. However, discrepancies 26 regarding the identity of these Lactobacillus species were encountered. Lactobacillus curvatus and 27 Lactobacillus sakei proved to be dominant by PCR-DGGE in milk and 4-and 13 week-old cheese samples; 28 however, Lactobacillus brevis, Lactobacillus plantarum, Lactobacillus paraplantarum and Lactobacillus 29 paracasei were the majority cultivable organisms. RAPD typing of lactobacilli isolates showed wide 30 genetic diversity among the different species. Moreover, species and strains evolve over manufacturing and 31 ripening. L. brevis and L. paraplantarum were dominant in milk but were replaced by L. plantarum and L. 32 paracasei strains as ripening progressed. 33 34 1. Introduction 35 Lighvan cheese is a semi-hard, starter-free, traditional Iranian cheese from the mountainous area of 36 Lighvan in the Province of Azerbaijan, Iran, made from a mixture of raw ewe's and goat's milk. The 37 manufacture of Lighvan cheese involves coagulation of evening and morning milk with lamb rennet at 28-38 32 ºC (depending on the season). The coagulum is cut into walnut-size pieces that are then transferred to 39 rectangular-shaped bags and piled up for whey drainage. The resulting curd mass is then cut into 25×25×25 40 cm 3 cubes and placed in a 22% brine flow for 6 h. After removal, the curd cubes are kept in a basin for 3-5 41 days, in which whey drainage continues. During this period the cubes are turned upside down between 9 42 and 15 times. Finally, they are packed in 10-12% brine. Ripening takes place in deep-natural or man-made 43 caves for 3-4 months at an average temperature of 10-12 ºC. 44 Despite the popularity of Lighvan cheese and its ever increasing consumption figures, its chemical 45 composition has been little studied. Even less is known about the microbial communities involved in its 46 manufacture and ripening; only the dominant bacterial genera of mature cheeses have been reported [1, 2]. 47 Knowledge in this area is of particular interest since the typical sensorial properties of traditional cheeses 48 rely on the complex biochemical processes driven by the indigenous microbiota [3] (as well as on the 49 Page 2 of 20 http://mc.manuscriptcentral.com/efrt European Food Research and Technology 65 population dynamics over cheese manufacture and ripening [17-21]. In some cases, however, a 66 combination of culturing and molecular techniques is preferred since complementary results are obtained 67 [22, 23]. In addition, culturing allows the isolation, identification and selection of starter and adjunct 68 cultures. 69 This paper reports the basic chemical characteristics of Lighvan cheese during manufacture and 70 ripening, as well as a preliminary inspection of the dominant microbial communities as determined by 71 DGGE. In addition, the Lactobacillus species in milk, curd and cheese at different stages of ripening 72 (lactobacilli were the majority species throughout ripening) were identified by phenotypic and molecular 73 methods. The characterization of these lactobacillus strains would be of much help in the design of specific 74 starter cultures for the production of standardized Lighvan cheese.

In this study, the effect of addition of three different levels of microbial lipase (0, 4, and 8.... more In this study, the effect of addition of three different levels of microbial lipase (0, 4, and 8.0 g lipase in 100 kg milk) was investigated on the physiochemical properties, free fatty acids, textural properties, and microstructure of Lighvan cheese during ripening. The addition of lipase did not significantly affect pH, acidity, moisture, and salt content of Lighvan cheese, but increased its free fatty acid content considerably. It also increased hardness and decreased the brittleness of Lighvan cheese in all stages of ripening. The number and the mean diameter of fat globules, which were entrapped in casein network, were affected by all levels of the added lipase. Following the addition of lipase to Lighvan cheese and after 90 days of ripening, individual fat globules or their aggregates totally disappeared and some fingerprints of fat were observed. Disappearance of fat globules along with increase in protein matrix junctions leads to uniform structure of casein consisting voids which are produced from fermentation.