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Showing 102 results for mahmoudi
Volume 17, Issue 4 (Winter 2013)
Abstract
Lack of a clear definition of loss of profit and confusing it with similar concepts has led to its ambiguity. Such ambiguity can be seen in the theoretical analysis as well as in the practices of the courts. This ambiguity persists while the concept of loss of profit has an important presence in industry, manufacturing and trade. Hence this concept has been accepted in the insurance industry in Iran and worldwide. This paper, through redefining the loss of profit and its comparison with similar institutions in the context of comparative studies, gives a clear definition of it, and shows that loss of profit is conceptually different from loss of benefit, loss of chance and economic loss. The study further reveals that the unconditional rejection of loss of profit, loss of benefit, loss of chance, and economic loss is in conflict with the economic, industrial and social realities, and that in certain cases, compensation should be awarded by applying common practice criterias.
Volume 17, Issue 5 (9-2015)
Abstract
The effects of dietary nucleotide (NT) were evaluated on some serum biochemical parameters and acute stress responses of the catfish (Pangasianodon hypophthalmus). Five experimental diets including 0, 0.25, 0.5, 0.75, and 1% NT were supplied to catfish fry for 10 weeks. At the end of the experiment, fish fed the control and 1% NT diets were subjected to handling and crowding stress. The results showed that the fish supplied with 0.25-0.75% NT had a lower level of lactate dehydrogenase (LDH) (P<0.05) while other serum enzymes including alkaline phosphatase (ALP), asparate transaminase (ASP), and alanine transaminase (ALT) were not significantly reduced by NT inclusion in the diet (P>0.05). The fish which received the highest doses (0.75 and 1%) of NT exhibited higher levels of triglyceride than the other groups (P<0.05) while they showed no significant differences in other biochemical parameters including total protein, albumin, globulin, cholesterol, and glucose (P>0.05). To investigate stress responses, cortisol (primary response), serum glucose, and serum ion concentrations including sodium, potassium and calcium (secondary responses) were measured. The results showed significant fluctuations in all the tested components during the sampling intervals for up to 48 h post-stress; the exceptions, however, were glucose in the group on the 1% NT diet as well as serum cortisol and calcium levels in those supplied with the control diet. Based on the results obtained, it may be concluded that dietary NT can improve liver function in iridescent catfish, but it has no obvious positive effects on other serum biochemical parameters and stress responses.
Volume 17, Issue 12 (2-2018)
Abstract
In the present paper, forming of clamped triangular plates by means of water has been investigated. The plates were made of st-12 and had the thicknesses of 1 and 2 millimeters. The experimental tests were performed at the impact laboratory of Guilan University using drop hammer system. Various aspects of numerical investigation were simulated by Abaqus software. As mentioned above, using drop hammer system as a hydrodynamic loading tool and carrying out different empirical tests in this study, the effect of factors such as thickness, standoff distance of hammer and its weight, i.e. the applied momentum to the system have been studied. In the numerical simulations, the deformations of triangular plates were simulated by smoothed-particle hydrodynamics method. Also, the Fluid-Structure Interaction was considered for simulating the fluid phase and the plate deformation was modeled using finite element method in the form of coupled SPH/FEM. Furthermore, the ultimate deformation, stress distribution, stress concentration of plates and position of maximum deformation on triangular plate have been investigated. Agreement between the obtained data from numerical simulations and experiments guarantied the accuracy of simulations.
Volume 17, Issue 67 (12-2020)
Abstract
At the end of safavid dynasty, Hazin-e- Lahiji was one of the most remarkable poets. In his youth, he witnessed the collapse of the dynasty. This collapse gradually changed the political atmosphere and sequentially socio-economic and cultural status which led to alteration in the dominant discourse if arts, thus literature took a turn from Hindi style to Literary restoration. Hazin had always been recognized as a poet of Hindi style. This article by useing content analysing method (descriptive-analytical and statistical) proves that Hazin ,as an artist of this transition period, as opposed to the common theory of being a poet of Hindi style, is actually one of the artists of literary restoration style and in his prose works he has been influenced by Safavid objective and also some of constitutional perspectives. This study investigates his life and studies his works, then for determining his style more accurately, reviews the stylistic characteristics of the first circle of Literary restoration and compares them to the characteristics of Hazin`s poems. Therefore suggests that Hazin should be considered as the beginner of restoration style more than he should be seen as a follower of Hindi style.
Volume 17, Issue 104 (October 2020)
Abstract
Maintaining the nutritional quality and preserving pomegranate seeds is a major challange due to the fast degradation of the texture, color and overall quality of pomegranate seeds. In order to investigate the freezing of coated pomegranate seeds with chitosan and determine its quality during freezing storage, an experiment was conducted, in a factorial arrangement in a completely randomized design with three replications. Factors were: chitosan at three levels (0, 1 and 2%), freezing temperature at two levels (-14 ° -24 ° C) and time at 5 different storage times (14 days, 30 days, 60 days, 90 days, and 120 days). The highest tissue firmness was observed for 14 days of storage under both chitosan concentrations. Interaction of different levels of chitosan coating and time had an increasing effect on the color component changes, so that the most color changes in the brightness (L*), redness (a*), and yellowness (b*) was related to the use of chitosan coating 2%, were maintained at 60 days. The highest total soluble solids were related to 1% chitosan under 4 months of storage at -14°C. Maximum total acidity (1.36 mg / L) was also attributed to coated pomegranate seeds during 120 days of storage under both freezing temperatures of -14°C and -24°C. The results of mean compares showed that the total phenol stability under freezing temperature was higher at -14°C and after 120 days of storage, more phenol content was observed in the seeds in -24° C. The overall results indicated a positive effect of chitosan on maintaining the quality of pomegranate seeds during freezing, and the freezing temperature of -24° C with decreasing color changes during storage, played an important role in reducing metabolic activity and reducing anthocyanin degradation and was effective in maintaining fruit quality.
Volume 17, Issue 107 (January 2021)
Abstract
In this research, the production of a probiotic drink based on jujube extract by means of fermentation with Lactobacillus plantarum and Lactobacillus delbrueckii as probiotic lactic acid bacteria has been studied. The fermentation was performed for 72 hours at 37°C. The changes in microbial population, pH and titratable acidity as well as sugar and organic acid metabolism during the fermentation period were evaluated. Appropriate growth of L. plantarum and L.delbruckii resulted in an increase in acidity to 1.86 and 1.75, and a decline in pH to 3.4 and 3.56, respectively after 72 hours. Glucose and fructose were significantly consumed by the strains. Citric acid concentration reduced to 1.12 g/l and 5.8 g/l in the extract fermented by L. plantarum and L. delbrueckii, respectively after 72 hours. Lactic acid was produced by L. plantarum and L. Delbrueckii with 23.8 and 11.4 g/l lactic acid, respectively at the end of fermentation. L.plantarum cells exhibited more resistance toward cold storage conditions. So that at the end of the third week of cold storage conditions, the viable cells of L. plantarum was 3.2 × 101 × CFU / mL, while no viable cells of L.delbruekii was observed at this week. In general, it can be concluded that the fermentation of jujube by L. plantarum and L. delbrueckii could be considered as an appropriate way to improve the functional properties of beverages.
Volume 18, Issue 2 (7-2018)
Abstract
Braces systems have been commonly used as load-bearing systems in steel structures due to their easy and rapid construction and erection, reduced amount of materials used for the lateral load-bearing system (as compared to the shear wall system), and higher conformity with structural deformations at upper stories Buildings in seismic regions are prone to severe damage due to large deformations and low capacity to absorb energy. X-bracing is effectively employed in maintaining the structure stability when earthquakes occur or extreme lateral loads act on the structure. The widespread use of X-bracing systems in steel structures reveals the importance of understanding mid-connections in this kind of braces. When applying a lateral force on X-braces, one structural member comes under tension while the second one is under stress. Buckling occurs to the member subjected to stress and when effective length factor reduces, the member handles a more critical load. X-brace effective length factor is not only influenced by end connection forces but it also depends on mid-connection and its implementation. If the stiffness of tensile bracing is considerable enough, the mid-connection can provide the interaction between the two braces. In fact, should the mid-connection have enough bond, stress brace buckling will be in the second mode. In this state, when the mid-connection slightly changes into a lateral sway, it stops and the stress bracing deforms as double-curved. Nevertheless, in its ideal state, the mid-connection lateral displacement is considered zero. This study aims to design based on Abaqus 3D software the two new mid-connections, flanged joint, and yielding ductile shear panel. Their buckling and post-buckling were also analyzed using nonlinear geometry and materials. In flanged joint, one member is bonded and two other ones are connected to this bonded member. Interior stiffener is used to prevent this bonded member from crushing. Furthermore, in new X-bracing systems instead of mid-connection sheets a yielding ductile shear panel is used. This sample was examined in two modes with and without stiffener. The results indicate that flanged joint increases the critical load and consequently decreases X-bracing effective length factor. This joint also leads to brace buckling coordinate or as it is known as X-bracing second mode buckling. This kind of buckling increases the ultimate strength and decreases displacement outside of bracing member sheet compared to that of the common joint. Furthermore, yielding ductile shear panel connection increases the X-bracing critical load as well as decreases X-brace effective length factor. The using of stiffener in this kind of connection improves loading and reduces X-brace effective length factor. The connection along with the stiffener comes with a 32 percent increase of the X-bracing ultimate strength due to the yielding of the shear panel and the lack of brace buckling. Also, this connection brings about a 23 percent increase in energy adoption by bracing frame. It is important to note that both connections increase the X-bracing behavior factor compared to the common connection. Yielding ductile shear panel connection not only shows the best stress performance among the connections but also with the lowest costs the X-brace can be repaired by changing mid-connection after the earthquake.
Volume 18, Issue 4 (winter 2018 2018)
Abstract
Considering poverty as income deprivation, neglects other types of poverty that people experience in reality. If we take poverty as capability deprivation, we can focus on other aspects of poverty beside the income poverty. Based on standard analysis of income and leisure subjects, people can substitute their income and leisure hours to increase their income and utility. According to capability approach, individual earnings are more valuable, if they originate from personal choices not his/her forced substitution leisure time for work time. This study tries to examine how to substitute time for income based on capability approach and to measure income, leisure and utility poverty lines among Tehran Men Teachers. To do this, we used a CES utility function. In addition, this study tries to recognize the attributes of people who cannot trade-off time poverty and income poverty.
Volume 18, Issue 6 (10-2018)
Abstract
The use of biomass by means of gasification to produce bio fuels and reducing the environmental impact of fossil fuels has been the focus of many researchers in recent years. In the present study, the computational fluid dynamics method is used to predict the process of gasification inside a downdraft gasifier. Recent studies have shown that although many studies have been carried out by various researchers to maximize the cold gas efficiency in the gasification process, so far, no study has been done to minimize the emission of pollutants as one of the other important design parameters along with the increase of cold gas efficiency. So, in this study, the effect of changing the equivalence ratio as design variable on the gasification efficiency as well as the amount of pollutant produced simultaneously is investigated. Also, in this study, CO/CO2 and H2 /H2O molar ratios are considered as another objective function in selecting the optimal process point. In order to verify the validity of the results, the simulation data was compared with the experimental results and the previous numerical study, and a good agreement was shown between their comparison. The results of this study show that in the ratio of 0.64, the rate of production of nitrogen oxides relative to cold gas efficiency is optimal considering the maximum production of CO/CO2 and H2/H2O molar ratios . This point is the optimal point. Under the working conditions of the gasification process.
Volume 18, Issue 7 (11-2018)
Abstract
In the present research, higher resonance frequencies are employed to improve the performance of the atomic force microscopy in the non-contact mode. Conventional models already used in the literature to study AFM microcantilever dynamics such as point-mass approach are not only incapable of modeling higher vibrational modes but also fail to predict microcantilever complicated dynamics with a sufficient accuracy. In this paper, the Hamilton’s extended principle is used to obtain equations governing the nonlinear oscillations of the AFM probe. Euler-Bernoulli beam assumptions and small deflection theory are assumed. The resulting partial differential equation is often converted to a set of ordinary differential equations and then this set is solved either numerically or based on perturbation methods. In the present research, however, the partial differential equation is attacked directly by a special perturbation technique. The accuracy of the present method is then verified by a combination of the Galerkin discretization scheme and a Rung - Kutta numerical solution. Finally, different behaviors of the AFM probe including static behavior, linear mode shapes and frequency response curves are investigated through several numerical simulations. It is found out that higher vibrational modes have smaller frequency shift. It is also found out that higher modes are faster in gathering surface information and also more sensitive to the excitation.
Volume 19, Issue 3 (5-2017)
Abstract
Transition from vegetative to reproductive growth is an important stage in plant’s life. Flowering pathways including photoperiod, vernalization, gibberellins, and autonomous pathway are regulated by different genes. Identification of flowering genes is essential for the development of bolting-resistant sugar beet cultivars. In this study, a set of 118 Arabidopsis thaliana genes involved in flowering time control were used as a reference to identify homologous counterparts in Expressed Sequence Tags (ESTs) and Transcriptome Shotgun Assembly (TSA) sequence of sugar beet. Based on obtained ESTs, primers were designed for Suppressor of Frigida 4 (SUF4), Curly Leaf (CLF), Constitutive Photomorphogenesis1 (COP1), and Cycling Dof Factor (CDF) genes. SUF4 and CLF are components of vernalization pathway and COP1 and CDF are in photoperiod pathway. The sequence regions of these genes were amplified using cDNA PCR technique, and compared with other identified sequences in Gene Bank. Four genes namely CLF, COP1, CDF and SUF4 were deposited in Gene Bank. Results showed that most of the flowering pathway genes in Arabidopsis are detectable in sugar beet which can be contributed to the understanding of the genetic control of bolting resistance.
Volume 19, Issue 3 (March 2019)
Abstract
Cavity receiver in solar tower concentrator usually experiences highly intense radiation. Due to asymmetric concentration of solar rays, non-uniform heat flux distribution occurs on the different parts of the cavity receiver. This non-uniform distribution leads to uneven thermal expansion and stresses in receiver, which affects the reliable operation and reduces life time of receiver parts. Therefore, it is necessary to reduce the non-uniformity of solar flux on the surface of the absorber tubes and different parts of the solar reactor. The aim of this study was to focuses on the distributions of concatenated solar flux over graphite tubes of a 50kW solar reactor, which was previously designed for methane thermal dissociation at the focus of a solar furnace. In this study, the absorbed solar power on the different parts of the reactor is determined by Monte Carlo ray tracing method. Moreover, the effect of aperture size and the absorptivity of receiver parts on the net magnitude and distribution of absorbed power in reactor are investigated. The results prove that the 16cm aperture absorbs the maximum power and leads to even better solar flux distributions. Replacing the absorbing walls by the reflective walls will also result in more power absorbed by the tubes and better uniformity of flux distribution around the tubes.
Volume 19, Issue 3 (10-2019)
Abstract
With rapid rise in development of urban districts, a ferocious demand for water-collecting urban sewer systems is inevitable. In fact, flexible sewer collecting systems and drainage systems should be developed for controlling sewage and runoff, respectively. In the case of underground, conducting water flow properly through high vertical distances needs reliable criteria design for dissipating flow energy. Vortex structure is taken into account as one of the economical infrastructures which can be used to eradicate destructive impacts of inflow over a drop with invert elevation. In the current investigation, a physical model, made of Plexiglas segments, was set up to study hydraulic performance of vortex drop structure in terms of flow energy dissipation efficiency (FEDE). 144 experiments were conducted and analyzed by means of full factorial method (FFM). Results of dimensional analysis demonstrated that Froude number (Fr), ratio of drop total height to shaft diameter (L/D), and ratio of sump depth to shaft diameter (Hs/D) were considered effective variables on the FEDE. Hence, a regression based equation in form of a quadratic polynomial was proposed to estimate FEDE variable. Experiments aims were to investigate simultaneous effects of approach flow Fr, L/D, Hs/D on the FEDE. Results of experiments indicated that FEDE variable had downward trends with an increase in Fr variable and additionally, FEDE has gone through upward trends with an increase of L/D and Hs/D ratios. Increase in , which causes remarkable effect of wall friction on vortex flow, leads to increase in FEDE in the structure. Moreover, observations showed that decrease in inlet discharge for smaller Froude number results in more rotations of vortex flow in vertical shaft than flow with larger discharges for larger Froude number. This causes reduction of FEDE due to increase in inlet discharge. In addition, shown that in the structures with smaller L/D (L/D=10), the reduction effect of on the FEDE is more. With respect to positive effects of sump depth range (Hs/D=1-1.6) on FEDE and flow patterns observed in the entrance outlet tunnel, range (Hs/D=1-1.6) can be replaced by Hs/D range (0.7-1) proposed Zhao et al. [11]. In addition, the results showed that the interaction of and Hs/D on the FEDE in the structure is not significant.
For Q between 9.7 and 27.1 l/s, formation of hydraulic jump in tangential inlet was not occurred and flow was drained freely to drop shaft. Additionally, water surface in tangential inlet was lower than that of approach channel. In the outlet part of vortex structure, flow hitting the baffle leads to relatively significant increase in flow elevation top of the baffle in comparisons with other parts. Moreover, for constant values of Q and Hs/D ratio, flow elevation over the baffle has increased with an increase in L/D ratio, while for constant values of Q and L/D ratio, flow elevation has plummeted with an increase in Hs/D. Observations of experiments indicated that baffle-hitting flow accelerated without existence of sump at the base of drop shaft. Then caused to detaching flow and consequently occurrence of cavitation increased.
For Q between 9.7 and 27.1 l/s, formation of hydraulic jump in tangential inlet was not occurred and flow was drained freely to drop shaft. Additionally, water surface in tangential inlet was lower than that of approach channel. In the outlet part of vortex structure, flow hitting the baffle leads to relatively significant increase in flow elevation top of the baffle in comparisons with other parts. Moreover, for constant values of Q and Hs/D ratio, flow elevation over the baffle has increased with an increase in L/D ratio, while for constant values of Q and L/D ratio, flow elevation has plummeted with an increase in Hs/D. Observations of experiments indicated that baffle-hitting flow accelerated without existence of sump at the base of drop shaft. Then caused to detaching flow and consequently occurrence of cavitation increased.
Volume 19, Issue 5 (12-2019)
Abstract
Dynamic properties of structures, such as natural frequency, shape modes, and damping ratios, play a decisive role in structure behavior against dynamic loads like earthquakes. Determining the earthquake forces imposed on structures based on the design spectra is one of the utilization of these properties. Other applications of these features could be utilized to update the finite element model, detect potential damage in structures, long-term health monitoring of structures, and evaluating the safety of structures after heavy loading. Therefore, accuracy and reducing the cost of extracting these properties would have a significant role in improving the efficiency and consequently of the useful life of structures. In other word, the more accurate of structural dynamic properties means, the more accurate determination of the seismic response of the structures. These properties depend on a great deal of detail, such as material behavior and the geometry of the structure, which could not be easily simulated in analytical models. So, performing seismic tests on structures is the most reliable method for obtaining these properties. Determination of these properties have been done in a variety of ways. However, various methods have been developed in many studies to extract these quantities by image processing. The aim of this article is presenting a novel approach to increase the accuracy of remote sensing by image processing. Therefore, the current paper is an attempt to apply the average method to improve efficiency as a cheaper method for obtaining the dynamic properties of structures. For this purpose, a cantilever aluminum beam and a Three-story frame with additional mass have been considered, and the commercial camera captures the vibration of the structure. The extracted displacements of each four points on the edge of the specimen are recorded as the input signals of the system. With two numerical derivatives of these displacements, the acceleration of the structure is obtained. Peak survey method utilized to extract natural frequencies, damping ratios, and mode shapes of the each selected point. The averaging method applied to calculate the final properties of the structure.
At last, the results are compared with the values obtained from the acceleration sensors embedded on the structure and the finite element results. Then the accuracy and error of the algorithm are evaluated. However, these results could be utilized as the input information in the health-monitoring of the structures. The results show that the novel method did not improve the accuracy of the first three natural frequencies modes of vibration in comparison with the standard method for the cantilever beam. It is also observed that the new method wouldn’t make a significant difference in the calculation of damping ratios of the system. On the other hand, although the existence of cables and sensors would reduce the accuracy of image processing and recorded displacements, the new algorithm improves the estimation of the first three shapes modes. In the same way, the same function was performed for the Three-story frame structure. Although its natural frequencies did not change for the first three modes of vibration, the mode shapes are closer to the values obtained from the accelerometer sensors.
Volume 20, Issue 5 (May 2020)
Abstract
The amount of entropy generation during the fatigue loading is treated as an indicator of the damage accumulation in the material. Using the thermography technique and recognizing the temperature field distribution at a specimen surface under cyclic loading and calculating the dissipated energy and also considering the possibility of the specimen heat transfer with the environment, the net entropy production rate of the system can be computed. This research has been conducted to feasibility study and applicability of the methodology through numerical modeling and analysis. In this thesis, using the finite element numerical method and in the framework of Abaqus software, simulations of fully reversed bending are carried out on the standard specimens of aluminum (Al6061-T6) whose experimental test results are available in the literature. Based on results of the mechanical and thermal analysis, calculating the entropy production rate, fatigue fracture entropy, damage variable and remaining life assessment based on this variable are performed. The results obtained from the numerical simulation are compared and validated with the results of experimental tests. Also, a numerical analysis is carried out to estimate the temperature enhancement and fatigue self-heating phenomenon due to the cyclic loading based on the strain-life curve characteristics and dissipated energy on the axial specimen made of (AISI 4340). The results obtained from the research indicate that the infrared thermography technique as a non-destructive evaluation method in the low cycle fatigue range, is a suitable tool for the temperature field evaluation and subsequently, the accumulated damage estimation in material.
Volume 20, Issue 5 (11-2020)
Abstract
The load type imposed on the structures is one of the important issues of the modal identification Experimental methods. Generally the loads applied to a structure for dynamic testing are divided into two categories: artificial stimulation and ambient loads. Applying artificial loads to large structures such as bridges and tall buildings is difficult, costly and in some cases impossible. For this reason, modal identification of such structures is generally done by ambient vibration tests. However this experimental methods, also include problems such as large noise amplitude relative to the measured responses that this causes errors in the results and in some cases leads to unrealistic modes. As a solution, modal information can be calculated from several different methods and compared with each other to ensure the accuracy of the results. In this paper, a new scheme for natural frequencies extraction of structures from their ambient vibration is presented. For this purpose, the combination of two mathematical techniques of random decrement (RD) and proper orthogonal decomposition (POD) methods were used. The reason for using these two methods, is their ability to reduce the noise effects. In other words, combining of these two methods can lead to a very powerful tool for extracting structural frequencies from its ambient vibration under high amplitude noise conditions. The proposed algorithm consists of three steps: In the first step, after measuring the acceleration response of the structure at the appropriate points, the effects of random vibration are eliminated from the response by RD method and only dynamic properties of the structure remain in the acceleration records. Secondly, the acceleration records are separated into several structural modes using the proper orthogonal decomposition technique and finally, at the last step, the proceeded responses are transformed by the fast Fourier transform into the frequency domain to extract the natural frequencies of the structure. The strength of the proposed method is its robustness to the use of very high amplitude noise data, which is one of the challenges in the ambient vibration experiments. The accuracy of the proposed algorithm was evaluated by numerical modeling and experimental study. To investigate the efficiency of the new method, the numerical and experimental results were compared with the frequencies obtained from commonly modal identification methods such as extended frequency domain decomposition (EFDD) and stochastic subspace identification (SSI). A very good agreement was observed between the results of methods. Furthermore, Studying the effect of noise on the new algorithm results shows that increasing the ratio of noise to acceleration amplitude up to 250, did not affect the results precision and the main frequencies of the structure can be obtained with good accuracy. In this study, the effect of the number of sensors used in the ambient vibration test also was investigated on the accuracy of the new algorithm results. It was concluded that the minimum number of sensors (even one number) and repetition of the experiment can be used to extract structural frequencies from its ambient vibration with high accuracy. The results of this study showed that the new method can be used as a suitable tool to determine the natural frequencies of structures from its ambient vibration under severe noise conditions and to control the results obtained from other methods.
Volume 20, Issue 145 (March 2024)
Abstract
Yogurt drink is one of the fermented dairy products. Probiotic yogurt drink has special health properties due to the presence of probiotics. Also, adding herbal-medicinal plants including chavil to this product can make it more attractive. However, the shelf life of probiotic bacteria in yogurt drink is not very long. This research was therefore carried out to increase the shelf life of Lactobacillus rhamnosus in yogurt drink by nanoencapsulation technique with Persian gum and whey protein isolate. Particle size and SEM was used for determination nanoencapsulated bacteria (bead) characteristics. In this regard, three samples of yogurt drink containing free Lactobacillus rhamnosus, its bead and the control were produced. Some characteristics including pH, acidity, sensory including color, taste, consistency and overall acceptability of yogurt drink were measured as well as the shelf life of probiotic bacteria under gastrointestinal conditions and storage in the refrigerator. The results showed that the beads had a size from 246.98 to 356.2 nm. The efficiency of nanoencapsulation was 87.2%, and the SEM images showed that the bacteria were covered well. At the end of the storage time, the decrease in pH (3.41) and increase in acidity (97.3 °D) of the sample containing beads was highest. The counting of free and beads also showed that the shelf life of bead was greater than free bacteria in yogurt drink. In the 21st day of storage, the product was eligible for probiotics. Moreover, the bead survival in simulation gasterointestinal condition was 3.33 log cfu/ml. The evaluation of the sensory parameters also showed that the sample containing bead had the lowest score among the panellist in all the sensory components except the texture. In conclusion, it can be stated that the yogurt drink containing the bead sample can qualify as a probiotic product during 21 days of storage time.
Volume 21, Issue 3 (5-2019)
Abstract
Four hundred strains isolated from Tunisian sheep and goat raw milks were initially screened for their ability to survive the GastroIntestinal Tract (GIT). Forty-three among the four hundred bacteria were resistant to pepsin, pH 2, pancreatin and bile salts at 0.3%, even after 5 hours of incubation. Identification using 16S rRNA gene sequencing was established and we obtained as a species Lactobacillus plantarum (29 isolates from sheep milk and 11 from goat milk) and Lactobacillus pentosus (2 isolates from sheep milk and 1 from goat milk). We showed the ability for auto-aggregation and/or hydrophobicity properties. Finally, both M63 and C78 strains showed an important level of adhesion to three intestinal epithelial cells Caco-2 TC7, HT29-MTX, and HT29-CL.16E. Taken together, these properties allow the lactobacilli strains to be considered promising beneficial strains for developing functional foods for consumers.
Volume 21, Issue 4 (7-2019)
Abstract
In this study, two essential oils including Cuminum cyminum (L.) and Lavandula angustifolia (Mill.) were nano-capsulated by solvent evaporation emulsion method and their fumigant toxicity was investigated against three important stored-products pest, Tribolium castaneum (Herbst), Sitophilus granarius (L.), and Oryzaephilus surinamensis (L.). Moreover, the sublethal concentrations of phosphine gas in combination with nano-capsules were evaluated to reduce their usage concentration. The synthetized nano-capsules were confirmed by Scanning Electron Microscope (SEM), Transmission Electron Microscopy (TEM) and Fourier Transform Infrared Spectroscopy (FTIR). The chemical compositions analysis of C. cyminum and L. angustifolia by GC-MS revealed that α-Pinene (44.63%) and Linalyl acetate (61.74%) were the major components of C. cyminum and L. angustifolia, respectively. The results showed that pure C. cyminum was more effective than L. angustifolia regarding the fumigant toxicity after 24 h treatment on the three mentioned stored products pests. The LC50 values of pure C. cyminum oil after 24 h treatment were obtained as 42.51 and 78.99 μL L-1 air by S. granarius and T. castaneum, respectively. However, the LC50 values of C. cyminum oil nano-capsule form were 220.34 (S. granaries) and 374.16 μL L-1 air (T. castaneum), which were determined as susceptible and resistant pests, respectively. The results indicated that the combination of nano-capsulated form of essential oil with reduced amounts of phosphine could be used as a suitable method for control of stored product pests.
Volume 21, Issue 5 (9-2019)
Abstract
In the present research work, the potential probiotic properties of Lactococcus lactis KMCM3 and Lactobacillus helveticus KMCH1 isolated from raw camel milk and traditional fermented camel milk (Chal), respectively, were studied. The probiotic properties of isolates that were investigated included the hemolysis, antibiotic resistance, antibacterial features, resistance to low pH and bile salts, survival under simulated GastroIntestinal Tract (GIT) conditions, adhesion ability to hydrocarbon, and their auto-aggregation and co-aggregation rates. None of isolates exhibited hemolytic activity. They were susceptible against tetracycline, penicillin, ampicillin, chloramphenicol, erythromycin and vancomycin. Lac. lactis KMCM3 and L. helveticus KMCH1 retained their viability at pH 3.0 (8.68 and 8.6 log cfu mL-1, respectively), 0.3% w/v bile salts (8.23 and 8.58 log cfu mL-1, respectively) and under simulated GIT conditions (8.31 and 8.46 log cfu mL-1, respectively). Both of these isolates inhibited the growth of E. coli, S. aureus, L. monocytogenes, B. cereus and S. enterica subsp. enterica serovar Typhimurium with MIC values of 6.25 to 25 mg mL-1. In addition, They exhibited an ability to adhere to hydrocarbon (xylene), and possessed a high auto-aggregation and co-aggregation rate (more than 40%).