جستجوی مقالات مرتبط با کلیدواژه « physical properties » در نشریات گروه « مکانیزاسیون کشاورزی »

Wild oat (Avena fatua) is the most common weed of wheat fields. Given that the presence of even small amounts of wild oat in the wheat grain mass may lead to a sharp drop in the quality of flour produced, separation of wild oat from wheat will increase the purity of the seed and enhance the economic value of the crop. In present study, some physical properties of wheat and wild oat, including geometric properties, gravity properties, frictional properties and initial moisture content were determened. A gravity separator - equipped with some tools to adjust  five parameters: air flow rate, frequency of oscillation, amplitude of oscillation, longitudinal slope and latitudinal slope of the table - was used to separate wild oats from wheat grain mass. The effects of these parameters were studied to achieve maximum separation of wild oat from wheat mass. Statistical analyses were performed in two factorial experiments in a completely randomized design. Also, using dimensional analysis, a dimensionless dimensional parameter V/aω was obtained (where v is air speed, a is oscillation and ω is oscillation frequency), which was effective in evaluating the effect and reducing the number of parameters. The results showed significant differences (1%) in moisture content, mass and particle density, boundary velocity and interaction between grain type and friction surface between two grain types. Also, the results indicated that the maximum separation of wild oats from wheat (70.47%) was obtained when the air flow rate was 6 m/s, the oscillation was 5 mm, the oscillation frequency was 395 cycl/min,, and the longitudinal slope and latitudinal slope were 2.5° and 1.5°, respectively.

Introduction:

 Edible Button Mushroom (Agaricusbisporus) is one of the crops that is widely used today as a food source. Mushrooms after harvesting due to high humidity, high respiration rate, lack of cuticle and severe enzymatic activity, with persistence and quickly than other vegetables rot and discoloration begins immediately after harvest. To increase shelf life, edible mushroom must undergo processing processes. Drying is one of the most common methods of processing and preserving edible mushrooms. Vacuum-infrared drying is conducted by lowering moisture at low pressure to improve the quality of the high nutritional value product. Since button mushrooms have many applications due to their high nutritional value and medicinal uses, the best drying mode should be chosen to have the least negative effect on the quality properties and ingredients of the powder.

Materials and Methods :

Fresh edible button mushroom After washing were cut by a cutter at 5 mm thickness and dried using a vacuum-infrared dryer at three temperature levels of 40, 55 and 70 ° C and three vacuum pressure levels of 20, 40 and 60 kPa. Then the dried mushroom slices were milled and powdered using a mill machine for one minute. To homogenize the particle size, the button mushroom powder was sifted by a laboratory sieve with mesh No. 50 (cavity size 0.5 mm).In this study, the effect of vacuum-infrared drying variables including indoor air temperature and vacuum pressure on the thermal properties (effective moisture diffusion coefficient and drying energy consumption) of  button mushroom and chemical (total phenol content) and qualitative (color indices as ΔL *, Δa * and Δb*) button mushroom powders were studied. Statistical analysis of data and optimization of drying process were performed using response surface methodology and central composite design (CCD). After determining the optimum point of vacuum-infrared dryer, loose and compacted bulk density, work index, Hassner ratio, angle of repose, and button mushroom powder slides were measured at optimum point and Finally the flow-ability of the edible button mushroom powder was determined.

Results and Discussion:

 The results showed that as the chamber temperature increased, the rate of evaporation of tissue moisture increased, which resulted in a decrease in the drying time of the edible button mushroom thin layers with vacuum-infrared dryer. Effective moisture diffusion coefficient of drying of edible button mushroom thin films ranging from 1.8 ×10-9 m2/s (40 kPa pressure and temperature 40 °C) to 8.9×10-9 m2/s (20 kPa pressure and 70 °C temperature) was varied. The results showed that the air temperature of the drying chamber had a positive effect on the effective moisture diffusion coefficient. This is because increasing energy and heat consumption increased the activity of water molecules and, as a result, more moisture penetrated outside the product at higher temperatures. The maximum amount of specific energy consumption was 1269.73 MJ/kg (60 kPa pressure and 40 ° C) and the lowest amount was 408.36 MJ/kg (40 kPa pressure and 70 °C). The results showed that at constant pressure with increasing temperature, as the drying time decreased sharply, the amount of specific energy consumption also decreased. The phenolic content of button mushroom powder was in the range of 270 mg/g (20 kPa pressure and 40 ° C) and 1.3 mg/g (40 kPa pressure and 70 ° C). As the temperature increased, the total phenol content decreased. The results showed that increasing the temperature caused a greater difference between the color indices of L*, a * and b* of button mushroom powder than fresh mushroom. Increase in temperature caused more darkening (decrease in L* index), decrease in redness (decrease in index a*) and decrease in yellowness (decrease in index b*) of mushroom powder. In general, color indices were closer to the values of fresh fungal samples at low temperatures. The optimum drying point of button mushroom was obtained at 40° C and vacuum pressure of 40.823 kPa. The optimum value of the independent variables including effective moisture diffusion coefficient, specific drying energy consumption, total phenol content and final color indices of edible button mushroom ΔL*, Δa* and Δb* were 3.06×10-9 m2/s, 1088 MJ/kg, 2.76 mg/g, 15.28, 2.55 and 9.26, respectively. The results showed that drying under lower temperature and medium vacuum pressure increased the desirability index. The flow-ability of edible button mushroom powder was reported to be good.

Conclusion:

 According to the results of drying tests of edible mushrooms, the following results of this study are obtained in infrared vacuum drying: 1- The effect of air temperature on all variables of button mushroom response was significant in vacuum-infrared dryer. 2- The air inlet temperature to the dryer had a negative effect on the specific energy consumption of the drying process and the total phenol content of the button mushroom powder. 3- Increase in air temperature caused a greater difference between the color indices of L*, a* and b* button mushroom powder than fresh mushrooms. 4. The results showed that drying under mild conditions (lower temperature and medium vacuum pressure) increased the desirability index. 5-Flow-ability of edible button mushroom powder was reported to be good.

The eggshell of birds, as a natural shield and package, protects the tissues inside it from microbial and mechanical damages. Proper intake of calcium, as an important and effective factor in increasing the strength and quality of the eggshell, could reduce complications. In this paper, the effect of dietary calcium at five different levels on engineering features of Japanese quail eggs in a in their first laying period was investigated. The values for an average of mass, volume, specific mass, shell thickness, major diameter, central diameter and rupture force along the longitudinal and transverse axes were measured. Rupture energy or toughness, slope of the rupture curve (hardness), deformation along the longitudinal and transverse axis to the point of rupture as well as longitudinal and transverse deformation of 450 tested quail eggs (3 period of time, 5 treatment of calcium, 5 replication, 6 observation) were measured. The characters of the specific mass, shell thickness, rupture force, and slope of the rupture curve of quail eggs indicate the strength of quail egg. In this study, variations in all parameters indicating shell strength at different levels of dietary calcium were consistent with each other. Five different treatments with 1.5%, 2%, 2.5%, 3%, and 3.5% calcium content were supplied for the study. By increasing the calcium content of the quail diet from 1.5 to 3 wt%, the volume and weight of quail eggs dropped and shell thickness was reinforced. According to the results, the shell strength of quail eggs along the transverse axis was slightly less than the longitudinal axis, but the flexibility and energy required for quail egg rupture were much greater across the longitudinal axis.

Optimal design for sourcing, grading and other post-harvest operations requires the availability of appropriate information about their physical properties. Also, achieving a high quality product requires the fight against weeds and impurities in the product. Therefore, in this research, some physical properties of wheat and barley were measured. A gravity separator was also used to separate the barley in the wheat mass. This machine has five customizable parameters includes air velocity, frequency of oscillation, amplitude of oscillation, longitudinal slope and latitudinal slope of the table. The effect of these parameters was investigated in the form of two factorial experiments in a completely randomized design to achieve maximum separation of barley from wheat mass. The results of experiments showed that in the conditions of air velocity of 6.75 m / s, the oscillation amplitudes of 5 mm, the longitudinal slope of 2.5 degree, the latitudinal slope 0.75 degree and the frequency of oscillation of 395 cycl / min, the maximum separation of barley from wheat mass to 20.6 % was achieved. In most cases, with increasing latitudinal slope from 0.75 degree to 2.52 degree , the longitudinal slope of the table from 2.5 degree to 4.5 degree and with the increase of the frequency up to 435 cycl / min, the separation of barley from the mass of wheat decreases. Also, the minimum amount of barley separation from wheat mass in condition of oscillation frequency of 455 cycl / min, l o n g i t u d i n a l slope of 4.5 degree, latitud in a l lope of 1.5 degree, oscillation a mplitude of 5 mm and air velocity of 6 m/s was obtained 9.417 %.

In this research via CT scan, the relationship between physical properties of pears and storage times with bruise due to loading force was investigated. Before dynamic loading force and storing, 45 pears were examined using Scan CT and 27 pears with zero bruise percentage were selected  and dimensions of pears (length, width, thickness) were measured, then properties such as the equivalent diameter, geometric mean diameter, spherical coefficient, surface area and aspect ratio of calculus were calculated, next selected pears were subjected to dynamic loading with three  mass of weights 300, 350 and 400 g and  5, 10 and 15 days storage was used to investigate the effect of impact on pears. Then, after dynamic loading and storing, using the CT scan in each period of storage, the rate of pear bruise was calculated. The results of the experiments showed that there is an inverse relation between geometric diameter, arithmetic diameter, equivalent diameter and surface area with the bruise percentage. Also a direct and unreasonable relationship between the spherical coefficient and aspect ratio and the percentage of bruising was absorbed. Also, according to the results obtained for mass weighing 300 g or less in 5-day storage period, the amount of geometric diameter, arithmetic and equivalent diameter, spherical and aspect ratio on percentage of bruising were not significantly affected and percentage of bruising can be almost zero and with increasing amount mass weighing and storage, the above parameter's will affect the percentage of bruising.

Grape fruit set its fruits and shortly after planting and due to high nutritious value and excellent food quality has been welcomed by many people in the world, but considering its soft tissue and high softening velocity and sensitivity to fungi attack it is known as an extensively vulnerable fruit. One of the most important ways to maintain fruit quality, decrease vulnerably and assist more appropriate storage, is the use of coating method and proper packing of agricultural products and combining these procedures to decrease damages in storage. Edible coatings provide a replacement and fortification of the natural layers at the product surface to prevent moisture losses, gas aromas, and solute movements out of the food, while selectively allowing for controlled exchange of important gases, such as oxygen, carbon dioxide, and ethylene, which are involved in fruit respiration. Chitosan is the most common polysaccharide-based coatings. Chitosan films have been successfully applied as edible material in films and coatings for the quality preservation of different fruit. In this study, the effects of the application of chitosan edible coatings and storage time on some physical, chemical, mechanical and rheological properties of grape were investigated during storage. Grape fruits were screened for physical damages, fungal infections, and size homogeneity after harvesting from the farm. Then fruits were divided into without coating and fruits with coating. Fruits being coated, prepared in chitosan emulsion and submerged for two minutes and kept at 20°C for one hour for drying the surface coating via airflow. In order to calculate the weight loss, three containers of each grape fruits (treatment and control) collected and after weighing and averaging weight loss were compared to initial weight during storage expressed as a percent. Color intensities were determined using colorimeter samples. In order to determine soluble solids from each sample, refract meter was used and pH amount of each sample was determined. Mechanical traits and fruit stiffness were measured through penetration test using materials test machine Zowick/ Roell having 500 N loadcell in line with the small diameter with concave probe (5 mm diameter), the penetration depth of 2 mm and loading rate of 10 mm s-1. Mechanical traits including stiffness and elasticity module calculated from the force-deformation curve. Viscoelastic materials have the properties of both viscous and elastic materials and can be modeled by combining elements that represent these characteristics. A viscoelastic model, called the Maxwell model which can predict behavior was evaluated. In this current study, the application of chitosan coating significantly reduced the fresh grape decay. Fruit decay of grape increased with storage time, but the coating reduced the rate of decay with the length of storage. According to the results, the application of these coatings has a positive impact on yield stress and energy of rupture product texture during the storage. Results of variance analysis showed that temperature, coating and storage time has a significant effect (1% level) on some of the engineering properties of the grape. Storage time has a significant effect on elasticity, while the coating does not have a significant effect on this parameter. Finally, results showed that the application of chitosan coating has an effect on relaxation time and stress. So during storage of coated samples these parameters decreased compared to uncoated. Edible films and coatings may reduce the moisture transfer, the rate of oxidation and respiration which are considered important to prolong the shelf-life of these products. This investigation showed that the chitosan coatings are effective for grape shelf life extension and retarded the senescence process compared with control. The coat has been as a physical barrier for the gas exchange between the fruit and the environment. It was demonstrated that the coating reduced the loss of firmness and delayed the softening of fruit and texture change.

In the past decades, environmental pollution caused by plastic packing materials, restrictions of petroleum resources and their high price attracted many researchers to produce biodegradable packaging materials. Poor mechanic properties and high water vapor permeability are two main defects of biodegradable polymers. Nanotechnology is a modification method in this case. In the current study, the effects of nanocellulose (NC) as a nano filler on the functional properties (i.e. solubility in water (SW), moisture content (MC), water vapor permeability (WVP), tensile strength (TS), elongation to break (EB), color and structural properties) of soy protein isolate-tragacanth gum (SPI-TG) were investigated. The results showed, the functional properties of SPI-TG-NC were improved. The highest yellowness index and total color difference was observed in SPI:TG (4.7:0.3), The lowest yellowness index and total color difference was observed in SPI-TG-NC (3%). The microstructure of film specimens was investigated using scanning electron microscope.

The hazelnut (Corylus avellana L.) is one of the most cultivated and consumed nuts in the world, not only as a fruit but also as a main constituent into a wide range of manufactured food products. Iran after Turkey, Italy, USA, Azerbaijan, Georgia and China, is the world's seventh largest producer of hazelnuts. Guilan province is the largest producer of hazelnuts in Iran. More than 90 percent of hazelnut of this province, after removing the initial green shell is sold at low prices. Therefore, design and optimization of harvesting machines and processing equipment to produce this product is important. Thus, the aim of this research was to study the physical, mechanical and nutritional properties of three common hazelnut cultivars in Guilan province of Iran.
In this study, two common local cultivars of hazelnut in north of Iran (Gerd and Badami), and an improved variety namely Keshavarzi were considered for all experiments. Experimental samples were supplied from Eshkevarat region as the major hazelnut producing part of Guilan province. All physical, mechanical and nutritional properties of both the hazelnut and kernel samples were measured and computed at moisture content of 2.3–3.3% dry basis.
Nutritional properties including crude protein, oil, crude fiber, ash, dry matter, carbohydrate and some minerals, i.e. N, P, K, Mn, Fe, and Zn contents of hazelnuts, were measured based on the standard methods. All nutritional and mineral data were analyzed through a completely randomized design with three replications.
Physical properties including dimensional properties, bulk and true densities, porosity, natural angle of repose, terminal velocity, and coefficient of friction on plywood structural surface and galvanized iron sheet were measured based on the standard procedures. All physical data were analyzed through a completely randomized design with five replications.
Mechanical properties including rupture force, deformation and energy absorbed at rupture point along with the hardness of nuts were determined by applying force to three major perpendicular axes of all nut samples. The energy absorbed for rupture nuts was determined by measuring the area beneath the strain-stress curves and hardness of nuts was computed as the ratio of rupture force to the corresponding value of deformation at rupture instant. All mechanical data were analyzed through a completely randomized design with five replications.
According to the variance analyses, there were significant differences between the hazelnut cultivars in terms of crude protein and fiber, ash and carbohydrate contents (p There were significant differences between a large number of physical and mechanical properties of three common hazelnut varieties in Guilan province, Iran. The differences among the engineering characteristics should be used in design and optimizing of hazelnut machineries and processing equipment.
The results showed that the improved hazelnut cultivar of Keshavazi had no considerable superiority to landraces cultivars of Gerd and Badami in terms of nutritional and mineral contents. Therefore, it is essential that along with the physical superiority of alternative hazelnut cultivars, their nutritional and mineral advantages be considered by the agricultural experts in Guilan province, Iran.

The present study examined the physical properties, rupture force, and milling characteristics of the common Hashemi, Alikazemi, and Tarom rice varieties in main and ratoon crops. The experiment was conducted as a factorial(3×2) randomized complete block design with five replications. The results revealed that the thickness (1.68 mm) and sphericity of grains (0.388) were less in the main crop thanin the ratoon rice (1.71 mm and 0.398, respectively). The Hashemi variety recorded the greatest length (7.58 mm). Alikazemi recorded the greatest width (2.03 mm), thickness (1.80 mm), geometric mean diameter (3.00 mm), sphericity (0.408), surface area (25.40 mm2), bulk density (561.54kgm-3), true density (1292.24 kgm-3), and thousand grain mass (26.96 g). The highest bending rupture force(24.68 N) and head rice yield (81.36%) was obtained for the ratoon rice crop of the Hashemi variety and the lowest corresponding values (19.6 N and73.41%, respectively) were recorded for the main rice crop of the Alikazemi variety (P<0.01). There was no significant difference in compressive grain rupture force between varieties or between the main and ratoon crops.

New edible composite films formed from salep (Orchis mascula) and 10%, 20%, and 30% (w/w) oleic acid were prepared by emulsification with the aim of improving the water vapor barrier and mechanical properties of the film. As oleic acid concentration increased up to 30% (w/w), oxygen permeability (27%), elongation at break (86%) and thickness (2%) of salep films increased significantly and the tensile strength (37%), solubility (39%), transparency (13%) and water vapor permeability (54%) decreased significantly (P<0.05). Increasing the oleic acid concentration produced a slight yellowish color in the salep film, but it was still transparent in appearance. It was found that oleic acid can be incorporated into the film and might be applicable for food packaging applications that require high water vapor permeability.

A‎ field study was conducted to compare the effects of four primary tillage implements (moldboard (MB), disk (DP), improved disk (IDP) and chisel (CH) ‎plows) and two vine killing methods (vine killed (VK) and without vine killing (NVK)) on some physical and hardness properties of potato tuber. The study was conducted using a 4‎‏×‏‎2 factorial experiment (strip plots) ‎with a randomized complete block design. Eight ‎treatments representing four primary tillage implement levels and two levels of ‎vine killing were replicated three ‎times. The results showed that tuber dry matter content in "MB.NVK" and "DP.NVK" treatment was significantly higher than that of "IDP.VK" at 5%‏ level. The multiple linear regression analysis with stepwise method showed that there was a linear regression model between tuber dry matter content and wet weight, moisture content, maximum diameter and spherisity.

Cumin is an annual plant suitable for cultivation in dry and semi-dry lands of Iran. It is harvested in two periods to prevent seed loss. Manual harvesting either by hand or using a scythe forms the initial stage. After drying and threshing, in the final stage, the seeds are manually sieved to be cleaned and separated from foreign material. This harvesting method is time-consuming and labor intensive and causes high loss, decreasing quality and increasing seed pollution. A combine harvester was used to study the function of effective factors on the separation and cleaning of cumin seeds after threshing. The effect of independent variables (type of straw walker, wind speed, sieve blade angle, sieve angle) on dependent parameters (percent of seed loss by weight from straw walker, from cleaner system, percent of straw by weight in seed hopper) was investigated using a randomized complete block design. As the size and moisture content of cumin seed increased, terminal velocity increased. The results showed that wind speed, sieve blade angle and sieve angle had significant effects (P < 0.01) on percent of seed loss by weight in the cleaner system and percent of straw by weight in the seed hopper. The percent of seed loss in the straw walker was also affected by the type of straw walker used.

Physical and cutting tests were performed at 70-day intervals on a variety of local garlic maintained at three different storage periods to determine the physical properties of garlic bulbs and cloves and the cutting properties of garlic cloves The height, mean width diameter, arithmetic mean diameter, geometric mean diameter, bulk density and sphericity of the bulbs were measured and determined. These values were, respectively, 27.81-28.72 mm, 36.11- 37.88 mm, 33.65-34.52 mm, 33.39-34.10 mm, 90.24%-92.48%, and 529.6-594.6 Kg/m. The length, width, thickness, arithmetic mean diameter, geometric mean diameter, sphericity, bulk density, particle density, porosity and volume for cloves were also calculated. The results showed that storage period has a significant effect on the mean width diameter, arithmetic mean diameter and bulk density of the bulbs and also on the length, bulk density, particle density, volume and arithmetic mean diameter of the cloves. Cutting tests are performed at three loading speeds and three storage periods. The maximum cutting force required to complete cutting of the cloves was 2.28-4.79 N and the mean energy required to complete cutting of the cloves per unit area was 17.297-29.270 mJ/mm2. The mean force required to complete cutting of the cloves per unit area was 1.442-2.98 N/mm2. Storage period had a significant effect on the cutting properties of the cloves.

It is essential obtain adequate data on the physical and mechanical properties of a crop to reduce crop loss and maintain the quality of crops at and after harvest and to design and optimize machines for post-harvest processing. In this investigation, the physical and mechanical properties of nectarines (var. Independence) from the Takestan region of Qazvin province were studied. The largest diameter (61 mm); mean diameter (59 mm); smallest diameter (57 mm); mass (97.74 g); volume (1123.17 cm); density (0.99 g/N); geometric mean diameter (59.10 mm); surface area (102/30 cm2); and sphericity coefficient (97%). The chemical properties showed acidity for Independence nectarines to be 1.3% and sugar to be 11%, making it tart. The coefficient of friction for multi-layer materials (wood, aluminum, galvanized sheet metal) showed a static friction coefficient varying from 0.321 for an aluminum surface to 0.389 for a wood surface layer. In addition, the break force was 58.9 N, deformation was 10 mm, and fracture energy at break point 0.3 J and 1.34 kJm-3.

This research was conducted with two varieties of almond kernel (thin shell and semi stone shell) for five moisture levels (5%, 10%, 15%, 20%, 25% d.b.) with five replications using completely randomized base factorial design. The results showed increases with increasing moisture content from 5% to 25% for the thin shell almond for the following variables: true density (851.12 to 1138.94 Kg/m3); porosity (35.69 to54.45%), terminal velocity (4.81 to 6.18 m/s); static friction coefficient on Plexiglas (0.471 to 0.591); static friction coefficient on galvanized iron (0.417 to 0.552); projected area (1.45 to 1.67 m2); repose angle (18.26° to 27.59°). Corresponding values for the semi stone shell almond were: true density (897.18 to 1123.84 Kg/ m3); porosity (32.09 to 47.22%); terminal velocity (5.35 to 6.53 m/s); static friction coefficient on Plexiglas (0.368 to 0.458); static friction coefficient on galvanized iron (0.356 to 0.447); projected area (1.36 to 1.53 m2); repose angle (16.33° to 22.45°). The results also showed that bulk density decreased as moisture content increased from 5% to 25% for the thin shell (547.26 to 518.76) and semi stone shell (609 to 592.94 Kg/m3).

Crops and agricultural products are subject to natural loading during growth. Different mechanical forces are also exerted on them during harvest. One product, sugar cane, experiences large shear forces are during harvest. An examination of the crop properties and machine parameters of sugar cane are necessary to develop appropriate cutting tools and the optimization and design of harvesting machines. The determination of such physical properties as diameter, moisture content, bulk density and mass per unit length is indispensable to this process. Mechanical properties related to cutting, such as maximum cutting force and strength, required energy and specific energy required for cutting are important. For this research, two experimental samples of sugar cane stalk (CP57, CP69) were collected from Amirkabir Research Farm in southern Khuzestan province. The samples were transported to the laboratory while maintaining the moisture content as constant as possible. The stalks were tested under quasi-static conditions using twotypes of blades (serrated and smooth) at three speeds (0.2, 0.5 and 1.35 m/min). The resulting data were analyzed using MSTATC and SPSS software. The effect of the variety on maximum cutting force was not significant, but cutting strength was observed to be significant at the 1% level. The effect of speed change on maximum cutting force was also significant at the 1% level. The effect of blade type on both maximum cutting force and cutting strength was significant at the 1% level. Increasing the speed from 0.2 to 0.5 and then to 1.35 m/min, especially using the smooth blade, increased the efficiency of cutting. However, increasing the speed from 0.5 to 1.35 m/min using the serrated blade increased cutting strength and energy. The serrated blade, at low speeds, was observed to require lower energy. Serration reduced energy consumption and lowered the required cutting strength because of adequate primary penetration of the blade into shell of the stalk, and the reduction of compression time.

In this study, the physical properties were determined for one type of Cornelian cherry (Cornus mas L.) fruit and pit from the Alamout region of Qazvin. The average values for length, width, thickness, 1000 fruit mass, unit mass, geometric mean diameter, unit volume, surface and projected areas, sphericity, fruit (true) and bulk densities, porosity and terminal velocity were 18.91, 13.74, 13.33 mm, 2309.78 and 2.31 g, 15.12 mm, 1841.96 mm3, 722.65 mm2, 180.66 mm2, 80.21%, 1.10 g/cm3, 0.63 g/cm3, 43.30% and 13.8 m/s, respectively. The respective values for the pits were 13.61, 6.07, 5.79 mm, 299.67 and 0.3g, 7.81 mm, 252.93 mm3, 192.57 mm2, 48.14 mm2, 57.59%, 1.21 g/cm3, 0.68 g/cm3, 44.05% and 7.4 m/s. The flesh/pit ratio obtained was 6.8. The static coefficient of friction was 0.38 for galvanized iron, 0.33 for plexiglass, 0.34 for steel and 0.43 for plywood.

The friction properties of granular materials play an important role in the determination ofspecifications for designing hoppers, transporting passages, dryers, silos and machines through which grain flows. In this study, the angle of repose and internal friction coefficient were determined for three common wheat varieties (Sardary, Gaspard and Saysoter) at four moisture contents (12, 15, 18, 21 w.b.%). Four contact surfaces (black, mild, aluminum and galvanized sheets) were used to measure the angle of repose. The tests were done in five replications. Analysis of variance was used to analyze the data and Duncan’s multiple range test was used to compare the effect of the means (P < 5%). The results showed that the effects of moisture content, variety and contact surface were significant for the angle of repose. The effects of grain moisture content and variety were significant for the internal friction coefficient (P < 1%). When moisture content of the grain increased, the angle of repose and internal friction coefficient increased significantly. Only where grain moisture level changed from 18 to 21%w.b. the internal friction coefficient did not change significantly. The highest and lowestinternal friction coefficients belonged to the Sardary and Saysoter varieties, respectively. The highest and lowest the angles of repose belonged to the Gaspard and Sardary varieties, respectively.