Iranian Journal of Biosystems Engineering
Year:2010 | Volume:41 | Issue:2|Papers Count:16

Performances of electronic and mechanical draft control systems on a MF399 tractor were the objectives of the study to be evaluated and compared under field conditions. Hence, the effects of two draft control systems (mechanical and electronic) under four ground speed levels and three set values of draft levels on rear wheel slippage, fuel consumption, compressive force within the top link and tillage depth in a sandy loam soil were assessed by conducting an experiment of a randomized complete block design. Results obtained from the statistical analysis revealed that there was a significant decrease in mean values of slippage as well as in fuel consumption when the system equipped with electronic control as compared with the mechanical one. It was found that the compressive force within the top link as well as mean depth value were significantly lower with the electronic control system resulting in a decrease in wheel slip as well as in fuel consumption. The results also revealed that fuel consumption decreased with increasing ground speed and decreasing the set values of draft. The mean value of slippage in electronic control system for all the treatments was recorded less than 20%, while with the mechanical system it reached level as high as 39%.

Mechanical damages inflicted upon seeds in harvesting, handling and further subsequent processes are worth attention because they unfavourably influence the quality of seed. Seed damage results in lower grain value, storage problems, and reduced seed germination and seedling vigor, resulting in a subsequent diminishing yield of future crops. The present experiments were conducted to determine the extent of mechanical damage to chickpea seeds (physical damage along with reduction in percent germination) due to impact. A completely randomized factorial design of three replications was employed for each combination of variables. Independent variables were consisted of chickpea seed varierty (Arman, Bivanij, Filip93-93, Hashem and ILC482) and impact velocity (10, 20 and 30 m/s). It was found out that chickpea seed variety and impact velocity had significant effects on percentage of seed damage (p=0.01). With increasing the impact velocity from 10 to 30 m/s, the percentage of seed damage increased from 17.79 to 87.57% (72.61% physical damage and 14.96% reduction in germination). Physical damage to seeds at impact velocities higher than 10 m/s was higher than damage from reduction in the germination rate. It was observed  that the Filip93-93 chickpea seeds were more susceptible to mechanical damage than other varieties and had 63.81% total damage (48.72% physical damage and 15.09% reduce in germination) and the Arman chickpea seeds had the lower total damage (35.47% physical damage and 11.66% reduce in germination).

The potential of Fourier Transform Near-infrared (FT-NIR) spectroscopy technique was applied to determine moisture and soluble solids content of Shahani date fruit. Spectral acquisitions were carried out in reflectance mode using a FT-NIR spectrophotometer in the range of 12000-4000cm-1. Three different preprocessing methods namely: Multiplicative Scatter Correction (MSC), first and second derivatives were employed with their effects on the ability of predictive models compared. The most suitable predictive models resulted from Partial Least Squares (PLS) method showed coefficient of determination (R2) values of 0.977 and 0.973 and root mean square errors of prediction of 1.4% and 1.6o Brix for the moisture and the soluble solids content, respectively. The relative high Residual Predictive Deviation (RPD) values (7.4 and 6.4 for the moisture and the soluble solids content respectively) showed FT-NIR spectroscopy technique can be applied as a nondestructive, rapid and accurate method for determination of maturity of the Shahani variety date.

Date fruit, containing a substantial amount of carbohydrates is considered as an important agricultural product in Iran. In this research, the objective was the use date fruit wastes to produce bioethanol. For better understanding of the fermentation process the changes in sugar content, as well as the amount of produced bioethanol and carbon dioxide were periodically measured and modeled while using different mathematical models. To conduct the experiments, water was added to date syrup with 75oBx to be diluted to 20oBx. For proper initiation of fermentation, S.Cereviea inoculums along with different nutritional compounds were added to the syrup. The fermentation was done at 30±1oC. Results indicated that the rate of changes had an increasing trend during the first 5 days of the process, while decreasing sharply for the next following 15 days. At the end of the process, the brix of the syrup dropped to near 8.0oBx. The bioethanol resulted from fermentation of the syrup was 72 g per liter. The produced carbon dioxide was figured out as 70 mL/L. A comparison of the applied models indicated that all the investigated models fitted well to the experimental data, but the decaying exponential model with an R2=0.99 was the most fitted for sugar reduction modeling while the Gompertz model (R2>0.98) was found out as the most suitable the best for bioethanol and carbon dioxide production.

Iran is believed to occupy the second place, following turkey, among the apricot producing countries in the world. Iran is faced with problems in export of apricot due to little or non-observance of drying principals and inattention to world market requirements. The physical and mechanical properties of agricultural products are the most needed and important parameters for design and development of such systems as handling, grading, sizing, processing and packaging systems. Therefore, the physical and mechanical properties of apricot fruit, pit and kernel of the commercial cultivar Ghermeze-Shahrood was followed in this study. The results indicated the average values of length, width, thickness, geometric mean diameter, mass, volume and sphericity of the fruit as: 52.34 mm, 38.44 mm, 38.39 mm, 42.42 mm, 44.21 g, 45.87 cm3 and 81.07%, respectively. The average values of length, width, thickness, geometric mean diameter, mass, volume and sphericity were respectively 33.36 mm, 14.89 mm, 8.08 mm, 16.35 mm, 1.35 g, 1.37 cm3 and 49.01% for the pit. The values of coefficient of friction on steel, galvanized steel and plywood sheets were on the average determined as 0.417 for the fruit, 0.426 the pit and 0.523 for the kernel, respectively. The moduli of elasticity of the fruit vs. pit were 2.04 and 175.13 MPa, respectively. The minimum rupture force, deformation and toughness of the pit along with its thickness were determined at 0.2 to 0.4 (d.b) moisture contents. The obtained data can be employed for the design and development of postharvest, handling, grading, packaging and other processing equipments needed for export enhancement of the fruit.

Green fig, a fruit usually consumed as dried is one of the important non-oil export agricultural commodities of Iran. Physical properties of green fig are vital parameters as regards the design of such post harvest processing equipments as dryers, sorters and storing chambers. In this research work the effect of moisture content on fruit characteristic dimensions, geometric mean diameter, sphericity and kernel density have been assessed. Moreover, bulk density and porosity of fig bed were found out for four filling arrangements. Airflow resistance across fig bed was studied for 11 airflow rates. All the experiments were carried out at three levels of moisture content, namely: 5.74, 20.40 and 34.08% (dry basis). Results indicated that all the measured parameters (except porosity and kernel density) increase with an increase in moisture content. As for porosity and kernel density they showed reduction by rise in fruit moisture content. The results further indicated that the airflow resistance across the fig bed increases with an increase in moisture content and at a given airflow rate. Among the proposed mathematical models for predicting the airflow resistance across a bed of different agricultural products, the Ergun model showed the best curve fitting results with the highest value for R2, and the lowest for RMSE and P%.

A knowledge of Physical and aerodynamic properties of agricultural crops is important and essentially required for the design and development of a crop’s harvesting and post-harvesting equipments. In the present research, experiments were conducted to determine physical and aerodynamic properties of Fars province pinto bean namely: Kernel size and shape (length, width, thickness, projected area, geometric mean diameter and sphericity), static frictional coefficient, terminal velocity, drag coefficient as well as Reynolds number needed for an assessment of kernel fluidization in air streams. The effect of moisture content on fluidization was investigated at three moisture levels of 8, 12 and 16% (w.b.). The static coefficient of friction was found out by use of an inclined surface covered with glass, wood, galvanized iron sheet and plexiglass materials. Aerodynamic tests were carried out through fluidization method at three kernel size groups and in nine replications. All the measured and computed physical and aerodynamic characteristics were significantly affected by moisture content (P<0.01). The surface material significantly affected the static frictional coefficient, the maximum of which(0.44)  belonged to the galvanized iron surface. Results also indicated that for all surface materials, the static coefficient of friction increased linearly by increase in moisture content (R2 higher than 0.83). The mean values of terminal velocity, drag coefficient and Reynolds' number were recorded as 13.79 m/s, 0.739 and 8438.88 respectively.

Rice is one of the most widely human consumed agricultural products. For a prevention or diminishing of rice cracking in its milling process, precision control of drying conditions is indispensable. In this research, a thin layer experimental dryer is employed to obtain paddy’s drying kinetics. Drying experiments were conducted at five inlet temperatures of drying air of 30, 40, 50, 60 and 70oC and four air velocities of 0.25, 0.5, 0.75 and 1 m/s, with three replications. The initial moisture content was about 27% (d.b.) at the start of all the runs. Equilibrium moisture content was attained through a use of conventional empirical isotherm equations. Drying curves of moisture ratio vs. time as well as drying rate vs. time were plotted from the obtained experimental data. Drying curves obtained from the experimental data were fitted to eight different empirical thin layer models and compared with the help of three statistical parameters (R2, RMSE and c2). Results show that approximation of diffusion model predicts moisture change in drying with a higher accuracy in comparison with the other models. The coefficient of determination (R2) for this model at the inlet drying air temperatures of 30, 40, 50, 60 and 70oC were 0.999, 0.999, 0.999, 0.998 and 0.996, respectively. These results indicate that an approximation of diffusion can very accurately model the moisture ratio vs. time variations of paddy, and they as well indicate the applicability of thin-layer dryer for experimental works.

Drying behavior, and the effect of different drying conditions (4 levels of microwave power, namely: 360, 600, 840, and 1200 watts along with 4 vacuum pressure levels of 200, 400, 600, and 800 mba) upon the traits of: “tendency to lose moisture", "effective moisture diffusion coefficient" as well as "activation energy rates" in the process of cherry drying were assessed. A microwave vacuum dryer set was employed to carry out the experiments. Results indicated a range of 3.21×10-9 to 20.005×10-9 m2/sec for the effective coefficient of moisture diffusion in cherry. Activation energy was calculated by use of an exponential relationship based upon Arhineus', for which the maximum and minimum values were found out as 23.91 and 21.23 watt/gr respectively. The activation energy figures for cherry, found by use of the microwave vacuum set at different levels of power and vacuum were very close to each other in 3 different methods of measurement.

Moisture sorption isotherms for pistachio powder were determined by gravimetric method according to COST 90 project at temperatures of 15, 25, 35, and 40oC. Maximum hysteresis level in sorption isotherms curve was observed at the range of water activity 0.2-0.7. On the other hand hysteresis was diminished between adsorption-desorption isotherm curves when temperature reached 40oC. Some mathematical models were tested to measure the level of fitness of the experimental data including BET, GAB, Smith, Oswin, Halsey and Henderson. The mathematical analysis proved that Smith model was the most appropriate one. Thermodynamic relationship of Clasius Clapeyron was applied to determine the isosteric heat of adsorption and desorption of pistachio powder. Finally, critical points of equilbrium moisture content for pistachio powder were found using adsorption-desorption isotherm curves and GAB equation in the range of 15-40oC.

Temperature profile during the salting process play an important role in cheese quality since microbial and enzymatic activities, are thereby affected. In this work a three dimensional model was developed for heat transfer in the ultrafilterated cheese by using numerical solution of Fourier's second law with finite difference method (Explicit scheme) as a function of internal variable (cheese chemical composition in any point within the product) and of external variables (temperature, relative humidity and air velocity of storage) as well. The comparison of the experimental and predicted temperature values, using MATLAB software indicated a reasonable agreement between the model and the experimental values.

The effect of oleic and stearic acids on the Water Vapor Permeability (WVP) and mechanical properties of Sodium caseinate films was investigated. Emulsifiers (Span 80 and 85) were employed to produce the base mixture of film. Tensile Strength (TS), Elongation (E) and Young's Modulus (YM) were obtained for both standard (without lipids) and hydrophobic films. Results showed that the addition of oleic and stearic acids caused a reduction in tensile strength and Young's modulus, however increased elongation of films. The presence of lipid compounds decreased the water vapour permeability of film (about 50%). Scanning Electron Microscope (SEM) pictures emphasized the presence of stearic acid on the outer and inner side of film which is indicative of the decrease in WVP of the films.

To evaluate the most suitable method as well as different conditions of blanching in the process of Green Tea Production from local tea green leaves, this research was conducted in split plot in time and on the basis of a randomized complete block design of six treatments in 3 replications (different plucking times). Two common methods of blanching by steaming and panning were used. Green leaf was plucked by hand from Lahijan Research Station. Treatments included two blanching methods, panning and steaming, each accomplished within three different heating times of: 8, 12 and 16 vs. 2, 4 and 6 minutes respectively. Color of liquor, organoleptic scores, water extract, tannin, chlorophyll, and nitrate percentage in green tea were either determined or evaluated. The data was analyzed through SAS package. According to the obtained results, the two methods did not significantly differ with respect to: the color of liquor, water extract and nitrate percentage. But in the panning method, organoleptic scores and parameters of tea appearance, liquor flavor and taste were more pronounced than in the steaming with chlorophyll degradation in steaming more than in the panning method. Increase in time duration of panning decreased the organoleptic scores, water extract and nitrate.