Hassan Jafari; Davood Kalantari; Mohsen Azadbakht
Abstract
In this study, the influence of different microwave powers (90, 270, and 450 W) and pulsation periods, i.e., On/Off times (30/60 and 30/120 ss-1) on drying rate and seed breakage of “Nemat” and “Hashemi” paddy varieties” was investigated. According to the results, the Midilli ...
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In this study, the influence of different microwave powers (90, 270, and 450 W) and pulsation periods, i.e., On/Off times (30/60 and 30/120 ss-1) on drying rate and seed breakage of “Nemat” and “Hashemi” paddy varieties” was investigated. According to the results, the Midilli et al.'s model showed the best prediction accuracy for drying rate of the "Nemat" variety in the pulsation period of 30/60. Furthermore, the two-term model was found as the best model for "Hashemi" variety in the pulsation periods of 30/60 and 30/120 and for "Nemat" variety in the pulsation period of 30/120.The 270 W microwave power and 30/120 pulsation period can be recommended as a final conclusion of this study for drying “Hashemi” paddy variety. The breakage percentage at this condition was 19.1%. Breakage percent of the Nemat variety was more than 40% at all of the conducted measurements, indicating that this variety is not suitable for microwave drying. The final concluding massage of this study is that a pre-test should be conducted before applying the microwave for paddy drying.
Mersad Ghorbannejad Shahroudi; Abdollah Golmohammadi; Davood Kalantari
Abstract
Introduction: Mechanical damages in agricultural products cause wastes directly and indirectly. Bruise damage due to quasi static load is one of the most important reasons of fresh fruit quality loss. Agricultural crops undertake many mechanical loads and physical damages during different stages of harvesting ...
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Introduction: Mechanical damages in agricultural products cause wastes directly and indirectly. Bruise damage due to quasi static load is one of the most important reasons of fresh fruit quality loss. Agricultural crops undertake many mechanical loads and physical damages during different stages of harvesting and post-harvest such as handling, transport, storage and processing. In many cases imported loads cause mechanical damages and cellular wall rupture and this rupture leads to perturbation of natural cellular interchanges. This object is one of the important problems of modelling and experimental studies in Biosystems engineering sciences. Tomato is one of the most important horticultural products and a widely produced products in the world. Larg amounts of tomato products are destroyed during the different stages of harvesting, transport and packaging. To study the viscoelastic behavior of agricultural crops, rheology science is used which is the science of biological materials deformation and flow ability under affection of loads at different times. For prediction and classification of materials behavior under different conditions of stress and strain, different rheological models are used. These models include different combinations of metallic body (spring) and Newtonian liquid body (dashpot) that illustrate complex behavior of agricultural products. Determining of factors that affect deformation value of tomato, lead to reduction of product waste.
Materials and methods: In this study, the effect of some important parameters such as static loading at three levels (2, 6 and 10 N), storage temperature at two levels (4 and 25 ˚C), loading at two directions for two cultivars (Supper-Beta and Petoerly-CH), were studied on deformation value. Samples were handy harvested at approximate ripeness level (reddish pink) from greenhouse and transported to the Lab. Some physical properties (mass, volume, major and minor diameters, height, sphericity coefficient, surface area) were measured. Samples were subjected to compressive loading using university made apparatus. The Experiments were performed in a fifteen-day period, at two different conditions, ones at temperature 4 ˚C and the other at environmental temperature 25 ˚C, using factorial test in form of completely randomized design. The first test was performed under constant load of 6 N in two directions of fruit axials (Z and Y directions), The second test was performed in three levels 2 and 10 N in direction of calyx face. By indicator, deformation value of tomatoes at 2, 4, 7, 10, and 15 days after loading was investigated. The third test was performed under constant loads of 15 N and deformation values of samples were recorded every 10 mins during a 60-minute period.
Results and conclusions: The Results showed at temperature 25 ˚C, with increasing load from 2 up to 10 N, deformation value of the product would be increased about 65%. Increase of deformation value indicates the effect of loading time for products such as tomatoes. This phenomenon can be a result of bulk density ratio reduction of product during the storage, because biochemical reactions are effective in fruit ripening, activating the destructive enzymes of cellular wall during the storage, softening and color changes. Maintaining fruits in direction of calyx face leads to lower deformation in comparison with 90 degrees proportion to calyx. This phenomenon is because of tomato tissue, its tissue in direction of calyx is harder and stiffer of normal direction, because of being flower. By reducing temperature from 25 to 4 ˚C, at constant load of 6N, deformation was decreased about 40%. With decreasing temperature, viscosity of biologic products would be increased and cellular walls get brittle and tissue stiffness increase. Therefore, it seems logical that deformation value of product at lower temperature decreases. Super-Beta cultivar had more durability in comparison with Petoerly-CH against compressive static loads. Under constant loading conditions, General Kelvin rheological model was considered suitable to estimate the strain versus time.
Rahmatollah Eshtavad; Davood Kalantari
Abstract
In this work, experimental studies of internal friction coefficient and porosity of four high productive rice varieties in Iran (Nemat, Neda, Pajouhesh and Pardis) have been presented. Moisture content varied in four different ranges between 8 and 20%. The obtained results indicated that the internal ...
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In this work, experimental studies of internal friction coefficient and porosity of four high productive rice varieties in Iran (Nemat, Neda, Pajouhesh and Pardis) have been presented. Moisture content varied in four different ranges between 8 and 20%. The obtained results indicated that the internal friction coefficient decreased with increasing the moisture content from 8 to 11%, then decreased with increasing the moisture content. The internal friction angles for Nemat, Neda, Pajouhesh and Pardis at the equilibrium moisture content, i.e., 11%, were 39.3, 37.5, 33.95 and 34.38° respectively. Based on results obtained in this study, the apparent physical properties of the rice varieties, e.g., length of the grain, cross sectional diameter of the grain, relative roughness of the external surface of the grain, etc. have significant influence on the normal stress-shear stress relationship. Meanwhile, porosity of the samples depends on the type of variety and moisture content. Porosities of the samples at equilibrium moisture content were 70.8% for Nemat, 63.9% for Neda, 62.7% for Pajouhesh and 66.5% for Pardis
