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In the scientific and engineering literature, there are various mathematical methods for modelling the equilibrium moisture content of agricultural and food materials. The objective of the present study was to statistically evaluate a total of thirty-two four-parameter moisture sorption isotherm models and subsequently compare their goodness of fit. The moisture sorption isotherm models considered were either originally developed or taken from the reference literature. The coefficient of determination and the graphical evaluation of residual randomness were utilized as the main assessment criteria for statistical evaluation of the moisture sorption isotherm models examined. The statistical performance of the models was tested according to the equilibrium moisture content of quinces. On the basis of the statistical analyses performed, the Popovski&Mitrevski model, i.e. the model with the reference numbers M25 and M30, and the McLaren&Rowen model were found to have the best statistical performance of all the models considered.

The question again arises as to how to dry certain types of agricultural grain products and seeds. Should it be indirect or direct? The reason for this is the occasional fires that occur in dryers. It is often and unprofessionally stated that the cause of the fires is the use of a direct dryer. However, the causes of fires are multiple, and it is seldom due to the type of dryer. Two factors determine the differences between direct and indirect drying, and these are the nutritional and safety aspects. The ambition of this study is to clarify all the important differences between direct and indirect grain drying and to eliminate the established misconceptions on this issue. Drying of sunflower, oilseed rape and sorghum is especially delicate.

In the food industry, convective drying is a widely used method due to its applicability to many food materials. Besides this advantage of the convective drying method, there are several shortcomings related to the rehydration capacity, low quality of dried material, loss of color, flavour, and nutrient of the final dried materials. In this paper, the convective drying kinetics of osmotically pre-treated potato slices (variety Carrera) were analyzed. Thin-layer drying kinetics of potato slices at four drying air temperatures 40, 50, 60 and 70°C and two drying air velocities 1 and 2 ms-1 were obtained on the experimental setup. For an approximation of the experimental data with regard to the moisture ratio three thin-layers drying, models from scientific literature and the model of Mitrevski et al., were used. For each model and data set the statistical performance index, ph chi-squared, and ch2, values were calculated and models were ranked afterward.

Numerous mathematical models for approximating the water sorption data of food materials are available in the scientific literature. Depending on the number of parameters included, such models are referred to as one-parameter, two-parameter, three-parameter, or multi-parameter models. The objective of this study was to evaluate a total of sixty two-parameter sorption isotherm models for approximating the equilibrium moisture content data of quince and to compare the goodness of fit between the models examined. On the basis of the statistical analyses performed, it can be concluded that the Popovski&Mitrevski model has the best statistical performance of all the models examined. The coefficient of determination was the main criterion for assessing the model performance, totalling R2 = 0.9913 for the best model performance.

The purpose of this paper is to examine the effects of storage and treatment with sulfur dioxide of different concentration on the overall change in the color of dried apricots. Upon sulfurization of the prepared apricot samples, they were dried using the combined osmotic-convective drying technology, and subsequently kept either in a storage unit at t ≈ 25 o C or in a cooled environment at t ≈ 3 o C over a period of six months. The sample color was measured on the inside and the outside of the dried apricot fruits. Statistical analysis was performed using the Dependent Samples T-test so as to determine changes in the color of dried apricots after 3 and 6 months of storage. After six months of storage, the smallest color change of ∆E = 6.56 was measured in the apricot samples stored in a cooled environment. After six months, the greatest color change of ∆E = 49.38 was measured in the apricot samples stored at an air temperature of 25 o C.

The mathematical modelling of the food drying process is of significant importance to scientific and engineering calculations. Thin-layer drying models represent valuable tools for modelling the drying curve and estimating the drying time. These models have wide application due to the ease of use and requirement of less data compared to complex mathematical models. In this paper, the thin-layer drying kinetics of some fruits (namely, pear and quince) was studied. Using an experimental setup designed to simulate an industrial convective dryer, the experimental results were obtained at five drying air temperatures (30, 40, 50, 60 and 70 oC) and three drying air velocities (1, 1.5 and 2 ms-1). For the approximation of the experimental data with regard to the moisture ratio, a new thin-layer model was developed. The performed statistical analysis shows that this model has the best performance features compared to other well-known thin-layer drying models found in the scientific literature.

The aim of this paper is to present the influence of convective drying of organic pear pulp and adding ascorbic acid on changes in color, the difference in vitamin C content and also show the kinetics of convective drying. It was a two-factor experiment. The first factor was the air temperature needed for drying, between 45 °C and 65 °C, with a constant speed of drying air of 1.5 m/s; the second factor of the experiment was the adding of ascorbic acid to the pear pulp in the amount of 1 % and 2 % of the full mass of the prepared pulp. The lowest change in color was achieved by adding ascorbic acid in the amount of 2 % of the full mass of the pulp and drying air temperature of 45°C (ΔE= 23.981). The highest change was accomplished at the air temperature of 65 °C and by adding ascorbic acid in the amount of 1% (ΔE= 30.039). With samples where ascorbic acid was added reduction of vitamin C was over 99 % with all samples. By examining the kinetics of convective drying based on statistical indicators R, X2, RMSE, models Page and Logarithmic are the best in representing convective drying of pear pulp at air temperatures of od 65 °C and 45 °C respectively.

The injector is a fluid machine of simple construction, featuring no moving parts. It is fluid stream machine. Should there be an occasional need for exhausting chemically aggressive fluids, this machine proves very convenient on account of its lower purchase price compared to other types of hydraulic machines. The injector discussed in this article has been originally designed for exhausting gases from the sulphur chamber, which is used in the pretreatment of fruit before drying. Once the sulphuring is completed, the SO2 gas should be exhausted promptly. Under realistic sulphuring conditions, the effect measurement was performed at a compressed air pressure of 2 bar. The compressed air pressures ranged from 0.5 to 2.5 bar. In the instance when the chamber was filled with fruit, at a pressure of 2 bar, the ratio between the exhausted and compressed air was 1.68, at an exhausted gas flow rate of 0.0327 kg/s. The volume of empty chamber was 0.2856 m3. According to these data, a period of 10.04 s is required for one air change in the chamber. As complete aeration of the empty chamber necessitates three air changes, the injector should be in operation for 30.12 s.

In this paper, a faster and easier way, in comparison with classical methods, to determine the equilibrium moisture content in food materials is shown. The equilibrium moisture content is determined only experimentally, with determination of sorption isotherms. However, the key issue that is a condition for application of certain experimental method for determining of sorption isotherms is the reliability of experimental data obtained for equilibrium moisture content, as well as the time required to determine specific sorption isotherm. Despite numerous advantages of the static gravimetric method, the long time to achieve equilibrium moisture content of the sample is its main drawback and reason why the researchers use other techniques and methods. Out of these reasons came the idea to apply relatively fast and simple method to determine equilibrium moisture content in food materials, based on the values of average material temperature change obtained from experiments including convective drying kinetics. Furthermore, the resulting temperature response from the conducted experiments can be successfully used to determine unknown parameters in the models for calculation of equilibrium moisture content, by applying of inverse approach method that is an essential tool in modeling of heat and mass transfer processes for different food materials.

A team of researchers from the Faculty of Agriculture in Novi Sad designed an original device for the regeneration of osmotic solution used in the process of osmotic drying. The effects of two types of ceramic (porcelain) fillings and air temperature on the regeneration process were studied. On the basis of Fisher's criterion, it was concluded that air temperature affects the specific energy consumption for a probability of 95%. Moreover, it was also concluded (on the basis of Fisher's criterion and for a probability of 95 %) that a type of a porcelain filler has no impact on the specific energy consumption. In addition, a mathematical model of the functional dependence of regeneration kinetics on regeneration temperature and duration was also established. The regression analysis resulted in the functional dependence of regeneration kinetics and energy efficiency on the air temperature and the type of examined fillers.

In this paper the thin-layer drying of quince slices as a function of drying conditions were examined. The experimental data set of thin-layer drying kinetics of quince at five drying air temperatures 30, 40, 50, 60 and 70 oC, and three drying air velocities 1, 1.5 and 2 m s-1 were obtained on the experimental setup, designed to imitate an industrial convective dryer. Ten well known thin layer drying models from scientific literature were used to approximate the experimental data in terms of moisture ratio. In order to find which model gives the best results, the numerical experiments were made. For each model and data set, the statistical performance index (φ) and chi-squared (x2) value were calculated and models were ranked afterwards. The performed statistical analysis shows that the model of Hii gives the best results for approximation of experimental drying data of quince.

The control system of organic products in Serbia was established on the model of a control system which is prescribed by regulations of the European Union. This paper describes the production processes of organic dried fruits and vegetables with combined drying technology which is developed at the Faculty of Agriculture in Novi Sad. Special attention is given to critical stages of drying that can threaten the organic status of the product. Since the osmotic solution, which is used in the drying process, becomes an integral part of the final product, it also must be organic. As a possible solution, usage of a solution of organic sugar cane or organic fruit syrup is recommended. Another critical point of drying is the process of sulphurisation. Sulphurisation is not allowed in organic production, the refore, in order to preserve the color of the final product, recommended treatments are treatments with ascorbic, citric or other organic acid.

The purpose of this paper is to examine the effects of osmotic drying on the mass transfer and shrinkage of quinces. The osmotic drying was performed in a sucrose and water solution. The temperatures of osmotic solution were 40 oC and 60 oC, and the initial concentrations were 50 oBx and 65 oBx. All four combinations were used in the experiment. An increase in the experimental parameter values intensified the mass transfer. According to the amount of exchanged matter, it is possible to determine the shrinkage of quince tissue. The most significant changes in quince tissue volume were measured at the highest levels of experimental parameters. After combined drying (osmotic + convective), the effects of exchanged matter on the shrinkage ceased. More notable volume changes were measured in the quince samples after convective drying (without osmotic drying) in comparison with the samples dried osmotically. The experimental results indicate the positive effects of osmotic drying on the volume of dried quinces.

There are different instances of grain aeration in a silo. Six models are displayed for cylindrical grain storages (silos): four models with coaxial air streaming and two models with radial air streaming. The airflow analysis was based on the use of a cylindrical coordinate system. This system facilitates the simplification of the mathematical problem. Air velocity changes in the coaxial streamlines stem from the equality of the total air pressure drop in the flow through the layer of grain. Radial airflow is directed from the axis or to the axis of the silo cells. Air velocity is higher near the axis, and the lowest on the peripheral perforated wall. In this case, the continuity equation is crucial because it determines the value of the velocity at various distances from the center. .

As a physical property, colour is an important indicator of the product quality. The purpose of this paper is to examine the effects of different pretreatments on the pear colour alteration during and after combined drying. Combined drying entails both osmotic and convective drying. The osmotic drying was done in a sucrose solution with the temperature of 50 oC and the concentration of 50 oBx. The duration of osmotic drying was 120 minutes. The convective drying was performed by the air temperature of 50 oC during the period of 23 hours. The following protective agents were used: sulphur dioxide, ascorbic acid, citric acid, boiling water, and a solution of alcohol vinegar and water. The most significant change in the value of internal colour L*parameter was recorded in the blanched samples. After the convective drying, notable changes in this parameter were not recorded. All the samples showed an increase in the value of b*parameter following the convective drying. After the osmotic drying, the most significant change in the value of external colour L*parameter was also recorded in the blanched samples. However, in contrast with the internal pear colour, the changes in the external colour L*parameter following the convective drying were more significant. The slightest changes of all colour parameters were recorded in the samples treated with sulphur dioxide.

Pumpkin seed and pulp has been used because of edible and medicinal values from ancient times as a source of quality oil and protein. Oil is consisting of saturated and unsaturated fatty acids. The mayor kernel composition of saturated fatty acids is palmitic and stearic acid (19.3% of the total) the rest of 80.7% are unsaturated fatty acids like oleic (C18:1), linoleic (C18:2) linolenic (C18:3), palmitic and gadoleic acids (Gohari Ardabili et al, 2011). The production of pumpkin crude oil is done by the help of equipment which squeeze the seeds by pressing using a screw press, actually this is the perform of external force. The slow loading compression test was done in order to gather information about intensity of force which raptures the single kernel of Gleisdorf express F1. The tests were conducted so that it was possible to identify the influence of seed moisture content and loading rates onto hybrid compressive behaviour. The range of kernel moisture content were 6.0%, 19.8%, 24.0% and 30.5%, and loading rates were 10 mm/min; 30 mm/min and 50 mm/min. The curve of rapture force versus kernel moisture content, express the decreasing tendency of force for loading rate of 10 and 50 mm/min as the moisture content increasing. Maximum value of force (491.6 N) was recorded an low moisture content (6.0% w.b.). The rapture forces had highest values of493.51 N (loading rate 50 mm/min) and 488.37 N (loading rate 30 mm/min) when moisture content was 19.8% w.b. The values of single kernel deformation were recorded at same moisture content for loading rate of 30 mm/min and 50 mm/min. The highest values of squeezing forces for tested range of kernel moisture content were observed during loading range of 10 mm/min. Specially, at kernel moisture content of 19.8% this force was 2.9 times larger compare to loading rate of 30 mm/min, or 1.7 times compare to loading rate of 50 mm/min.

This paper presents the analysis of the current state of grain dryers and storages in the Republic of Srpska in terms of their age structure, installed capacities, working order and geographical distribution. The current state of grain dryers and storages which have storage capacities over 1000 t was determined through a survey conducted in all centres in the Republic of Serbia. The survey results showed that the total installed capacities for storing grain in the Republic of Srpska are 317,917 t of wheat, while the total installed capacities of grain dryers are 207.4 t/h.

The aim of this research was to determine the shear force of root and leaf mass depending on the basic physical properties of root vegetables: carrot, parsley, parsnip and celery. TMS-PRO (Food technology) measuring instrument and TMS flat shear blade set (Warner-Bratzer shear test) were used for measuring the shear force. Dependence of instant shear force on the shearing distance was determined in the laboratory conditions. Also, maximum shear force (Fmax) and average shear force (Fav) were determined and specific shear force (Fsp) was calculated per unit of sheared part. As it was expected, the correlation between maximum shear force and root diameter (0.49-0.80) was high and positive. Calculation of specific shear force per unit of sheared part was general and objective indicator of shear force. The measured quantitative values of shear force are of technological importance for the design of machines for mechanical harvesting and processing plants. .

An objective of this study was to evaluate and compare the behaviour of three domestic sunflower fruits (Bačvanin, NS H111 and Šumadinac hybrids) during compressive loading considering the seed moisture content. The fruits of NS H111 and Šumadinac, demonstrated low values of bio yield force ranging from 29.3 N to 45.2 N when fruits had low moisture content (between 3.7 and 5.9% w.b.). Opposite results occurred for Bačvanin hybrid (60.6 N) within the same fruit moisture content. For all hybrids, the machine head displacement (deformation) increased as the seed moisture content increased. This conclusion is especially valid for NS H111 hybrid. The linear model shows a decreasing trend of bio yield modulus of elasticity for three tested hybrids as the moisture content of seeds increased.

The aim of this research was to determine possible mechanical handling of consumable tomato fruit and processing. The dry mass content in consumable tomato fruit was 6.08% which made the tested hybrid of tomato fruit interesting for processing. The mechanical properties of the tested tomato fruit hybrids were determined based on the puncture and compression tests. The obtained values for energy absorbed before the rupture point was: 51.18 mJ and 74.67 mJ for the puncture test and 480.15 mJ and 169.43 mJ for the compression test. Consumable tomato fruit skin is more resistant to penetration related damages in comparison with the industrial tomato fruit skin which has a direct effect on the fruit shelf life. Generally, industrial tomato fruit is characterized by greater toughness. Both hybrids give fruits that allow mechanized harvesting and handling during their processing. .

The objectives of the research presented in this paper are rheological properties of a mash made of Senga Sengana strawberries. Organically grown strawberries were washed in cold water, blended and in order to be conserved, treated with sodium benzoate. Rheological properties of the mash with solids concentration of 10.53% were examined at a rotational rheometer at the temperatures of 20˚C, 30˚C and 40˚C. The aim of the research was to investigate the rheological properties (rheological behavior) of a strawberry mash with emphasis on the effects of temperature. It was found that the strawberry mash behaves as non-Newtonian, pseudo­plastic fluid, where the apparent viscosity decreases with increasing of shear rate (velocity gradient). The strawberry mash has thixotropic properties, where the apparent viscosity changes with time slowly and where the strawberry mash has no gel properties. Dependence of shear stress and the velocity gradient is modeled by Ostwald de-Waele equation. It was stated that the increase of a mash temperature leads to consistency index reduction and flow behavior index increase. The dependence of the apparent viscosity and temperature is modeled by Arrhenius equation, where the activation flow energy increases with shear rate reduction.

The objectives of the research presented in this paper are rheological properties of a mashed quince, variety Leskovac (Cydonia oblonga "Leskovačka"). The aim of this study was to investigate the influence of solids to the rheological properties of quince puree. For this purpose an experimental rheological testing of three samples of quince puree at room temperature of 20°C for different concentrations of dry matter: 8%, 10% and 12% was conducted with the rotational viscometer. It was found that the quince puree act as non-Newtonian, pseudoplastic fluid. The quince puree is thixotropic, with the apparent viscosity slightly variable with time. The change of apparent viscosity with time indicates that the quince puree hasn't got gel properties. Due to perceived yield stress, shear stress dependence on the shear rate (velocity gradient) is modeled with the Herschel - Bulkley model. The dependence of the apparent viscosity on the concentration of solids is modeled with exponential, power and logarithmic model, where it was found that the exponential model best represents the measured data, followed by the power and logarithmic model.

The aim of this research was to determine quantitatively carrot root mass and dimensions depending on the cultivation type (flat ground and ridge), as well as to determine the differences in the root texture by measuring the puncture force in xylem and phloem. Due to higher coefficient of variation and statistically significantly higher values of maximum diameter and xylem diameter, lower quality of carrot root dimensions was determined on flat ground. Puncture force measuring was conducted by TMS-PRO instrument (Food technology) having the cylindrical punch diameter of 6 mm. Statistically significant differences in the puncture force between xylem and phloem were determined for maximum and average values of puncture force, as well as for the slope of puncture curve, for both types of cultivation. No significant differences in the yield point were determined between xylem and phloem. By testing the dependence between carrot root shape and mass, with regard to the puncture force, the highest interdependence was determined by coefficient of simple regression for critical puncture points in phloem.

The aim of this research was to analyze the physical characteristics of root vegetables: carrot, parsley, parsnip and celery. These root vegetables are sold fresh on the market which is why it is important to specify its shape, structure and root texture. Carrot, parsley and parsnip were grown in ridge cultivation and celery was grown on the flat ground. The yields of root and leaf, as well as the dry matter were measured. Root physical characteristics were tested by the puncture test. The puncture force was measured by TMSPRO instrument (Food technology) having the cylindrical punch diameter of 6 mm. The puncture test was performed for every root at three measuring points located at the point of maximum diameter: sideways into the whole root and at the cross section of xylem and phloem. Critical points were determined on the puncture curve: puncture point ('yield point'), maximum and average value of the puncture force for the distance of 10 mm, as well as the slope of the puncture force. Also, the shape of the puncture curve was analyzed with respect to the depth of the cylindrical punch penetration. The puncture test showed statistically significant and clearly expressed differences in the measuring points of the carrot, parsnip, parsley and celery which confirmed the heterogeneous structure of the tested root vegetables. The measured quantitative values of the puncture force are very important in the technological sense since they can contribute to the design of the machinery used for mechanical harvesting and processing.

The aim of this study was to acquire data on the physical properties and mechanical behaviour of the six seed corn hybrid varieties. One variety was semi-flint, while others were dent types. The mean values of length, width, thickness, geometric diameter, surface area, porosity, single kernel mass, sphericity, bulk and true density, 1000 kernel weight and coefficient of friction were studied at a single level of moisture content. The longest kernels were those of the ZP 677 hybrid, which ranged from 10.51-11.50 mm in length. The largest width was observed for ZP 684 (7.51-8.50 mm) and ZP 677 (6.51-7.25 mm) kernels, while kernel thickness was greatest in ZP 434 (3.56-4.55 mm) and ZP 684 (3.31-5.55 mm) hybrids. The mean geometric diameters were 7.18; 7.15; 6.91 and 6.72 mm for NS 4015, ZP 644, NS 640 and ZP 677, respectively. The highest value of sphericity, 0.75, was measured for ZP 684, followed by 0.71 for NS 640; the hybrids NS 6010 and ZP 677 had the lowest value of sphericity (0.60). The measured bulk density values ranged from 784.75 kg/m3 (ZP 677) and 779.58 kg/m3 to 633.56 kg/m3 (NS 6010), while true densities ranged from 1176.63 kg/m3 (ZP 677) and 1175.65 kg/m3 (NS 640) to 900.94 kg/m3 (NS 6010). The linear model showed a decreasing tendency of secant modulus of elasticity for all ZP hybrids as the moisture content of seeds increased, with high values of the coefficient of regression. Similar results were attained for NS hybrids but with lower coefficient of regression values.

Quince fruit is characterized by pleasant smell, taste and ability of long-term storage. However, beside these good characteristics, the high quality of hardness and firmness of the fruit influences the decrease in its usage in the fresh state. Drying process is not a regular method in processing this type of fruit. Combined drying is a method developed at the Faculty of Agriculture in Novi Sad and it consists of osmotic and convective drying. Disadvantages of the product got from convective drying only are eliminated with this method. The experiment tested the influence of osmotic drying on the force of rupture and quince color. Osmotic drying was done with the following combinations of temperature and concentration of sucrose solution in water: 40oC i 50oBx, 60oC i 50oBx, 40oC i 65oBx i 60oC i 65oBx. The convective drying of the samples was uniformly done by air drying at the temperature of 400C for 20 hours. Osmotic drying time was 180 minutes. Every 20 minutes samples were taken for the measurement of color, force of rupture and moisture. Sample testing by pressure was used for the analysis of rupture force of the quince. During osmotic drying on the samples, test was done on the samples of approximate size 10x10x10 mm. After convective drying, the same test was done on the samples with the original dimensions of 15x15x15 mm. The measuring instrument used in testing rupture force was TMS-PRO (Food Technology Coorporation - USA). Color measurement was performed by Konica Minolta colorimeter CR-400. CIE Lab values were used for color parameters. The change in color is defined by overall change in size of ΔE. With the analysis it was determined that the concentration of osmotic solution is an important factor in rupture force of the quince samples. The concentration of osmotic solution, has also shown an important influence on the changes in quince color. The collected results have been statistically processed in software Statistica 9.1.

Measuring changes in moisture content of halves, during the drying was done to assess the influence of pre-treatment, temperature and drying air velocity l on the kinetics of convective drying nectarine varieties 'Fantasia.' Based on the results of dispersion analysis three - factors experiment, the statistical probability of 99% rated it applied. Pre-treatment and selected levels of air temperature affect the drying kinetics. Selected levels of air velocity in front of layers of material within the tested range, and mutual interaction between the factors are less influential on the kinetics. A careful analysis of the results moisture changes during the drying time (kinetic drying curves) there has been a light influence of chosen level of drying rate on the kinetics, but less pronounced. With the increase of air temperature and drying air velocity for drying outside layer of the material increases and the drying rate. Using osmotic dehydration as pre-treatment lowers the rate of convective drying process for forming a relationship of adsorption of moisture, solvent and dry matter in the tissue of nectarine halves. The newly-formed links cause the increase in value of equilibrium moisture osmotic treated materials, and rapid achievement of equilibrium moisture. Seen from the aspect of the total drying time for a final product, more quickly achieve equilibrium moisture content apparently excludes the negative effect of osmotic pre-treatment on the kinetics of convective drying nectarine halves.

The scope of this paper is the determination of viscosity of sucrose solutions using the Coriolis flow meter. Previous research showed that the Coriolis flow meter can be successfully applied to determine the viscosity of water, where instead of the straight pipeline section pressure drop is measured on the Coriolis tube. In this paper a technical solution applied to a sucrose solution is proposed. The goal of this research is to consider the possibility of applying this proposed technical solution to reliable sucrose solution viscosity measurement during the evaporation process in the evaporator. Experimental studies were conducted with the evaporator developed at the Laboratory of Bioengineering, the Faculty of Agriculture in Novi Sad. Two sets of measured data were used for data processing. One set of data was used for mathematical modeling, and the other was used for verification of the mathematical model. It has been proven that if the temperature of the solution t, concentrations C and hydraulic parameter Δp/Q of the system are taken into account, the proposed concept of the measuring system can reliably be used for continuous measurement of viscosity of a sucrose solution. This is true even if conditions for the Hagen-Poiseuille flow are violated. This proposed solution for measuring reduces the number of sensors required for viscosity measurement. This increases compactness and simplifies construction of the evaporator in which the measuring system is built in. Since the Coriolis meter measures the density of the fluid, the proposed technical solution makes it possible to determine the dynamic and kinematic viscosity of the sucrose solution in the process of evaporation.

The designing of appropriate equipment is of great importance for the success of technology. Therefore, it is necessary that researchers who introduce a certain technology into practice constantly bear in mind the possible engineering solutions which would be compatible. This technology comprises osmotic dehydration, as a pretreatment, and hot air convective drying. The limit criteria for selection of the technology parameters were formed based on the requirement that the product quality is preserved to a high degree. Another important quality of this technology is energy sustainability, which is based on renewable energy sources. Special attention was given to the protection of fruits and vegetables from mechanical damage. For this purpose, the system of material handling in shallow crates was designed during the process of osmotic drying and sulphurisation. Adhering to the previously mentioned principles, the following original equipment was designed and constructed: osmotic dryer, sulphuring chamber, convective dryer with racks, evaporator of osmotic solution and solar air heater.

Quince (Cydonia oblonga mill.) is fruit which is neglected in fruit production in our country despite its pleasant aroma. Due to its high values of hardness and firmness, quince is not used much for drying. Osmotic drying, within combined drying technology, decreases these deficiencies. The objective of this paper is to examine the effects of certain factors of osmotic drying on physical properties of quince. Leskovačka cultivar of quince, prepared in a form of quarters, was used for osmotic drying. The experiment was conducted as a three-factor experiment. The experiment factors were solution temperature, solution concentration and the duration of the process. The solution concentration varied having the values of 50°Bx and 65°Bx, the temperature had the values 40°C and 60°C, while the drying time was 100 and 180 minutes. The effects of these factors on the changes of the length, moisture content and volume of quince samples were examined. The changes of physical properties during the osmotic drying were graphically presented, and the results were approximated by the second degree polynomial. The coefficients of the suggested models as well as the coefficients of determination were calculated using the mathematical method of regressive analysis. The coefficients of determination are quite high regarding moisture content change and volumetric shrinkage, and with regard to the change of dimension, they also prove to be dependant on the duration of drying. By increasing the concentration and the temperature of osmotic solution, the changes of physical properties become more prominent. The changes of physical properties are more intensive in the first 100 minutes of osmotic drying.

This paper presents the research results on the color change of quince during combined drying. The applied combined drying includes osmotic drying in sucrose solution and convective tray drying with heated air. Quince cultivar Leskovačka was used in the experiment. The experiment was conducted with 15x15x15 mm samples. Osmotic drying was performed with the following combinations of the solution temperature and concentration: 60oC and 65oBx, 40oC and 50oBx, 60oC and 50oBx and 40oC and 65oBx. Color measuring in this experiment was performed with a three-filter colorimeter Konica Minolta CR-400. This instrument is capable of expressing quantitative color parameters in different systems. CIE L*a*b*color system was selected, based on the three-filter method. The change of the value L*, which describes sample brightness, has the similar trend to all the experimental units except for 60oC and 50oBx. A small decrease of the value L*was determined, which denotes small changes of sample brightness. The negative value a* expresses mostly the green color, while the positive values expresses the red color. For all the experimental units, the negative value was within the range of -2 to -5. Significant increase of the value b*was observed in all the experiments. This fact points to the more intensive and 'cleaner' yellow color. Convective drying influences the value reduction of the parameters L* and b*values. During the convective, as well as the osmotic drying, the value of a*parameter did not change.

The results of some physical properties three domestic wheat cultivars are presented in this paper. Three axial dimensions of the seed length, width and thickness were measured only at equilibrium moisture content. The length of Simonida kernel is 5.2-5.7 mm, Dragana 5.1-6.0 mm and NS 40S is 5.0-5.9 mm. The other two dimensions are similar within the varieties: the width is 2.3-2.8 mm, 2.0-3.0 mm and 2.2-3.0 mm for Simonida, Dragana and NS 40S respectively. The thickness for Simonida seed is 1.9-2.4 mm, Dragana has 1.9-2.7 mm and NS 40S kernel dimension is 2.0-3.4 mm. Those surveying indicate that the shape of kernels is rather prolong elliptical then spheroid. This conclusion confirms the sphericity of the grains, so this value for Simonida cultivar is 0.57 as well as for Dragana, while NS 40S seed shpericity is 0.6. The bulk densities are 791.34 kg/m3, 788.51 kg/m3 and 731.77 kg/m3 for Simonida, Dragana and NS 40S. The porosity of Simonida kernels is 28.28%, for Dragana 31.46% and for NS 40S is 31.59%. The results of slow compressive test demonstrate that Simonida and Dragana are hard wheat. The highest value of mean rapture force of 244.4 N was observed for Simonida variety at the 13.6% of moisture content. Cultivar Dragana value of mean rapture force was 241.4 N at 13.3% of moisture content and cultivar NS 40S had mean rapture force of 106.8 N at 14.1% grain moisture content.

The main aim of this research is to establish the effects of moisture content on some physical properties of soybean seeds. Testing was performed for the Balkan and Sava varieties. The following physical properties were measured: dimensions, equivalent diameter, sphericity, grain density, apparent density, coefficient of friction, dynamic angle of repose, grain volume and mechanical properties. Moisture content of soybean seeds ranged from 8 to 20%. This paper presents the preliminary results from the first year of research. It was noted that most of the soybean physical properties depends on the humidity in the measured range. It is known from science literature that soya seed (grain) deforming, may cause two cases. The final outcome of dry seeds is grinded grain, and in case of wet grains they may be crushed . This research presents preliminary values of rupture force in the case of grinding grain and analyze the change of modulus of elasticity.

The scope of this paper is continual measurement of volumetric flow rate of sucrose solution during evaporation process. This process is nonstationary, i.e. temperature and concentration of solution change in time. Hence, flow rate measurement of solution is pretty difficult. The aim of this research is to examine possibility to apply angle valve for continual flow rate measurement of sugar water solution in process of solution evaporization during which temperature and concentration rise in time. It is concluded that it is possible to use angle valve for successful flow rate measurement of sugar water solution. Angle valve simplifies measurement, although has some disadvantages. The first one is long-lasting a calibration procedure and the second one is that too many parameters have to be kept constant during calibration.

The paper presents results of the research on the effects of osmotic dehydration, applied as a pre-treatment, on convective drying kinetics of pear cultivars 'William', in the form of ¼ of fruit, i.e. slices. Three-factor experiment of convective drying of pear slices was performed, while the experiment factors were pre-treatment, drying air temperature and velocity of drying air in front of the layer of materials. The following pre-treatment forms were applied: osmotic drying with solution temperature 40oC and solution concentration 50Bx, osmotic drying with temperature 60oC and solution concentration 65 Bx, and pear slices placed in a convective dryer with no pre-treatment. The statistical method of dispersion analysis in the three-factor experiment was used to evaluate the effects of the analyzed factors on the kinetics of convective drying of slices. On the basis of the analysis it was determined that the selected pre-treatments and drying air temperature are important for kinetics of convective drying, while air velocity in front of the layer of material is less important, as well as the mutual interaction of the factors.

In this paper continuous measuring of water viscosity by Coriolis flow meter is analyzed. The idea of technical solution for determining fluid viscosity by Coriolis flow meter and Hagen-Poiseuille equation was elaborated. Pressure drop was measured at the Coriolis tube instead of at the straight pipeline section. The aim of the research is to consider the possibility of applying the proposed technical solution for reliable determination of water viscosity. It was proved that by taking into account the temperature of water t and hydraulic parameters of measurement system Δp/Q, the proposed technical solution can be a reliable method for continuous monitoring of water viscosity, even if Hagen-Poiseuille flow was not achieved. The proposed solution decreases the number of necessary sensors for viscosity measuring, and makes the system and facility more compact. Compared to the conventional parallel mounted capillary viscometer with constant flow pump, the proposed technical solution is much cheaper. The presented technical solution of the measurement system requires a long process of calibration in real terms.

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