Mihail Melenciuc’s research while affiliated with Technical University of Moldova and other places

The aim of the work is to significantly increase the efficiency of the dehydrating process of fruits with seeds, by treating it with microwaves in combination with convection. To achieve the purpose, an electrical installation was designed, produced, tested, optimized and implemented, which applies the combined technological treatment method in the dehydration process. Pears were selected as the object of the research in particular, because currently the production of these seeded fruits is not fully exploited, but they are of an increased interest for the agricultural producers and for specialized enterprises, and their dehydration by the methods currently used is difficult, especially because of the browning effect that occurs in the heat treatment process. The essential results obtained based on the research carried out, regarding the application of the elaborated installation, are: reduction of electricity consumption and treatment duration, increase in productivity and quality of dehydrated fruits. At the same time, the developed installation is simple in construction, has low cost and is easy to use, and during fruit processing it allows strict monitoring of the technological parameters, and researches demonstrated a high level of safety in operation. The significance of the obtained results lies in the solution to a series of problems, which are currently faced by the enterprises specialized in fruit processing, in particular by significantly increasing the efficiency of the process of dehydration of pears, based on the proposed method of combined treatment, predominantly with increasing the speed of dehydration, energy efficiency, quality of final products and profitability.

The authors present a study on the reduction of electric energy consumption in the process of preserving agri-food products. Refrigeration facilities used to cool various easily perishable agri-food products were examined in order to establish solutions for increasing energy efficiency in the storage process. The proposed solution provides for the combination of the refrigeration installation with step cooling, with the infl ow cooler with fan installed in the outside environment, which during the cold period of the year supplies the installation with artificial cold. The experimental results have shown that this system allows the reduction of approximately 27% of the electric energy consumption consumed annually by the existing installations.

One of the biggest problem encountered in drying area of food processing are the losses in food quality. While drying process is held, there is an important damage done to vitamins, polyphenols and other important nutriments. Being easily affected by high temperature and oxygen exposure, our concern was to find out what will be the effect of convective drying in air flow and CO2 modified atmosphere upon pears, “Conference” variety quality. Testing took place with temperatures between 60 and 100°C for both drying methods, one also used three different CO2 concentration regimes for the modified atmosphere approach, namely 30, 60, and 80%. The usage of carbon dioxide instead of air inside the drying chamber is expected to reduce oxygen exposure of the product during drying process, thus reducing oxidative reactions. Using CO2 as air substituent for convective drying showed good results from the organoleptic point of view by preserving a more natural pear color closer to the row material one, reduced damage done to ascorbic acid and total polyphenols concentration presumably thanks to reducing oxygen concentration and a slight drying duration reduction. There was deducted and established a mathematical model for the convective modified CO2 drying atmosphere as well as a pilot drying installation was designed for combined dying methods equipped with a CO2 recycling system.

The aim of this work is to determine the optimal technical parameters such as temperature, air speed and slice thickness when drying by the forced convection method and magnetron intensity for the method of applying microwaves in the process of dehydration of vegetable products. As a result of the research, the optimal technical parameters for drying by convection and by applying microwaves were determined. As raw material for the research, the peach was used, a valuable but perishable fruit, with an untapped potential in the Republic of Moldova and which, in the dehydrated version, could align among the strategic products on the national market and for export. A comparative research was carried out on the dehydration of peaches by two methods: the forced convection method and the application of microwaves. In the study process, the optimal drying parameters were determined, depending on the external appearance and energy consumption: product slice thickness (3-4 mm), air temperature for convection (50-70 °C), air speed (2-2.5 m/s) and magnetron power (180-270 W) for microwaves. It has been shown that the efficiency of using microwaves is 5 times higher than when drying by the convection method.

The aim of this work is to increase the efficiency of the fruit drying process with the SHF treatment in a uniform rectilinear movement. In order to achieve the purpose of the work, an experimental installation for fruit drying was developed with the application of the SHF treatment in the uniform rectilinear movement, on the basis of which the research was carried out. The efficiency of the drying process with the application of the experimental installation was estimated for 3 types of fruits: peaches, pears and apples. These types of fruit have been selected for the study because their drying is currently problematic, and they are of great interest to consumers and to processing and marketing businesses. The main results obtained regarding the application of the plant developed for fruit drying are: the drying process speed increase, the heat processing time decrease, the electricity consumption reduction, the dried fruit quality improvement and the processing costs reduction. Moreover, the installation is simple in terms of construction, low cost and easy use. At the same time, the installation allows the automation of the process, and during the research it demonstrated a high level of safety. The significance of the results obtained lies in solving a number of current problems faced by primary agri-food processing companies, by streamlining the process of drying fruit in rounds, mainly by reducing the technological processing costs and improving the quality of dried fruit for storage, marketing and use in nutrition.

Articolul este consacrat eficentizării procesului de deshidratare a fructelor prin tratarea cu microunde în tunel, urmărindu-se în prim plan reducerea consumului de energie electrică. Pentru abordarea acestei probleme a fost elaborat un sistem experimental pentru deshidratarea fuctelor care aplică un deshidrator de tip tunel, în baza căruia au fost realizate cercetările. Experimentele au fost realizate pe exemplul caiselor, piersicilor și prunelor. Cercetările au demonstrat că deshidratarea fructelor în baza noului sistem propus, permite reducerea consumului de energie electrică de circa 1,37 ori în comparație cu tehnologia clasică.

This article describes a low-energy fruit dehydration method. To evaluate the effectiveness of this method, an experimental fruit dehydration plant of the tunnel type was developed, on the basis of which the studies were carried out. Convection and microwaves have been used to treat the fruits during the dehydration process. The results obtained on the basis of the proposed method were com-pared with those obtained when using the classical dehydration method. Thus, studies have shown that dehydration of fruits by the new method allows of reducing electric energy consumption by 4.69 times.

Universitatea de Științe Agricole şi Medicină Veterinară „Ion Ionescu de la Brad”, Iași Grape seeds are the raw material from which vegetable oil is subsequently extracted. One of the pressing problems of the drying processes of wet vegetable products is the long duration of their thermal processing, which leads to increased energy consumption and decreased quality indices. This problem is exacerbated by the drying of seeds, which are rich in fatty acids and receptive to oxidation processes. For seeds, including grape seeds, it is beneficial to dry in a suspended layer with the application of microwaves. The application of currents with super high frequency essentially intensifies the drying process, ensuring a much higher quality of seeds. This method allows the automatic selection of already dried particles from the total seed mass and their removal from the heat treatment area, thus ensuring a maximum reduction in the heat treatment time, and therefore in the favorable conditions for oxidation of fatty acids.

This article presents the study of the kinetics of the process of convection drying and the application of microwaves of the sugar sorghum cultivated under the conditions of the Republic of Moldova. The kinetics of the convection drying process were studied at different temperatures: 50°C, 60°C, 70°C, 80°C, 90°C and by microwave application at different magnetron powers: 150W, 240W, 360W, 480W, and 550W. The external appearance of the samples obtained in order to determine optimal drying parameters, both quantitatively and qualitatively, was also analyzed.

The engineering calculation of such dryer could be approximately done using Id-diagrams. There is such a diagram for air based dryers graphical and analytical calculation. The use of this diagram for CO2 modified environment is impossible; because it shows the thermo-physical characteristics for air which significantly differs from those of CO2. We made a tentative of modeling and calculate all the necessary parameters based on which there was created an Id-diagram for CO2 modified environment. Obtained graphical relations for temperature, enthalpy, moisture content and partial pressure will allow one to use them for CO2 modified environment based dryers.