The intensification of dehydration process of pectin-containing raw materials

The process of intensifying dehydration of pectin-containing raw materials by using centrifugation with simultaneous application of low-frequency oscillations to the working container creates an electroosmotic effect in unilateral diffusion to improve the filtration process. It is established that to reduce the technological resistance in the presented methods; it is necessary to create a fluidized bed of products due to the oscillating motion of the working capacity. An experimental vibration unit has been developed to determine the rational parameters of the vibrocentric moisture removal process using the electroosmotic effect. It is proved that the complex of the designed equipment provides consecutive carrying out of three-stage vibration filtration-convective drying of high-moisture production by an alternation of action of a stream of the heat carrier, an electromagnetic field, low-frequency fluctuations. According to the research results, the dependences of the kinetics of the moisture diffusion process on the electric field strength are obtained; frequency of electric current and duty cycle of pulses, which allowed to optimize the process parameters according to the criteria of minimizing energy consumption. It was found that the processing time to achieve the desired humidity with the application of vibration, filtration, and electroosmotic effect was twice less than for filtration drying in a fixed bed. In combination with the noted physical and mechanical factors, the proposed technology improves the technical and economic parameters of the studied process.

THE EFFECT OF DRYING TEMPERATURE, CUTTING TYPES, STORAGE DEGREE AND PERIOD ON PHYSICAL, CHEMICAL AND PHYSICOCHEMICAL PROPERTIES OF RED CAPIA PEPPER

This work was undertaken to evaluate the effects of different drying temperatures ​​(50, 60 and 70 oC) and cutting types (ring and cube) on the physical, chemical and physiochemical properties of red capia pepper during storage (14 days) both at room temperature and cold storage. Convective drying (CVD) at 50, 60 and 70 oC was applied to obtain dried red capia peppers. The effects of CVD on color values (L*, a*, b*), rehydration ratio, selected chemical properties (dry matter, pH and titratable acidity) and bioactive compounds (total phenolic content and antioxidant capacity) of thirteen dried red capia peppers were compared. The samples dried at 60 oC in ring forms under cold storage (6R-CD samples) showed the highest dry matter, pH, titratable acidity and rehydration ratio (87.06%, 5.69, 807.15 mg citric acid/100 g, 6.72%, respectively). The closest L*, a*, b*values to the fresh pepper samples were achieved for 6R-CD samples (L*:29.87, a*:12.83, and b*:17.03). In addition, 6R-CD samples resulted with highest antioxidant capacity and total phenolic content in all storage times.

RESEARCH OF THE ULTRASONIC DRYING PROCESS OF VARIOUS MATERIALS

В статье рассматривается процесс конвективной сушки тканых материалов и продуктов растительного происхождения. Показано, что длительность процесса может быть уменьшена за счет дополнительного воздействия ультразвуковыми колебаниями высокой интенсивности. Для определения ускорения процесса сушки ультразвуковыми колебаниями были разработаны лабораторные установки, позволяющие организовать комбинированное воздействие потока теплого воздуха и ультразвуковых колебаний. Комбинированная сушка ткани проводилась при трех различных температурах сушильного агента. Было установлено, что сокращение времени процесса по сравнению с конвективной сушкой зависит от температуры сушильного агента и составляет от 10% при температуре 40 0C до 20% при температуре 60 0C. В свою очередь, сушка овощей проводилась на резонансных промежутках от излучающего диска, при этом овощи нарезались толщиной 5 мм и располагались тонкими слоями. Комбинированная сушка моркови и картофеля позволила достичь сокращения времени сушки на 45-47%. При этом затраты на электроэнергию для ультразвукового аппарата составляют не более 30% от затрат на конвективную сушку. В результате проведенной работы была показана эффективность применения комбинированной ультразвуковой и конвективной сушки прежде всего для обезвоживания овощей, тогда как для ткани эффект не столь очевиден. Лабораторные исследования проводились при малом объеме высушиваемого материала, из-за слабого проникновения ультразвуковых колебаний на большую глубину, поэтому дальнейшие исследования необходимо направить на разработку полупромышленных и промышленных сушильных аппаратов для ультразвуковой сушки овощей и других термолабильных материалов. The article deals with the process of convective drying of fabrics and vegetables. The duration of the process can be reduced by additional exposure to high-intensity ultrasonic vibrations. To carry out drying, laboratory installations were developed that allow organizing the combined effect of a stream of warm air and ultrasonic vibrations. The combined drying of the fabric was carried out at three different temperatures of the drying agent and it was noted that the greatest reduction in drying time compared to convective drying was achieved at a temperature of 60 ° C. Although the overall reduction in drying time ranged from 10% to 20% depending on the temperature of the air flow. Drying of vegetables was carried out at resonance intervals from the emitting disk, while vegetables were cut 5 mm thick and placed in thin layers. Combined drying of carrots and potatoes made it possible to achieve a reduction in drying time of 45-47%. In this case, the cost of electricity for the ultrasonic apparatus is a small part of the cost of convective drying. As a result of the work carried out, it is possible to draw conclusions about the effectiveness of the use of combined ultrasonic and convective drying for dehydration of vegetables, while the effect is not so obvious for tissue. Laboratory studies were carried out with a small volume of dried material, due to the weak penetration of ultrasonic vibrations to a great depth, therefore, further research should be directed to the development of semi-industrial and industrial dryers for ultrasonic drying of vegetables and other heat-sensitive materials.

Quality of Milled Rice from Large-Scale Dried Paddy Rice by Hot Air Combined with Radio Frequency Heating

A scaled-up process for paddy drying was developed using hot air (HA) combined with radio frequency (RF) heating. The study was conducted using hot air (control treatment) arranged in descending order in four temperature levels, namely 80 °C at moisture content of 25–26%, 70 °C at moisture content of 20–25%, 60 °C at moisture content of 17–20%, and 50 °C at moisture content of 13–17%, as well as with hot air combined with radio frequency (HA/RF) at different paddy temperatures (45–60 °C) by adjusting the appropriate RF energy when passing through RF heating chamber, namely HA/RF45, HA/RF50, HA/RF55, and HA/RF60. Each treatment was performed in three replicates and data were statistically analyzed in a randomized complete block design. The quality attributes of paddies affected by the drying process were assessed: fissure percentage, color, milling quality, and sensory evaluation. The drying efficiency showed that the drying time and the specific energy consumption could be decreased by up to 54.44% and 23.17% at HA/RF60 and HA/RF45, respectively. As the RF heating temperature increased, the fissure percentage of brown rice kernels at HA/RF45 and HA was not significantly impacted. Regarding color evaluation, combining RF heating and convective drying at all given conditions could be statistically applied in terms of the b*, WI, and ΔE* value. Considering the milling yield of HA as the baseline, head rice yield was maximized at HA/RF45, while bran yield reached the maximum at HA/RF60. The liking score of cooked rice after it was dried using the HA method was the highest. This study concludes that the HA/RF45 was the most appropriate drying condition, and this may provide preliminary exposure to the industrial drying of paddies.

Color, microstructure, physicochemical, textural and sensory properties with the retention of secondary metabolites in convective-, microwave- and freeze-dried carrot (Daucus carota) slices

Purpose This work was undertaken to evaluate the impact of different drying methods (convective, microwave and freeze drying) on color, selected secondary metabolites (total phenolic substances, ascorbic acid, beta-carotene and antioxidant capacity), texture (hardness), sensory properties and microstructure of carrot slices.Design/methodology/approachConvective drying at three different temperatures (55, 65 and 75 °C), microwave drying at two different power levels (100 and 200 W) and freeze drying were applied.FindingsSignificant differences were found among fresh and dried-carrot slices. Convective-dried carrots showed better quality characteristics in comparison with microwave-dried carrots. The convective-dried carrots at 65 °C exhibited the highest retention of bioactive compounds and best color among all convective drying conditions. The microwave-dried carrot slices at lower power (100 W) showed higher quality characteristics compared to the dried carrots at 200 W. The freeze-dried carrots exhibited the highest retention of secondary metabolites, sensory properties and best color among all drying methods.Originality/value The results from this study are significant for the processing of dried carrots by optimizing the conditions to obtain a high-quality product. Overall, freeze drying is a promising application as shown in the present study by its capability to better retention carrot quality underlying color, sensory, texture, microstructure and secondary metabolites.