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The effect of four soaking regimes: 5 °C/20 °C with/without changing of soaking water followed by oven-drying at 40 °C–70 °C on various characteristics of buckwheat-based products was evaluated. Soaking buckwheat groats, hazelnuts and prunes at 5 °C was more favourable to total phenolic content, quercetin level and significantly decreased Escherichia coli counts in comparison with those obtained at 20 °C. The highest contents of phenolic, flavonoid and antioxidant capacity were observed upon drying at 40 °C followed by its decrease with the increase in drying temperature. While quercetin content seemed to be unaffected by drying temperature, rutin content increased. A small but gradual increase of Maillard products was observed at 40 °C–60 °C followed by a steep rise at 70 °C. Total coliforms and E. coli counts increased to >6.0 log cfu/g in products dried at 40 °C but decreased below 1.0 log cfu/g when dried at 50 °C–70 °C. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the airflow distribution in a mixed-flow dryer (MFD) and to study the effect of different bed materials and air duct arrangements. The results were used to validate the numerical model developed in a previous work based on Computational Fluid Dynamics (CFD). A series of experiments have been conducted at a semi-technical MFD test dryer with horizontal and diagonal air duct arrangement. Wheat and rapeseed were used as bed materials. The experiments were performed under isothermal conditions. Two experimental methods were selected and adapted to the measuring problem—the measurement of the isobar distribution within the grain bed and the residence time analysis using the tracer gas pulse method. As could be shown, the isobar distributions measured for wheat and rapeseed agreed well with the model predictions. The numerical model could calculate the influence of the bed material with its different particle characteristics (e.g., particle shape, particle size, bed porosity). The results obtained from the residence time analysis confirmed the known quartering of the air stream flowing from one inlet air duct to the four surrounding outlet air ducts for the horizontal air duct arrangement; in the diagonal air duct arrangement, the air stream from one inlet air duct was nearly halved flowing to the two adjacent diagonal outlet air ducts. These results were confirmed by investigations of the air velocity distribution within the grain bulk. Further experiments are necessary to refine the model. The residence time and isobar measurements will be extended to study the influence of different air properties under real drying conditions, the effect of structural elements, and dryer designs. [ABSTRACT FROM PUBLISHER]

A new coupled mathematical modeling to predict heat and moisture (liquid and vapor) transfer in capillary-porous bodies with particular reference to wheat kernel is presented. The mathematical model is based on the non-equilibrium thermodynamics by considering the wheat as prolate spheroid, variable transport coefficients and equilibrium boundary conditions at the surface of the solid. All the partial differential equations presented in the model have been written in prolate spheroidal coordinates. The finite-volume method has been used to obtain the numerical solution of the governing equations. Results of the average moisture content, average temperature, heat flux, liquid flux, vapor flux, and moisture content and temperature distributions inside a wheat kernel during drying process (T=87.8 oC, RH=5.6% and v=1.71 m/s) are presented and analyzed. [ABSTRACT FROM AUTHOR]

A mathematical model of temperature and wheat moisture content distribution inside a triangular spouted bed dryer was developed. The model is based on analysis of heat and mass transfer inside the dryer. In addition to that, an empirical bulk density model has been developed for wheat and included in the drying simulation. A laboratory-scale triangular spouted bed (TSB) dryer was used to dry wheat grain to validate the model. The dryer was divided into three sections, namely spouting, downcomer, and fountain. A series of drying runs were conducted to record moisture and temperature profile. There were two distinct regions observed during wheat drying. A constant rate period was observed during the initial drying stage and the falling rate period took place at the later drying stage. Initial moisture content and operating drying temperature governed the timing of transition from constant rate period to falling rate period. The model can be used to accurately predict the moisture content of wheat during drying. The temperature prediction inside the TSB dryer was less accurate, especially at high temperatures due to heat losses in the experimental dryer. Further studies are needed to improve the accuracy of this model, especially with regard to the temperature prediction. [ABSTRACT FROM AUTHOR]