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This work investigated the effects of pulsed electric field (PEF) pretreatment, combined with different drying methods, on the quality of dried yams. The results showed that the pretreatment resulted in the formation of large pores in the yam tissues, thereby affecting the rehydration capability and hardness of the dried yam slices. The type of drying method after treatment did not alter the free radical stretching bands of yam. Additionally, the pretreated samples had a higher peak viscosity, through viscosity, final viscosity and break down, alongside lower pasting temperatures, To, Tp, Tc, and △H. Rheological measurements further indicated that all doughs exhibited solid-like behavior to different extents. The pretreatment also decreased the amount of allantoin and polysaccharides in dried yam slices, while negatively influencing their antioxidant activity. Finally, the choice of drying methods significantly affected the quality of the dried yams. In highlighting the effects of PEF pretreatment, combined with different drying methods, on dried yam, the results can help to expand their application within the food industry. [ABSTRACT FROM AUTHOR]

Relatively large drying collapse has restricted the utilization of low-density oil palm wood (OPW), an agricultural waste in the palm oil industry, for several decades. This work reports a simple pretreatment that allows OPW from all sections of the trunk having a thickness of up to 0.2 m to be severely kiln-dried up to the temperature of 200 °C without any drying defects and with relatively low drying shrinkage. Lightweight characteristics and mechanical, thermal and acoustic properties of the dried OPW are maintained. The pretreatment process involves water impregnation of fresh OPW followed by freezing the OPW below the eutectic temperature of sap (water–sugar) of about −10 °C before kiln drying. This strategy creates localized microcracks at the pit cavities that connect between the parenchyma cells. These microcracks allow the short-range flow of intercellular liquid at atmospheric pressure to compensate for the negative capillary pressure of the intracellular liquid inside the parenchyma cell cavity during drying. A fraction of the intercellular liquid plays a crucial role in the formation of microcracks during freezing and the reduction of cell collapse during drying. The technique is also found to be applicable to the drying of the porous trunk of other palm species. [ABSTRACT FROM AUTHOR]

Seera produced by different drying techniques was evaluated regarding its various physicochemical properties. The rheological properties of the batter showed a shear thinning behavior and Herschel-Bulkley model was best fitted with R² = 0.9987. The results revealed that water absorption capacity increased as compared to the wheat flour and maximum absorption was found in freezedried seera (1.91 g g-1), followed by oven-dried (1.62 g g-1) and sun-dried (1.13 g g-1). Oil absorption capacity of seera decreased as compared to wheat flour, with minimum values obtained for freeze-dried (0.93 g g-1 of seera). Carbohydrate content increased significantly in seera sample to 81.76%, while fat, protein, and moisture content decreased significantly. L* values increased significantly, while as both a* and b* values decreased. Bulk density also showed an increasing trend with maximum value in freeze-dried seera. Transition temperatures changed significantly for the seera samples along with enthalpy of gelatinization. Fourier transform infrared pattern did not change with drying. [ABSTRACT FROM AUTHOR]

This study investigated the foam mat drying process parameters (temperature and concentration of foaming agents, albumin, and an emulsifier blend) and evaluated their effects on drying kinetics, color, carotenoid retention, and solubility of the mango pulp powder. Fick’s model was able to represent the foam mat drying kinetics. The foaming agents and high temperatures enhanced the carotenoid retention. This was explained by the greater effective water diffusion coefficients that allowed obtaining products with low moisture contents and water activities in short processing times of up to 3 h, with high carotenoid retention and color maintenance. [ABSTRACT FROM PUBLISHER]

The objective of this study was to dry–wet distillers grains and centrifuged solubles and to examine the effect of two different drying media, superheated steam and hot air, at different drying temperatures (110, 130, and 160°C), moisture contents (5–30% wb), and percentages of solubles’ presence (0 or 100%) on some thermophysical properties of laboratory-prepared corn/wheat dried distillers co-products, including geometric mean diameter (dg), particle density (ρp), bulk density (ρb), bulk porosity (ϵb), specific heat (C), effective thermal diffusivity (αeff), and bulk thermal conductivity (λb). The values ofdgof corn/wheat dried distillers co-products ranged from 0.358 ± 0.001 to 0.449 ± 0.001 mm. Experimental values ofρp, ρb,andϵbvaried from 1171 ± 6 to 1269 ± 3 kg m−3, from 359 ± 7 to 605 ± 5 kg m−3, and from 0.54 ± 0.01 to 0.71 ± 0.01 kg m−3, respectively. The values ofαeffwere between 0.58 × 10−7and 0.93 × 10−7 m2s−1. The calculated values ofCranged from 1887 ± 11 to 2599 ± 19 J kg−1K−1, and the values of λbof corn/wheat dried distillers co-products ranged from 0.06 ± 0.01 to 0.09 ± 0.01 W m−1K−1. Multiple linear regression prediction models were developed to predict the changes indg, ρp, ρb, ϵb,C, αeff, and λbof laboratory-prepared corn/wheat dried distillers co-products with different operational factors. [ABSTRACT FROM AUTHOR]

The structural and thermophysical properties of freeze-dried agricultural products (potatoes, mushrooms, and strawberries) were investigated to determine whether these properties were affected by freeze drying conditions. The true density of freeze-dried products was measured with a helium stereopycnometer, and apparent density was obtained by measuring their geometric characteristics. Porosity and pore size distribution were also measured with a mercury porosimeter. The mechanical properties of freeze-dried agricultural products were obtained using a universal testing machine. Dried products were equilibrated in saturated salt solutions of constant water activity and scanned with a differential scanning calorimeter (DSC) for the evaluation of glass transition temperature. Simple mathematical models were developed in order to correlate the structural and mechanical properties with process conditions. The apparent density and mechanical properties of freeze-dried products increased with the applied freeze-drying pressure, whereas the porosity decreased. The glass transition temperature decreased with the increment of moisture content and it was not highly influenced by process conditions. [ABSTRACT FROM AUTHOR]

The thermal conductivity and specific heat of paper are important in determining its response to heat pulses encountered in applications such as copying or digital printing. This work reports measurements of the thermal conductivity, contact resistance, and specific heat for a number of commercial copy paper sheets. The experimental setup was designed to measure transient and steady-state temperature distribution in stacks of paper sheets from which the thermal properties were determined. Steady-state measurements of the temperature difference were used to determine the thermal contact resistance and the thermal conductivity of the sheets. The specific heat was determined from the transient temperatures recorded during heat-up and cool-down periods. The thermal conductivity depends upon the sheet density, filler content, and nature of the fibers. It also showed a small increase with temperature of approximately 10−4 W/(mK)/K. Models of thermal conductivity based on the resistance of the fibers and the fillers were developed. The thermal contact resistance increased with the surface roughness as measured by the Gurley permeability (referring to surface roughness). The specific heat of paper was dependent on its ash content. [ABSTRACT FROM AUTHOR]

This research aims at modeling the rotary drying of carton packaging waste and analyzing the energy performance of the process. Drying data were obtained in a semi-pilot rotary dryer, 0.45 m diameter and 2.7 m rotating drum long, operating with an air velocity of 1 m/s and air inlet temperature of 90°C and 10 rpm. Under the operating conditions employed, the analysis of the data showed that the energy performance of the drying process increased from 5 to 75% as the inlet wet solid feed rate increased from 1.8 to 19 kg/h. In addition, at this latter wet-solid feed rate, the reduction of the air velocity in the dryer to 0.8 m/s also led to an increase in the performance of drying process from 80 to 94%. Furthermore, with a 95% confidence interval, the model used was adequate to predict the air and solid temperature as well as the air humidity and the solids moisture content. [ABSTRACT FROM AUTHOR]

An advanced theoretical model of unsteady coupled heat and mass transfer and breakage of wet particles in two-stage drying processes is presented. The numerical simulations of drying of silica slurry droplets have shown that both temperature and mechanical stresses emerge in the wet particle during drying. It has been found that mechanical stresses play a substantial role at the beginning of the second drying stage, whereas the thermal stresses are much more considerable at the end of drying. In addition, tangential stresses in the crust of wet silica particles are predominant over the radial component (approximately five times greater). Compared to the proposed breakage criterion, the model predicts that the total stresses can be a reason for wet particle cracking/breakage and this depends on granule diameter, drying agent temperature, and size of primary particles. To prevent granule breakage at given drying conditions, the slurry droplets with primary particles as small as possible are recommended for drying. [ABSTRACT FROM AUTHOR]

A crispy amorphous food was equilibrated to different moisture contents. These samples were tested for the glass transition temperature (Tg) using mechanical methods. The brittle-ductile transition temperature (Tb) was determined using force-deformation methods. Finally, the temperature where the onset to the sharp decrease in crispness intensity occurred (Tci) was determined by a 10-member sensory panel rating the crispness intensity. The relationships of the Tg, the Tb, and the Tci were determined using three different statistical methods. The results of this research indicated that the Tg, the Tb, and the Tci were related to one another as a function of moisture content. [ABSTRACT FROM AUTHOR]

As a dry amorphous food system absorbs moisture or increases in temperature, the brittle food becomes soft and deformable. The temperature at which this transition occurs in the food system for a given moisture content is called the brittle-ductile transition temperature (Tb). Three different methods of determining this transition were used. The method that was chosen to best describe the food system was the intersection of brittle strength and yield strength measured in flexure as a function of both temperature and moisture content. Tb decreased linearly with increasing moisture content with a strong linear relationship (r² = 0.98). [ABSTRACT FROM AUTHOR]

The center temperature of wetted pharmaceutical powder samples dried under combined microwave-convective conditions in an experimental system (2.45 GHz, 90 W) was monitored. Introduction of convective air to the microwave system facilitated a reduction in the material temperature, with the extent of the decrease being dependent on the air temperature and velocity. In general, the variation in center temperature of a sample dried under microwave-convective conditions consisted of three distinct stages: a short“warming-up” period; a constant temperature stage, and a decreasing temperature phase. Towards the end of the constant-rate period, a local“peak” superimposed on the temperature curve was observed. The temperature history was found to be material dependant, with the dielectric, physical and thermal properties of the solvent and powder being contributory factors. The variation was also dependent on bed geometry (surface area and depth), with an increase in surface area and decrease in depth providing reduced product temperatures. The surface temperature remained lower than the center temperature throughout processing, with the gradient increasing on reducing the moisture content. [ABSTRACT FROM AUTHOR]