DIFFUSION OF MOISTURE IN DRYING OF SUGAR CANE FIBERS AND BUNDLES

Sugar cane fibers and arrangements of fibers in cylindrical bundles were dried in a thermoanalyzer and their diffusive coefficients were calculated using the slope method. The effect of temperature, moisture content as well as structural changes were analyzed. Diffusion coefficients changed nanlineariy with moisture content and followed an Arrhenius-like functionality with temperature. The analysis of these effects suggested a liquid diffusion transport mechanism of moisture transfer inside sugar cane fibers and bundles.     

Texture analysis of dried papaya (Carica papaya L., cv. Maradol) pretreated with calcium and osmotic dehydration

The application of pretreatments before to convective drying improves the textural characteristics of minimally processed fruits. The aim of this work was to evaluate the texture of papaya (Carica papaya L., cv. Maradol) dried by convection pretreated with calcium hydroxide solutions and osmotic dehydration. Texture profile analysis was performed on fresh and dried cubes by convection at 70?°C not pretreated, as well as on those pretreated with calcium and osmotic solutions. During calcium immersion, the firmness increased, the TSS decreased, and the calcium gain was higher to low temperature. Water loss and solids gain were higher using high concentrations and temperatures during osmosis, resulting in lower values of moisture content and higher values ??of TSS. Calcium and osmotic pretreatments resulted in a product with intermediate moisture, stable color, firm, and minimal shrinkage. The modification of the papaya structure during all treatments caused a change in the textural characteristics. Statistical analysis of textural characteristics of dry cubes pretreated showed a significant difference (α?=?0.05) compared to fresh ones and not pretreated. The pretreatments formed a firm (outer) and a soft (inside) structure that reduced the shrinkage and the deformation of dry cubes and decrease the drying time up to 37% compared to dry cubes no pretreated.     

Effects of Drying Air Temperature on the Structural Properties of Garlic Evaluated During Drying

Second order phase transitions may occur in foodstuffs during the convective drying process. These transitions involve physicochemical changes, which influence both structural properties and drying behavior. The aim of this study was to examine the effects of drying air temperature and the second order phase transition of garlic on the changes in particle density, apparent density, apparent porosity, effective diffusivity, and cracking produced during drying. Garlic slices were dehydrated at three air temperatures (40, 50, and 60°C). The moisture content (X), inside temperature (T_i), surface temperature (T_s), apparent (ρ_b) and particle (ρ_p) densities of garlic slices were measured during drying. Porosity (?) was calculated based on the data collected for ρ_p and ρ_b. Glass transition temperatures (T_g) and micrographs were obtained for both raw and dehydrated garlic. A critical point in the intersection of T_i, T_s, and T_g was found; this point was identified as a second order phase transition. Diffusivity and slope changes in ρ_b, ρ_p, and ? with respect to moisture content were found to be related to this critical point. Experimental data for ρ_b, ρ_p, and ? was fitted to a nonlinear equation with three exponential terms with respect to moisture content, with an R² > 0.85. Less dense products were found to be more porous, with more cracking, higher moisture diffusivity, and lower T_g at the end of the drying process.     

DIFFUSION OF MOISTURE IN DRYING OF SUGAR CANE FIBERS AND BUNDLES

ABSTRACT

Sugar cane fibers and arrangements of fibers in cylindrical bundles were dried in a thermoanalyzer and their diffusive coefficients were calculated using the slope method. The effect of temperature, moisture content as well as structural changes were analyzed. Diffusion coefficients changed nanlineariy with moisture content and followed an Arrhenius-like functionality with temperature. The analysis of these effects suggested a liquid diffusion transport mechanism of moisture transfer inside sugar cane fibers and bundles.