Dry fractionation and gluten-free sourdough bread baking from quinoa and sorghum

The roller milling of sorghum and quinoa seeds into flour fractions (coarse, middle, and fine) was investigated, chemically analysed, and applied in the baking of gluten-free sourdough bread. The gap settings were adjusted to 0, 5, 8, and 10 for quinoa, and 3, 5, and 7 for sorghum. The fine fractions reached values of up to about 41% (gap 8) for quinoa and around 20% for sorghum (gap 5). SEM pictographs illustrated the clear separation of each fraction with the chemical analysis showing high contents of protein, TDF (total dietary fibre), and IDF (insoluble dietary fibre) in the coarse fraction. Up to 77% starch content was obtained in the fine fraction with significant amounts of SDF (soluble dietary fibre), which has good health benefits. Increasing the dough moisture up to 90% helped in decreasing the bread crumb firmness, while low Avrami parameters and RVA pasting behaviour indicated a slow bread-staling rate for both sourdough breads

Effects of superheated steam on the drying of rubberwood

Rubberwood drying is the most time and energy consuming step in the processing of wood product. This research studied the effect of superheated steam drying on the drying time required and the physical and mechanical properties of rubberwood after drying. In this study, a cylindrical drying chamber with a length of 1.2 m and a diameter of 0.5 m was constructed and injected with superheated steam. The dimensions of the wood lumber were 1 m × 7.62 cm × 2.54 cm. The wood samples were impinged with alternating cycles of superheated steam and hot air at ratios of 6:1, 4:1 and 1:6 hours until the moisture content was less than 15% dry basis. The conditions inside the chamber were 110ºC and ambient pressure. Continuous superheated steam and continuous hot air were also used for comparisons. The drying rate and the temperature profile for each process were determined.Initial acceptability of the dried wood was conducted using the prong test and visual inspection. Results showed that if the drying rate was too fast, the dried wood did not pass the prong test due to stress buildup. Therefore, an optimum drying condition was developed based on minimizing defects and reducing the drying time. For the optimum condition, the following schedule was carried out: (1) saturated steam at 100ºC was used during the first 4 hours of drying to prevent the wood surface from drying too quickly which would minimize the moisture gradient between the center and wood surface, (2) superheated steam at 105ºC and 110ºC was used in alternating cycle with hot air (80ºC) during the main drying stages to rapidly remove the free water and majority of the bound water inside the wood, and (3) hot air was used continuously during the final stages of drying to reduce the relative humidity inside the chamber making it possible for the removal of the residual bound water. This process successfully reduced the drying time to less than 2 days without causing any defects which compared favorably to the conventional hot air drying process of 7-8 days. Moreover, results of the mechanical properties for the optimum condition showed that the shear-parallel-to-grain was 13.46 MPa and the compression strength parallel-to-grain was 37.73 MPa, both of which were higher than the literature values. Thus, using superheated steam in conjunction with hot air presents a substantial saving in operating time and energy consumption compared to the conventional method while retaining the desired mechanical properties of the wood

Simulation of the heat and mass transfer processes during the vacuum frying of potato chips

A fundamental two-dimensional model to predict the heat and mass transfer that occur during the vacuum frying of potato chips was solved using the Finite Element toolbox in MATLAB 6.1. The simulation of the heat transfer process included the convection of heat from the surface to the product, the conduction of heat into the product, and a loss of heat using the heat source term representing evaporation. The mass transfer process was divided into two periods: (1) water loss and (2) oil absorption. The first scenario included a diffusion term and a source term. The source term represented the convection and evaporation of water from the product. For the second period, the diffusion term represented the gradual absorption of oil through capillary diffusion.From the simulation, a good agreement between the experimental data and the predicted values was obtained. From the heat transfer model, the rapid increase in temperature of the product toward the boiling point of water (at the associated pressure) followed by its steady increase toward the temperature of the oil was validated. Furthermore, by separating the rate of moisture loss into two parts to represent the constant rate and falling rate period of drying, the model was able to predict an initial period of rapid moisture loss followed by a decreasing rate of moisture loss. The simulation also demonstrated the formation of the crust and the gradual movement of the crust inward. Finally, using two sets of diffusion coefficients that correlated to the two schemes of moisture loss, the model predicted the rapid flux of oil into the product during the constant drying stage, followed by a small amount of oil absorption into its interior once the crust had been established

Silica gel derived from palm oil mill fly ash

Agro-wastes, especially ash containing silica, are promising sources of silica for synthetic amorphous silica production. In this research, palm oil mill fly ash (POMFA) was used as a raw material for silica gel production. The response surface method-central composite design was applied to study and to optimize the temperature and stirring speed for silica extraction from POMFA using sodium hydroxide solvent. Filtrates were analyzed using inductively plasma optical emission spectroscopy to measure their silica content. At the optimum condition, 60.42±0.83% of the silica can be extracted from the POMFA. The extract silica was acidified using 10% (v/v) H2SO4 to form silica gel. The chemical composition, the phases, and the micrograph of silica gel product are similar to the commercial silica gel

Drying characteristics of unshelled kernels of candle nuts

Candle nuts are cultivated in approximately 170000 ha. in Indonesia, and yield around 140000 tons of fruit per year. Prior to removing the shells, drying is an important process in the post-harvesting practice of candle nuts to obtain kernels as the final products. This paper gives a brief description of the efforts to obtain the basic drying characteristics of candle nuts, which is a pre-requisite for dryer design. The measurements were taken for unshelled kernels of candle nuts, for both fresh and stored samples, at temperatures of 40, 50, and 60 °C and drying air velocity of 0.67 m/s and 1 m/s using a forced convection dryer. The total drying time was substantially reduced with an increase in temperature, and the effect of drying air velocity was relatively small. Page's model adequately describes the drying behavior for the range of temperatures measured. The dependence of the drying constant on air temperature can be described by the Arrhenius model