Experimental Drier Research Articles

Experimental drier climates affect hydraulics and induce high mortality of seedlings of three northern conifer species

The future climate of northern temperate forests is projected to be drier and warmer by the end of this century. As a result, more drought-induced forest dieback events are anticipated in northeastern North America, and assessing the vulnerability of dominant tree species to drought is critical for understanding the future composition of these forests. In a greenhouse experiment, we exposed two-year-old seedlings of Picea glauca (Moench) Voss, Picea mariana (Mill.) B.S.P. and Pinus strobus L. to three future climate treatments for southern Quebec, Canada, and evaluated their mortality, growth, and foliage water status responses to soil water availability and atmospheric drought. Using a unique approach, climate treatments emulated droughts of different frequencies, durations, and intensities. Treatments closely simulated one growing season, with changes in air temperature and relative humidity every six hours and daily adjustment in the amount of water delivered to the seedlings. The three species experienced high mortality (75%) in all water-limited treatments compared to a control treatment that provided non-limiting soil moisture (0% mortality). The biomass of the seedlings that survived was 40% lower than that of control seedlings. Our results confirmed that the hydraulic safety margins, defined as the difference between seasonal minimum water potential and xylem water potential leading to 12, 50 and 88% of hydraulic conductivity loss, were good predictors of probability of tree mortality. Therefore, hydraulic safety margins are useful functional traits that can be used to compare the vulnerability of various species to drought and then provide crucial information to practitioners and policymakers to adjust forest management to climate change. We showed that three dominant conifer species of northern temperate forests were highly vulnerable to drought in future climates. Because drought is projected to be a significant threat to forests, understanding potentially adaptive physiological responses to drought, such as hydraulic safety margins of tree seedlings, is important for predicting the response of forest regeneration and composition in warmer and drier climates.

Effect of Drying Temperature in the Physiological Quality of Jatropha curcas Seeds

Stimulating the use of renewable energy instead of fossil fuels, especially biofuels, has become one of the alternatives to the issue of global warming. Of these species listed for the production of biodiesel is the Jatropha curcas crop. The aim of this study was to analyze the drying of the seeds of Jatropha, as well as to verify the effect of the different temperatures on the quality of the product, germination percentage and Emergence speed index (ESI). The experimental design was a completely randomized design, with four replications. Experimental drier was used to test the temperatures of 29, 35, 40, 45 and 50 °C and the data were compared by regression equation. The vigor and germination of the jatropha seeds were little affected as the drying temperatures were increased to 50 °C.

Adzuki beans (Vigna angularis) seed quality under several drying conditions

This study analyzed the drying process and the seed quality of adzuki beans (Vigna angularis). Grains of adzuki beans, with moisture content of 1.14 (decimal dry basis) at harvest and dried until the moisture content of 0.11 (decimal dry basis.) were used. Drying was done in an experimental drier maintened at controlled temperatures of 30, 40, 50, 60, and 70 ºC and relative humidity of 52.0, 28.0, 19.1, 13.1, and 6.8%, respectively. Physiological and technological seed quality was evaluated using the germination test, Index of Germination Velocity (IGV), electrical conductivity, and water absorption, respectively. Under the conditions tested in the present study, it can be concluded that drying time for adzuki beans decreases with the higher air temperatures of 60 and 70 ºC, and it affected the physiological and technological seed quality. Thus, to avoid compromising adzuki seeds quality, it is recommended to promote its drying up to 50 ºC.

Modelagem matemática e difusividade efetiva das sementes de pinhão-manso (Jatropha curcas L.) durante a secagem

O presente trabalho teve o objetivo de ajustar diferentes modelos matemáticos aos dados experimentais da secagem de sementes de pinhão-manso (Jatropha curcas L.), bem como determinar o coeficiente de difusão efetivo e obter a energia de ativação para a faixa de temperatura utilizada. As sementes de pinhão-manso com teor de água de 0,67 (decimal b.s.) passaram por um período de pré-secagem em ambiente natural para reduzir e homogeneizar o teor de água para 0,30 (decimal b.s.). Em seguida, a secagem foi realizada em secador experimental mantendo-se as temperaturas controladas de 30; 40; 50; 60 e 70 ± 1 ºC e umidades relativas de 55,98; 41,44; 35,35; 26,21 e 13,37 ± 3%, respectivamente. Aos dados experimentais foram ajustados onze modelos matemáticos utilizados para a representação do processo de secagem de produtos agrícolas. Conclui-se que, dentre os modelos analisados, Page e Henderson e Pabis Modificado apresentaram os melhores ajustes aos dados experimentais, sendo o modelo de Page selecionado para a descrição das curvas de secagem do pinhão-manso devido a sua simplicidade; o coeficiente de difusão efetiva aumenta com a elevação da temperatura, apresentando magnitudes entre 3,93x10-10 e 9,19x10-10 m² s-1 para o intervalo de temperatura de 30 a 70 ºC, respectivamente; e a energia de ativação para a difusão líquida do pinhão-manso durante a secagem foi de 15,781 kJ mol-1.

Description of the Convective Air-Drying of a Food Model by Means of the Fractal Theory

A slab-shaped model food prepared using glucose solutions and agar as jellifying agent was subjected to drying in an experimental drier. Drying kinetics and surface temperature (ST) distribution along drying were evaluated. When fractal analysis was applied to ST distributions it was possible to observe three stages: the first one, at the beginning of the process, was very short and could not be associated with a fractal dimension. The second one, by far the longest, had a constant value of the fractal dimension of the ST distribution and towards the end of the process, as temperature of the surface of the material tended to homogenise, a final linear stage was found which corresponded to equilibrium conditions. Images of the slab along drying were recorded and showed an increasing heterogeneous appearance as drying proceeds. Grey level intensity plots corresponding to these images also showed an increasing irregularity (higher values of fractal dimension) with drying time. Fractal analysis probed to be a useful tool for describing drying kinetics and for characterising images of samples subjected to dehydration.

Design and development of a conduction drier for accelerated drying of peanuts

A rotary conduction drier using sand as the heating medium was designed and developed for accelerated drying of high moisture peanuts. The performance characteristics of the drier were evaluated in terms of peanut quality and drying time. Drying characteristics of peanuts at different drying conditions were also studied. The effect of varying the operating conditions was investigated to determine the optimum operating conditions of the system and these were compared to conventional (sun) and convection (oven) drying methods. Results revealed that quality indexes of peanuts, i.e. % breakage, % shiriveled and flavor were greatly dependent on the operating conditions of the drier. The optimum quality indexes were obtained at a drying temperature of 70°C, a feed rate of 7 kg/min and a rotational speed of 8 rpm. Drying characteristics of peanuts in the drier followed an exponential model. The drying time required to reduce moisture content to 10% wet basis for safe storage was significantly shorter in the developed unit than in conventional and convection drying methods. On the other hand, the quality indexes of peanuts dried in the experimental drier were comparable with conventional and convection drying methods at lower temperatures, although lower quality indexes were observed at higher temperatures. The results indicated that kernel temperature during conduction drying should not exceed 40°C in order to produce good quality dried peanuts.

The measurement of drying rates in thin-layers of ryegrass seed

To enable weight loss to be determined during the drying of “thin-layers” of seed, modifications were made to an 8 unit experimental drier. These, and the associated computer programmes for analysing the data, are described and some initial results are presented for Aberystwyth S.23 ryegrass seed ( Lolium perenne ). Samples of directly-harvested seed at initial moisture contents from 117 to 40% d.b. were dried at aii temperatures of from 27·7 to 61·7°C. From an examination of 3 alternative exponential equations for describing the drying curves it was concluded that the values of a drying constant, k , obtained by fitting a double exponential equation to the data, could be used to predict drying curves by means of an exponential series equation. The germination of seed of more than 84% m.c.d.b. was seriously reduced by quite small increases in drying air temperature. For moisture contents below this, the effect of drying air temperature on germination was expressed by means of a polynomial.

THE DRYING OF TIMOTHY SEED

On 6 dates during a period of 14 days, S48 timothy seed was combine harvested directly and then dried in layers 6 in. deep at air temperatures of 77, 95, 104 and 122° F and airflows of 20 and 35 ft/min. The effect of these drying conditions upon subsequent laboratory germination was measured. An experimental drier of 8 units developed for this work is described. Results showed that the depression of germination by increasing temperatures depended on the stage of ripeness when the initial moisture content was greater than 30% wet basis.* Below this moisture level, no significant depression was found at temperatures up to 1223F. Seed of acceptable commercial standard was obtained when harvested at 41·3% m. c.w. b., but only under the gentlest drying treatment, 77°GF and 20 ft/min.