Low Initial Water Content Research Articles

Ability of a “very low-cost extruder” to produce instant infant flours at a small scale in Vietnam

Extrusion cooking is a useful process for the production of instant infant flours, as it allows gelatinisation and partial dextrinisation of starch, as well as reduction of the activity of some antinutritional factors. But existing extrusion equipment is not suited to the context of developing countries as it requires considerable financial investment and the production capacity (minimum 300 kg/h) is too high. The aim of our study was to improve traditional extruders with low production capacity (about 30 kg/h) manufactured in Vietnam and to test their performance in the production of infant flours. Several blends made with rice, sesame and/or soybean have been extruded with the modified equipment that we name “very low-cost extruder”. In the case of blends containing soybean, starch gelatinisation was not complete, and decreased with an increase in the lipid content of the blend. The rate of trypsin inhibitor destruction evolved in a similar way. Adding water before extrusion, or extruding the blends twice was not effective in increasing the rates of starch gelatinisation or trypsin inhibitor destruction. However, the “very low-cost extruder” proved its ability to process the rice–sesame blend that had a lipid content of less than 6 g/100 g DM, and low initial water content [around 10%, wet basis (wb)]. In this case, extrusion led to total starch gelatinisation and the extent of starch dextrinisation, which was measured by comparing the viscosity of gruels prepared from crude and corresponding extruded blends, was sufficient to prepare gruels with substantially increased energy density. With the addition of roasted soybean flour, sugar, milk powder, vitamins and minerals, this blend could provide a nutritious instant flour usable as complementary food for infants and young children.

Water Content Profiles with a 1D Centric SPRITE Acquisition

The purpose of this work is to develop a rapid MRI method amenable to profiling with minimal or no T1 relaxation weighting. The behavior of a signal during a centric SPRITE acquisition is analyzed. It is shown that the technique can be made immune to a broad range of T1 changes. In a properly executed measurement, only T2* and proton density parameters define the image intensity. A T2* mapping technique can be easily applied, separating T2* and proton density contributions to the image. A drying soil sample with low initial water content is experimentally studied as a demonstration of the technique. A characteristic baseline artifact is easily removed from the profiles by a simple operation.

On-farm assessment of regional and seasonal variation in sunflower yield in Argentina

Using an on-farm approach, we investigated constraints to actual yield of sunflower in six agroecological zones within the Argentine Pampas during three growing seasons. In 249 large, grower-managed paddocks, we quantified a series of variables related to: (1) crop phenology, growth, and yield; (2) the physical and biological environment; and (3) management practices. Variation in yield among zones and seasons was analysed on the basis of four biologically-founded assumptions: (1) grain number accounts for a large proportion of the variation in yield; (2) grain number is associated with a photothermal coefficient, Q= R ( T- T b) −1, where R and T are average solar radiation and air temperature respectively, during the 50-day period bracketing anthesis; and T b is a base temperature; (3) crop growth and yield are proportional to light interception, and therefore proportional to canopy ground cover; and (4) yield is proportional to the fraction of seasonal rainfall that occurs after anthesis. Average yield ranged from 1.1 to 2.7 t ha −1, grain number from 2400 to 5400 m −2, individual grain mass between 40 and 69 mg and grain oil concentration between 42 and 52%. Grain number accounted for 43% of the variation in average yield while Q accounted for 23% of the variation in grain number. Low yield was associated with deficient ground cover in 25% of the crops; part of the remaining variation in yield was accounted for by sets of measured variables particular to each zone, including soil shallowness, low available P, low initial water content, weeds and diseases — chiefly Verticillium wilt ( Verticillium dahliae) and Sclerotinia head rot ( Sclerotinia sclerotiorum). Across zones and seasons, the proportion of seasonal rainfall occurring after anthesis accounted for 28% of the variation in crop yield. A trade-off is highlighted whereby beneficial effects of rainfall that favours growth and yield may be offset by the detrimental effect of abundant moisture that favours major fungal diseases. We emphasised the value of combining experimental studies — which provide biological background in the form of working hypotheses — with on-farm research that realistically quantifies yield response to key factors.

Investigation of three methods for evaluating swelling pressure of soils

Abstract Determination of the swelling pressure of six types of clayey soils obtained from northern Jordan were measured using three methods, the Free Swell method, Different Pressure method, and the Zero Swell method. These methods show different values in swelling pressure of the soil. For all six soils, the Free Swell method provided the highest value, whereas the Different Pressure method provided the lowest. Discrepancy in the value of swelling pressure among the methods increases with lower initial water content, higher plasticity index, and clay content. This paper compares the three different methods for evaluating soil swelling pressure and presents mathematical models to predict the soil swelling pressure for each method.

Effects of Block Lengths and Initial Water Content on the Swelling and Degradative Characteristics of an Injectable Poly(propylene Fumarate-Co-Ethylene Glycol) Block Copolymer Hydrogel

AbstractThe overall goal of this project is to develop an in-situ polymerizable, biodegradable material for use in cardiovascular applications that minimizes non-specific cell adhesion and contains functional moieties for the attachment of peptides to induce specific cell attachment. A novel block copolymer has been developed incorporating poly(propylene fumarate) (PPF) and poly(ethylene glycol) which satisfies these criteria. PPF is a new biodegradable polymer currently being investigated for orthopedic and cardiovascular applications while PEG is a hydrophilic polymer that has been extensively studied for biomedical applications. The copolymer is chemically crosslinked with PEG diacrylate using an ammonium persulfate-ascorbic acid redox initiator system to form the hydrogel. The PEG and PPF block lengths can be varied to modulate the properties of the hydrogel formed. In this study, the following three parameters were studied, (1) PPF block length, (2) PEG block length, and (3) initial water content, were varied to examine their effects on swelling, degradation and elastic modulus. A factorial experimental design was implemented to assess which of these three parameters had the greatest impact on swelling, degradation and elastic modulus. Swelling was found to be most affected by the initial water content followed by PEG block length and PPF block length. The swelling of the hydrogels ranged from 48% water uptake with low initial water content to up to 77% water uptake with the high initial water content. After three weeks, degradation of the hydrogels ranged from 4-13% mass fraction lost. Elastic modulus was determined by tensile testing of the various hydrogel formulations and ranged from 0.4 to 7.7 MPa.

Conversion of Conservation Reserve Program (CRP) Grassland for Dryland Crops in a Semiarid Region

Information was needed regarding practices suitable for returning grassland to cropland when Conservation Reserve Program (CRP) contracts expired. A study on Pullman soil (Torrertic Paleustoll) involved seven tillage treatments (no‐tillage and reduced, sweep, disk, moldboard plus disk, burn–sweep, and burn–disk tillage) with vegetation retained and the five non‐burn tillage treatments with vegetation removed before treatment. Fertilizer (NH4NO3) was applied at 0, 34, and 67 kg N ha−1 in 1995 and at 0, 67, and 134 kg N ha−1 in 1996 and 1997. Initial soil water contents were low, and soil never was filled with water at planting time. Sorghum [Sorghum bicolor (L.) Moench] yielded ≤720 kg ha−1 in 1995, and the 1995–1996 wheat (Triticum aestivum L.) crop failed. Sorghum was not planted in 1996 because of a drought. Sorghum yielded 2260 to 4700 kg ha−1 in 1997. Wheat yielded 1410 to 1980 kg ha−1 in 1996–1997. Vegetation retention or removal affected yields slightly. Fertilization affected sorghum yields slightly and increased wheat yields. Vegetation control was difficult with no‐tillage. Disk tillage to dislodge grass, followed by reduced‐ or no‐tillage, appears best for converting CRP grassland to cropland in this semiarid region. Because of low initial soil water contents, a 90‐d period is inadequate for obtaining adequate soil water storage unless precipitation is much above normal. Forgoing planting a crop soon after killing the vegetation when precipitation is low would provide more time for storing soil water and increase the potential for obtaining favorable yields.

Estimating Long‐Term Drainage at a Regional Scale Using a Deterministic Model

AbstractThis study discusses the use of a deterministic model, at a regional scale, when the soils have small heterogeneity. Long‐term soil drainage was simulated on 3500 ha in Beauce (France), taking into account variation in soil thickness, agricultural practices, and climate characteristics for a 32‐yr period. The model was based on a numerical solution of Richards' equation, using a finite element method. Hydraulic properties were determined at four sites that are 4 km apart. The results show a small variability of hydraulic parameters, with coefficient of variation (CV) ranges from 1 to 16% for the α parameter, the empirical constant n, the saturated water content θs, and the residual water content θr, and from 60 to 75% for the saturated hydraulic conductivity Ks. Hence, the spatial and temporal variability of drainage are mainly related to soil thickness, agricultural practices, and climate characteristics. Assigning small spatial variability to hydraulic properties, we analyzed the role of soil thickness and initial water content (IWC), induced by agricultural practices and climate characteristics, on drainage prediction. Five IWC were defined: 100, 90, 80, 70, and 55% of field capacity (FC). Four soil thicknesses were studied: 30, 60, 100, and 150 cm. The IWC appeared as a significant factor in drainage prediction for 60% of the 32 yr, regardless of soil thickness. Soil thickness became the most significant factor (20% of the 32 yr) for low IWC. The model was spatially extrapolated by combining the calculated drainage (which varied with soil thickness and IWC) and the spatial distribution of crops and soil thickness classes. Simulated drainage was closely related (r = 0.90) to groundwater recharge during the 32 yr, indicating that the model could be applied to other areas with appropriate parameters.

Corn, Sunflower, and Soybean Emergence Influenced by Soil Temperature and Soil Water Content

AbstractThe influence of soil temperature and initial soil water content on subsequent germination and emergence of corn (Zea mays L.), sunflower (Helianthus annuus L.), and soybean [Glycine max (L.) Merr.] needs to be understood. Previous research has not determined whether emergence of corn and sunflower is reduced by soil water content that is high enough for seed imbibition but too low for radicle emergence from the testa. Our objective was to evaluate corn, sunflower, and soybean emergence influenced by initial seed‐zone soil water content of 0.05, 0.07, and 0.09 kg kg−1 and soil drying at three day/night (17/8, 21/12, 25/16°C) soil temperature regimes as the number of days of soil water deficit and temperature stress increased. A factorial experiment with two replicates was conducted under controlled temperature conditions in an incubator. This experiment was conducted using a Glyndon silty clay loam (coarse‐silty, frigid Aeric Calciaquolls). Corn emergence was >85% at all three initial soil water contents and temperature regimes. Sunflower emergence increased from 59% at the low initial soil water content to 90% at the higher initial soil water content. Soybean emergence was 22% after stress was imposed by a 0.07 kg kg−1 initial soil water content (high enough for seed imbibition but too low for germination). If soil water content is sufficient to imbibe seeds of soybean and sunflower, but too low for germination during the 6 d after planting, producers may need to replant, especially when soil temperature is above 21/12°C.

Nonmonotonic matric pressure histories during constant flux infiltration into homogeneous profiles

Constant flux infiltration experiments were performed at rates less than saturated hydraulic conductivity (Ksat) on uniform columns of soils and glass beads with low initial water contents. Tensiometers measured matric pressure (ψ) histories at various depths in the 0.05‐m diameter, 0.73‐m‐tall columns. One of two devices applied the steady fluxes: one was a ceramic plate applicator that allowed monitoring of pressures above the plate, and the other was a rain applicator that sprinkled water uniformly over the surface. Two columns were used. One allowed destructive sampling for water content in a way that prevented postrun changes in water content. The other allowed prerun replacement of pore air with gases of different solubilities. Contrary to predictions based on the Richards equation, transmission zone ψ values passed through maxima, then decreased continuously as wetting fronts moved down columns. Such nonideal behavior was observed in Aiken silt loam, Hanfoird sandy loam, Delhi sand, Oakley sand, and glass beads. At an infiltration rate equal to 70% of Ksat, values of ψ at 2, 5, and 8 cm depths in the glass beads column decreased an average of 52% from their respective maxima in about 3 hours. In the soil columns the nonmonotonic behavior was less pronounced but statistically significant at all rates examined (3–59% of Ksat). Matric pressure reversals were larger, and corresponding maxima higher, when a given rate was preceded by a series of step wise increasing rates. Tests of possible explanations provided no evidence to support hypotheses involving trapped‐air dynamics, convective air flow, particle rearrangement, or experimental artifacts. The results cast doubt on the ability of the Richards equation to predict the course of constant flux infiltration including the initiation of runoff.

Measuring the Water Content of a Textile Fabric Using a Radio Frequency Sensor

Application of radio frequency sensors for the automatic control of a pilot-scale infrared drying range for textiles is described. This was most successful for the classical proportional-integral-differential (PID) negative feedback control system, but with some important restrictions—the drying of a single fabric with a relatively low initial water content and at constant tension. The radio-frequency sensor detects changes in water content of the textile from capacitance variations arising from changes in the dielectric constant of the wet fabric. This parameter was influenced by many variables in addition to the amount of water in the fabric. In particular, the dielectric constant depended on the characteristics of the fabric and was very sensitive to the presence of ionic substances in the water. Thus, this sort of sensor is less appropriate for control of textile drying under industrial conditions.

Water Transport in Unsaturated Nonisothermal Salty Soil: I. Experimental Results

AbstractThis paper presents observed soil moisture redistribution within unsaturated soil in response to imposed boundary temperatures. Both salinized and solute‐free soil conditions are studied. Two different uniform initial soil water contents and solute concentrations are used for the salinized soil columns. Likewise, two different uniform initial soil water contents are used for solute‐free soil columns. High and low boundary temperatures are similar for all of the soil columns. Thus, the experiments are designed to directly observe the impacts of thermal, soil matric, and osmotic gradients on redistribution of soil water. In all cases, appreciable amounts of water move in the direction of decreasing temperature within the soil columns. This is not a general rule of soil water movement, but a result of the uniform initial water content, the presence of solute, and the imposed boundary temperatures under salinized soil, or the initial water content and the imposed boundary temperatures under solute‐free soil. For both solute‐free and salinized soils, the net amount of transported water to achieve steady‐state conditions is greater for low initial water content than for high initial water content. Therefore, the steady‐state variations in the soil moisture content increased by decreasing the initial moisture content. When the same initial water content is used for both salinized and solute‐free soils, the net water transported to achieve steady‐state conditions is greater for the solute‐free soil than for salinized soil. These observations indicate clearly that solute concentration affects soil water transport with unsaturated, nonisothermal conditions.

Kiruna-type deposits; their origin and relationship to intermediate subvolcanic plutons in the Great Bear magmatic zone, Northwest Canada

Magnetite-apatite-actinolite rocks, similar to those at Kiruna, Sweden, and the St. Francois Mountains, Missouri, are associated with seven epizonal plutons that intrude andesitic stratovolcanoes of a broadly folded, early Proterozoic continental magmatic arc located in the northwestern Canadian Shield. The plutons, mainly medium-grained quartz monzonite-monzodiorite-diorite (IUGS) sheets and laccoliths 5 to 25 km in diameter, are spatially, temporally, and compositionally related to host andesitic stratovolcanoes. They were emplaced at 2 to 3 km depth, are compositionally heterogeneous, metasomatically altered, and had plagioclase as the liquidus phase. In addition they have kilometer-wide alteration halos comprising an inner zone of nearly complete wall-rock albitization, an intermediate zone of magnetite-apatite-actinolite veins, pods, breccias and wall-rock replacement, and an outer zone of disseminated sulfides. One pluton (Balachey) has a halo that is more or less completely outside the body, but another (Rainy Lake) has a halo that is partly superimposed over it. Separation of iron phosphate and silicate melts by liquid immiscibility is not supported by: (1) the gradual replacement of plagioclase by chessboard albite toward the roof of the Rainy Lake pluton, (2) the chemical trends in the Rainy Lake intrusion, (3) the mineralogical zoning, low temperature mineralogy, and replacement textures of the magnetite-apatite-actinolite, and (4) the relationship of the magnetite-apatite-actinolite veins and bodies to the plutons. However, all available data are compatible with a deuteric origin. It is concluded that high temperature, low initial water content, and shallow-level emplacement by intermediate plutons are necessary for the development of Kiruna-type deposits.

Water absorption in samples of different types of forest humus

A study has been made on water absorption properties of samples of different types of forest humus developed under different biotic and habitat conditions. Samples for study were taken from the following subhorizons: the litter (AoL) subhorizon of the mull type humus, the litter (AoL) and fermentation (AoF) subhorizons of the hygromoder type humus, and the litter (AoL), fermentation (AoF) and epihumus (AoH) subhorizons of the mor type humus. Samples with various initial water contents were irrigated under laboratory conditions by spraying them with 10 mm h −1. It has been found that samples from subhorizon AoL of different types of humus show similar absorption properties despite the different botanical composition of the remains that make them up and the different biotic and habitat conditions under which they had developed. Samples with a higher degree of disintegration and humification showed different absorption properties. A correlation has been found for all the humus forms studied between the initial water content in the samples and the amount of water absorbed. Samples with low initial water contents showed a low absorption rate in the first phase of irrigation, whereas at higher initial water contents, water absorption proceeded at a much higher rate. A significant effect of the initial moisture content on the amount of water absorbed was still observed even after 12 h of irrigation. The initial water content, while affecting comparatively little water absorption in samples from subhorizons AoL, has a crucial effect on water absorption by samples from subhorizons with a higher degree of disintegration and humification. The general conclusion from the above is that the essential factors modifying the absorption properties of organic soil matter are the processes of decomposition and humification.

DSC measurement of frozen water in liquid foods.

We investigated the state of water in frozen liquid foods, supposed to influence the performance of freeze-drying, by DSC. The amount of unfreezable water in milk was constant irrespective of the initial water content. As expected from the phase equilibrium, the water content of the non-ice part of CAS was constant among the samples with different initial water contents. The volume fraction of ice crystals, which should be known in the analysis of the freeze-drying rate, was significantly smaller at the low initial water content than the one usually estimated with the assumption that the water was all freezable.

Stability analysis of water movement in unsaturated porous materials: 2. Numerical studies

In an earlier paper a detailed theory was presented in which the principles of hydrodynamic stability analysis were used to develop a linear perturbation equation for vertical water movement with nonsharp fronts. In the present study the analysis is applied to the stability of several soil water systems some of which are potentially unstable. The first stage in the analysis requires the generation of water content and pressure head profiles using a computer‐based numerical solution for the flow equation for unsaturated porous materials. These profiles permit the calculation of certain differential terms which appear in the specification of the coefficients required in the stability analysis. Results for the growth rate of imposed disturbances of wavelengths of 1, 5, and 25 cm together with the appropriate eigenvectors are presented for infiltration into a homogeneous profile, redistribution following infiltration, infiltration into a scale heterogeneous medium, and infiltration into a fine‐over‐coarse stratified profile. Although instability was expected for the redistribution, heterogeneous, and layered systems, the results, whilst showing a noticeable trend towards instability, did not predict the occurrence of such a condition. The reason for this is discussed, in particular the evidence which suggests that small amounts of initial water can have a significant effect on the damping‐out of instabilities that otherwise would occur under dry initial conditions. Reference is made to a projected further paper documenting the effect of initial water content on wetting front instability and to the need for additional numerical studies at very low initial water contents.

Infiltration Prediction based on Estimation of Green‐Ampt Wetting Front Pressure Head from Measurements of Soil Water Redistribution

AbstractA simple, physically based algebraic equation was derived to calculate the wetting front matric pressure head, Hf, in the Green‐Ampt equation of infiltration. The derivation of the equation involved combining the simple hydraulic conductivity function with the wetting front matric pressure head function proposed by R. G. Mein and C. L. Larson (1971). The parameters in the derived equation were determined from fitting a power function to the experimental data of soil water content and soil water pressure head vs. elapsed time obtained during the post‐infiltration redistribution period. In the derived equation, Hf is expressed as a function of antecedent soil water content. At low initial water contents, the equation shows that Hf is essentially a constant. Evaluation of the calculated Hf values was accomplished by utilizing Hf in the Green‐Ampt equation to predict infiltration at seven field sites for soils at initial water contents below field capacity. Predicted cumulative infiltration was compared with infiltration measured with a double‐ring infiltrometer. The resulting Green‐Ampt predictions were accurate for initially dry soils, with a correlation value of r = 0.94 and a relative error of 12.1%.

MOVEMENT OF WATER AND NITRATE IN AN UNSATURATED AGGREGATED SOIL DURING NONSTEADY INFILTRATION—A SIMPLIFIED SOLUTION FOR SOLUTE FLOW

Dynamics of water and nitrate movement during infiltration under unsaturated conditions is examined in highly aggregated (0–2 mm size) Molokai soil. Experiments involved mainly horizontal infiltration into packed soil columns at three different initial water contents. Ammonium nitrate was mixed in the top 5 cm of soil immediately before or a week preceding the start of water application. After 3 or 4 different depths of wetting, the columns were sectioned to determine water content and nitrate distribution in the soil. Uniqueness of the experimental soil-water content vs. distance/time1/2 relationships and soil-water diffusivities for different initial soil-water contents indicated the validity of the simple diffusion theory for flow of water in this aggregated soil. Measured nitrate profiles also showed that the initial water within the micropores is mobile and miscibly displaced by applied water to form the wetting front. Comparison of the velocity of movement of the nitrate peak with the velocity of movement of water at the peak indicated that nitrate ions moved with water at a medium initial soil-water content. At a higher initial value, the nitrate peak was retarded by a factor of 0.75, while at a very low initial water content it was somewhat enhanced (by a factor of 1.13). The velocity of water at the peak was very nearly equal to the velocity of water at the inlet end of the column. A simplified solution derived from solute flow under the time-dependent velocity, considering the dispersion coefficient as a linear function of velocity, is shown to have useful predictive value.

THE RESPIRATION OF TOBACCO LEAVES AFTER SYSTEMIC INFECTION WITH TOBACCO MOSAIC VIRUS

The rate of CO, production per g. dry matter of the younger leaves of tobacco plants systemically infected with tobacco mosaic virus was about 10 yo less than that of comparable healthy leaves. Older infected leaves, showing well‐developed mosaic symptoms, had the same respiration rate as comparable healthy leaves. These results were independent of seasonal change in light conditions during the growth of the plants. Older leaves, but not younger leaves, of infected plants had a lower initial water content, and both absorbed less water during the experimental period, than leaves from healthy plants. The effects of TMV infection on water content were so great that the rate of CO, production per g. fresh weight was sometimes significantly increased by infection. This reversal of the apparent effect of infection on respiration rate, depending on the basis of reference may partly account for contradictory results reported previously by other workers. Other causes for contradictory results are discussed.