Moisture profile determination in urea prill. II. Fertiliser caking implications

In a previous study, Karl Fischer (KF) titration was used to measure the mass of water in concentric layers of urea prill. The obtained data demonstrated that the grains of this fertiliser have a linear moisture profile. In the present paper, complementary to the previous one, a theoretical analysis of the behaviour of a spherical grain sample with a linear moisture profile during KF titration is presented. The obtained curve of titration fits the experimental data perfectly. The moisture content at the grain centre is four times greater than the average moisture content, and the layer with the highest water content is located at two‐thirds of the radius from the centre. Using this theoretical grain model and assuming that the intensity of caking is proportional to the area and moisture content of the flat contact surface between broken or deformed grains, it is possible to explain many observed experimental data on fertiliser caking. Copyright © 2007 Society of Chemical Industry     

Deactivation of tannin in high tannin milo by treatment with urea

Experiments were conducted to determine the effectiveness of urea in deactivating tannin in high tannin milo. High tannin milo (Pioneer B 815, 3.4 +/- .3% tannin) was reconstituted with aqueous urea solutions to give combinations of 26, 30, and 34% moisture with 2, 3, and 4% urea (percentage of urea per dry weight of milo). All treatments were maintained at 25 degrees C and were effective in deactivating tannin with no differences among moisture or urea content. The average rate of tannin deactivation was 68 +/- 2% d-1. Temperature affected rate of tannin deactivation in milo reconstituted to 30% moisture and 3% urea when stored at 25 or 60 degrees C. Rate of tannin deactivation was 44 +/- 5 and 89 +/- 18% d-1 at 25 and 60 degrees C, respectively. Tannin in high tannin milo can be deactivated rapidly and completely by reconstitution with aqueous urea. These studies demonstrate that tannin is deactivated completely under conditions where urea is an effective preservative of high moisture milo.     

The Effect of Moisture Content on Mechanical Properties and Texture Profile Parameters of Corn Meal Extrudates

Two corn meal extrudates with initial moisture contents of 22% and 31% W.B. were partially dried to moisture contents from 7% to 31% W.B. and stored in hermetically sealed containers to allow redistribution of the water. Compressive strength, compressive relaxation and instrumental texture profile analyses (fracturability, cohesiveness, springiness, gumminess and chewiness) were measured. Compressive strength increased with decrease in moisture content from 31-15%, reached a maximum between 15-10% and then decreased below 10%. Stiffness showed a similar relationship, with the maximum occurring between 10-6%. Relaxation modulus increased with decrease in moisture content over the range studied. Relaxation time was a minimum at 15% moisture content. Fracturability had a similar relationship to moisture content as that of compressive strength. The textural behavior was ductile and chewy at moisture contents above 15% but became crisp or crunchy and collapsed with brittle fractures at lower moisture contents. Both compressive properties and texture profile parameters of the corn meal extrudates changed considerably with changes in moisture content.     

MRI Observation and Mathematical Model Simulation of Water Migration in Wheat Flour Dough During Boiling

Existing cooking rate equations fail to describe the change of moisture content profile in starchy foods during cooking. There is a need for a new model. In this paper, an experiment on water migration during boiling was performed using a slab of wheat flour dough. The moisture content profile was measured by an MRI method. The result was compared with predictions made using mathematical models. The existing mathematical model was found to predict a much more rapid change than that measured by experiment. The accuracy of the prediction was considerably improved when a new model was applied: a mathematical model based on a new concept that water migration is driven by water demand.     

Investigation of drying characteristics in superheated steam drying of UF-impregnated Chinese fir

Urea formaldehyde (UF) resin-impregnated Chinese fir (Cunninghamia lanceolata (Lamb.)Hook.) was dried at different temperatures in an atmospheric pressure superheated steam dryer. Drying characteristics, moisture content, drying rate, temperature profile, drying defects, and color change were investigated. The moisture content was reduced from 66.21 to 11.79% within 30 h without causing severe drying defects; in contrast, the conventional hot air process required 7–8 days. After 25 h of drying, the temperatures at both the center and the surface of wood remained stable. After 34.5 h, the surface temperature gradually approached the steam temperature. The color of the superheated steam dried Chinese fir appeared slightly more intense yellow and red than the control. Investigation of the UF-impregnated Chinese fir wood by scanning electron microscopy (SEM) revealed that the majority of the lumens and voids, including the microvoids in wood structure, was filled with urea formaldehyde resin.     

An Approach for Monitoring the Moisture Content Changes of Drying Banana Slices with Laser Light Backscattering Imaging

Moisture content is an important quality attribute that directly influences storability of fruits and vegetables. The main goal of the present work was to test laser light backscattering imaging technique as a monitoring tool during drying of banana (Musa × cavendishii L.) slices. Laser diode emitting at 670 nm was used as the light source, whereas a charge-coupled device camera served as detector. The photon migration into the tissue was recorded as the average profile of the intensity gradient and expressed by two parameters, the size of the total illuminated area (square centimeters) on the surface and the radius (centimeters) of this area. The two attributes correlated with each other (r = 0.97–0.98). Backscattering images of slices were acquired each hour during the drying process at three different temperatures: 53, 58, and 63 °C. The two parameters of the intensity profile responded sensitively to changing moisture content. Significant relationship was found between changes in backscattering area and moisture content, especially at lower temperatures (r = 0.76, T = 53 °C), when almost no tissue browning occurred. At higher temperatures, correlations were observed between the parameters extracted by image processing and a* standard color index, especially at increased drying temperature due to the browning of the tissue.     

Change in the Status of Water in Japanese Noodles During and After Boiling Observed by NMR Micro Imaging

ABSTRACT: A correlation between moisture content (M, g water/ g dry matter) and transverse relaxation time ( T ₂) of water protons in standard wheat gel samples was established by NMR. Changes in moisture distribution in Japanese noodles were estimated from T ₂ of water protons obtained by NMR micro imaging using the correlation. Penetration of water from the surface to the core during boiling and homogenization of moisture content after boiling were clearly observed in the MR images and moisture profile. A local minimum of T ₂ of water protons was detected in the moisture profile of noodles boiled in tap water.     

猪通脊肉脱水后体积收缩及内部水分分布特征

研究了不同干燥条件下,猪通脊肉体积收缩以及内部水分分布。实验气流速度分别为1.0、1.5 m/s和2.0 m/s,温度分别为40、50℃和60℃。通过分析样品半径方向上不同点的水分含量以及体积收缩系数与时间和(无因次)水分含量之间的关系得出:猪通脊肉在脱水过程中,内部水分迁移连续进行,中心水分含量最高,从里到外,水分含量依次降低。猪通脊肉非各向同性,样品同一半径上各处水分含量不相等。风速是影响体积收缩的主要因素,体积收缩系数与水分含量线性相关。在温度40℃时,风速对体积收缩系数的影响非单调,风速为1.0 m/s的体积收缩系数最大,风速为1.5 m/s时体积收缩系数最小,即S1.0S2.0S1.5。     

不同储藏条件下筒仓中大豆堆高安全域研究

建立筒仓中大豆分层压缩平衡微分方程,实验测定微分方程中的参数,数值求解压缩平衡微分方程得到筒仓内大豆堆应力分布值;建立筒仓中大豆籽粒堆放模型,求解大豆籽粒堆放模型得出筒仓内大豆堆应力与籽粒压力的关系;实验测定大豆籽粒压缩力与塑性应变关系;设定大豆籽粒产生0.4 %的塑性应变为籽粒损伤阈值,结合筒仓内不同深度大豆堆应力、籽粒压力与塑性应变,给出大豆的堆高安全域。计算与实验结果表明：含水率为8.58%～15.01% w.b.并且储藏时间为60 d～240 d的大豆,在半径为10 m的筒仓内安全堆高的范围是47.6 m～20.6 m;在半径为15 m的筒仓内安全堆高的范围是40.2 m～19.3 m;在半径为20 m的筒仓内安全堆高的范围是37.4 m～18.8 m;筒仓内大豆堆的安全堆高随着含水率的增大而减小,随着筒仓直径的增大而减小,随着储藏期的增大而减小。     

Studies on electrical properties of wheat bread as a function of moisture content during storage

Bread undergoes several physicochemical changes during storage that results in a rapid loss of freshness. These changes depend on the moisture content present in the bread product and collectively termed as staling. The present work explains how the electrical properties of bread vary with time and moisture content at its crust and crumb. An instrument based on electrical impedance spectroscopy with multichannel electrodes is developed for the present investigations. Detailed studies have been carried out to understand the influence of changes in moisture profile at bread crust and crumb in terms of electrical properties during the storage of 120 h. A linear relationship is observed between the measured impedance and capacitance and residual moisture content in bread at crust during storage. It is observed that the measured Resistance at bread crumb has a nonlinear mathematical relationship with moisture content present at crumb.     

Prediction of temperature and moisture content of frankfurters during thermal processing using neural network

An artificial neural network (ANN) was developed to predict temperature and moisture content of frankfurters during smokehouse cooking. Fat protein ratio (FP), initial moisture content, initial temperature, radius of frankfurter, ambient temperature, relative humidity and process time were input variables. Temperature at the frankfurter centre, average temperature of the frankfurter and average moisture content (d.b) of the frankfurter were outputs. Network training data were obtained from validated heat and mass transfer models simulating temperature and moisture profiles of a frankfurter. Backpropagation method was used for ANN training. Selection of hidden nodes, learning rate, momentum and range of input variables were important to ANN prediction. The FP was not an important factor in predictions.     

Evaluating the profile of myofibrillar proteins and its relationship with tenderness among five styles of dry-cured hams

In order to investigate the relationship between profile of myofibrillar proteins and tenderness among 2 kinds of Chinese hams (Jinhua and Xuanwei) and 3 kinds of European hams (Iberian, Serrano and Parma), shear force, myofibril fragmentation index (MFI), SDS-PAGE, carbonyls content and Raman spectroscopy were investigated. The shear force and salt content of Chinese hams were significantly higher than that of European hams, while moisture content was lower than that of European hams (p < 0.05). MFI values and SDS-PAGE profile revealed that the degradation of myofibrillar proteins in Chinese hams was lower than in European hams. In addition, Chinese hams showed significantly higher carbonyls content and β-sheet content compared with European hams, indicated that proteins aggregation intensively inhibited the degradation of myofibrillar proteins in Chinese hams. These results indicated that the higher shear force in Chinese style hams could be attributed to the lower moisture content and limited proteolysis.     

Zum Sorptionsverhalten von Holzspanplatten

Investigations carried out on the influence of some typical additives (salts as hardners, sulphite liquor, and wax) on the equilibrium moisture content of particleboards led to the following results: From a certain level of relative humidity salts acting as hardners increase the equilibrium moisture content. This increase depends on the amount of salt used as well as on the nature of the salt itself. Salts having a high relative vapour pressure on their saturated aqueous solutions are less effective in increasing the moisture content of particleboards at equilibrium conditions than those with low vapour pressure on their saturated aqueous solutions. Partial substitution of urea formaldehyde resins by sulphite liquor increases the equilibrium moisture content of particleboards at high relative humidity; by contrast particleboards bonded with sulphite liquor and subjected to post thermal treatment at 180–200°C for several hours according to the Pedersen technology are by far less hygroscopic than all other known particleboards. Wax has only a slight effect on the equilibrium moisture content.     

Effect of blend proportion on moisture management characteristics of bamboo/cotton knitted fabrics

This study reports an investigation of the effect of the blend-ratio of bamboo and cotton fibres on the moisture management properties of single jersey knitted fabrics composed of them. The moisture management properties of the fabrics were measured in SDL-ATLAS moisture management tester. The liquid transport properties of textiles, such as wetting time, maximum moisture absorption rate, maximum wetted radii, spreading speeds, cumulative one-way transport capacity and overall moisture management capacity (OMMC), have been considered and correlated to the blend ratio of bamboo/cotton yarn single jersey knitted fabrics. It was observed that as the bamboo content increased, the wetting time decreased, maximum wetted radius decreased, rate of absorption increased, spreading speed decreased and OMMC decreased.     

Sequential modeling of fluidized bed paddy dryer

A sequential method was developed to model a continuous plug flow fluidized bed dryer. The method is based on dividing the dryer into sections in series with ideal mixing for both solid and gas phases in each section. In order to determine the proper number of sections, drying experiments were carried out using paddy at different operating conditions. It was shown that the number of sections can be correlated to Damköhler number, which includes kinetic and hydrodynamic parameters of the process. The model is able to predict the particle’s moisture profile along the bed as well as the moisture content of dried product. It was shown that the model fits the experimental data satisfactorily with the correlation coefficient of 0.989. Moreover, the model was tested against available data in the literature at different scales and operating conditions for which an error of less than 4.5% was observed in predicting the paddy moisture content at the outlet.     

Measurement of Moisture Profiles in Pasta During Rehydration Based on Image Processing

A method using an image processing technique was developed to measure the moisture profile in pasta during its rehydration process. The method is based on the increase in sample color brightness with increasing moisture content. Compared to currently used methods, this method has the advantage that moisture contents around 0.1 kg-H₂O/kg-d.m. can be easily measured at a spatial resolution of 1.6 μm. The moisture profiles obtained by this method suggested that penetration of water into small holes and cracks on the pasta surface, water diffusion in the pasta, and structural relaxation of the protein matrix play important roles in the rehydration mechanism. It was also suggested that starch granule gelatinization prevented water migration into the interior portion of the pasta.     

Development of thick layer re-wetting model for brown rice packaged with LDPE and PBT films

A mathematical model was developed to predict a moisture content profile during the thick layer re-wetting process of brown rice unpackaged and packaged with low density polyethylene (LDPE) and polybutylene terephthalate (PBT) films. Model validation was carried out by comparing predicted with measured moisture content derived from relative humidity data obtained from the brown rice re-wetting test for 6 days at 25 °C and 90% RH. The moisture standard errors of the model validation for brown rice packaged in LDPE and PBT films were 0.08% wet basis (wb) and 0.11% wb, respectively. It was concluded that the proposed re-wetting model could successfully describe the thick layer re-wetting of brown rice under the experimental conditions. Using this model, re-wetting simulations were carried out to estimate the time required to condition the moisture content of brown rice at various water vapor permeabilities of film. The cracking ratio of brown rice was also investigated empirically during the re-wetting process of packaged and unpackaged brown rice.     

Moisture Management Properties of Bamboo Viscose/Tencel Single Jersey Knitted Fabrics

Effect of bamboo viscose/tencel blend ratio on the moisture management properties of single jersey knitted fabrics has been studied. Moisture management properties, such as wetting time of top and bottom fabric surfaces, maximum moisture absorption rates of top and bottom surfaces, maximum wetted radii of top and bottom surfaces, spreading speeds of top and bottom surfaces, and cumulative one-way transport capacity and overall moisture management capacity have been considered and correlated to the blend ratio of bamboo viscose/tencel yarn single jersey knitted fabrics. It is observed that as the tencel content increases, the wetting time, absorption rate, spreading speed, overall moisture management capacity decreases but maximum wetted radius increases.     

Cold tack of urea formaldehyde resins as an important factor in plywood production

The ability of urea formaldehyde (UF) resins to develop cold tack is needed in plywood production during pre-pressing in a cold press to ensure that the veneers stick together, can be transported, and fit into a multi-daylight hot press. The influence of defined factors on the cold tack was analyzed by determining the tensile shear strength of uncured birch veneers bonded with UF resin, and the statistically significant impact factors were determined. The factors tested were lay-up time, resin amount, resin age, moisture content, veneer temperature and pre-press time. Moisture content and veneer temperature had the highest impact on the cold tack of UF resins. A negative impact of high moisture content on the tensile shear strength and therefore on the cold tack of UF resins was proven as well as a positive impact of a comparably high (30 °C) veneer temperature. Lay-up time and pre-press time showed a minor impact on the tensile shear strength. Models were created using Design-Expert software to calculate the optimum operation conditions for cold tack.     

Nutritive value of high moisture alfalfa hay preserved with urea

Urea (2 and 4%) was added to high moisture hays and compared with untreated wet or dry hays. Means for bale temperatures (degree C) for 1 wk postharvest were highest for wet control (41.2), lowest for dry control (31.4), and intermediate for urea treatments (36.7). By 4 wk postharvest, all temperatures were equal. Protection from molding was most effective for 4% urea, and 2% urea was superior to wet control. By 4 mo postharvest, CP for low urea had decreased due to NH3 loss, and CP for wet control had increased due to DM loss, so they were not different. Initially, ADF was similar for the hays, but after 4 mo storage the wet control was highest (41.7%), the dry control lowest (36.0%), and urea treatments intermediate. Lignin and NDF followed similar trends. In vitro DM digestibilities were highest for the wet control at harvest but lowest at 120 d with high urea and dry control greater than low urea. Feed intakes and milk yields in lactating cows fed the hays were not different. These data show that addition of 2 or 4% urea improved quality of hay baled at about 25% moisture; high urea was more effective than low urea.