Richard L. Stroshine

The effect of process variables during drying on the physical and chemical characteristics of corn dried distillers grains with solubles (DDGS) - Plant scale experiments

Corn dried distillers grains with solubles (DDGS) are highly valued as an animal feed for its nutrient content. The amount of wet distillers grains (WDG) and condensed distillers solubles (CDS) blended together during drying affects nutritive value and physical characteristics of DDGS. Effect of changing the ratio of WDG and CDS, and recycled DDGS during drying on particle size, particle size distribution, particle and bulk densities, color, chemical composition, and amino acid content was studied. Moisture content and particle size of DDGS decreased with decreasing amount of CDS added. About 80% of the particles were within a narrow size range (<1500 microm). Bulk density and tapped density of samples produced with different CDS content ranged from 420.5 to 458.1 and 498.8 to 544.3 kg/m(3), respectively. True density decreased with reduction in CDS added. As the CDS content reduced, DDGS became lighter in color. Insoluble fiber contents (protein and insoluble fiber) and amino acids increased while fat, total soluble sugars and glycerol decreased as the CDS content added to WDG reduced. The correlation coefficient of individual chemical components with CDS was above 0.90. Results from this study will be helpful in predicting the physical and nutritive property changes due to variable ratios of blending CDS to WDG during the drying process.

Finite element analysis of drying with application to cereal grains

A finite element procedure for two sets of non-linear coupled drying models for three-dimensional axisymmetric and two-dimensional problems are presented. The models consider temperature and moisture dependent material properties. The two different solution procedures used are the implicit two-level and the explicit three-level time stepping schemes. Application is made to drying of single soybean, barley and corn kernels. The simulation results from the heat and mass transfer models agree well with the available experimental results. Model one accounts for diffusion of moisture through vapour and liquid phases. Model two assumes that moisture diffuses to the outer boundaries of the kernel in the liquid form and that evaporation takes place only at the surface of the grain. In all simulations, temperature predictions using model one approached the equilibrium temperature faster than model two. The overall grain kernel temperature and moisture predictions from model two were better than model one. The choice of a model depends upon the type of application and availability of material properties.

Grain kernel drying simulation using the finite element method.

A finite element formulation and solution of a set of coupled conductive heat and diffusive moisture transfer equations to improve grain drying simulation of axisymmetric bodies is presented. The model considers the temperature and moisture dependence of the diffusion coefficient, thermal conductivity, and specific heat. It assumes that moisture diffuses to the outer boundaries of the kernel in liquid form and that evaporation takes place only at the surface of grain. Application was made to drying of a barley kernel and predicted results agreed well with the experimental data. The simulated temperature and moisture profiles and gradients are directly usable for stress cracking analyses of grain. The results of the finite element analysis can be used for grain quality evaluation and drying simulation studies.

NONLINEAR FINITE ELEMENT ANALYSIS OF COUPLED HEAT AND MASS TRANSFER PROBLEMS WITH AN APPLICATION TO TIMBER DRYING

A finite element formulation and solution of a set of nonlinear coupled heat and mass transfer equations for porous capillary media is presented. The model considers temperature and moisture dependent material properties and can accomodate diffusion of moisture as either a liquid or a vapor. Application was made to drying of timber and predicted results agreed well with the experimental data.

Nondestructive Sugar Content Measurements of Intact Fruit Using Spin-spin Relaxation Time (T2) Measurements by Pulsed 1H Magnetic Resonance

A technique to estimate sugar content of intact fruit using 10 MHz pulsed proton magnetic resonance (IH-MR) was investigated. The values of spin-spin relaxation times (T2) were calculated from the data. A correlation model between T2 values and sugar contents was developed from the principle of chemical exchange between sugar and water protons. The chemical exchange between sugar and water changed the values of T2. The correlation model was verified by experiments on intact fruit. The T2 of intact grapes and sweet cherries were correlated with soluble solids as measured with a refractometer. These results suggest that T2 measurements on intact fruit can be used as a rapid, noninvasive and nondestructive indicator of sugar content.

Moisture measurement in cheese analogue using stretched and multi-exponential models of the magnetic resonance T2 relaxation curve

The dairy industry would benefit from rapid and non-destructive determination of moisture content of cheese products. The two components primarily responsible for the low-field magnetic resonance (MR) spin-spin relaxation (T2) signal of cheese products are fat and the water bound to protein. If the moisture component of the signal can be distinguished from the fat component, it should be possible to measure moisture using an MR sensor. Therefore, a key aspect of the development of an MR moisture measurement method is examination of techniques for analysis of T2 relaxation curves. One common method of T2 analysis of complex foods, such as cheese, is to fit multi-term exponential models to the curves. An alternative approach is proposed which uses stretched exponential models. The single-term stretched exponential model has been used for porous rock systems and polymers, but not for foods. The T2 relaxation curves were analysed using both models and the results were compared. The number of unknowns in the three-term exponential and two-term stretched exponential models was reduced by assuming the relaxation curve of the fat component was the same as the relaxation curve of pure fat. In each model, one of the exponential terms described the behaviour of the water in the cheese analogue, while the remaining term or terms described the behaviour of the fat. For each model the T2 relaxation time associated with the water was well correlated with moisture content. Coefficients of determination of the relaxation time versus moisture from each of the two models were nearly identical. The advantages and disadvantages of the two models are discussed.

Particle Segregation Within a Pile of Bulk Distillers Dried Grains with Solubles (DDGS) and Variability of Nutrient Content

ABSTRACT Piling Dried Distillerss Grains with Solubles (DDGS) using gravity discharge is common in the corn-ethanol industry. This study investigated the occurrence of particle segregation within piles of DDGS formed by gravity discharge and subsequent spatial nutrient variability. Particle segregation tests were performed in a laboratory study where piles of DDGS were formed using samples collected from two fuel ethanol plants (an “old” and a “new” generation plant), and a plant study performed on piles of DDGS formed at the same two fuel ethanol plants. In both the laboratory and plant studies, the piles were formed by gravity-driven discharge and sampled at various categorized sections from the center of the pile to the periphery. Our results gave similar conclusions to a prior bench-scale study and confirmed that particle segregation does result in significant differences in particle size at the sampled locations of the pile. Particle size expressed as the geometric mean diameter (dgw) increased from...

Proton magnetic resonance measurement of self-diffusion coefficient of water in sucrose solutions, citric acid solutions, fruit juices, and apple tissue

Proton magnetic resonance (1H-MR) studies were conducted on sucrose solutions, aqueous solutions, filtered apple juice, unfiltered apple juice, red grape juice, orange juice, and tissue from ‘Red Delicious’, ‘Golden Delicious’, and ‘Granny Smith’ apples. The Pulse Field Gradient Spin-Echo (PFGSE) technique was used to measure the self-diffusion coefficient of water (Dw) and the Carr-Purcell-Meiboom-Gill (CPMG) technique was used to measure spin-spin relaxation (T2). The 1H-MR system operated at 5.40 MHz and used a permanent magnet with a field strength of 0.1256 T. Two different quadrupole gradient coil probes were built to generate gradient pulses of 0.058 T/m and 0.108 T/m. The Dw measurements were correlated with titratable acids, insoluble solids, and refractometer measurements of percent soluble solids. The results give insight into factors that influence Dw in fruits and vegetables. The Dw increase with increasing temperature depends on soluble solids level. Dw is influenced by pH and titratable acids only in proportion to their contribution to soluble solids levels. However, T2 showed a dependence on pH, buffering, soluble solids, and insoluble solids. In the apple tissue, Granny Smith was the only variety that showed a statistical dependence for Dw on both refractometer brix and percent insoluble solids (R2 = 0.98).

II. APPLICATION TO GRAIN KERNELS

ABSTRACT An incremental finite element formulation was devdoped to simulate the viscoelastic behavior of soybean and corn Kernets during drying. Failure was predicted in a soybean kernel dried at 75°C and a corn kernel dried at 85°C, using von Mises failure criteria and experimentally determined strenglh propenies. Calculated tangential stresses

A Modified Hahn Echo Pulse Sequence for Proton Magnetic Resonance (1H-MR) Measurements of Percent Soluble Solids of Fruits

A fruit ripeness sensor being developed uses proton magnetic resonance to nondestructively determine percent by weight soluble solids in whole fruits. Results were compared to refractometer measurements of soluble solids content. In many fruits, soluble solids is nearly equivalent to percent sugar content, which is in turn related to ripeness. The principle used measures the effect of simple sugars (which constitute the majority of the soluble solids in many fruits) on self diffusion of water. Self diffusion can be measured using the Hahn Echo pulse sequence in the presence of a static magnetic field gradient. A modification of the Hahn Echo pulse sequence is described which solved two practical problems related to the application of the technique to rapid sorting; it increased the speed of the measurement and it greatly reduced the effects of sample size and shape. The improvement was demonstrated using experiments on cylindrical samples cut from apples.