Effect of DDGS,Moisture Content,and Screw Speed on Physical Properties of Extrudates in Single‐Screw Extrusion

Three isocaloric (3.5 kcal/g) ingredient blends containing 20, 30, and 40% (wb) distillers dried grains with solubles (DDGS) along with soy flour, corn flour, fish meal, and mineral and vitamin mix, with net protein adjusted to 28% (wb) for all blends, were extruded in a single‐screw laboratory‐scale extruder at screw speeds of 100, 130, and 160 rpm, and 15, 20, and 25% (wb) moisture content. Increasing DDGS content from 20 to 40% resulted in a 37.1, 3.1, and 8.4% decrease in extrudate durability, specific gravity, and porosity, respectively, but a 7.5% increase in bulk density. Increasing screw speed from 100 to 160 rpm resulted in a 20.3 and 8.8% increase in durability and porosity, respectively, but a 12.9% decrease in bulk density. On the other hand, increasing the moisture content from 15 to 25% (wb) resulted in a 28.2% increase in durability, but an 8.3 and 8.5% decrease in specific gravity and porosity, respectively. Furthermore, increasing the screw speed and moisture content of the blends, respectively, resulted in an increase of 29.9 and 16.6% in extruder throughput. The extrudates containing 40% DDGS had 8.7% lower brightness, as well as 20.9 and 16.9% higher redness and yellowness, compared with the extrudates containing only 20% DDGS. Increasing the DDGS content from 20 to 40% resulted in a 52.9 and 51.4% increase in fiber and fat content, respectively, and a 7.2% decrease in nitrogen free extract. As demonstrated in this study, ingredient moisture content and screw speed are critical considerations when producing extrudates with ingredient blends containing DDGS, as they are with any other ingredients.     

Cross‐Sectional Staining and Surface Properties of DDGS Particles and Their Influence on Flowability

With the U.S. fuel ethanol industry projected to grow during the next several years, supplies of distillers dried grains with solubles (DDGS) are anticipated to continue to grow as well. DDGS is used primarily as livestock feed. Much of the DDGS must be shipped, often over large distances, outside the Corn Belt (which is where most of the corn‐based ethanol plants are currently located). Stickiness and caking among particles is a common issue for DDGS, and it often leads to flowability problems. To address this, the objective of this study was to understand the cross‐sectional and surface natures of DDGS particles from five ethanol plants, and how they interact with DDGS properties. This study examined the distribution patterns of chemical components within cross‐sections, within section edges (i.e., surface layers), and on surfaces using standard staining techniques; chemical composition was determined using standard protocols; and physical and flowability properties were also determined. Crude protein in the samples was 28.33–30.65% db, crude fat was 9.40–10.98% db, and neutral detergent fiber (NDF) was 31.84–39.90% db. Moisture contents were 4.61–8.08% db, and geometric mean diameters were 0.37–0.52 mm. Cross‐sectional staining showed protein levels of 19.57–40.39%, and carbohydrate levels of 22.17–43.06%, depending on the particle size examined and the production plant from which the DDGS was sampled. Staining of DDGS particles indicated a higher amount of surface layer protein compared with carbohydrate thickness in DDGS particles that had a lower flow function index (which indicated potential flow issues). Additionally, surface fat staining suggested that higher surface fat also occurred in samples with worse flow problems. This study represents another step toward understanding why DDGS particles stick together during storage and transport, and will hopefully help to improve DDGS material handling strategies.     

Properties of Starches from Several Low‐Amylose Rice Cultivars

The starch properties of five low‐amylose rice cultivars, Yawarakomachi, Soft 158, Hanabusa, Aya, and Snow Pearl, were compared with those of two normal amylose rice cultivars, Nipponbare and Hinohikari. There were no large differences in the distributions of the amylopectin chain length determined by high‐performance anion‐exchange chromatography, and the starch gelatinization properties determined by differential scanning calorimetry, between normal and low‐amylose rice cultivars. Results obtained using rapid viscosity analysis indicated that low‐amylose rice starches had lower peak viscosity, breakdown, and setback values than normal amylose rice starches. Starch granules from low‐amylose rice cultivars had a higher susceptibility to glucoamylase than those from normal amylose rice cultivars. The results of this study showed some differences between normal and low‐amylose rice starches in pasting properties and enzymatic digestibility.     

Probing the Properties of Dough with Low‐Intensity Ultrasound

Ultrasonic assessments of the properties of dough have been used over the past 15–20 years to complement studies of dough properties that use other physical testing techniques. After the principles and techniques of low‐intensity ultrasound are introduced, its use as a tool for investigating the rheology and structure of dough is reviewed. One important outcome from ultrasonic assessments of dough properties is an understanding of how bubbles alter dough rheology.     

Effect of Harvest Moisture Content on Selected Yellow Dent Corn: Dry‐Grind Fermentation Characteristics and DDGS Composition

Efficiently utilizing the nongrain portion of the corn plant as ruminant food and the grain for ethanol will allow the optimization of both food and fuel production. Corn and corn stover could be more effectively used if they were harvested earlier before dry down. Corn harvested at different moisture contents (MCs) may exhibit different processing characteristics for the ethanol industry, because of differences in physical and chemical properties. Therefore, the objective of this study was to investigate the effect of corn harvest MC on dry‐grind fermentation characteristics and dried distillers grains with solubles (DDGS) composition. Pioneer hybrid 32D78 was harvested at seven different dates from August 21 to November 23, 2009, with harvest MCs ranging from 73 to 21% (wb). The corn samples with different harvest MCs were evaluated by a conventional dry‐grind process. Final ethanol concentration from the corn with harvest MC of 54% (kernel dent stage) was 17.9% (v/v), which was significantly higher (0.5–1.2 percentage points) than the mature corn with lower harvest MCs (P < 0.05). Ethanol conversion efficiencies for the corn with harvest MCs of 73 and 54% (wb) were 98.5 and 93.2%, respectively, whereas ethanol conversion efficiencies for the corn with lower harvest MCs were significantly lower (P < 0.05), ranging between 83.2 and 88.3%. For DDGS composition, with corn harvest MC decreasing from 73 to 21% (wb), the residual starch concentration increased from 7.7 to 15.2%, the crude protein concentration decreased from 29.4 to 24.9%, and the neutral detergent fiber concentration decreased from 26.6 to 20.6%.     

Tensile Properties of Extruded Corn Protein Low‐Density Polyethylene Films

The strength of films extruded from powder blends of corn zein or corn gluten meal (CGM) with low‐density polyethylene was investigated. Tensile strength, percent elongation at break, and elastic modulus of the extruded films were measured. The tensile strength decreased from 13 MPa to ≈10.5 MPa with zein addition, while CGM addition resulted in tensile strength of ≈6 MPa. The higher the level of biological material (CGM or zein) in the films the lower the tensile properties. Films containing CGM exhibited significantly lower tensile properties than those containing zein. Extrusion processing of biological films is a step toward commercial viability.     

Field Performance and Essential Oil Production of Mycorrhizal Rosemary in Restoration Low‐Nutrient Soils

The establishment and growth of Rosmarinus officinalis L. under field conditions in two low‐nutrient‐content soils were evaluated, as well as the effect of arbuscular mycorrhizal (AM) fungi on essential oil production. The reclamation was conducted in two experimental sites: a limestone quarry and a wasteland soil, both surrounded by Mediterranean vegetation. Mycorrhizal R. officinalis plants inoculated with different AM fungal isolates were used to revegetate the sites. Pre‐transplant inoculation with mycorrhizal fungi resulted in an increased survival of R. officinalis with similar results in both experimental areas. Mycorrhizal inoculation enhanced plant growth, increased essential oil yield and improved the establishment of plants under field conditions. The results indicate that the presence of the symbiosis can accelerate plant growth and alter the biosynthesis of secondary metabolites, thus improving the yield of medicinal plant extracts. It also confirmed the importance of selecting plant/symbiont combinations adapted to the environmental constraints of low‐nutrient‐content soils to design a successful application of mycorrhizal technology in marginal soils. Copyright © 2013 John Wiley & Sons, Ltd.     

Rheological Properties of Starch‐Oil Composites with High Oil‐to‐Starch Ratios

Many applications have been developed for aqueous dispersions of jet‐cooked starch‐oil composites prepared by excess steam jet cooking. Previous formulations have typically contained 20–50% oil by weight based on the weight of starch. To expand the range of potential applications, new preparation methods were investigated to increase the oil content to as high as four times the weight of starch. High‐amylose corn starch was cooked in an excess‐steam jet cooker in the presence of oleic acid, and soybean oil was added to form the starch‐oil composites. Amylose is removed from solution by forming helical inclusion complexes with the oleic acid and, if the materials are cooled sufficiently quickly, the helical inclusion complexes only form small aggregates and shells around the oil droplets. Depending on the composition and preparation method, a wide range of stable, high‐oil materials from low‐viscosity liquids to smooth pastes can be formed. The flow, textural, and structural properties of these materials are shown. The materials can be used in a wide range of applications, including spray lubricants, lotions, and for fat delivery in cake mixes.     

Determining Weight and Moisture Properties of Sound and Fusarium‐Damaged Single Wheat Kernels by Near‐Infrared Spectroscopy

Single kernel moisture content (MC) is important in the measurement of other quality traits in single kernels because many traits are expressed on a dry weight basis. MC also affects viability, storage quality, and price. Also, if near‐infrared (NIR) spectroscopy is used to measure grain traits, the influence of water must be accounted for because water is a strong absorber throughout the NIR region. The feasibility of measurement of MC, fresh weight, dry weight, and water mass of single wheat kernels with or without Fusarium damage was investigated using two wheat cultivars with three visually selected classes of kernels with Fusarium damage and a range of MC. Calibration models were developed either from all kernel classes or from only undamaged kernels of one cultivar that were then validated using all spectra of the other cultivar. A calibration model developed for MC when using all kernels from the wheat cultivar Jagalene had a coefficient of determination (R²) of 0.77 and standard error of cross validation (SECV) of 1.03%. This model predicted the MC of the wheat cultivar 2137 with R² of 0.81 and a standard error of prediction (SEP) of 1.02% and RPD of 2.2. Calibration models developed using all kernels from both cultivars predicted MC, fresh weight, dry weight, or water mass in kernels better than models that used only undamaged kernels from both cultivars. Single kernel water mass was more accurately estimated using the actual fresh weight of kernels and MC predicted by calibrations that used all kernels or undamaged kernels. The necessity for evaluating and expressing constituent levels in single kernels on a mass/kernel basis rather than a percentage basis was elaborated. The need to overcome the effects of kernel size and water mass on single kernel spectra before using in calibration model development was also highlighted.     

Effect of Single‐Screw Extruder Die Temperature,Amount of Distillers' Dried Grains With Solubles (DDGS), and Initial Moisture Content on Extrudates

Corn distillers' dried grains with solubles (DDGS) was extruded with corn meal in a pilot plant single‐screw extruder at different extruder die temperatures (100, 120, and 150°C), levels of DDGS (0, 10, 20, and 30%) and initial moisture contents (11, 15, and 20% wb). In general, there was a decrease in water absorption index (WAI), water solubility index (WSI), radial expansion, and L* value with an increase in DDGS level, whereas a* value and bulk density increased. Increase in extruder die temperature resulted in an increase in WSI and WAI but a decrease in L* and bulk density. Peak load was highest at 30% DDGS as compared with 0, 10, and 20% DDGS extrudates. Die temperature of 120°C and initial moisture content of 20% resulted in least peak load. The a* value remained unaffected by changes in extruder die temperature. Radial expansion was highest at extruder die temperature of 120°C. Maximum WAI, WSI, radial expansion, and L* value were obtained at 15% initial moisture content. An increase in initial moisture content, in general, decreased L* value and bulk density but increased a* value of extrudates.     

High‐Speed NIR Segregation of High‐ and Low‐Protein Single Wheat Seeds

Wheat breeders need a nondestructive method to rapidly sort high‐ or low‐protein single kernels from samples for their breeding programs. For this reason, a commercial color sorter equipped with near‐infrared filters was evaluated for its potential to sort high‐ and low‐protein single wheat kernels. Hard red winter and hard white wheat cultivars with protein content >12.5% (classed as high‐protein, 12% moisture basis) or < 11.5% (classed as low‐protein) were blended in proportions of 50:50 and 95:5 (or 5:95) mass. These wheat blends were sorted using five passes that removed 10% of the mass for each pass. The bulk protein content of accepted kernels (accepts) and rejected kernels (rejects) were measured for each pass. For 50:50 blends, the protein in the first‐pass rejects changed as much as 1%. For the accepts, each pass changed the protein content of accepts by ≈0.1%, depending on wheat blends. At most, two re‐sorts of accepts would be required to move 95:5 blends in the direction of the dominant protein content. The 95:5 and 50:50 blends approximate the low‐ and high‐protein mixture range of early generation wheat populations, and thus the sorter has potential to aid breeders in purifying samples for developing high‐ or low‐protein wheat. Results indicate that sorting was partly driven by color and vitreousness differences between high‐ and low‐protein fractions. Development of a new background specific for high‐ or low‐protein and fabrication of better optical filters for protein might help improve the sorter performance.     

Effect of Oil Content and pH on the Physicochemical Properties of Corn Starch‐Soybean Oil Composites

Starch‐lipid composites are a new category of fat replacers. The physicochemical properties of reconstituted corn starch and soybean oil composites (CSSBOC) were evaluated and compared with the properties of reconstituted jet‐cooked corn starch (JCCS). Gel firmness, thermal properties, and hot pasting properties at two pH levels and two oil content levels were studied. Amylose content of CSSBOC was unaffected by processing. Buffer pH significantly affected the firmness of the gels made with JCCS. Gels appeared to have a more ordered structure and were firmer at pH 3.4 than at pH 6.0. The firmness of gels made with CSSBOC was not affected by pH or oil content. Retrogradation enthalpy of the gels made with JCCS was significantly affected by pH. Differences in the thermal characteristics of gels made with CSSBOC were attributed to pH and oil content. Peak viscosity, cold paste viscosity, and breakdown viscosity changed significantly when CSSBOC pastes were reconstituted in different pH buffers. Only hot paste viscosity and cold paste viscosity changed significantly when JCCS pastes were reconstituted in different pH buffers. Results establish critical parameters for processing decisions and for the understanding of the behavior of CSSBOC in food system models in which pH is an important factor.     

Comparison of Modified Dry‐Grind Corn Processes for Fermentation Characteristics and DDGS Composition

Three different modified dry‐grind corn processes, quick germ (QG), quick germ and quick fiber (QGQF), and enzymatic milling (E‐Mill) were compared with the conventional dry‐grind corn process for fermentation characteristics and distillers dried grains with solubles (DDGS) composition. Significant effects were observed on fermentation characteristics and DDGS composition with these modified dry‐grind processes. The QG, QGQF, and E‐Mill processes increased ethanol concentration by 8–27% relative to the conventional dry‐grind process. These process modifications reduced the fiber content of DDGS from 11 to 2% and increased the protein content of DDGS from 28 to 58%.     

Effect of Moisture Content and Soluble Level on the Physical,Chemical, and Flow Properties of Distillers Dried Grains with Solubles (DDGS)

Distillers dried grains with solubles (DDGS) is a bulk material that has been widely used as a protein source for ruminants and nonruminants for more than two decades. DDGS is the nonfermentable processing residue (i.e., protein, fiber, fat, and ash) from fuel ethanol manufacturing. With the exponential growth of the fuel ethanol industry in the past several years, significant quantities (≈13.0 million tons in 2007) of distillers grains are now being produced. To effectively utilize these coproduct streams in the domestic market, DDGS must be transported greater distances and must be stored until final use. DDGS flow is often problematic as it can become restricted by caking and bridging that occur during shipping and storage. This flowability problem can present itself during dynamic and static flow conditions. This issue most likely results from physical or chemical interactions between particles (including particle size and shape), storage moisture, temperature, and relative humidity variations, as well as storage time. The objective of this study was to examine the effect of five moisture content levels (10, 15, 20, 25, and 30% db) on the resulting physical and chemical properties of DDGS with four soluble levels (10, 15, 20, and 25% db). To produce these materials, condensed distillers solubles (CDS) were combined with DDG, and appropriate quantities of water were added to adjust moisture contents. Carr indices were used to quantify the flowability of the DDGS samples. The results showed that both soluble level and moisture content had noticeable effects on physical and flow properties (e.g., aerated bulk density, packed bulk density, and compressibility). According to dispersibility, flowability index, and floodability index, flowability generally declined significantly (P < 0.05) with an increase in moisture content for most of the soluble levels under consideration. The color values and protein content of the DDGS were significantly affected (P < 0.05) as soluble level increased as well.     

Effects of Steam,Moisture, and Screw Speed on Physical Properties of DDGS‐Based Extrudates

A fractional factorial design with a replicated central composite point was used to investigate the effects of extrusion processing on physical properties of distillers dried grains with solubles (DDGS) based aquafeeds using a twin‐screw extruder. Extrusion cooking trials were performed with a nutritionally balanced ingredient blend for Nile tilapia, with two levels of screw speed (350 and 450 rpm), two levels of extruder water (0.236 and 0.302 kg/min), and two levels of conditioner steam (0.1 and 0.15 kg/min). The central point was 400 rpm screw speed, 0.271 kg/min extruder water, and 0.12 kg/min conditioner steam. Effects of these processing conditions on extrudate characteristics were extensively analyzed and included moisture content, water activity, thermal properties, expansion ratio, unit density, bulk density, color, water stability, sinking velocity, water absorption and solubility indices, and pellet durability index. Increasing the extruder water and conditioner steam resulted in a 5.3% decrease and nearly 8.6% rise in mass flow rate, respectively. As screw speed increased from 350 to 400 rpm, water stability and water activity increased by 13 and 58%, respectively. Increasing extruder water from 0.236 to 0.302 kg/min led to a significant increase in water stability by 12.5% and decreases in water absorption index, water activity, and expansion ratio by 13, 21, and 5.5%, respectively. As conditioner steam increased from 0.1 to 0.15 kg/min, sinking velocity and water absorption index decreased by 25 and 15%, respectively. Increasing conditioner steam from 0.1 to 0.12 kg/min resulted in 20, 5.5, 10, and 3% decreases in moisture content of the extrudates, brightness (L*), water stability, and expansion ratio, respectively. It also increased bulk density by 5.8% and unit density by 4.2%. Overall, all trials produced viable extrudates with properties appropriate for Nile tilapia feeding.     

Extraction and Film Properties of Kafirin from Coarse Sorghum and Sorghum DDGS by Percolation

The high cost of kafirin and zein restricts their use for bioplastic and food applications. Effective, simple, and rapid kafirin/zein isolation processes are required. Here a percolation‐type aqueous ethanol solvent extraction process from coarse meals (grits) and coarse sorghum distillers dried grains and solubles (DDGS) for kafirin and zein isolation employing a low ratio of extractant to meal (2.5:1) was investigated, which is potentially applicable in the grain bioethanol industry. Postextraction filtration times were more than twice as fast using coarse meals compared with fine flours. Washing the meals prior to extraction to remove starch improved protein preparation purity to 73–85% compared with 68–72% for unwashed meals. Hence, no subsequent filtration or centrifugation step is required to clean up the kafirin/zein solution prior to solvent evaporation. With a single extraction step, kafirin/zein yields were 48% (protein basis) for DDGS and 53–70% for washed sorghum/maize meals. Cast films were used as a model bioplastic system to evaluate extracted kafirin/zein functional properties. DDGS kafirin films had rough surfaces but had the lowest water uptake and in vitro digestibility, owing to heat‐induced disulfide crosslinking during DDGS processing. Extraction by percolation using coarse meal/DDGS has potential to improve kafirin/zein viability.     

土壤蒸发及水热传输研究综述

土壤蒸发与水热传输是地表能量与水分平衡的重要组成部分。本文综述了几十年来土壤蒸发、水热传输以及土壤水力、热力特性基本理论及发展过程,并提出了今后进一步研究的方向。     

Effects of Gelatinization and Moisture Content of Extruded Starch Pellets on Morphology and Physical Properties of Microwave‐Expanded Products

Extruded pellets were prepared from normal corn starch using a corotating twin‐screw extruder (25:1 L/D ratio, 31 mm diameter screw), and then expanded by heating in a conventional microwave oven for 70 sec. The effects of gelatinization level and moisture content of the extruded pellets on the morphology and physical properties of the microwave‐expanded products such as puffing efficiency, expansion bulk volume, and bulk density were investigated. The expanded shape and air cell structure differed according to the degree of gelatinization of the pellets. Maximum puffing efficiency and expansion volume with the pellets containing 11% moisture were achieved at 52% gelatinization. For this level of gelatinization, starch was extruded at 90°C barrel temperature. In addition, the moisture content of the pellets critically affected the expansion behavior. The maximum puffing efficiency and expansion volume were achieved in a moisture range of 10~13%. For optimum product shape and uniform air cell distribution, the pellets should undergo sudden release of the superheated vapor during the microwave‐heating. The expansion by microwave‐heating was optimized at ≈50% gelatinization.     

Low‐molecular‐weight organic acids enhance desorption of polycyclic aromatic hydrocarbons from soil

The impact of low‐molecular‐weight organic acids (LMWOAs) on desorption of phenanthrene and pyrene as representative polycyclic aromatic hydrocarbons (PAHs) from a contaminated soil was investigated by using a laboratory batch experiment. Three LMWOAs were used in this study and were citric, oxalic and malic acids. The LMWOAs in aqueous solution promoted desorption of PAHs from soil significantly and demonstrated an increasing trend as the concentration of LMWOAs increased. When compared with desorption of phenanthrene and pyrene from soil to water, the addition of LMWOAs enhanced desorption of test PAHs by up to 285 and 299%, respectively. Among the three LMWOAs studied, citric acid demonstrated the greatest efficiency in promoting PAH desorption from soil. Solutions of LMWOA continuously promoted PAH removal from soil during the multiple cycles of desorption. Overall, the experimental results suggest that LMWOAs in aqueous solution could disrupt soil organic matter (SOM)–metal cation–mineral linkages in soils, resulting in the release of SOM from soil and simultaneous increase of dissolved organic carbon (DOC) in solution. The loss of SOM from soil and increase of DOC in solution are responsible for the enhanced PAH desorption from soil. The positive correlation between DOC in solution and desorbed PAHs from soil suggests that the loss of SOM from soil plays an important role in LMWOA‐enhanced desorption of PAHs from soil.