Methods for Characterization of Residual Starch in Distiller's Dried Grains with Solubles (DDGS)

The objective of this study was to establish methods for determining the content and components of residual starch in distiller's dried grains with solubles (DDGS), a coproduct from dry‐grind corn ethanol production. Four DDGS prepared in our laboratory and one DDGS obtained from a commercial ethanol manufacturer were used for the study. Quantitative analysis of total residual sugar (TRS) in DDGS was performed by determining d ‐glucose produced by enzymatic hydrolysis of oligosaccharides and residual starch remaining in hexane‐defatted DDGS after being dispersed in 90% DMSO. The TRS consisted of free glucose, oligosaccharides, and residual starch. The commercial manufacturer's DDGS contained more TRS (15.8%, w/w db) than the laboratory‐processed DDGS (2.4–2.9%, w/w db). The content of residual starch remaining in the commercial DDGS (5.5% w/w db) was also larger than the laboratory‐processed DDGS (1.9–2.5% w/w db). Analyses of molecular weight distribution showed that the residual starch in DDGS consisted of short‐chain amylose and amylopectin, respectively, as the major and minor components. The short‐chain amylose molecules constituted 86.5–94.1% of the residual starch. The major population of the short‐chain amyloses had an average degree of polymerization (DP) of 85, closely resembling the length of enzyme‐resistant fragments of amylose‐lipid complexes.     

Flowability Properties of Commercial Distillers Dried Grains with Solubles (DDGS)

Distillers dried grains with solubles (DDGS), the major coproduct from the corn‐based fuel ethanol industry, is primarily used as livestock feed. Due to high protein, fiber, and energy contents, there is a high demand for DDGS. Flowability of DDGS is often hindered due the phenomenon of caking. Shipping and handling of DDGS has thus become a major issue due to bridge formation between the DDGS particles. The objective of this investigation was to measure flowability characteristics of DDGS samples from five ethanol plants in the north central region of the United States. Carr and Jenike tests were performed and the resulting data were mathematically compared with a previously developed empirical model. The largest particles had an average geometric mean diameter (GMD) of 1.19 mm, while the lowest particle size had an average GMD of 0.5 mm. Soluble solid levels were ≈10.5–14.8% (db). The effective angle of friction (δ) was 43.00–57.00°. Additionally, a few parameters exhibited fairly high linear correlations, including aerated and packed bulk densities (r = 0.97), geometric standard deviation and Carr compressibility (r = 0.71), geometric standard deviation and Hausner ratio (r = –0.70). Overall flowability assessment indicated that the commercial DDGS samples did have the potential for flow problems, although no samples exhibited complete bridging. Quantifying DDGS flowability is a necessary step toward overcoming this logistical challenge facing the fuel ethanol industry.     

Separation of Fiber from Distillers Dried Grains with Solubles (DDGS) Using Sieving and Elutriation

A process was developed to separate fiber from distillers dried grains with solubles (DDGS) in a dry‐grind corn process. Separation of fiber from DDGS would provide two valuable coproducts: 1) DDGS with reduced fiber, increased fat, and increased protein contents; and 2) fiber. The process, called elusieve process, used two separation methods, sieving and elutriation, to separate the fiber. Material carried by air to the top of the elutriation column was called the lighter fraction and material that settled to the bottom of the column was called the heavier fraction. We evaluated the compositions of fractions produced from sieving and elutriation. Two commercial samples of DDGS were obtained from two dry‐grind corn plants. Sieving over four screens (869, 582, 447, and 234 μm openings) created five size categories. The two smallest size categories contained >40% (w/w) of the original DDGS and had reduced fiber and increased protein and fat contents relative to the original DDGS. Elutriation of the remaining three size categories increased protein and fat contents and reduced fiber contents in the heavier fractions. Elutriation at air velocities of 1.59–5.24 m/sec increased the protein content of the heavier fraction by 13–41% and increased the fat content of the heavier fraction by 4–127% compared with the bulk fractions of each size category. This process was effective in separating fiber from both DDGS samples evaluated. Elusieve process does not require changes in the existing dry‐grind process and can be implemented at the end of the dry‐grind process.     

Economics of Fiber Separation from Distillers Dried Grains with Solubles (DDGS) Using Sieving and Elutriation

Separation of fiber from distillers dried grains with solubles (DDGS) provides two valuable coproducts: 1) enhanced DDGS with reduced fiber, increased fat and increased protein contents and 2) fiber. Recently, the elusieve process, a combination of sieving and elutriation was found to be effective in separating fiber from two commercial samples of DDGS (DDGS‐1 and DDGS‐2). Separation of fiber decreased the quantity of DDGS, but increased the value of DDGS by increasing protein content and produced a new coproduct with higher fiber content. Economic analysis was conducted to determine the payback period, net present value (NPV), and internal rate of return (IRR) of the elusieve process. The dependence of animal foodstuff prices on their protein content was determined. Equipment prices were obtained from industrial manufacturers. Relative to crude protein content of original DDGS, crude protein content of enhanced DDGS was higher by 8.0% for DDGS‐1 and by 6.3% for DDGS‐2. For a dry‐grind plant processing corn at the rate of 2,030 metric tonnes/day (80,000 bushels/day), increase in revenue due to the elusieve process would be $0.4 to 0.7M/year. Total capital investment for the elusieve process would be $1.4M and operating cost would be $0.1M/year. Payback period was estimated to be 2.5–4.6 years, NPV was $1.2–3.4M, and IRR was 20.5–39.5%.     

Fiber Separated from Distillers Dried Grains with Solubles as a Feedstock for Ethanol Production

In the dry-grind process, corn starch is converted into sugars that are fermented into ethanol. The remaining corn components (protein, fiber, fat, and ash) form a coproduct, distillers dried grains with solubles (DDGS). In a previous study, the combination of sieving and elutriation (air classification), known as the elusieve process, was effective in separating fiber from DDGS. In this study, elusieve fiber was evaluated for ethanol production and results were compared with those reported in other studies for fiber from different corn processing techniques. Fiber samples were pretreated using acid hydrolysis followed by enzymatic treatment. The hydrolyzate was fermented using Escherichia coli FBR5 strain. Efficiency of ethanol production from elusieve fiber was 89–91%, similar to that for pericarp fiber from wet-milling and quick fiber processes (86–90%). Ethanol yields from elusieve fiber were 0.23–0.25 L/kg (0.027–0.030 gal/lb); similar to ethanol yields from wet-milling pericarp fiber and quick fiber. Fermentations were completed within 50 hr. Elusieve fiber conversion could result in 1.2–2.7% increase in ethanol production from dry-grind plants. It could be economically feasible to use elusieve fiber along with other feedstock in a plant producing ethanol from cellulosic feedstocks. Due to the small scale of operation and the stage of technology development for cellulosic conversion to ethanol, implementation of elusieve fiber conversion to ethanol within a dry-grind plant may not be currently economically feasible.     

Twin-Screw Extrusion Processing of Feed Blends Containing Distillers Dried Grains with Solubles (DDGS)

Extrusion trials were conducted with varying levels of distillers dried grains with solubles (DDGS) along with soy flour, corn flour, fish meal, vitamin mix, mineral mix, and net protein content adjusted to 28% using a Wenger TX-52 twin-screw extruder. The properties of extrudates were studied in experiments conducted using a full-factorial design with three levels of DDGS content, two levels of moisture content, and two levels of screw speed. Increasing the DDGS content from 20 to 60% resulted in a 36.7% decrease in the radial expansion, leading to a 159 and 61.4% increase in the unit density and bulk density of the extrudates, respectively. Increasing the DDGS content resulted in a significant increase in the water absorption index (WAI) but a significant decrease in the water solubility index (WSI) of the extrudates. Changing the screw speed and moisture content had no significant effect on the radial expansion ratio but resulted in a significant difference in the bulk density of the extrudates, which may be due to the occurrence of longitudinal expansion. Even though changing the moisture content and screw speed had no significant effect on the WSI of the extrudates, significant differences in the WAI of the extrudates were observed. The ingredient components in the blend and moisture content had an influence on the color changes of the extrudates, as did the biochemical changes occurring inside the barrel during processing. Overall, it was determined that DDGS could be included at a rate of up to 60% using twin-screw extrusion, and that viable pelleted floating feeds can be produced.     

Effect of Fractionation of Distillers Dried Grains With Solubles (DDGS) on Pelleting Characteristics of Broiler Diets

Recently, the Elusieve process, a combination of elutriation (air classification) and sieving (screening) was developed to separate fiber from distillers dried grains with solubles (DDGS) to increase DDGS utilization in nonruminant (poultry and swine) diets. Elusieve process produces three products: 1) Pan DDGS, with 5% higher protein content than conventional DDGS, which would be used at higher inclusion levels in broiler diets because of low fiber content; 2) Big DDGS, with nearly the same protein content as conventional DDGS, which would be used at same inclusion levels as conventional DDGS; and 3) Fiber product. The objective of this study was to determine and compare pellet‐mill throughput, power consumption, and pellet quality for broiler diets incorporating different levels (0, 10, and 20%) of conventional DDGS and DDGS products from Elusieve process. Poultry oil contents were lower (1.5–1.6%) in diets comprising Pan DDGS and diets without DDGS than in the other diets (2.2–3.1%). The feed throughput was not affected by inclusion levels or type of DDGS. Pellet quality (pellet durability index [PDI]) for diets comprising Pan DDGS (both 10 and 20% inclusion levels) was significantly better than PDI for diets comprising conventional DDGS, Big DDGS, and the diet without DDGS. Better pellet quality of diets comprising Pan DDGS could be due to lower quantity of poultry oil used as well as compositional characteristics such as low fiber and high protein. Diets with Big DDGS had similar pelleting characteristics to those with conventional DDGS. Pellet quality deteriorated at higher inclusion levels of conventional DDGS, Big DDGS, and Enhanced DDGS. Considering that Pan DDGS would be included at higher inclusion levels in broiler diets, superior pellet quality of diets comprising Pan DDGS is beneficial.     

Modeling Distillers Dried Grains with Solubles (DDGS) Mass Flow Rate as Affected by Drying and Storage Conditions

Ethanol production in 2015 was over 15 million gallons in the United States, and it is projected to increase in the next few years to meet market demands. With the continued growth in the ethanol industry, there has been enormous expansion in distillers grains production. Because the local market for distillers dried grains with solubles (DDGS) is often saturated, it is essential to transport DDGS long distances, across the United States and to international markets. Caking and agglomeration of DDGS particles in hoppers and other storage structures are typical during transportation. The current study deals with DDGS prepared by combining condensed distillers solubles (CDS) with distillers wet grains and then drying at varying temperatures. DDGS was stored in conical hoppers under varying ambient temperature, consolidation pressure, and time conditions. We investigated the effects of CDS (10, 15, and 20% wb), drying temperature (100, 200, and 300°C), drying time (20, 40, and 60 min), cooling temperature (0, 25, and 50°C), consolidation pressure (0, 1.72, and 3.43 kPa), and consolidation time (0, 3, and 6 days) levels on various flow parameters. To examine these factors, Taguchi's experimental design with an L ₁₈ orthogonal array was implemented. Response surface modeling yielded mass flow rate = f (Hausner ratio, angle of repose) with R ² = 0.99, and it predicted moisture content for good, fair, and poor flow. Results showed that drying temperature, drying time, and cooling type were the main factors in predicting mass flow rate. The Johansson model for predicted mass flow rate was calibrated with experimental data, and a new parameter, compressibility factor, with a value of 0.96 g²/(min cm³), was determined to quantify the divergence of compressible and cohesive materials (such as DDGS) for free‐flowing bulk solids. Thus, the predicted models may be beneficial for quantitative understanding of DDGS flow.     

Artificial Neural Network Modeling of Distillers Dried Grains with Solubles (DDGS) Flowability with Varying Process and Storage Parameters

Neural network (NN) modeling techniques were used to predict flowability behavior of distillers dried grains with solubles (DDGS) prepared with varying levels of condensed distillers solubles (10, 15, and 20%, wb), drying temperatures (100, 200, and 300°C), cooling temperatures (–12, 25, and 35°C), and storage times (0 and 1 month). Response variables were selected based on our previous research results and included aerated bulk density, Hausner ratio, angle of repose, total flowability index, and Jenike flow index. Various NN models were developed using multiple input variables in order to predict single‐response and multiple‐response variables simultaneously. The NN models were compared based on R², mean square error, and coefficient of variation obtained. In order to achieve results with higher R² and lower error, the number of neurons in each hidden layer, the step size, the momentum learning rate, and the number of hidden layers were varied. Results indicate that for all the response variables, R² > 0.83 was obtained from NN modeling. Compared with our previous studies, NN modeling provided better results than either partial least squares modeling or regression modeling, indicating greater robustness in the NN models. Surface plots based on the predicted values from the NN models yielded process and storage conditions for favorable versus cohesive flow behavior for DDGS. Modeling of DDGS flowability using NN has not been done before, so this work will be a step toward the application of intelligent modeling procedures to this industrial challenge.     

Selected Factors Affecting Crude Oil Analysis of Distillers Dried Grains with Solubles (DDGS) as Compared with Milled Corn

With increasing production of distillers dried grains with solubles (DDGS), both fuel ethanol and animal feed industries are demanding standardized protocols for characterizing quality. AOCS Approved Procedure (Am 5‐04) was used for measuring crude oil content in milled corn and resulting DDGS. Selected factors, including sample type (milled corn, DDGS), sample origin (ethanol plant 1, 2, 3), sample particle size (original matrix, <0.71 mm, <0.50 mm mesh opening; the last two materials were obtained by grinding and sieving), solvent type (petroleum ether, hexane), extraction time (30, 60 min), and postextraction drying time (30, 60 min) were investigated by a complete factorial design. For milled corn, only sample origin and extraction time had significant effects (P < 0.05) on crude oil values measured, but for DDGS, besides those two factors, sample particle size, solvent type, and drying time also had significant effects. Among them, the particle size of DDGS had the most effect. On average, measured oil content in DDGS ranged from 11.11% (original matrix) to 12.12% (<0.71 mm) and to 12.55% (<0.50 mm). For measuring the crude oil content of DDGS, particle size reduction, 60 min of extraction, and 60 min of drying are recommended. Regardless of the underlining factors, the method was very repeatable (standard errors <0.05). The observed particle size effect on crude oil analysis of DDGS suggests the need for similar confirmations using other analytical methods.     

Association of Starch Granule Proteins with Starch Ghosts and Remnants Revealed by Confocal Laser Scanning Microscopy

Starch suspensions (0.25%) were gelatinized to 70 and 100°C, and starch ghosts (defined as gelatinized starch granule envelopes after the majority of internal starch polymers have been released) and remnants were collected by centrifugation and washed with water. Protein was revealed in isolated gelatinized normal starch ghosts using confocal laser scanning microscopy and a protein‐specific dye that fluoresces only after reaction with primary amines in protein. This technique eliminates background interference from residual dye. Observation of fluorescent‐labeled protein in the starch ghosts at different optical depths of field revealed that protein was concentrated in the envelopes of swollen, gelatinized potato, maize, and wheat starch ghosts. Only traces of protein were found in gelatinized starch granule remnants of waxy maize and amylose‐free potato starches after they were heated to 100°C, indicating that the proteins observed in gelatinized normal maize starch were largely granule‐bound starch synthase (GBSS). Moreover, fragility of the gelatinized waxy and amylose‐free starch granule remnants might be caused in part by the lack of GBSS. Gel electrophoresis of proteins in starch ghosts confirmed that GBSS in potato and maize was tightly associated with the starch ghosts. The study provides a structural explanation for a role of granule‐associated proteins in maintaining the integrity of starch ghosts and remnant structures, and their consequent effect on paste rheology.     

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

Piling Dried Distillers's 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 (d_gw) increased from the core of the pile to the periphery. Of all the nutrient composition tested, only crude protein and moisture correlated with particle size. While the correlation of crude protein with particle size was not consistent and clearly discernible in all the piles sampled in both the bench‐scale and plant studies, the correlation of particle size with moisture showed a strong positive correlation. Based on these findings, we recommend the development of a standard sampling protocol following good sampling practices for bulk granular solids.     

Effects of Different Mill Types on Ethanol Production Using Uncooked Dry‐Grind Fermentation and Characteristics of Residual Starch in Distiller's Dried Grains (DDG)

This study aimed to investigate impacts of milling methods on ethanol production using an uncooked dry‐grind (cold fermentation) process and characterize residual starch in the distiller's dried grains (DDG) coproduct. Four corn lines with different chemical compositions were ground with cyclone, ultra‐centrifugal, or hammer mills equipped with a screen of 0.5 mm opening and used for the cold fermentation process. Greater starch hydrolysis and ethanol yield were obtained from cyclone‐milled corn, resulting from larger damaged starch contents and smaller particle sizes of the ground corn. Corn grains and ground corn after five‐month storage showed less starch hydrolysis than the freshly ground counterpart. Residual starch (2.8–8.0%) with large proportions of intact amylopectin contents (up to 42.5%) was found in the DDG from all types of milling. The results suggested that the entrapment of starch granules in ground corn and a low activity of amylolytic enzymes at a high ethanol concentration were accountable for the remaining of starch in the DDG.     

Measurement and Comparison of Glass Transition and Sticky Point Temperatures of Distillers Dried Grains with Solubles (DDGS) with Varying Condensed Distillers Solubles (CDS) and Drying Temperature Levels

Distillers dried grains with solubles (DDGS) is the main coproduct of the U.S. fuel ethanol industry and has significantly impacted the livestock feed markets in recent years. Particle agglomeration and subsequent flowability problems during storage and transport are often a hindrance, a nuisance, and expensive. This paper aims at characterizing the glass transition (T_g) and sticky point (T_s) temperatures of DDGS samples prepared with varying condensed distillers solubles (CDS) levels (10, 15, and 20%, wb), drying temperatures (100, 200, and 300°C), and moisture contents (0, 10, and 20%, db), and it discusses implications on DDGS flowability behavior. Distillers wet grains were combined with specified levels of CDS and dried in a convection‐style laboratory oven to produce DDGS. Subsequently, predetermined amounts of water were added to the DDGS to achieve desired moisture content levels. To determine T_g (°C), a differential scanning calorimeter was used, whereas T_s (°C) was determined through a novel technique with a rheometer. Results indicated high correlations between observed T_s and observed T_g (R² = 0.87) data for DDGS samples. Also, the empirical model for predicted T_g = f (drying temperature, CDS level, and moisture content) based on the Gordon–Taylor model showed favorable R² (0.74). Stickiness of DDGS increased with an increase in moisture content, indicating flow problems resulting from moisture. It was found that drying temperatures and CDS levels each had significant effects on T_g and T_s as well.     

Single‐Screw Extrusion Processing of Distillers Dried Grains with Solubles (DDGS)‐Based Yellow Perch (Perca flavescens) Feeds

This study was conducted to investigate the production of balanced diets for juvenile yellow perch (Perca flavescens) feeds. Six isocaloric (≈3.21 kcal/g), isonitrogenous (30.1 ± 0.4% db) ingredient blends were formulated with 0, 10, 20, 30, 40, and 50% distillers dried grains with solubles (DDGS), and appropriate amounts of soybean meal, fish meal, vitamins, and minerals. Extrusion cooking was performed using a laboratory‐scale single‐screw extruder at a constant barrel temperature profile of 40–90–100°C, and a constant screw speed of 230 rpm (24.1 rad/sec). The mass flow rate was determined during processing; it generally increased with progressively higher DDGS content. Additionally, moisture content, water activity, unit density, expansion ratio, compressive strength, compressive modulus, pellet durability index, water stability, and color were extensively analyzed to quantify the effects of DDGS content on the physical properties of the resulting extrudates. Significant differences (P < 0.05) between blends were observed for color and water activity for both the raw material and extrudates, respectively, and for the unit density of the extrudates. There were significant changes in brightness (L), redness (a), and yellowness (b) among the final products when increasing the DDGS content of the blends. Expansion ratio and compressive strength of the extrudates were low. On the other hand, all blends showed high pellet durability (PDI ≥ 96.18%). Overall, it was ascertained that DDGS could be successfully included at rates of <50%, and that each of the ingredient blends resulted in viable, high quality extrudates.     

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.     

Development and Utilization of Reflectance Confocal Laser Scanning Microscopy to Locate Reaction Sites in Modified Starch Granules

A new method of locating reaction sites within modified starch granules was developed and applied. The method involves converting anionic groups introduced into starch granules into their silver salt form, reducing the silver cations to silver atoms, and locating the silver atoms by means of reflectance confocal laser scanning microscopy. The method was tested on three types of starch (normal maize, waxy maize, potato) containing two types of derivatizing groups (mono‐ and distarch phosphate ester groups and the 2‐hydroxy‐3‐sulfonylpropyl ether group). The method also revealed anionic sites in native granules, presumably due to proteins, ionic lipids, or native phosphate ester groups.     

Twin‐Screw Extrusion Processing of Rainbow Trout (Oncorhynchus mykiss) Feeds Using Various Levels of Corn‐Based Distillers Dried Grains with Solubles (DDGS)

Increasing demand for seafood products and rising demand for fish meal for commercial fish feeds is driving the search for effective alternative protein sources. Twin‐screw extrusion trials were conducted to study the production of nutritionally balanced feeds for rainbow trout fingerlings (Oncorhynchus mykiss). Six isocaloric (≈4.61 kcal/g) ingredient blends with a target protein content of >45% db were formulated with 0, 10, 20, 30, 40, and 50% distillers dried grains with solubles (DDGS) and other feed ingredients. The moisture contents of the diets were initially adjusted to 5–7% db, and then extruded at 250 rpm using dual 1.9 mm dies with varying amounts of steam (7.2–7.7 kg/hr) injected into the conditioner and water (4.3–6.5 kg/hr) into the extruder. Mass flow rates, moisture contents, and temperatures were measured during processing and moisture content, water activity, unit density, bulk density, expansion ratio, compressive strength, compressive modulus, pellet durability index, water stability, and color were analyzed to quantify the effects of varying DDGS content on the extrudate physical properties. Significant differences (P < 0.05) among the blends were observed for color and bulk density for both the raw and extruded materials, respectively, and for the unit density and pellet durability index of the extruded products. There were also significant changes in redness and yellowness, but only minor changes in brightness, among the final products with increasing DDGS content. The compressive strength of the extrudates increased significantly with increasing DDGS. Expansion ratio of all pellets was low. All extruded diets achieved very good water stability.     

Functional Attributes of Proteins Withdrawn from Different Stages of a Commercial Ethanol Fuel/Distillers Dried Grains with Solubles Process Using a Wheat Feedstock

The functional attributes of proteins withdrawn from different stages of a commercial ethanol fuel/distillers dried grains with solubles (DDGS) process that used a wheat feedstock were investigated. Specifically, protein coproducts were examined postliquefaction (PL), postdistillation (PD), and postdrying (DDGS) and related to those from the native wheat feedstock (WF). Water hydration, oil holding, foaming, and emulsifying properties of all materials were assessed. The WF and the PL coproduct showed similar water hydration capacities (WHCs), ranging between 80 and 110%, whereas WHCs for the PD and DDGS coproducts were significantly higher (ranging between 264 and 356%). WHC for all products was found to be independent over the pH range of 2.00–10.00. A similar trend was found for the oil holding capacities, for which both WF and PL materials showed lower values (≈120%) than both the PD (203%) and DDGS (171%) materials. Foam capacity and stability for the WF were found to be 32.8 and 61.4%, respectively, whereas no coproducts were foam forming. Emulsion stability decreased from ≈45% for the WF to <10% in all other materials. Findings indicated that initial changes to the protein's functional attributes occurred in the PL stage of ethanol/DDGS processing.