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User HandbookPhysical & ChemicalCharacteristics of DDGSPhysical & ChemicalCharacteristics of DDGS 08 - Physical & Chemical Characteristics of DDGS 1Physical & Chemical Characteristics of U.S. DDGS Physical and chemical characteristics of distiller’s dried grains with solubles (DDGS) vary among sources and can influence its feeding value and handling characteristics. These characteristics include color, smell, particle size, bulk density, pH, flowability, shelf life stability and hygroscopicity. Color Color of DDGS can vary from being very light yellow in color to being very dark brown in color. Differences in color among DDGS sources are influenced by; • the natural color of the feedstock grain being used, • the amount of solubles added to grains before drying, • drying time, and drying temperature. The color of corn kernels can vary among varieties and has some influence on final DDGS color. Corn-sorghum blends of DDGS are also somewhat darker in color than corn DDGS because of the bronze color of many sorghum varieties. When a relatively high proportion of solubles are added to the mash (grains fraction) to make DDGS, the color becomes darker. Noll et al. (2006) conducted a study where they evaluated color in batches of DDGS where approximately 0, 30, 60 and 100% of the maximum possible of syrup was added to the mash before drying. Actual rates of solubles addition to the mash were 0, 12, 25 and 42 gallons/minute. As shown in Table 1, increasing solubles addition rate to the mash resulted in a decrease in L* (lightness of color) and b* (yellowness of color), with an increase in a* (redness of color). Similar results were also reported by Ganesan et al. (2005). Table 1. The Effect of the Rate of Solubles Addition to Mash on Color Characteristics of DDGS 0 gal/min 12 gal/min 25 gal/min 42 gal/min Pearson Correlation P Value Color (CIE Scale) L* 59.4 56.8 52.5 46.1 - 0.98 0.0001 a* 8.0 8.4 9.3 8.8 0.62 0.03 b* 43.3 42.1 40.4 35.6 - 0.92 0.0001 Adapted from Noll et al. (2006). Dryer temperatures in dry-grind ethanol plants can range from 127 to 621º C. The amount of time DDGS spends in the dryer also influences the color. In general, the higher the dryer temperature and the longer DDGS remains in the dryer, the darker the resulting DDGS will be. Smell High quality DDGS has a sweet, fermented smell. DDGS that has a burned or smoky smell has been overheated. 08 - Physical & Chemical Characteristics of DDGS 2 Particle Size, Bulk Density and pH Particle size and particle size uniformity of feed ingredients are important considerations of livestock and poultry nutritionists when selecting sources and determining the need for further processing when manufacturing complete feeds or feed supplements. Particle size affects: 1. Nutrient digestibility – as particle size is reduced, nutrient digestibility and feed conversion is improved. This is due to the increasing amount of surface area of an ingredient that is exposed and available for digestive enzymes to act upon. 2. Mixing efficiency – a more uniform particle size in a mixture of ingredients will reduce mixing time in order to achieve a uniformly distributed mix of ingredients in a complete feed. 3. Amount of ingredient segregation during transport and handling – particle and ingredient segregation (separation) occurs when particles of different sizes and bulk densities are blended together and transported or handled. 4. Pellet quality – is often defined as the hardness of the pellet and percentage of fines in the complete feed after pelleting. For corn-soybean meal based diets, a low mean particle size (400 microns) generally results in a higher quality pellet (less % fines). 5. Bulk density – is a measure describing the weight of an ingredient per unit volume. In general, bulk density can be increased by reducing particle size to increase the weight of a feed ingredient or complete feed per unit of volume. 6. Palatability and sorting of meal or mash diets – depending on the animal, a finely ground, powdery feed will reduce feed intake and cause bridging in feeders and storage bins. Extremely coarsely ground feeds can also reduce palatability. 7. Incidence of gastric ulcers – in swine, the incidence of gastric ulcers increases as the mean particle size of the diet is reduced. Bulk density is an important factor to consider when determining the storage volume of transport vehicles, vessels, containers, totes and bags. Bulk density affects transport and storage costs. Low bulk density ingredients have higher cost per unit of weight. It also affects the amount of ingredient segregation that may occur during handling of complete feeds. High bulk density particles settle to the bottom of a load during transport, whereas low bulk density particles rise to the top of a load. Several unpublished studies have been conducted at the University of Minnesota to compare particle size and bulk density among DDGS sources. The first study was conducted during the summer of 2001 where representative samples of DDGS (4.5 kg) were obtained from 16 ethanol plants in Minnesota, South Dakota and Missouri. From these samples, a 200 gram subsample of DDGS from each plant was screened through five U.S. sieves and the weight of the DDGS not filtering through each screen was determined and recorded. The fine particles that filtered through all screens were collected in the pan and weighed. The U.S. sieve numbers and their corresponding size of screen openings (microns) were #10, #16, #18, #20 and #30 representing 2000, 1180, 1000, 850 and 600, respectively. The size of DDGS particles collected in the pan was less than 600 microns. The weights of DDGS collected on each screen were then used to calculate the percentage of weight of each fraction of the total separated. In addition to determining the average particle size (geometric mean), the coefficient of variation (CV) and 08 - Physical & Chemical Characteristics of DDGS 3standard deviation (SD) of particle size within and among ethanol plants were calculated. These results are shown in Table 3. Bulk density (lbs/cubic foot) was determined by filling a one quart container and weighing the amount of DDGS to fill the container (results shown in Table 3). Samples were also visually evaluated for color and the presence of “syrup balls.” The average particle size among the 16 ethanol plants was 1,282 microns (SD = 305, CV= 24%), and ranged from 612 microns in plant 6 to 2,125 microns in plant 15. Thus, there is considerable variation in average particle size of DDGS originating from these modern ethanol plants. As a point of reference, the target mean particle size for meal or mash diets for swine and poultry is 600-800 microns. Only plants 6 and 7 were close to this target range. All other plants produced coarser DDGS particles suggesting that further grinding of DDGS may be warranted to reduce the mean particle size, improve particle size uniformity and optimize nutrient digestibility of DDGS in a complete mixed feed. Plant 15 had the highest mean particle size (2125 microns). Ethanol plants that produced DDGS with high amounts of syrup balls tended to have a higher mean particle size. Bulk density averaged 35.7 lbs/cubic foot (SD = 2.79, CV = 7.8%), but ranged from 30.8 to 39.3 lbs/cubic foot. However, the correlation between mean particle size and bulk density was surprisingly very low (r = 0.05) which may be due to the variable amounts of syrup balls among the samples collected. Table 3: Mean and Variation of Particle Size Among Ethanol Plants and Bulk Density of DDGS in 2001 Plant Particle Size Mean Standard Deviation Bulk Density CV % 68% of the particles will fall between: 1 1398 2.32 36.3 0.17 603 3243 2 1322 2.00 39.2 0.15 661 2644 3 1425 1.62 36.8 0.11 880 2309 4 1370 1.84 36.3 0.13 745 2521 5 1255 1.68 33.5 0.13 747 2108 6 612 2.75 39.3 0.45 223 1683 7 974 2.15 36.1 0.22 453 2094 8a 1258 1.70 33.7 0.14 740 2139 8b 1142 1.84 30.8 0.16 621 2101 9 1337 1.78 31.8 0.13 751 2380 10 1488 1.62 38.2 0.11 919 2411 12 1235 1.75 31.4 0.14 706 2161 13 1198 1.87 35.9 0.16 641 2240 14 1229 2.09 39.2 0.17 588 2569 15 2125 1.56 37.6 0.07 1362 3315 16 1148 2.25 35.1 0.20 510 2583 Average 1282.25 1.93 35.7 0.15 697 2406 Two additional DDGS nutrient analysis and physical characteristics surveys were conducted by researchers at the University of Minnesota in 2004 (34 samples from ethanol plants in 11 different states) and 2005 (35 samples). As shown in Tables 4 and 5, average particle ranges 08 - Physical & Chemical Characteristics of DDGS 4were 665-737 µm, but the range in particle size is extremely large 73 to 1217 µm. The pH of DDGS sources averages 4.1 but can range from 3.6-5.0. Table 4: Particle Size, Bulk Density, and pH of 34 DDGS Sources Analyzed in 2004. Average Range SD CV, % Particle size, µm 665 256 - 1087 257.48 38.7 Bulk density, lbs/ft3 31.2 24.9 – 35.0 2.43 7.78 pH 4.14 3.7 – 4.6 0.28 6.81 Table 5: Particle Size, Bulk Density, and pH of 35 DDGS sources analyzed in 2005. Average Range SD CV, % Particle size, µm 737 73 – 1217 283 38.0 Bulk density, lbs/ft3 25.2 22.8 – 31.5 8.6 34.2 pH 4.13 3.6 – 5.0 0.33 7.91 Flowability Flowability is defined as the ability of granular solids and powders to flow during discharge from transportation or storage containments. Flowability is not an inherent natural material property, but rather a consequence of several interacting properties that simultaneously influence material flow (Rosentrater, 2006). Flowability may be affected by a number of synergistically interacting factors including product moisture, particle size distribution, storage temperature, relative humidity, time, compaction pressure distribution within the product mass, vibrations during transport and/or variations in the levels of these factors throughout the storage process (Rosentrater, 2006).Other factors that may affect flowability include chemical constituents, protein, fat, starch and carbohydrate levels as well as the addition of flow agents. Under certain conditions, DDGS can exhibit poor flowability (AURI and MN Corn Growers Assoc., 2005). (National Corn-to-Ethanol Research Center, 2005). “Clumping” or “caking” can occur as a result of loading DDGS into trucks, rail cars or containers if it has not been cooled and “cured” properly before loading. This often causes flowability problems and difficulty unloading DDGS. Reduced flowability and bridging of DDGS in bulk storage containers and transport vehicles has limited the acceptability of some DDGS sources for some customers and rail car owners. Research studies are being conducted to determine the factors that cause flowability problems and potential solutions to reduce these problems The Agricultural Utilization Research Institute and the Minnesota Corn Growers Association (2005) studied a limited number of DDGS samples under laboratory conditions. They reported that relative humidity greater than 60% seemed to reduce flowability of a DDGS sample, which is likely due to the product’s ability to absorb moisture. While moisture from both the environment and the DDGS itself likely influence flowability, many other factors have been suggested as possible controllers of flowability such as particle size, content of solubles, dryer temperature, moisture content at dryer exit, and others. Interventions to improve flowability of DDGS have been limited to trial and error approaches within ethanol plants. Some of these interventions involve regulating the completeness of fermentation, adjusting moisture content and changing particle size. However, results from these studies have not been published in the scientific literature. Iowa Limestone Company Resources (2003) investigated the effectiveness of including 2% calcium carbonate in DDGS as a 08 - Physical & Chemical Characteristics of DDGS 5flowability agent. They reported a 6-12% reduction in the angle of repose determined in a laboratory setting when calcium carbonate was added to DDGS after drying. Determination of flowability under practical industry conditions was not attempted in their study. Because moisture and relative humidity seem to play an important role in flowability of DDGS, some have suggested that the use of zeolites and/or grain conditioners may control moisture migration in DDGS. However, no controlled studies of this concept have been reported. Since flow behavior of a feed material is multidimensional, there is no single test that completely measures the ability of a material to flow (Rosentrater, 2006). Shear testing equipment is the primary equipment used to measure the strength and flow properties of bulk materials. They also measure the amount of compaction as well as the bulk strength of materials (Rosentrater, 2006). Another approach for measuring the flowability of granular materials involves measuring four main physical properties: angle of repose, compressibility, angle of spatula, and coefficient of uniformity (e.g. cohesion) (Rosentrater, 2006). Shelf Life Stability Since the moisture content of DDGS is usually between 10-12%, there is minimal risk of spoilage during transit and storage unless water leaks into transit vessels or storage facilities. No research studies have been conducted to demonstrate that preservatives and mold inhibitors are necessary to prevent spoilage and extend shelf life of DDGS. Unless the moisture content of DDGS exceeds 12-13%, the shelf life of DDGS appears to be many months. In a U.S. Grains Council field trial, DDGS was shipped from an ethanol plant in South Dakota in a 40 ft. container to Taiwan. Upon arrival in Taiwan, DDGS was put into 50 kg bags and stored in a covered steel pole barn for 10 weeks during the course of the dairy feeding trial on a commercial dairy farm located about 20 km south of the Tropic of Cancer. Environmental temperatures averaged more than 32 °C and humidity was in excess of 90% during this storage period. Samples of DDGS were collected upon arrival at the farm and again after the 10 week storage period. There was no change in peroxide value (measure of oxidative rancidity of oil) during this trial. Presumably, this may be due to the high amount of natural antioxidants present in corn which are further increased during a heating process. Hygroscopicity Limited information exists regarding the hygroscopicity (ability to attract moisture) of DDGS. However, it appears that under humid climatic conditions, DDGS will increase in moisture content during long-term storage. The U.S. Grains Council sponsored a broiler field trial in Taiwan, where moisture content of DDGS was monitored during storage at a commercial feed mill from March 16 to June 10, 2004. A random sample of DDGS was obtained weekly from storage at the feed mill and analyzed for moisture over a 13-week storage period. Moisture content of DDGS increased from 9.05% at the beginning of the storage period to 12.26% at the end of the 13-week storage period (Table 6). As expected, crude protein concentration did not change in DDGS and no aflatoxin was present initially or at the end of the storage period. 08 - Physical & Chemical Characteristics of DDGS 6Table 6: Laboratory analysis results for moisture, crude protein and aflatoxin of DDGS during storage at the commercial feed mill in Taiwan. Sample Date Sample Number Moisture, % Crude protein, % Aflatoxin, ppb 16-Mar-04 9.05 27.60 0.00 17-Mar-04 10.17 27.61 0.00 24-Mar-04 1 10.65 27.59 0.00 31-Mar-04 2 10.70 27.63 0.00 7-Apr-04 3 10.71 27.62 0.00 14-Apr-04 4 10.76 27.73 0.00 21-Apr-04 5 10.93 27.71 0.00 28-Apr-04 6 11.02 27.62 0.00 5-May-04 7 11.28 27.54 0.00 12-May-04 8 11.16 27.61 0.00 19-May-04 9 11.70 27.63 0.00 27-May-04 10 11.88 27.61 0.00 3-Jun-04 11 12.13 27.50 0.00 10-Jun-04 12 12.26 27.53 0.00 References Agricultural Utilization Research Institute (AURI), and Minnesota Corn Growers Association. 2005. Distiller’s Dried Grains Flowability Report. Waseca, MN. Cromwell, G.L., K.L. Herkleman, and T.S. Stahly. 1993. Physical, chemical, and nutritional characteristics of distillers dried grains with solubles for chicks and pigs. J. Anim. Sci. 71:679-686. Ferrer, E., A. Algria, Farre’, G. Clemente, and C. Calvo. 2005. Fluorescence, browning index, and color in infant formulas during storage. J. Agric. Food Chem. 53:4911-4917. Noll, S., C. Parsons, and B. Walters. 2006. What’s new since September 2005 in feeding distillers co-products to poultry. Proceedings from the 67th Minnesota Nutrition Conference & University of Minnesota Research Update Session: Livestock Production in the New Millenium, St. Paul, MN. pp. 149-154. Ganesan, V. K.A. Rosentrater, and K. Muthukumarappan. 2005. Effect of moisture content and soluble levels on the physical and chemical properties of DDGS. ASAE paper No. 056110. St. Joseph, MI. ILC Resources. 2003. CaCO3 treatment of DDGS. In house study provided by R.H. Bristol. National Corn to Ethanol Research Center (NCERC). 2005. Website at: www.ethanolresearch.com/. Accessed June 13, 2006. Pederson, C., A. Pahm, and H.H. Stein. 2005. Effectiveness of in vitro procedures to estimate CP and amino acid digestibility coefficients in dried distillers grain with solubles by growing pigs. J. Anim. Sci. (Suppl. 2) 83:39. Rosentrater, K.A. 2006. Understanding Distiller’s grain Storage, Handling, and Flowability Challenges. Distiller’s Grains Quarterly. First Quarter 2006. pp. 18-21. Shurson, J., S. Noll, and J. Goihl. 2005. Corn by-product diversity and feeding value to non-ruminants. Proc. MN Nutr. Conf. pg. 50 – 68. University of Minnesota. 2005. DDGS website at: www.ddgs.umn.edu. Accessed October 3, 2006. 08 - Physical & Chemical Characteristics of DDGS 7The U.S. Grains Council (USGC) provides these feeding recommendations to assist potential buyers in understanding generally-accepted feeding levels. However, all rations for specific herds should be formulated by a qualified nutritionist. The USGC has no control over the nutritional content of any specific product which may be selected for feeding. Potential buyers should consult an appropriate nutritionist for specific recommendations. USGC makes no warranties that these recommendations are suitable for any particular herd or for any particular animal. The USGC disclaims any liability for itself or its members for any problems encountered in the use of these recommendations. By reviewing this material, buyers agree to these limitations and waive any claims against USGC for liability arising out of this material. . Scale) L* 59.4 56.8 52.5 46.1 - 0.98 0.0001 a* 8.0 8.4 9.3 8.8 0.62 0 .03 b* 43.3 42.1 40.4 35.6 - 0.92 0.0001 Adapted from Noll et al. (2006). Dryer. Density CV % 68% of the particles will fall between: 1 1398 2.32 36.3 0.17 603 3243 2 1322 2.00 39.2 0.15 661 2644 3 1425 1.62 36.8 0.11 880 2309 4 1370