User Handbook
Physical & Chemical
Characteristics of DDGS
Physical & Chemical
Characteristics of DDGS

08 - Physical & Chemical Characteristics of DDGS
1
Physical & 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


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.

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


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/ft
3
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/ft
3
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