Post on 20-Oct-2015
description
Post-Harvest Grain Handling
Quality Grain Management
Lecture 1
Grain Quality Factors
Lecture 1
Study Questions Lecture 1
(1) What are three categories of grain quality properties?
(2) What are the primary grain properties in each category?
(3) How does the moisture content affect the friction coefficient and angle of repose?
(4) What is the difference between the piling and funneling angle of repose?
(5) What are the primary flow patterns of grain during emptying from a bin?
Grain Quality
Grain quality is affected by:
Variety and quality of seeds selected
Agronomic practices
Environment during the growing season
Timing of harvest and system used
Post-harvest handling & drying treatment
Storage structures and practices
Transportation system and procedures
Grain Quality
Grain Quality Factors Affecting End-use:
Test weight (bulk density)
Nutritive value
Starch content and quality
Oil content and recovery
Protein content and quality
Viability and germination
Kernel traits that affect milling
Grain Quality Properties
Physical
Thermal
Chemical
Response to biological processes
Physical Grain Properties
Structure kernel morphology
dimensions length, width, thickness
equivalent spherical diameter
Weight single kernel, 1000-kernel weight
Density single kernel
bulk
Physical Grain Properties
Hardness
Porosity
resistance to airflow
Coefficient of Friction
Angle of internal friction
Terminal velocity
Angle of Repose
Color
Grain Structure
Kernel morphology
Dimensions
Affects:
Drying rate
Dryer design
Resistance of bulk grain to airflow
Structure Kernel Morphology
Three main components of grain kernels:
Wheat Rice Corn
Pericarp
Endosperm
Germ
Pericarp
Germ
Endosperm
Structure Kernel Morphology
Weight Proportions of Principal Parts of Grain Kernels
Grain Pericarp (%)
Germ (%)
Endosperm (%)
Corn 5 7 10 12 82 84
Soybeans* ~9% ~2% ~90%
Rice (brown) 5 7 3 4 89 92
Wheat 13 15 2 3 82 - 85
Sources: Brooker et al. (1992)
* Markley (1950)
Structure Dimensions
Intermediate Diameter
Major Diameter
Minor Diameter
Structure Dimensions
Major Diameter (Length) the longest dimension of the maximum
projected area
Minor Diameter (Thickness) the shortest dimension of the minimum
projected area
Intermediate Diameter (Width) the minimum diameter on the maximum
projected area, often assumed to be equal to the longest diameter of the minimum projected area
Structure Dimensions
Influenced by:
Growing season and location
Weather
Solar Radiation Index, Rain frequency, Rain Volume, timing
Cultural practices
Irrigation, Fertilization, Pesticide Use vs
Sustainable Agriculture
Variety
Structure Dimensions
Grains
Major Diameter (mm)
Intermediate Diameter (mm)
Minor Diameter (mm)
Avg. Std. Dev. Avg. Std. Dev. Avg. Std. Dev.
Corn
Wheat
Soybeans
Oats
Barley
Rye
12.01
6.02
7.29
10.84
8.76
6.65
1.52
0.41
0.66
1.65
1.19
0.69
8.15
2.79
6.43
2.67
3.15
2.21
0.71
0.37
0.51
0.37
0.38
0.25
5.18
2.54
5.38
2.03
2.51
2.11
1.00
0.08
0.20
0.33
0.38
0.25
Source: Edison and Brogan (1972)
Dimensions - Separation Intermediate sieve
(round holes)
Minor sieve
(slotted holes)
Dimensions - Separation Major cylinder or disc separators
Enlargement
Trough to Collect Smaller seeds
Cylinder With indents
Cylinder Separator
A
A
A portion of section A-A through the disk
A portion of the disk of a disk separator dots are holes into which the seeds can fall
Disc Separator
Structure Dimensions Equivalent spherical diameter
The diameter of a sphere having the same volume as the kernel.
Roundish seeds soybeans, sorghum, pulse/lintels
Elongated seeds corn, wheat, sunflower, rice, oats, barley, edible beans
Application:
Drying: moisture from the center of the kernel moves to the surface the larger the equivalent diameter, the slower the drying rate
shape also has an effect on drying
Weight
1000-Kernel Weight
The weight of 1000 grain kernels, usually determined as an appropriate multiple of the weight of 100-300 kernels counted and weighed
Affects:
Drying rate -- well correlated with kernel weight
Bulk density
Terminal velocity (weight, shape, surface texture) affects impact damage
* structural/floor & kernel-kernel impacts
Weight
2.9 325 330
20 28
33 125
15 27
77 167
12 33
32 40
0.0029
0.325 0.33
0.020 0.028
0.033 0.125
0.015 0.027
0.077 0.167
0.012 0.033
0.032 0.040
Canola
Corn (shelled)
Oats
Pulse
Rice
Soybeans
Sorghum
Wheat
Kernel Weight
gm per 1000 seeds
Kernel Weight
gm per seed
Grain Type
Sources: Stroshine (2001); Brooker et al. (1992)
Density
Particle density weight per unit volume of an individual kernel
Bulk density weight per total volume occupied by many
kernels
Affects: Storage volume
Grain velocity in continuous-flow grain dryer
Density
Source: Stroshine (2001)
1.13 1.33
1.10 1.15
1.27 1.30
0.95 1.06
1.08 1.15
1.11 1.12
1.13 1.18
1.22 1.26
1.29 1.30
Barley
Canola
Corn (shelled)
Oats
Pulse
Rice
Soybeans
Sorghum
Wheat
Kernel Density gm cm-3
Grain
618
669
721
412
662
579
772
721
772
Bulk Density
kg m-3
Bulk Density
lb/bu
48
52
56
32
46
45
60
56
60
Corn Hardness
The greater the proportion of translucent (hard) endosperm in the kernel, the greater the hardness
Affects: Breakage susceptibility
Dry milling quality
Porosity
The percentage of the total container or storage volume occupied by air versus grain inter-kernel/intergranual or interstice air void space
Affects:
Resistance of grain bulk to airflow
Intergranular air velocity
Heat exchange during drying and cooling
Porosity
39.5 57.6
38.0 42.0
47.6 55.5
46.5 50.4
33.8 36.1
36.8 37.0
40.1 42.6
Barley
Corn (shelled)
Oats
Rice
Soybeans/Pulse
Sorghum
Wheat
Porosity Percent Grain/Seed
Source: ASAE Standard (1988)
Coefficient of Friction Resistance to movement of kernels -- across a
structural surface (hopper floor, down spout, drag conveyor), or -- kernel to kernel flow down grain surface greatly affected by grain fines and trash
Affects:
Power requirement for conveying
Forces exerted on storage structure walls
Ease of unloading a structure
Velocity in downspouts
Example Truck Dump
Friction between the kernels and the truck bed affects the angle of elevation required to achieve grain flow from trucks and trailers
Coefficient of Friction Influenced by:
Material properties (including grain fines/trash)
Moisture content (significant variations)
Type of surface (steel vs concrete vs wood)
Surface conditions rust
oxidation
buildup of waxes/oils from kernels/seeds
Effect of Wheat Moisture Content on
Coefficient of Friction
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
15.9 15.0 13.0 11.2
Moisture Content (%)
Coef. of
Friction
Coef. ofFriction
Static Coefficients of Friction for Grains Source: Brubaker & Pos (1965); Chung et al. (1982)
Material Surface & Characteristics Moisture Coef.
contentBarley Concrete, wood float finish 12.3 0.52
Corn (shelled) Concrete, wood float finish 13.9 0.54
Concrete, plastic smooth finish 13.9 0.35
Wood, Douglas fir, grain par. 13.9 0.37
Galvanized sheet metal 13.9 0.37
Polyethylene 13.9 0.38
Teflon 13.9 0.12
Rubber 13.8 0.44
Material Surface & Characteristics Moisture Coef.
contentOats Concrete, wood float finish 13.0 0.44
Rice (rough) Galvanized sheet metal ~14. ~0.45
Soybeans Concrete, wood float finish 12.2 0.52
Wheat Concrete, wood float finish 11.2 0.51
Wood, Doughlas fir, grain par. 11.2 0.31
Wood, Bouglas Fir, grain perp. 11.2 0.35
Galvanized sheet metal 11.2 0.10
Galvanized sheet metal 15.0 0.27
Static Coefficients of Friction for Grains Source: Brubaker & Pos (1965, 1976)
Angle of Repose The angle of grain in reference to the flat
surface on which it is stored -- coefficient of friction, moisture, f.m./trash are major factors
Grain
Repose Angle
Surface
Angle of Repose
Piling (filling) Angle of Repose
The angle formed when grain is allowed to form a pile after flowing from a spout or conveyor outlet
Repose Angle
Grain
Surface
Grain Flow
Grain Flow
Repose Angle
Surface
Grain
Emptying (funneling) Angle of Repose
The angle formed when grain is being emptied from a storage structure
Angle of Repose Influenced by:
Internal friction
Moisture content
Particle size distribution
F.M. and trash
Affects:
Maximum depth of an outdoor pile -- bunker
Maximum height of peaked grain in a storage structure
Maximum size of transport conveyors needed
Angle of Internal Friction The relative motion among kernels is resisted by the
internal friction between kernels. The angle of internal friction is the angle whose tangent equals the internal coefficient of friction (24 - 34).
Influenced by: Moisture content
Shape & size of kernels
Seed or kernel surface texture
Affects: Angle of repose
Grain flow & pattern
Grain Flow Patterns
Funnel Flow
(Rat-holing)
Source: Stroshine (2001)
Mass Flow
(Plug Flow)
Grain Flow Pattern
17%
13%
10.6%
11%
Moisture Content
Sorghum
Flour
Wheat
Grain
< 17O
< 20O
< 15O
< 21O
Hopper Angle for Mass Flow
Source: Stroshine (2001)
Terminal Velocity When an object is dropped for a
sufficient distance, the force of gravity will accelerate the object until the drag force exerted by the air balances the gravitational force.
At that point the object falls at a constant velocity, which is called the terminal velocity
Terminal Velocity
Source: Garrett and Brooker (1965)
24.0 29.6
32.2 37.1
23.0 27.3
36.8 39.5
27.6 31.9
Barley kernels
Corn kernels
Oat kernels
Soybeans
Wheat kernels
Grain Terminal Velocity, vt
(m/s)
7.3 9.0
9.8 11.3
7.0 8.3
11.2 12.0
8.4 9.7
Terminal Velocity, vt
(ft/s)
Grain Quality Properties
Physical
Thermal
Thermal Grain Properties
Specific heat
The energy required to increase the temperature of a unit mass of grain by one degree
Thermal conductivity
A measure of how well the grain conducts heat the greater the thermal conductivity, the faster the rate of heat conduction
Values of Specific Heat and Thermal Conductivity
0.091
0.079
0.054
0.36
26.5
Shelled Corn
Wheat
Oats
Water
Steel
Type of Grain or Material
Specific Heat
Btu/hr ft F
0.48
0.40
0.45
0.998
0.11
Thermal Conductivity
Btu/lb F
Grain Quality Properties
Physical
Thermal
Chemical
Chemical Grain Properties Composition
Protein
Amino acid profile
Oil
Fatty acid profile
Starch
Starch type & extractability
Fiber
Moisture
Odor
Taste
Composition Chemical Composition of Grain at 14%
moisture content (w.b.)
Grain Protein (%)
Oil (%) Starch (%)
Fiber (%)
Corn 9.8 4.9 63.6 2.0
Rice (brown) 7.3 2.2 64.3 0.8
Soybeans 35.0 18.4
Wheat 10.6 1.9 69.7 1.0
Source: USDA; Brooker et al. (1992)
Composition
Moisture Contents (% w.b.) of Grain at Harvest and for Safe Storage
Grain Maximum Harvest Moisture
Optimum Harvest Moisture
Storage
6 12 months
Over 1 year
Corn 25 23 14.5 13
Rice (paddy) 38 22 14 13
Soybeans 20 15 13 12
Wheat 20 18 14 13
Source: Brooker et al. (1992)
Composition Moisture Distribution in Freshly
Harvested Corn Kernel
Kernel Part MC (% w.b.)
Whole kernel 36.0
Germ 48.2
Endosperm 30.7
Pericarp 52.6
Source: Brooker et al. (1992)
Odor
Objectionable Odors:
Musty
Sour
Commercially objectionable foreign odor
Grain Quality Properties
Physical
Thermal
Chemical
Response to biological processes
Grain Properties and Biological Processes
Grain varieties vary in susceptibility to:
insect damage
Bio-pesticidal transgenes for stored-product insect control is primarily an extension of the same for field crop insect control
fungal invasion
mycotoxin development
Grain Quality:
Uniformity
vs.
Variability
High Oil Corn Composition
Starch Protein Oil
HOC 1 56.6% 9.2% 4.0%
HOC 2 53.6% 8.6% 7.2%
Plot Avg. 55.2% 8.7% 6.1%
Composition of two high oil corn hybrids and averages for a test plot in Southern Indiana
(1997 data; 15% mc basis; Purdue GQ-33)
Soybean Composition
Grain Quality Properties The Highs
1. Kernel-to-kernel uniformity
2. Test weight (TW)
3. Milling yield & quality dry milling, wet milling, masa milling, flour milling
4. Oil content & recovery oilseed crushing
5. Protein content & quality
6. Starch content & quality
7. Nutritive value
8. Viability & germination
Grain Quality Properties The Lows
1. Kernel-to-kernel variability
2. Appropriate moisture content (MC) for safe storage and marketing
3. Foreign material (FM)
4. Discolored, heat-damaged (HD), shrunken and broken kernels (SBK)
5. Breakage susceptibility
6. Mold count & mycotoxin level
7. Insect damage & pesticide residue
8. Carcinogen content
Quality Grain is Job #1!
Summary Grain Quality Factors
(1) Although the definition of grain quality depends on the grain and its end use, grain quality properties are of the physical, chemical or biological type.
(2) High kernel-to-kernel uniformity and low kernel-to-kernel variability of grain quality properties is generally most important to end users.
(3) Managing and maintaining grain quality requires a systems approach because quality grains depend on seed selection, agronomic practices, environment during growth, timing and system of harvesting, post-harvest handling & drying treatment, storage structures and practices, and transportation system and procedures.
Study Questions Lecture 1
(1) What are three categories of grain quality properties?
(2) What are the primary grain properties in each category?
(3) How does the moisture content affect the friction coefficient and angle of repose?
(4) What is the difference between the piling and funneling angle of repose?
(5) What are the primary flow patterns of grain during emptying from a bin?
The development and updating of these lectures was made possible through support from:
Fulbright Commissions of the United States and Argentina
Purdue University Post-Harvest Education & Research Center
Department of Agricultural & Biological Engineering
Grain Elevator & Processing Society (GEAPS)
Kansas State University Department of Grain Science & Industry
International Grains Programs
Quality Grain Management
Effect of Wheat Moisture Content on
Coefficient of Friction
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
15.9 15.0 13.0 11.2
Moisture Content (%)
Coef. of
Friction
Coef. ofFriction