Lecture 1

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


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


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


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


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



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)


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


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)


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


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


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


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

Lecture 1

Documents

Transcript of Lecture 1