This document provides an overview of important engineering properties of agricultural crops including cereals, pulses, and oilseeds. It discusses various physical properties like size, shape, density, and thermal properties. It describes the structure and milling processes of various cereals like wheat, rice, and corn. It also discusses properties of pulses and common oilseeds and their uses. The document is intended to familiarize students with these engineering properties and how they influence the design of processing equipment.

1. 1
University Institute of Agriculture
sciences

2. University Institute of Agricultural Sciences
Dr.Ambika
Name of Topic: Chapter 2.5
Important Engineering properties such as
physical, thermal and aero & hydrodynamic
properties of cereals, pulses and oilseed, their
application in PHT equipment design and
operation
Lecture 5
DISCOVER . LEARN .
EMPOWER

3. Objectives
To acquaint students with principles of green house technology
To provide basic knowledge of types of green houses
3
To strengthen the understanding of basics of protected
cultivation.
To focus on principles of Green Technology
Course Outcome

4. Important Engineering properties such as physical, thermal and
aero & hydrodynamic properties of cereals, pulses and oilseed,
their application in PHT equipment design and operation
Engineering properties are the properties which are useful and necessary in the
design and operation of equipment employed in the field of agricultural processing.
They are also useful for design and development of other farm machinery. As
mentioned earlier unit operations such as cleaning, grading, drying, dehydration,
storage, milling, handling and transportation, thermal processing of foods are
among the important operations in agricultural processing. In these operations
while handling of grains and other commodities the properties which play and
important role are physical, mechanical, frictional, rheological, aero and
hydrodynamic, electrical and optical properties of the bio materials. Basic
information on these properties are of great importance and help for the
engineers, food scientists and processors towards efficient process and equipment
development. An attempt has been made to describe some of the engineering
properties usually encountered in postproduction handling of agricultural crops.

5. Physical properties
The physical properties such as size, shape, surface area, volume, density, porosity,
colour and appearance are important in designing particular equipment or
determining the behaviour of the product for its handling. Various types of cleaning
grading and separation equipment are designed on the basis of physical properties
of seeds such as size, shape, specific gravity, surface roughness, colour etc. For
designing an air screen grain cleaner, the shape and size of the grain determine the
shape and size of screen openings, angle of inclination and vibration amplitude and
frequency of screens. The density of the grains decides the size of screening
surface. The frontal area and related diameters and density are essential for
determination of terminal velocity of the grain.

6. Physical characteristics of raw, unprocessed, as well as
processed food materials include particle size and shape,
particle and bulk density, porosity, and surface area. The size
and shape of a raw food material can vary widely. The
variation in shape of a product may require additional
parameters to define its size. The size of spherical particles like
peas or cantaloupes is easily defined by a single characteristic
such as its diameter. The size of non-spherical objects like
wheat kernels, bananas, pears, or potatoes may be described
by multiple length measurements. The longest diameter
(major) and shortest diameter (minor) will adequately
describe the size of an ellipsoidal object such as grain kernel or
potato

7. •The shape of an irregular object can be
described by terms such as the following:
•Round- Approaching spheroid
•Oblate- Flattened at the stem end and apex
•Oblong- Vertical diameter greater than the
horizontal diameter
•Conic- Tapered toward the apex
•Ovate- Egg-shaped and broad at the stem end
Oblate- Inverted oblate Lopsided Axis
connecting stem and apex slanted
•Elliptical -Approaching ellipsoid

8. •Various formulas and methods have been
devised to estimate cross sections and other
characteristics of the materials. Roundness, as
defined by Mohsenin (1970), “is a measure of
the sharpness of the corners of the solid.”

9. Sphericity

10. Density
Density (ρ) of a material is the amount of that material occupying a certain
space and is expressed in units of mass per unit volume. Materials
consisting of particles or grains with interstitial air spaces have different
values of particle density and bulk density. Materials without internal air
spaces, such as fluids and solids, have equal particle and bulk density.
Particle density is the mass divided by the volume of the particle alone.
Bulk density is the mass of a group of individual particles divided by the
space occupied by the entire mass, including the air space. Density of food
materials is useful in mathematical conversion of mass to volume. The
grain industry determines the amount of agricultural grains by converting
the weight to volume (bushels). Even though grain marketing is done in
terms of bushels, grain weight, not actual bushels, is the property
measured. The density of processed products dictate the characteristics of
its container or package. Product density influences the amount and
strength of packaging material

11. Porosity and specific
gravity
Porosity
Porosity is the percentage of air between the particles compared to a unit
volume of particles. Porosity allows gases, such as air, and liquids to flow
through a mass of particles referred to as a packed bed in drying and
distillation operations. Beds with low porosity (low percentage air space)
are more resistant to fluid flow and thus are more difficult to dry, heat, or
cool. With high porosity, air flows easily through the bed, drying is fast, and
the power required by fans and pumps is low.
Specific gravity
The specific gravity is defined as the ratio of the mass of that product to the
mass of an equal volume of water at 4°C, the temperature at which water
density is greatest. A reference temperature other than 4°C may be used if
that temperature is explicitly specified with the specific gravity value.

12. CEREALS
Cereals are plants that yield edible grains.
They are consumed worldwide and make up a majority of the worlds calories and
50% of protein consumption.
Rice is the world’s most important food with wheat not far behind. Over 90% of
rice is grown in Asia where it is consumed.
In the U.S., corn is the leading grain but most is used for animal production while
wheat is used directly for human consumption.
Physical Characteristics of Grain
Starchy endosperm- main part of the grain or kernel.
Protective outer layers- bran or hull
Embryo or germ- typically located at the bottom of the kernel.

13. STRUCTURE OF CEREAL
GRAIN
Bran layer 14%: fibre,
vitamin B, calcium, iron.
Endosperm 84%:
Starch, protein, vitamin
B.
Germ 2%: protein, fat,
vitamins B & E, iron.

15. Milling of Cereal Grains
In most milling operations, the hulls are removed which are largely
indigestible by humans.
The dark-colored bran is also removed.
The germ, which is high in oil, is enzymatically active and under certain
conditions would be likely to produce a rancid condition in the grain.
Thus, the main component of interest is the starchy, proteinaceous
endosperm.
Since the bran is rich in B vitamins and minerals, it is a common practice to
add these back to processed grains from which they came. This is known as
“enrichment”.

16. Typically cereal grains contain a moisture of 10-14% if properly dried.
When the moisture content is higher than this, they must be dried or they may Mold or
rot in storage before they can be used.
Cereal grains contain about two-thirds carbohydrate, most is in the form of digestible
starches and sugars.
The operations of milling generally remove much of the indigestible fiber and fat
from these grains
when they are to be consumed for human food.

17. Wheat is classified into one of two types –
Hard wheat is higher in protein than soft and produces a stronger dough used for
bread- making. Soft wheat is better for batters and cake baking.
Wheat milling is basically a succession of pulverizing steps to break down the
endosperm.
Wheat

18. CONVENTIONAL WHEATMILLING
Milling is a progressive series of disintegrations followed by sieving. The
disintegrations are made by rollers set progressively closer and closer together.
The first rollers break open the bran and free the germ from the endosperm. The
second and third rollers further pulverize the brittle endosperm and flatten out the
semi plastic germ.
The flakes of bran and flattened germ are removed by the sieves under the first few
sets of rollers.

19. USES OF WHEAT FLOUR
The uses of wheat flour in the baking industry include the making of breads, sweet
doughs, cakes, biscuits, doughnuts, crackers and the like.
Another use of wheat flour and courser milled fractions of wheat are alimentary pastes
such as macaroni, spaghetti and other forms of noodles and pasta.
Alimentary pastes are mostly milled wheat flour and water. The wheat is usually hard
durum and is milled to yield course particles called semolina”.
Alimentary pastes may also contain eggs, salt and other minor ingredients.
They differ from bakery doughs in that alimentary pastes are not leavened.
Alimentary pastes are usually made with 100 parts wheat flour/ 30 parts water, mixed,
and extruded into thin sheets, cut into noodles or other shapes and then dried.

20. RICE Milling
Rice is unusual compared to other grains in that it is not ground into flours before consumption.
Worldwide, rice is primarily consumed as an intact grain.
The milling process is designed to remove only the outer bran layer and hull without breaking the kernel.
It is often used in the U.S. as a carbohydrate source for making beer because its bland flavor.
RICE MILLING
Rice milling begins with whole grains of rice being fed by machine between abrasive disks or
moving rubber belts.
These machines, known as shellers or hullers, do not crush the grains but instead rub the
outer layer of hull from the underlying kernels.
The hulls are separated from the kernels by jets of air and the kernels, known as brown rice,
move to another abrasive device called a rice-milling machine.

21. ENRICHMENT
Rice can be enriched in one of two ways;
1)Coat the polished rice with the enrichment mixture (thiamin, niacin and iron) and
then coat the grains with a waterproof film material.
2)Parboiling whole rice including the hulls, bran and germ in water for 10 hr at 70C.
This causes the B vitamins and minerals from the hulls, bran and germ to leach into the
endosperm. The rice is then dried, milled and polished. This is often referred to as
“converted rice”.

22. CORN
Corn is consumed as both whole kernels ( a vegetable) or as a flour.
Popcorn pops because the moisture expands upon heating and
explodes because it cannot escape.
Corn can be dry-milled like wheat or wet-milled.
Wet milling is popular and is used to make corn syrups and high
fructose corn syrup

23. GRAIN STRUCTURE OF CORN

24. WET MILLING OF CORN
In wet milling, corn kernels are placed in large tanks of warm water with generally an
acid and sulfur dioxide as a preservative.
The softened kernels are then run through an attrition mill to break up the kernels. The
pasty mass is then pumped to settling troughs. Here is where the oil rich germ floats to
the top, is skimmed off to be pressed for oil.
The watery slurry is then filtered to remove the hulls.

25. The watery slurry now containing the starch and protein fractions is passed
through high speed centrifuges to separate the heavier starch from the
lighter protein fraction.
The starch is dried to yield “corn starch”.
The protein fraction is dried and referred to as corn gluten or zein which
is commonly used for animal feed.

26. BARLEY, OATS ANDRYE
Barley is also used to produce barley malt. In this process, the barley seed is allowed
to germinate to a sprout.
The dried barley sprout is now called barley malt and is used in the brewing industry
to help digest starchy material into sugars for rapid yeast fermentation. The malt
also adds a distinctive flavor to beer.
Malt further adds flavor to breakfast cereals and malted-milk concentrates.

27. CEREAL
PRODUCTS
Cereal Products
Wheat Flour, semolina (couscous), pasta, weetabix and
other breakfast cereals.
Rice Ground rice, rice flour, rice wine, rice cakes,
Rice Krispies, rice paper.
Maize/c
orn
Corn on cob, sweetcorn, maize meal, corn
flour, corn oil, popcorn, cornflakes.
Oats Oatmeal, pinhead oats, rolled oats for
porridge and muesli, oatmeal biscuits.
Rye Rye bread, crispbread, whiskey.
Barley Pearl barley, barley water, whiskey.

28. •Pulses constitute essential components of vegetarian diet. Pulses are major source of
protein in Indian vegetarian diet.
•These are main source of protein providing most of the essential amino acids to a
certain degree.
•Economically, pulses are cheapest source of protein. Pulses are Bengal gram, pigeon
pea, black gram, green gram, lentil, etc.
•Pulses are mainly consumed in the form of dehusked split pulses, as these are rich in
proteins. In vegetarian diet pulses are main source of protein.
Pulses

29. PULSE MILLING
• Pulses are usually converted into Dhal by decutilating and splitting.
• Both dry and wet milling processes are employed. By and large carborundum emery
rollers are used for dehusking and burr grinders for splitting.
• Decuticling is seldom complete in single pass requiring multiple passes, each pass
producing 1.5 to 2% fines reducing recovery of dal.

30. OILSEED
• Oilseeds are rich sources of energy and nutrition.
• The oils and fats present in them are useful as food fats and industrial
raw material.
• The proteins present in some oilseeds and their cakes are edible to
humans while the others are useful as animal feeds.
• Oilseeds also contain carbohydrates, vitamins and minerals.
• Oilseeds and oilseed meals have an important
role in relieving the
malnutrition and calorie nutrition of human and animal population.

31. Soybeans
•Soybeans are very versatile food products used for both animal and human foods.
•Soybeans can have up to 23% fat.
•Soy protein is quite extensively used for animal feed as a protein source.
Peanuts
•Peanuts contain 25% protein and 50% oil.
•They are used mainly to produce peanut butter (50% of the crop).
•They can also be used to make flour and used for oil.

32. Thermal properties
•Food materials often experience the movement of heat around and
through them in various forms and degrees during growth, harvest,
handling, processing, transport, storage, and preparation for consumption.
Only a few foods such as fresh fruit and some vegetables go from field to
the table without any thermal processing. Most foods are thermally
processed to extend their shelf life and maintain high quality. Foods are
exposed to heat transfer numerous times during heating, cooling, freezing,
frying, and/or baking. Thermal operations are also used to insure safe food
products for extended periods. A classic example is the pasteurization of
milk, a heating process that eliminates bacteria. Pasteurization, followed
by proper cooling, provides a safe milk product for weeks. Canned foods,
which are good for years, are sterilized with heat processes. Juice, having
been heated and aseptically packaged in boxes, is shelf stable without
refrigeration for months

33. •Heat transfer occurs by conduction, convection, and radiation. These
mechanisms can occur individually or simultaneously. In food processing,
heat transfer is usually a combination of conduction and convection.
Conduction is principally involved during heat transfer within solid-like
materials, i.e., solids or static liquids. Convection is the transfer between
solids (walls of pipes, vats, rooms) and fluids (food materials). In other
cases, the food may be the solid and the fluid might be air or water.
Radiant heat transfer is less frequently used but is becoming more
common in microwave and infra red heating The thermal properties are
unique for each food. Each mechanism of heat transfer has an associated
thermal property. Specific heat (cp) or heat capacity is the heat required to
increase the temperature of one unit of mass by one degree. The subscript
(p) is included because specific heat of solids and liquids is determined at
constant pressure. In steady state conduction through a solid-like material
the important thermal property is thermal conductivity (k). Thermal
conductivity is a measure of the ease with which heat flows through a
material. Heat is conducted quickly through a metal like copper, hence its
thermal conductivity value is high

34. Electromagnetic Properties
•Electromagnetic radiation encompasses a wide variety of
phenomena as represented by the various regions along its
broad spectrum .Utilizing selective parts of the
electromagnetic spectrum is the basis for our modern
electrical power distribution system and the many forms of
transmitted communication including radar, radio, television,
and satellite. Short wavelength energy is used for medical
purposes including X-rays and radiography. The intermediate
range includes the infrared, visible, and ultraviolet portions of
the spectrum. Only a few specialized, narrow regions are
utilized in food applications. These include light, infrared, and
microwave frequencies

35. Electrical properties
•The electrical properties of biological materials have long
been utilized for rapid, non-destructive measurement of
moisture content. The moisture in agricultural grains is
routinely sampled for making decisions about drying, storing,
and marketing. Moisture content can be measured rapidly,
with low cost electronic sensors, as food products flow
through processing operations. For these reasons, moisture is
the primary quality factor used in the agricultural grain trade
.Electrical conductance and resistance of water differs
significantly from dry matter so that property can be utilized in
determining moisture in food materials

36. Aero and Hydrodynamic properties
The aero and hydrodynamic properties such as terminal
velocity of agricultural products are important and required
for designing of air and water conveying systems and the
separation equipment. The physical properties such as density,
shape and size, drag coefficient etc., are required for
calculating the terminal velocity of the material. For example,
in pneumatic conveying and separation processes of the
material is lifted only when the air velocity is greater than its
terminal velocity.