The document presents an overview of milling and parboiling processes in agricultural processing, detailing methods of size reduction such as crushing, impact, shearing, and cutting. It explains the parboiling process as a pre-milling treatment that enhances rice yield and quality while outlining both advantages and disadvantages. Additionally, it covers various equipment used in oil extraction and the parameters involved in the soaking, steaming, and drying of paddy.

2. INTRODUCTION TO
MILLING AND
PARBOILING
presentation on :-

3. - :Subject: -
AGRICULTURAL PROCESSING
PRESENTED BY:-
 Kaushal. V. Gadariya (PAGEN-097-2012)
 Baria Dipak (PAGEN-091-2012)
 Dave Dhruv (PAGEN-094-2012)
 Chovatiya Chintan(PAGEN-093-2012)

4. MILLING
 Milling refers to the size reduction and separation
operations used for processing of food grains into
edible form.

5. PRINCIPLES OF SIZE REDUCTIONS
Followings are some laws of energy required to size
reduction : -
- Rittinger's law
- Kick's law
- Bond's law

6. RITTINGER’S LAW
• It is states that the work required in crushing is
proportional to the new surface created.
• Rittinger’s assumed that size reduction is essentially a
shearing procedure.
• Therefore, energy requirement is proportional to the
square of the common linear dimension .
• The value of n = 2
Where,
E is energy requirement for size reduction
Xp is length of product
Xf is length of feed

7. SIZE REDUCTION METHODS
 The size of agriculture products may be reduced
by several ways, but mainly the following four
methods are used in size reduction machines.
1.Compression or crushing.
2.Impact.
3.Shearing.
4.Cutting.

8. SIZE REDUCTION PROCEDURES

9. Crushing :-
 In crushing the particle produced after crushing
are irregular in shape & size.
 The type of material and method of force
application affects the characteristics of new
surfaces and particles.
 Food grain flour, grits and meal, ground feed for
livestock are made by crushing process.
 Crushing is also used to extract oil from oilseeds
and juice from sugarcane.

10. CRUSHING ULTRAFINE MILL

11.  Impact:-
When a material is subjected to sudden blow
of force in excess of its strength, it fails, like a
cracking of nut with the help of a hammer. For
example Hammer mill.

12.  Shearing:-
-It is a process of size reduction which
combines cutting and crushing. The shearing units
consist of a knife and a bar.
 Cutting:-
In this method size reduction is
accomplished by forcing a sharp and thin knife
though the material. The size of vegetables and
fruits are reduced by cutting.

13. SIZE REDUCTION MACHINARY
Size reducing devices are grouped as follows:-
SIZE
REDUCTION
MACHINARY
GRINDER
FINE
DRINDER
CUTTING
MACHINES
CRUSHER

14. WHEAT FLOUR MILL

15. HAMMER MILL

16.  Crushers : -
- These type of reducing machines squeeze or press the
material until it brakes.
- Crushers are mostly used to break large pieces of
solid materials into small lumps.
- Crushers are used in industrial operations, like mines
etc.
- Use of crushers in agricultural operations is limited.
The crushers in use are,
1.Jaw crushers. 2. Gyratory crushers. 3. Crushing rolls.

17.  Grinders:-
- The grinders are used to mill the grains into
powder.
- The grinder comprises a variety of size
reduction machines like attrition mills, hammer
mills, impactors and rolling compression mills.

18.  Cutting machines: -
- Size reduction of fruits and vegetables are
mostly performed by cutting operation.
- To make thin slices of fruits and vegetables
knife cutter are used.
- Few types of knife cutters have been developed
for cutting slices / chips of potatoes, banana etc.

19. SIZE REDUCTION MACHINES
OPERATION AND PERFORMANCE
To achieve good results from any size reducing machines
the followings should be given due care,
 Feed should be of proper size and feeding rate should be
uniform.
 Hard or unbreakable material is not allowed to enter the
mill.
 After grinding the product is removed as soon as
possible.
 There should be some arrangement to remove the heat
generated during milling operation.

20. OIL EXPRESSION
 Expression is the process of mechanically
pressing liquid out of liquid containing solids.
 Screw presses, roll presses and mill, collapsible
plate and frame filler presses, disk mill are some
of examples of a wide range of equipment used
for expression of liquid.
FIG: OLIVE OIL PRESS

21. MECHANICAL EXPRESSION
DEVICES
 Hydraulic press: -
- It considered of a series of horizontal
corrugated iron plates.
- These plates are separated by 4 to 14 remolded
oil seed cakes.
- Pressing is completed in two stages.
- In the first stage, the oil samples are pressed at
approximately 5MPa for 15 to 20 minutes.
- Afterward a pressure of 28MPa is applied for 5
to 10 minutes to complete the expression process.
- The output of the press varied depending on the
sizes seed being pressed.

22. H
Y
D
R
A
U
L
I
C
P
R
E
S
S

23.  Screw press: -
- In screw press, the press has a horizontal main
shaft.
- The screw assembly is formed integrally with this
shaft.
- This screw rotates within a cage of barrel.
- Barrel is made of case hardened, tool steel bars or
this may be made out of assembly of rings.
- Spacers are used between the lining bars or rings
to allow drainage of the oil as the pressure on the
feed material is increased.

24. FIG: SCHAMETIC VIEW OF HYDRAULIC PRESS

25. OIL EXTRACTION
 Extraction is the process of separating a liquid
from a liquid-solid system with the use of
solvent.
 Extraction may also be said as a process to
extract oil from oil bearing material through
process of diffusion with the help of low boiling
point solvent.
 This process gives a higher recovery of oil and a
drier cake then expression.

26. OIL EXTRACTION METHOD
 Extraction methods include: -

27.  Traditional methods:-
- Oil is extracted from, for example, fresh
coconut, olive, palm fruit Shea nut by separating
the flesh and boiling it in water.
- Salt can be added to break any emulsion which
is commonly formed and the oil is skimmed from
the surface. In palm oil processing the fruit is first
heated in a digester.

28. • Manual methods:-
- Oil can be extracted by pressing softer oilseeds
and nuts, such as ground nuts and Shea nuts,
whereas harder, more fibrous materials such as
copra and sunflower seed can be processed using
ghanis.
- Pulped or ground material is loaded into a
manual or hydraulic press to squeeze out the oil-
water emulsion.

29. MECHANIZED EXTRACTION
 Ghani (kolhus):-
- The Ghani consists of a large mortar and pestle, the
mortar being fixed in the ground and the pestle being
moved within the mortar by animal traction (donkey or
mule) or a motor.
- Oilseeds are placed in the mortar and the pestle grinds
the material to remove the oil.
- The oil runs out of a hole in the bottom of the mortar and
the cake is scooped out by hand.
- This method is slow and requires two animals, replacing
the tired one with another after about 3-4 hours of work.

30. ANIMAL DRAWN KOLHUS

31.  Expeller :-
- The basic steps involved in processing
oilseeds by expeller are shown in the flow diagram
below.

32. PARBOILING
 It is a pre milling treatment given to paddy prior to its
milling to achieve maximum recovery of head rice and to
minimize breakage.
 In this process paddy is soaked and the wet paddy is
heated and dried.
 During soaking of paddy water penetrates into starch
granules and result in swelling of grains.
 In heating, the energy weakens the granule structure and
more surface becomes available water absorption and
result in irreversible granule swelling.
 This phenomenon is called gelatinization of starch.

33.  The main objectives of parboiling are –
1. to increase the total and head rice yield of
paddy.
2. to prevent the loss of nutrients during milling.
3. to salvage wet or damaged paddy.
4. to mill the rice according to requirement of
consumers.

34. ADVANTAGES OF PARBOILING
 The milling yield increases and the quality is
improved.
 The milled rice becomes translucent and shining.
 Shelling of parboiled rice is easier.
 Bran of parboiled rice has more oil.
 Parboiled rice retains more proteins, vitamins and
minerals.
 Parboiled rice is more digestible and less solids are
left behind in the cooking water.

35. DISADVANTAGES OF PARBOILING
 Parboiling process needs extra capital investment.
 Parboiling adds to the cost of drying.
 More power is required for polishing of parboiled rice.
The process becomes difficult and lowers the capacity of
polisher.
 Parboiled rice takes more time to cook than raw rice and
may have characteristics off flavor which may not be
liked by raw rice eaters.
 The heat treatment during parboiling destroys some
natural anti-oxidants.

36. SOAKING STEAMING DRYING
 Parboiling of paddy is carried out in three steps,

37. PARBOILING OF PADDY
 Soaking of paddy is carried out by dipping in water.
Dipping in water at ambient temperature takes long
time (72 h) for soaking, making paddy susceptible to
development of micotoxins.
 Hence, soaking at elevated temperature of water is
considered better. The soaking duration varies with
water temperature.
1.Soaking of paddy: -

38. S. No. Temperature, °C Time, h
1 Water heated to 50°C and allowed to come to
ambient temperature
24
2 Water heated to 75°C and allowed to come to
ambient temperature
12
3 Maintained at 60°C 8
4 Maintained at 65°C 6
5 Maintained at 70°C 4
6 Maintained at 72°C 3.5
7 Steam at 0.5 atm. pressure 0.4
 The following time-temperature combination is considered optimum
for soaking:
Time-temperature combination for soaking of paddy:

39. 2. Steaming of paddy: -
PARBOILING OF PADDY
 Steaming is carried out to gelatinize starch.
 Generally, saturated steam at a pressure of 1-5
kg/cm2 is used for steaming of soaked paddy.
 Duration of steaming depends upon quantity of
paddy. For small batch, 2-3 min whereas for large
batch (6-8 tones), 25-30 min of steaming is
required.

40. PARBOILING PLANTS
FIG: -Household parboiling unit FIG: -Industrial parboiling units

41. 3. Drying of paddy: -
 Drying of parboiled paddy from 45-50% (db) to 14-
16% (db) needs to be done for proper milling and
storage.
 Sun drying of paddy is generally practiced.
 For uniform drying, it is important that paddy is spread
in 2-3 cm thickness layer and stirred at an interval of
half hour.
 It is also important that paddy is dried in two passes
instead of continuous drying. In first pass, paddy
moisture content should be brought down to 18-20%
and rest in second pass.

42.  Parboiling tank is filled with clean water and heated to
about 85°C.
 Paddy is dumped into hot water in tank for soaking. the
temperature of paddy-water mixture comes down to 70°C
which is maintained for 3-3.5 h.
 After soaking, water is drained from tank and then
exposed to steam at a pressure of 4 kg/cm2 until husk
starts splitting.
 Steamed paddy is dried in multiple passes. During parboiling, the water requirement is about 1.25
times the weight of paddy and requirement of steam is
about 200 kg/ton of paddy.
CFTRI PARBOILING METHOD

43. Thanks for
your attention
Have a good day………….