1.a Agricultural
processing are those operations which maintain or raise the quality of raw
materials, change its form, or prepare it for market. It is value
addition or conditioning of agricultural products.
The operations connected with agricultural processing
are: Cleaning, grading, sorting, drying, decortications soaking, steaming,
boiling, concentration, dehydration etc (5marks)
1b. Storage
is done to fulfill the national and domestic needs of food, feed and seed
between two consecutive harvests (5marks)
1c. The advantages of processing and storage
of agricultural products are
____ Economy in transport
____ Provision of employment
opportunities
____ Change of perishable products
to stable commodity
____ Prevention of insect and pest
infestation during storage.(5marks)
1d. The
four operations that could be portioned on food materials to improve the
quality and shelve life of the product are - physical -thermal - hydrothermal
and pneumatic operations.
The value addition is referred to as primary
processing - secondary processing -Tertiary processing - Combinations of the
operations.
2ai. Indigenous Rice Hullers
ii. Disk type Hullers
iii. Roller type hullers (5 marks)
2b. The terms used in rice milling industry
are as follows:
i. - paddy - rice in the hull (husk)
after threshing.
ii. Husked rice - Kernels with out husk
iii. Milled rice - white rice from brown
milled rice
iv.
Degree of milling - the extent of the removal of bran layers and germ (4- 6%).
v. Milling
yield - head rice + broken after
milling.
2ci. Free moisture
ii. Bound moisture
iii. Unbound moisture
Free
moisture is retained by the grain before EMC stages.
Bound
is contained inside the grain and held by chemical substances.
Grains
are not fund with unbound moisture or it will behave like free water surface.
(d) Milling
process can be presented diagrammatically thus:
Paddy
â
Clearing
â
Hulling Husking
â
Polishing 3 – 4 step
â
Grading and packaging
â
Milled Rice
3a. Paddy grain structure shows the presence
of voids and spaces which are usually filled by moisture and air which cause
cracks during milling.
Parboiling
is the process of preheating of rice paddy before drying and milling and the
idea is to close the voids and the cracks that usually occur during milling, in
addition to other advantages. (5 marks)
3bi. During
the cold or hot soaking starch granules swell. During hot soaking energy
supplied in the form of heat weakness the granule structure by disturbing
hydrogen bonds, giving more surfaces for water absorption by starch granules.
This permits irreversible granule swelling and further hydration a process
called gelatinization.
(5 marks).
3bii. The four
methods by which gelatinization of starch may be done include:
- Soaking
of paddy in water at or below its gelatinization temperature
- Soaking
of paddy at or above its gelatinization temperature.
- Paddy
soaking for a short duration may be to steam pressure for gelatinization.
- Paddy
soaked fully in water or freshly harvested high moisture paddy may be subjected
to conduction heating to achieve parboiling.
3c. Advantages
of parboiling are:
i. Shelling
of parboiled rice is easier
ii. Broken
are reduced to considerable extent
iii. Parboiled
rice retains more proteins, vitamins and minerals.
iv. It is
more resistant to insect infestation.
v. Less
loss of solids during cooking.
vi. It
could with stand over cooking.
vii. Superior
quality rice bran with 29 – 30% oil. (5
marks)
3d. Parboiling
disadvantages include:-
i. Heat destroys
some natural antioxidants.
ii. It
takes more time to cook
iii. Micro
toxins could develop which is hazardous to human health.
iv. Re-drying
from moisture content of 45 – 50 percent to 14-16 percent for proper milling.
v. It
needs an extra investment of capital.
vi. It has
harder shells that are more difficult to polish. (5 marks)
4a. The
avoidable reasons that cause breakage of rice during milling are:-
i. Harvesting
should be done at the optimum when moisture content is between 19 and 23
percent at maturity.
ii. Paddy
should be dried under controlled condition (hot mechanical dryer)
iii. Milling
should be done at the suitable moisture content (14%)
iv. Proper
storage to avoid weakening of kernels by insects.
v. Non
use of Rubber Roll shellers and Emery
vi. Non
use of constant feed rate
vii. Degree
of milling should be normal
viii. Non
pretreatment of parboiling. (5 marks)
4b. Food
may spoil through
i. The activities
of micro-organisms;
ii. Metabolic
process in living foods, leading to decay.
iii. Direct
oxidation from the atmosphere, leading to rancidity
iv. Absorption
of foreign orders and flavours
v. desiccation
and withering.
vi. Faulty
preparation.
4c. Their
growth pattern is as follows:
i. Up to
10oC the growth is slow
ii. At
about 300C, the growth rate is rapid, and
iii. At
about 360C, the growth stops entirely
iv. At
about 75oC, the spores may be killed in about 3 days.
v. At a
pH of 4 to 7, mould grows fast whereas the growth is restricted below pH of 2
or very alkaline pH values of 8 to 9.(5
marks)
4d. Feature
of food processing industries is that they are engaged in processing highly
perishable commodities, such as fruits and vegetables, milk and eggs, fish and
meat etc.
Because
the products of these industries are for mass consumption availability of
adequate funds and other resources are always ensured. We accord higher priority
to these industries because they are intensive labour industries which
generate employment in rural a areas and thus improve their standard of living.
5a. The
basic principles involved in freezing are to inactivate the living
micro-organisms causing decay or to change the liquid water present in foods
into crystals of ice rendering food assist as if it would have been dried. (5 marks)
5b. Sharp freezing
consists of placing foods in a cold room with temperatures maintained from
-15 to - 28oC. It is relatively slow process but is still used for
freezing boxed poultry, fish, packaged meat and some cold packed fruit.
5c. Foods may
be quick frozen by:
i. Freezing
by direct immersion in a refrigerating medium (brine or special sugar solution
held at – 18oc)
ii. Freezing
by indirect contact:(refrigerating medium at - 28oC to -45oC)
iii. Freezing
in a blast of could air (- 18oC -62oC)
iv. Fluidized
bed freezing.
5d. After
freezing as in the methods above, bacterial activities come to stand still, but
still there are few enzymes which remain active. To over come this problem,
the food (particularly the vegetables) may be blanched in boiling water or low
pressure steam before freezing it by one of the above mentioned methods of
freezing. (5 marks)
6a. The Ten
sequences of order of seed processing include.
i. Receiving
(ii).Storing (iii) conditioning and processing (iv) Basic cleaning (v) Separating and upgrading (vi) Drying
(vii) Treating
(viii) Bagging (ix) Storage (x) Shipping.(10 marks)
6b. The visibility
and percentage germination of seeds may be affected by a number of separate but
interacting factors during storage, including moisture content, relative
humidity, temperature, breakage, gaseous atmosphere and chemical treatment.
(5 marks)
6c. Packaging
is done to protect the contents placed inside the package and also to make
good impact on the mind of the consumers to attract them. Novelties of
good packaging are(i) transparency of the pack giving clear visibility of the
content, (ii) thermo stability, (iii) new protective coatings for hard packages
(glass etc.), (iv) lighter and thinner tin plates, (v) hygienic aluminum foils
and (vi) steel foils.(5 marks)
7a. - Unheated or natural air drying
- Unheated
air drying with supplemental heat
- Heated
air drying
Unheated air drying refers to the use of atmospheric
air forced around the grain for the removal of moisture.
Unheated
air with supplemental heat is desirable during periods of high humidity (when
atmospheric air cannot accomplish drying with unheated air installation). A
small amount of heat is added to the air to decrease the humidity there by
increasing the water holding capacity of the air.
Heated air drying makes use of
forced air movement around the grain with the addition of large amount of heat
for removing moisture rapidly.
7bi. Dried zone;
ii. The drying zone; and
iii. The wet zone
The
air pass through the dried zone to the drying zone and finally to the wet zone.
The air picks up moisture as it passes.
7c. Agricultural
materials are hygroscopic because they have the ability to absorb or give
out moisture to the atmosphere depending on their equilibrium moisture content
(EMC)
7d. At any
given temperature there is a condition of grain MC and RH of the air, when the
moisture retaining tendency of grain and moisture withdrawing tendency of the
air come into balance. The air and the grain are then said to be in
equilibrium. Under these conditions the grain no longer loses moisture to the
air nor does it pick up moisture from it. This MC of the grain is called
equilibrium moisture content (EMC) and the corresponding RH is called
equilibrium Relative Humidity (ERH).