388 OCTIBER 2019

V SEM AGRICULTURAL TECHNOLOGY Post harvest Technology

PART A 1. Write the formula to calculate the moisture content on wet basis?

% Mcwb = (Wm / Wt) x 100 = [Wm / (Wm + Wdm)] x 100 Where Mcwb = Moisture content wet basis. Wm = Weight of the moisture in the grain Wt = Total weight of the grain and Wdm = Weight of dry matter in the grain

2. List the disadvantages of re-circulatory batch type dryer? Disadvantages:

1. Drying is not so uniform as compared to mixing type 2. Perforations of the cylinder may be clogged with the parboiled paddy after using it for

a long time.

3. What is sack drying? Sack drying method: This method is particularly suitable for drying of small quantity of seed to prevent mixing of varieties and conserve strain purity and viability. The grain bags are laid flat over holes cut on the floor of a tunnel system so that heated air can be forced up through the grain from an air chamber underneath. Usually an air temperature of 45° C with an air flow rate of 4 M3 / min at 3 – 4 cm static pressure per bag of 60 Kg is used for fastest drying operation. The sack drying process involves higher labour cost.

4. What is soaking? Soaking of paddy: Paddy, being a hygroscopic material, can absorb water both as a vapour and as a liquid, and thereby swells. The process of simultaneous water absorption and swelling is known as soaking, steeping or imbibitions. It is basically a diffusion process. The movement of water into the paddy will continue as long as the vapour pressure inside the grain is less than that of the soak water and will stop when equilibrium is reached.

5. Define milling? Milling refers to the size reduction and separation operations used for processing of food

grains into edible from by removing and separating the inedible and undesirable portions from them. Milling may involve cleaning / separation, husking, sorting, whitening, polishing, grinding, sifting etc.,

To increase the milling quality or to improve the quality and quantity of their end products grains are sometimes subjected to hydrothermal treatment prior to milling called conditioning.

6. Give the classification of grinding?

Cereal grinding system can be divided into two groups: a. Plain grinding and b. Selective grinding.

7. Write the composition of rice bran? Composition of rice bran:

1. Saturated acids ----- 16 - 20% (i) Palmitic acid ----- 13 - 18% (ii) Myristic acid ----- 0.4 - 1% (iii) Stearic acid ----- 1 - 3% 2. Unsaturated acids ---- 80 - 84% (i) Oleic acid ----- 40 - 50% (ii) Linoleic acid --- 20 - 42% (iii) Linolenic acid --- 0 - 1%

8. Write down the Henderson’s equation with usual notation? 1 – RH = exp [-cTMen]

where, RH = Equilibrium Relative Humidity (Decimal) Me = Equilibrium moisture content, dry basis percent T = Temperature, ° K and c & n = Product constants , varying with materials.

PART B

9. Classify moisture measurement methods? Grain moisture can be determined by two methods

1. Primary or Direct method a. Vacuum – Oven method b. Air - Oven method

i. Single stage method ii. Two stage method

c. Water – Oven or Air – Oven method d. Brown – Duvel Fractional Distillation Method

2. Secondary or Indirect method a. Electrical resistance method b. Dielectric method c. Chemical method d. Hygrometric method

10. Write down the factors affecting moisture measurement methods?

The factors affecting moisture measurement methods are as follows: a. The form in which water is present (absorbed, colloidally bound, mechanically

occluded, and water of crystallization). b. The nature of the product analyzed (whether easily oxidized or decomposed) c. The relative amount of water present in the product. d. The rapidity of the determination. e. The accuracy desired and f. The cost of equipment required

11. Name the general components of convection drying method?

The general components of a convection drying methods are: a. Storage unit b. Aeration system and c. Air distribution system

12. What is fluidized bed drying? When the hot gas (drying agent) is supplied at a velocity higher than the terminal velocity

higher than the terminal velocity of the wet solid (grain), the drying of the wet solid occurs in a suspended or fluidized state. This phenomenon is known as ‘fluidized bed drying’.

13. What is double boiling?

Double boiling method: In this method, steam is injected into the raw paddy in the steaming kettle before soaking.

This hastens the soaking process. The hot steam raises the temperature of the soak water to 45 - 50° C which reduces the soaking time to 24 hrs. Thereafter, soaked paddy is steamed as in single boiling method.

14. What is cleaning? The removal of impurities from the grains is essential to protect the subsequent milling

machinery from unusual wear and tear and to improve the quality of the final product. Any mixture of solids materials can be separated into different fractions according to their difference in length, width, thickness, density, roughness, and drag in moving air, electrical conductivity, colour and other physical properties.

15. Why cotton seed flakes are cooked before extraction of oil from it? Cotton flakes are cooked before the extraction of oil is

a. To precipitate the phosphatides b. To detoxify the gossypol c. To coagulate the protein and d. To bring down the moisture content of the flakes from about 12 to 5%.

16. What are the factors affecting storage of rice bran oil?

The factors affecting storage of rice bran oil are as follows: a. Storage temperature b. Moisture content of bran c. Storage relative humidity d. Variety, type and particle size of bran and e. Contamination of bran with micro flora or insects.

PART C

17. a. Draw a graph showing moisture content of grain on wet basis versus moisture content of grain on dry basis. Take moisture content of grain on wet basis from 10% to 60%at equal intervals of 5%?

17.b. Explain the structure of grain with suitable sketch?

Structure of grain: Different grains have different structure. Wheat consist of Pericarp, Seed coat,

aleurone layer, germs and endosperm, whereas Oats, barley, Paddy, Pulses and some other crops consists not only of the above five parts but an outer husk cover also. The husk reduces the rate of drying.

The embryo or germ is the principal part of the seed. All tissues of the germ consist of living cells which are very sensitive to heat. The endosperm, which fills the whole inner part of the seed consists of thin-walled cells, filled with protoplasm and starch granules and serves as a kind of receptacle for reverse food stuff for the developing embryo. The structures of a few important grains are shown in figure.

18. a. Explain the construction and working of LSU dryer with neat sketch? Louisiana state university dryer (LSU Dryer): This is a continuous flow - mixing type of grain dryer which is popular in India and USA. Construction: It consists of (1) A rectangular drying chamber fitted with air ports and the holding bin (2) An air blower with duct (3) Grain discharging mechanism with a hopper bottom, and (4) An air heating Rectangular bin: Usually the following top square sections of the bin are used for the design of LSU dryers.

(i) 1.2m X 1.2m (ii) 1.5m X 1.5m (iii) 1.8m X 1.8m and (iv) 2.1m X 2.1m

The rectangular bin can be divided into two- holding bin and bottom drying chamber. Air distribution system:

Layers of inverted V – shaped channels (inverted V) are installed in the drying chamber. Heated air is introduced at many points through the descending grain bulk through these channels. One end of each air channel has an opening and the other end is sealed. Alternate layers are air inlet and air outlet channels. In the inlet layers, the channel openings face the air inlet plenum chamber but they are sealed at the opposite wall, where as in the outlet layers, the channel openings face the exhaust but are sealed other side. The inlet and outlet ports are arranged one below the other in an offset pattern. Thus air is forced through the descending grain while moving from the feed end to the discharge end. The inlet ports consist of a few full size ports and two half size ports at two sides. All these ports of same size are arranged in equal spacing between them. The number of ports containing a dryer varies widely depending on the size of the dryer.

Each layer is offset so that the top of the inverted ‘V’ ports helps in splitting the stream of grains and flowing the grains between these ports taking a zigzag path. In most models, the heated air is supplied by a blower. Grain drying mechanism: Three or more ribbed rollers are provided at the bottom of the drying chamber which can be rotated at different low speeds for different discharge rates of grain. The grain is discharged through a hopper fixed at the bottom of the drying chamber. Causing some mixing of grain and air the discharge system at the base of the dryer also regulates the rate of fall of the grain. Air heating system: The air is heated by burning gaseous fuels such as natural gas, butane gas, etc. or liquid fuels such as kerosene, furnace oil, fuel oil etc. or solid fuels like coal, fire wood etc. Heat can be supplied directly by the use of gas burner or oil burner or husk fired furnace and indirectly by the use of heat exchangers. Indirect heating is always less efficient than direct firing system. However, oil fired burner or gas burners should be immediately replaced by husk fired furnace for economy of grain drying. Advantages:

1. Uniformly dried product can be obtained if the dryer is designed properly. 2. The dryer can be used for different types of grains.

Disadvantages: 1. High capital investment. 2. Cost of drying is very high if oil is used as fuel.

Fig. LSU Dryer

17. b. Explain thin layer drying. State its limitations? Thin Layer Drying:

The depth of grain is less than 20cm, and then it is called thin layer drying. In thin layer drying, theoretically it is assumed that all the grains are exposed to drying air under uniform and constant drying conditions and dried uniformly. But in actual, there is no such possibility of correct and finite thin layer. It is due to the fact that the shape and size factor of the drying biological materials. The rate of drying or loss of moisture from wet surface of grains under thin layer drying is given by Newton’s equation is

dt ---- = - K (t – tc ) dθ If the temperature term ‘t’ is replaced by the moisture term ‘m’, then dm --- = - K (m – me) dθ Where m = moisture content dry basis in percent θ = time in hour me = E.M.C. in dry basis percent and K = drying constant per hour Rearranging the above equation and integrating the above equation within proper limits we get

M - Me -------- = e-Kθ Mo - Me

M - Me --------- is known as Moisture Ratio (MR). By solving the above equation we get, Mo - Me

1 (Mo - Me)

θ = --- ln --------------- K (M - Me) Where θ = time taken for drying This equation does not take the shape factor of the grain into account. Suitable correction factors should be taken into consideration for shape factor also. The drying constant ‘K’ can be found out using either graphical method or half-life period method. Limitation of thin layer drying equation:

1. The theoretical drying equations layer of grain which is not true for finite mass depths.

2. The grain drying equations developed from diffusion equation are based on the incorrect assumptions.

3. It is not possible to choose a accurate boundary conditions and shape factors for drying of biological materials.

4. Drying equation developed from Newton’s equation for heating or cooling does not take into account of the shape of the material.

19. a. Explain the traditional method of parboiling and state its disadvantages? Traditional methods: The traditional process consists of soaking in Water at room temperature for 24 -48 hr or more steaming in kettles, and drying in the sun. a. Single boiling method:

Paddy is soaked in ordinary water for 24 – 72 hr and then transferred to cylindrical iron kettles for steaming in small batches under atmospheric pressure. The parboiled paddy is then dried in the sun before milling. b. Double boiling method: In this method, steam is injected into the raw paddy in the steaming kettle before soaking. This hastens the soaking process. The hot steam raises the temperature of the soak water to 45 - 50° C which reduces the soaking time to 24 hrs. Thereafter, soaked paddy is steamed as in single boiling method. Disadvantages of traditional method:

1. During prolonged soaking, fermentation starts and the paddy acquires a smell 2. It is conducive to the development of micro toxins, like Alfa toxins, which are known

to be quite harmful to human. 3. In the process of drying, loss due to manual handling and consumption by birds,

rodents and insects occurs and may amount to about 1.5 – 2.0%. 4. Sun drying is quite uncertain and is dependent on bright sunny weather. 5. Sometimes an entire batch of parboiled paddy is spoiled because of delayed drying. 6. Unhygienic conditions exist as a result of people treading on the paddy and

contamination by dust and birds. 7. It requires a large area of land for drying and

8. Labour requirement is high.

b. Explain Kissan Continuous parboiling method with neat sketch? Kissan continuous parboiling method: It is a simple, cheap and versatile process. A hexagonal tank with 12 compartments is filled with hot water into which paddy is discharged from an elevator head. These compartments are filed in a sequential order starting with number one and leaving an interval of 15 minute between successive compartment fillings. By the time the 12th compartment is filled, the first on is ready for steaming. By opening the discharge gate, water and paddy can be taken to the dump pit below the tank. This pit has a perforated floor plate that permits the drainage of water. From this pit a screw conveyor with a capacity of 2 ton / hr, removes the soaked paddy for steaming. Because each compartment contains only 0.5 ton, the pit is emptied in 15 min. however, at the end of the 15 min period, the paddy in the second compartment is emptied into the pit to continue the operation. Therefore, a series of batches emptied from the hexagonal tank continually feeds the parboiling unit. The size and ratings of the batches can be modified to suit individual requirements. The steaming cylinder is a simple device in which paddy flows vertically down an annular chamber as a horizontal flow of steam radically heats and gelatinizes the grain. The size and speed of the paddy flow can be varied as desired.

This unit can be operated both as a continuous parboiler and as a batch system. The steaming unit can serve as a paddy drier if hot air is used instead of steam. Because it is possible to dry some other cereals in the drier during the off – season, it is a versatile piece of equipment that can be optimally utilized throughout the year. The escaping steam from the parboiler is used to heat either the water tank or the paddy soaking tank. If a steam heat exchanger is employed to produce hot air in a mechanical drier, steam from the parboiler may be used in the heat exchanger.

20. a. Explain the construction and working of Rubber roll sheller with simple sketch?

RUBBER ROLL SHELLER: Construction: Figure shows the constructional features of the paddy husker. It consists of two major parts, the upper part is the husking section and the lower part is the husk aspirating section. Clean paddy is delivered through a shutter and a feeding roll, fixed below the shutter feed rate is controlled by a feed regulating valve. The paddy is then passed through the gap between a fixed (stationary) roll and an adjustable (movable) roll and husked. After reducing the grain speed with the help of resistance (rubber) plate the mixture is allowed to pass through the aspiration section to aspirate husk. Mature grain being heavy is collected in the husked rice outlet. Immature grain being light is collected and discharged by a screw conveyor. The husk is aspirated and thrown out of the mill building by a fan. Both rolls have the same diameter. Diameter of the rubber rolls varies from 150 to 250 mm depending on the capacity of the husker. The wear of the rubber is considerable and with the reduction of the roll diameter, capacity is also reduced. The main reason for the capacity reduction is the decrease in the relative speed of the two rolls. The clearance between the two rolls can be adjusted manually. A sophisticated pneumatic device for automatic adjustment of the clearance has been introduced in place of manual adjustment.

Now a day’s rubber roll huskers are equipped with a blower to blow air on the rubber rolls surface and bring down their temperature rise due to friction between husk and roller during husking.

Working: When the husk is in operation for a certain period, the faster revolving roll wears more than the slower revolving roll. As a result the diameter of the former becomes smaller than the latter and the difference in peripheral velocity between the two rolls becomes less. Through the speed ratio is kept constant, yet it causes lowering of husking efficiently. To encounter this difficulty in application of high pressure is not the proper means as it would break the grains. However, the rubber rolls are to be interchanged at a regular interval of time. Advantages:

Highest percentage of sound and whole husked rice is produced as the risk of breaking the kernel is small and the chance of forming scratches on the kernel is also nil.

The mixture of different sizes and varieties of paddy can be used without any significant increase of brokens is husked rice.

Husking ratio can be increased to 0.9 without reduction in head yield. It does not remove germ.

Disadvantage: Operating costs are high due to wear of rubber rolls. Storage life of rubber roll is limited as storage deteriorates its quality and in

consequence shortens its working life. If the paddy separator fails to separate paddy completely and the husked rice is

returned to the husker along with paddy the constituent of the rubber may impart colour and odour to the rice.

It requires skilled labour to operate the machine efficiently. Sometimes on account of uneven grain distribution and uneven thickness of

rubber, the rolls surface wears out unevenly which adversely affects the efficiency and capacity. If the roll surfaces are corrected by turning, the life of the rubber rolls will be reduced considerably.

In general the husking capacity of the rubber rolls in tropical countries is low due to (a) high temperature and humidity of the atmospheric air (b) structure, and (c) layer surface area of the long grain husk in contact with the rubber rolls.

20. b.Write a short note on (i) Hulling an abrasive drum in cylindrical steel shell (ii)

Husking by scourers and blade type huskers? (i) Hulling by an abrasive drum in a cylindrical steel shell: Grains with hull firmly attached to the kernel such as barley, wheat, etc, can be husked by a more drastic treatment. Hollander can be used for the above purpose. It comprises of rapidly rotating abrasive roll encaged in a slowly rotating steel shell. In a batch huller the grains enter into the space between the abrasive roll and the perforated cylindrical shell and take a considerable period to travel from one end to the other. The shell rotates slowly in the opposite direction. In Hollanders the hull is removed from the grain because of the friction among the grain, abrasive roll and perforated steel shell and friction between grain and grain

Disadvantages:

The machine is heavy and bulky. It consumes high power and Due to batch system, continuous production is not possible and operational

schedule becomes complicated. (ii) Husking by scourers and blade type huskers: It consists of a rotating horizontal shaft fitted with blades engaged in a cylinder. When grains are fed to the cylinder they come in contact with revolving blades and are thrown to the internal abrasive surface of cylinder which rebounds them. The grains impinge on the blade again. Two impacts per revolution between the grain and the abrasive cylinder and friction amongst the grains result in removal of husk from the grain. The holding time of the grain in the scourers depends on the peripheral speed of the abrasive cylinder and the blade – angle.

Advantages:

The machine is easy to operate. It does not require much attention.

Disadvantages: Yield of cracked and crushed grain is high.

21. a. Explain the uses of bran, bran oil and its various constituents?

Uses of bran, bran oil and various constituents: a. Edible grade oil:

Because of the very low content of Linolenic acid and high content of tocopherol, bran oil has distinct advantages over other vegetable oils. Different grades of bran oil such as salad oil, cooking oil and so also shortenings can be produced by refining and suitable hydrogenation of bran oil.

b. Industrial grade crude oil: Soap manufacture: Rice bran oil with high FFA content is highly suitable for the manufacture of soft soap and liquid soap. In addition to alkali soaps other metallic soaps obtained from bran oil, namely, aluminium, barium and calcium soaps find market as components of lubricants. Free fatty acid manufacture: The process consists of hydrolysis of the triglycerides of fatty acids into fatty acids and glycerol, separation of glycerol and purification of mixed fatty acids. The use of hydrogenation in combination with fractional distillation enables the manufacture of pure Stearic and oleic acid of desired quality. Protective Coatings: The manufacture of surface coatings like alkyl and resin based paints, enamels, varnishes and lacquers also represent the usage of rice bran oil. Plasticizers: Recently fatty acids and fatty oil based plasticizers are being used in the plastic and rubber industries. Tocoferol: Tocoferol has nutritional and anti acid effects. Crude oil contains 2 – 4 % tocoferol. During deodorizing process a significant amount of it is lost. Only 1 - 2% of tocoferol remains in edible oil

c. Rice bran wax: Rice bran wax is a proper substitute of carnauba wax due to high melting point (72° - 84°C), hardness and non stickiness. It is being used for coatings of candy, fruits and vegetables as it prevents moisture loss and shrinkage of the said products. It can also be used as component in formulations like carbon paper base, stencils, candles etc. Uses of defatted bran and bran:

a. Feed: Defatted bran can be best utilized as an ingredient of cattle and poultry feed. In regard to this aspect defatted bran is more suitable than raw bran due to its higher protein and fat contents, higher digestibility and more stability towards storage quality. b. Food: Defatted bran can be successfully used as an ingredient in the bakery products such as bread, cake, biscuits, etc. after finer grinding; it can be added to baking flour up to 20%. c. Fertilizer: On account of the presence of high fat and wax contents, regular raw bran is not only unsuitable for plants but also harmful for their roots. But defatted bran contains all the three manurial factors (NPK values) in right proportion. d. Medicinal use: As rice bran contains valuable vitamin B – complexes, amino acids, phosphoric acid compound etc., it is useful in the field of medicine and dietrics. Protein can also be easily extracted from rice bran.

21.b. Explain the solvent extraction method of extracting soya bean oil with neat flow diagram? Solvent extraction of soybean oil:

Soybeans are subjected to preliminary cleaning and milling operations as usual. The Soya meal is cooked. But the cooking of meal by heat treatment is done under mild conditions. The heat treated meals are then converted into flakes using smooth flaking rolls. Solvent extraction of the cooked flakes can be done batch wise or continuously. In continuous extraction method counter current solvent flow is preferred. The oil from the miscella is separated by distillation and stripping under vacuum. The extracted meal is desolventized by heating with live steam in a desolventizer. The solvent from the distillation and stripping columns as well as from the desolventizer is condensed and recovered and stored in the solvent storage tank. The oil, separated from the miscella in the distillation column goes to oil storage tank after cooling. The de-oiled cake contains about 1% residual oil.