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GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER-VI(NEW) - EXAMINATION - SUMMER 2019
Subject Code:2161403 Date:14/05/2019
Subject Name:Food Engineering Operations - IT
Time:10:30 AM TO 01:00 PM
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Total Marks: 70
Instructions:
- Attempt all questions.
- Make suitable assumptions wherever necessary.
- Figures to the right indicate full marks.
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Q.1 (a) Do as directed.
- State Stoke’s law.
- Differentiate between Clarifier and Separator.
- Propeller agitators are effective in larger vessels. Justify the statement.
(b) Fruit Puree is commercially sterilized at 110°C in a can to reduce the number of heat resistant organism (D120 = 0.24 min., Z=10°C) from an initial count of 1 million per can to a probability of survival of 1 in million. Determine the total processing time.
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(c) Derive the operating line equation for rectifying and stripping section for continuous distillation with reflux.
Q.2 (a) Differentiate between pasteurization plant and sterilization plant.
(b) Highlight on the working of continuous ice-cream freezer.
(c) Classify different pasteurization processes employed for liquid food products. Discuss HTST pasteurization process with flow line sketch.
OR
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(c) Explain homogenization mechanism in liquid food products with a neat and well labeled sketch.
Q.3 (a) Define Vacreation. State the objectives of vacreation.
(b) Calculate the rate of movement and the distance travelled by a fat globule in a centrifugal separator if the diameter of fat particle 6um, radius of bowl 12 cm, rpm of bowl 7000, capacity of the separator 3000 lit./hr, volume of milk in bowl 3 lit.
(c) What are the different types of heat exchanger fouling? Suggest the effective means to reduce fouling.
OR
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Q.3 (a) Compare direct heating and indirect heating methods in thermal processing.
(b) Enlist the mechanical and product factors affecting freezing time of ice cream mix.
(c) A process was calculated such that the probability of spoilage from an organism with Do value of 0.5 min is 2 in 1,00,000 from an initial spore load of 1000. To verify this process, an inoculated pack is prepared. Calculate the level of inoculum of an organism having Do value of 1.4 min that must be used on 1000 cans such that a spoilage rate of 10 cans will be equivalent in lethality to the calculated process.
Q.4 (a) Draw a feed line on the equilibrium diagram for various values of ‘q’, q<0, q=0, q=1, q>1 and 0<q<1. Also write the thermal condition of the feed in each case.
(b) Describe the stepwise procedure for obtaining the number of theoretical plates required in a fractionating column.
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(c) What do you understand by flash distillation?
Q.5 (a) A feed containing 50 mole % hexane and 50 mole % octane is fed to a pipe still through a pressure reducing valve and then into flash separator. The vapour and liquid leaving the separator are assumed to be in equilibrium. If 50 mole % of the feed is vaporised, find the composition of top and bottom products. The equilibrium data for the system is :
| Mole fraction of hexane in liquid | 0.045 | 0.1775 | 0.304 | 0.45 | 0.675 |
|---|---|---|---|---|---|
| Mole fraction of hexane in vapour | 0.1775 | 0.456 | 0.538 | 0.69 | 0.78 |
OR
(b) Write the overlapping principle for crystallization.
(c) A salt solution weighing 10000 kg with 30% weight Na2CO3 is cooled to 293 K. The salt crystallizes as decahydrate. What will be the yield of Na2CO3.10H20 crystal if the solubility is 21.5 kg anhydrous NaCO3/100 kg of total water? Do this for following cases:
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- Assume that no water is evaporated.
- Assume that 3 % of total weight of the solution is lost by evaporation of water in cooling.
Q.5 (a) What are the methods of generation of supersaturation?
(b) Describe a crystallization equipment where method of achieving supersaturation is by adiabatic evaporation and cooling alone.
(c) Describe in brief with suitable diagram supercritical fluid extraction process.
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OR
(b) Write important applications of the solid—liquid extraction in the food industry.
(c) What are the factors that influence the rate of leaching?
(c) Derive the lever-arm rule for a ternary system A (solvent), B (solute), and C (carrier).
OR
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(b) What are the three main groups of filters? Write one important property of each.
(c) Describe the centrifugal sedimentation process for the separation of solids from liquid with suitable diagram.
(c) Discuss the principle of cake formation in filtration. Derive the equation for constant pressure filtration.
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