Download PTU (Punjab Technical University) B.Tech (Bachelor of Technology) / BE (Bachelor of Engineering) 2021 January Food-Technology 5th Sem 78651 Food Processing Engineering Previous Question Paper
Total No. of Pages : 02
Total No. of Questions : 18
B.Tech. (Food Technology) (Sem.?5)
FOOD PROCESSING ENGINEERING
Subject Code : BTFT-506
M.Code : 78651
Time : 3 Hrs. Max. Marks : 60
INST RUCT IONS T O CANDIDAT ES :
1 .
SECT ION-A is COMPULSORY cons is ting of TEN questions carrying TWO marks
each.
2 .
SECT ION-B c ontains F IVE questions c arrying FIVE marks eac h and s tud ents
have to atte mpt any FOUR q ues tions.
3 .
SECT ION-C contains THREE questions carrying T EN marks e ach and s tudents
have to atte mpt any T WO questio ns.
SECTION-A
Write briefly :
1)
Differentiate between equivalent diameter and geometric mean diameter.
2)
Which size reduction law is used to calculate energy in coarse grinding? Define the same.
3)
Define thermal death time.
4)
Differentiate between dead-end filtration from cross flow filtration.
5)
What is the difference between dew point and wet bulb temperature?
6)
Define water activity. How it differs from moisture content?
7)
"The freezing time predicted by Plank's equation is less than that of actual freezing time."
Comment and give reasons.
8)
How dry steam differs from wet steam at the same pressure.
9)
How boiling point elevation influence the evaporation process?
10) What is Mollier diagram? Can it be used to determine properties of wet steam?
SECTION-B
11) a) What is difference between sorting and grading? Write a brief on the various graders
and sorters used for fruits.
b) Describe various types of mixers used for low viscosity liquid mixing. Mention their
distinguished features and applications.
1 | M - 7 8 6 5 1
( S 2 ) - 3 5 1
12) A tunnel dryer is used to dry potatoes from initial moisture content of 75% (w.b.) to final
moisture content of 5% (w.b.). An experimental drying curve for the potatoes indicate that
the critical moisture content is 30% (w.b.) and the time for constant drying is 10 min.
Based on this data, estimate the total drying time for the potatoes.
13) Differentiate between sedimentation and centrifugation. With suitable line sketch describe
the construction, working and applications of any centrifuge used in dairy industry.
14) Name the four common ways of breaking solids in size-reduction machines. Write in brief
the construction, operation and applications of hammer mill.
15) Discuss the methods to improve the economy of an evaporator.
SECTION-C
16) a) Differentiate between Survivor curve and thermal death time curve. Derive an
expression for microbial inactivation rate at constant temperature.
b) A thermal process is accomplished by instantaneous heating to 138?C followed by a
4 sec hold and instantaneous cooling. Estimate the lethality at 121?C when the thermal
resistance constant (z) for the microorganism is 8.5?C.
17) a) Explain the crystallization process using different theories. Describe a batch crystallizer
with a neat diagram.
b) A food block of size 25cm x 50cm x 75cm is to be frozen in refrigerated with the plate
temperature at 239 K. How long it will take to freeze if the food is wrapped in a
package of 0.1 cm thickness. What would be the freezing time without packaging?
Assume that for the plate freezer surface heat transfer coefficient is 600J/ms?C, thermal
conductivity of frozen meat and packaged material is 1.6 and 0.06 J/ms?C. The latent
heat of fusion of the food is 256 kJ/kg and density is 1090 kg/m3. Assume that meat
freezes at 271K. Use Plank's equation and take values of shape factors P= 0.275 &
R= 0.078.
18) a) Discuss the criteria for the selection of a suitable evaporator. Explain the factors that
influence the rate of heat transfer and economy of evaporators.
b) The orange juice is being concentrated from 5 to 30% solids in a single-effect
continuous evaporator. The juice at 20?C is fed to the evaporator at 5000 kg/h. Steam is
available at 100?C. The saturation temperature of vapour in the evaporator is 50?C. The
condensate leaves the evaporator at 75?C and the solution has a negligible boiling point
elevation. The latent heat of vaporization at 50?C is 2382.7 kJ/kg. The specific heat of
orange juice is 4.05 kJ/kg?C. Calculate the steam requirement and steam economy.
NOTE : Disclosure of Identity by writing Mobile No. or Making of passing request on any
page of Answer Sheet will lead to UMC against the Student.
2 | M - 7 8 6 5 1
( S 2 ) - 3 5 1
This post was last modified on 26 June 2021