Download PTU B.Tech 2021 Jan Food-Technology 5th Sem 78651 Food Processing Engineering Question Paper

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Roll No. [ ] [ ] [ ] Total No. of Pages : 02

Total No. of Questions : 18

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B.Tech. (Food Technology) (Sem.=5)

FOOD PROCESSING ENGINEERING

Subject Code : BTFT-506

M.Code : 78651

Time : 3 Hrs. Max. Marks : 60

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INSTRUCTIONS TO CANDIDATES :

1. SECTION-A is COMPULSORY consisting of TEN questions carrying TWO marks each.
2. SECTION-B contains FIVE questions carrying FIVE marks each and students have to attempt any FOUR questions.
3. SECTION-C contains THREE questions carrying TEN marks each and students have to attempt any TWO questions.

SECTION-A

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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.

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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?

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10. What is Mollier diagram? Can it be used to determine properties of wet steam?

SECTION-B

1. 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.
2. 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.

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3. Differentiate between sedimentation and centrifugation. With suitable line sketch describe the construction, working and applications of any centrifuge used in dairy industry.
4. Name the four common ways of breaking solids in size-reduction machines. Write in brief the construction, operation and applications of hammer mill.
5. Discuss the methods to improve the economy of an evaporator.

SECTION-C

1. a) Differentiate between Survivor curve and thermal death time curve. Derive an expression for microbial inactivation rate at constant temperature.
   

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   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.
2. 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.
3. 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.

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