Mpa Mega Pascal by M4C19On

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                      UNIT OPERATIONS IN FOOD PROCESSING
                                  FINAL EXAM
                               DECEMBER 14, 2000

Part I. (30 - 3 pts each) Please indicate whether the following statements are true or false. If
the statement is false explain why the statement is false or provide the correct statement.

1. Log phase is the initial phase in the growth of a microorganisms. It is the phase where the
organism is viable however there isn’t much growth taking place. At this stage the organism is
merely getting adjusted to the surrounding medium.



2. In a food processing plant, all food contact surfaces of equipment and utensils should be
constructed of stainless steel or other materials which are smooth, nontoxic, noncorrosive
nonabsorbent and durable under normal use conditions.



3. Temperature of storage, relative humidity of the environment and concentration of gases are
all extrinsic parameters that control the growth of a microorganism. Whereas presence of
nutrients, pH and redox potential are intrinsic parameters.



4. Separation is a mechanical process. In case of milk, separation refers to the reduction of the
size of the milk fat globule to prevent gravity separation of the cream layer. Milk is typically
separated using a dual stage separator.



5. Irradiation of foods refers to the exposure of foods to ionizing energy source. The sources of
ionizing energy may be Cobalt 60 or Cesium 137 or electrons generated from machine sources.
Irradiation is an effective method of food preservation although this technology has received
much consumer resistance.




6.Destruction of Clostridium botulinum spores is the minimum requirement for the heat
sterilization of low acid (high pH) canned foods. Whereas in high acid (low pH) canned foods

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this organism is not a concern since it cannot grow in acidic conditions.



7.Recrystallization in frozen foods refers to the change in size, shape, number of crystals
following completion of initial solidification. Recrystallization is one of the primary factors that
contribute to quality deterioration in frozen foods. Recrystallization can be minimized by
maintaining a low constant storage temperature.



8. Sublimation as in the case of freeze-drying process can be accomplished when the vapor
pressure and temperature of ice surface at which the sublimation takes place are below the triple
point of water which is 4.58 torr of pressure and 0oC.



9. In the U.S. -18oC (0oF) is generally accepted as the satisfactory storage temperature for frozen
foods.



10. In quest for better quality shelf stable, low acid foods, a number of emerging technologies
have been considered. Of these technologies, only high pressure has proven to be effective in
eliminating all spores and enzymes while retaining a quality level equal to or better than frozen
foods.



Part II. (60 - 3 pts each) Please define and discuss the following in relations to unit operations
in food processing.

1. Mpa (Mega Pascal):




2. Lyophilization:



3. IQF:


4. Dew point:

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5. Cryogenic freezing:




6. Scraped surface freezer:




7. Blanching:




8. Pascalization:




9. Turbulent flow:




10. Fluidized bed:




11. Supercooling:




12. MAP (Modified Atmosphere Storage):



13. Atomizer:


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14. Freeze concentration:




15. Reverse osmosis:




16. Permeate:




17. Aseptic process:




18. Retort:




19. Water activity:




20. HTST:




Part III. (60 - 3 pts each) Please match the equipment listed below with the schematic diagram
of the unit operation on the next page.

1) Refrigerator


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2) Centrifugal Separator


3) High Pressure Processor


4) High Temperature Short Time Pasteurizer


5) Spray Dryer


6) Extruder


7) Single Effect Falling Film Evaporator


8) Drum Drier


9) Liquid Nitrogen Freezer


10) Spiral Freezer




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