Unit Operations in Food Processing

Name

FSC229

UNIT OPERATIONS IN FOOD PROCESSING

EXAM II

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. 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.

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

3. Gray is the measure of intensity of radiation. Previously rads (radiological units) were used.

One gray equals 100 rads.

4. In their position statement the American Dietetic Association has stated that food irradiation is one way to enhance the safety and the quality of the food supply. ADA continues to encourage the government, food manufacturers, commodity groups, and qualified professionals to educate the consumers with regards to irradiation.

5. Heat treatment is one of the most widely used methods of food processing and preservation. Heat treatment typically improves the eating quality of a food as well as preserve foods by inhibiting enzymes and microorganisms.

6. Although, steam blanchers may be more expensive they provide for better nutrient retention compared to hot-water blanchers. With the hot-water blanchers typically you have larger losses of water soluble components such as vitamins and minerals.

7. Falling film evaporators are most often found in the industry and are used primarily to concentrate low viscosity fluids. A falling film evaporator consists of vertical tube where the product forms a thin film inside the tube. Evaporation takes place under vacuum to prevent heat damage to the product.

8. Regeneration efficiency or percent heat recovery in the continuous pasteurizer is of very little or no value to anyone in a real processing situation. It is just a theoretical formula for students to memorize and for professors to talk about.

9. Flash cooling during UHT processing refers to quick cooling and heating and cooling cycle of the product. This is the most efficient way to process liquid food products under aseptic conditions.

10. Extrusion cooking is a HTST process which reduces microbial contamination and inactivates enzymes. However, the main reason for the long shelf life of extruded food products is their low water activity.

Part II. (30 pts 3 pts each) Please discuss the following in relations to unit operations in food processing.

1. Retort:

2. F value:

3. Thermocompressor:

4. Coxiella burnettii:

5. Extrusion:

6. Coextrusion:

7. 12 D process:

8. Aseptic processing:

9. F0:

10. Polyphenolooxidase:

Part III.

1. (10 pts) Please label the four (4) main components of the continuous (HTST) pasteurizer shown below.

2. (5 pts) Please show the flow of product in the above diagram.

3. (10 pts) Please discuss the differences between a single screw and a twin screw extruder.

4. (10 pts) Please calculate the equivalent heat process needed at 100oC to eliminate Clostridium Botulinum spores in canned green beans. (If at 121oC, D=0.21 min. and z=10oC). Please show all equations and calculations.