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Flashcards in Food between farm gate and consumption Deck (138)
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Compare food processing and food preservation

Food processing: – Conversion of raw animal and plant tissue into forms that are convenient and practical to consume – All the operations from field and farm to consumers • Food preservation – Use of specific thermal and non-thermal techniques to minimize the number of spoilage and pathogenic microorganisms in foods, making them safe and extending the shelf life


What are the 12 unit operations?

1. Materials Handling 2. Seperating 3. Cleaning 4. Disintergrating 5. Pumping 6. Mixing 7. Heat exchange 8. Evaporation 9. Drying 10. Forming 11. Packaging 12. Non-thermal methods


What is materials handling?

From farm to harvest. Transport to processor. Movement within a plant of conveyor belt. Distribution of processed product


What is separating?

-solid from liquid.... ex) peeling potatoes, juice from oranges, oil from water, air removal. Sorting good from bad.


What is cleaning?

Brushing off micro filtration of bacteria from a liquid. Plant equipment and surfaces.



Subdivision of food into smaller particle size. ex) grinding,cutting,dicing,roller mixing. ex) Homogenizing oil/water mixture to create emulsion.



Moving semi-solid paste or liquids in the plant in pumps.



Wide range for materials (solid, liquid, gas). and for purpose (dispersion of ingredients, emulsifying, whipping air into foam)


Heat exchange

Application or removal of heat ex) cooking, canning, pasteurization, freezing. These must be very efficient for mix heat loss.



Removal of moisture from food to concentrate its solids. ex evaporated milk, juice concentrates. Often under vacuum so lowers boiling pt.



For more extensive moisture removal than evaporation -tunnel or cabinet (solids) -Spray drying (liquids)


Describe spray drying....




Formation of specific shapes of foods

ex) burger patties, breakfest cereal, pasta.


Why package food?

Provides protection from

-Microbial contamination

-physical dirt



-air (ox)

-Moisture gain or loss

-Can be good marketing tool


What does high pressure porcessing do?

It is a non-thermal food preservation method (NO HEAT).

Used high pressure to destroy pathogenic bacteria.


What is gamma irradiation?

Non-thermal food preservation method. The radiation kills all bacteria and can make fruit and veg last way longer before going bad naturally.


What is controlling? (13th unit operation)


 to continuously measure the steps to make sure that desired product remains quality. ex) valves, thermometers, scales....

On-line analysis and adjustments.


The NEW definition of food processing....?

The systematic combination of unit process operations into a complex total processes.


Describe the three types of food deteriorations:

Physical deterioration

chemical deteriration

biological deterioration

Physical deterioration- Phase seperation, undesired drying, loss of structure and damage due to handling

chemical deterioration- Undersired chem rxns in food, enzymatic action, lipid oxidation, toxins.

biological deterioration- microbial growth and food spoilage.


What are the 9 major causes of food deterioration?

1. Growth and activity of microorganisms,

primarily bacteria, yeast and molds – Food spoilage and food safety issues

2. Activity of endogenous food enzymes and other

chemical reactions within the food itself – Lipoxygenase catalyzes lipid oxidation, PPO for enzymatic browning

3. Infestation by insects, parasites and rodents – (5-10% in North America, >50% some countries) 

4. Inappropriate temperatures for a given food, both heat and cold – e.g., chill injury for bananas, cucumbers and tomatoes can occur below 10°C

5. Gain or loss of moisture • Surface moisture controlled by humidity in air around food and barrier properties of the package 

6. Reaction with oxygen – Oxidation of nutrients (vitamin A and C, essential fatty acids), colours, flavours, mold growth

7. Exposure to light – Light induced oxidation

8. Physical stress or abuse

9. Time - specific time interval when quality is the highest


What are the two most common preservation techniques used?

Heating (thermal processing)



Describe what these food preservation strategies do?




Dehydrating/drying- prevents microorganism growth by removal of water

Acidification- Gives foods with high degree of acidicty longer perservation (pickles)

Fermentation- Desirable microbial growth that can lead to chem and physical changes that help in preservation. Can also add new flavour and colour. (yogurt, cheese, beer, bread)


Describe what these food preservation strategies do?


-Modificed/controlled atmosphere packaging

smoking- kill surface bacteria (wood burning produces antimicrobial components). Surface drying. Smoked flavour. Heating increases spoilage control.

Modified/controlled atmosphere packaging- Increase shelf life by controlling the gas environment in direct contact with the product.  Can control anaerobic pathogenic bacteria.


Examples of different types of chemical preservatives:





Traditional – Salt, Sugar

• Acidulants – Benzoic acid salts, sorbic acid salts, lactic acid

• Gaseous – SO2, CO2

• Antioxidants – Vit E, ascorbic acid, BHT, TBHQ, BHA


What are the three main mechanisms by which heat is transferred?

Conduction, convection and radiation


Describe conduction


– Heat energy is transferred from one molecule to an adjacent molecule (through containers)

without a gross change in the relative positions of the molecules

– Heating of solid foods


Describe convection


– Transfer of heat by groups of molecules that move as a result of differences in density or as a result of agitation

– Heating of fluid foods


Describe radiation


– Heat transfer by electromagnetic waves emitted by hot objects (infrared range, wavelength 750 nm to 1 mm)

– Infrared, microwave, dielectric heating


What is the primary objective to cooking?

Preservative changes?

Other desierable changes?

Undesirable changes?

What is the primary objective to cooking? In crease palatability. Baking, roasting, dry heat

Preservative changes? Some destruction of spoilage and pathogenic microrganisms. Inactivation of deteriroative enzymes

Other desierable changes? Inactivation of some anti-nutritional factors (Lectins in pulses). Improved digestability of some food constitients

Undesirable changes? Loss of nutrients. Decline in sensory quality (with too much heating).


How is there nutirent loss during cooking?

• Lysine bioavailability reduced by nonenzymatic browning

• Heat sensitive vitamins: decrease in bioavailability (not concentration) – vitamin A, vitamin D

• Loss of water soluble vitamins: decrease in concentration (and bioavailability) – thiamine, niacin, folate