Food Technology

Question 1

Define food technology

Answer 1

Food technology is the study of how different foods can be used and made into food products from production to consumption

Question 2

What is the main aims of food preservation

Answer 2

Minimising microbial growth therefore promoting longer shelf life and reduced hazards from eating food

Question 3

Name the 6 intrinsic factors which affect microbial behaviours in food

Answer 3

1. Nutrient content of food
2. Natural antimicrobial substances in food
3. pH change and the food’s ability to resist pH change
4. The oxidation-reduction potential, and its ability to resist redox change
5. The water activity of the food
6. Mechanical barriers to microbial invasion

Question 4

What are the nutritional requirements of microorganisms to grow in food (x4)

Answer 4

Water
Energy source e.g. sugars, amino acids, alcohols
Source of nitrogen - primary source is amino acids
Vitamins and minerals

Question 5

Name some antimicrobial substances which naturally reside in food

Answer 5

Essential oils in some plants e.g. garlic and cloves
Milk - lactoferrin, rotavirus inhibitor, conglutinin, lactoperoxidase system
Lysozyme in eggs and milk

Question 6

Discuss how pH affects microbial growth in food

Answer 6

Most microorganisms grow best around pH 7, few grow below pH 4
Buffered foods resist pH change best e.g. meat is more highly buffered than veg

Question 7

Discuss how the oxidation-reduction potential of food relates to microbial growth

Answer 7

Aerobic microorganisms require an oxidised environment to grow
Anaerobes require a reduced environment t grow

Question 8

What determines the oxidation-reduction potential of food

Answer 8

1. The resistance to change in potential of the food (poising capacity)
2. The oxygen tension of the atmosphere around the food.
3. The access that the atmosphere has to the food.

Question 9

How does water activity relate to microbial growth

Answer 9

Reducing the amount of water available for microbial growth is an extremely important and very ancient way of preserving foods:

Question 10

Give an example of a mechanical barrier agains micro-organisms

Answer 10

Skin - meat or veg
Fermented meat products

Question 11

Name the 4 extrinsic factors that affect microbial growth in food

Answer 11

1. Temperature
2. Gaseous atmosphere surrounding food
3. Relative humidity surrounding the food
4. Time

Question 12

What is the optimum temperature of growth for psychrotrophs

Answer 12

Optimum = 20-30 degrees
Will grow at 7 degrees

Question 13

What is the optimum temperature of growth for psychrophiles

Answer 13

Optimum = 15 degrees or lower

Question 14

What is the optimum temperature of growth for mesophiles

Answer 14

Optimum = 30-40 degrees

Question 15

What is the optimum temperature of growth for thermophiles

Answer 15

Optimum = 55-65 degrees

Question 16

What is the D value when referring to the thermal destruction of bacteria

Answer 16

The time taken for the population to pass through a log cycle (90% of the population is killed) at a certain temperature.
E.g. D121 = the time required to kill 90% of a population of microorganisms at 121 degrees

Question 17

What does the thermal processing of 1D, 2D, 3D and 4D mean

Answer 17

1D = causes a 90% reduction of the original population
2D = causes a 99% reduction of the original population
3D = 99.9% reduction
4D = 99.99% reduction

Question 18

Why are some bacteria so much more heat resistant

Answer 18

They are spore forming

Question 19

What is the Z value when referring to the thermal destruction of bacteria

Answer 19

The Z value is the temperature change that is required to change the D value by a factor of 10.

Question 20

Which atmospheric gas is the most important in controlling microorganisms in food, and wha other gas can be used

Answer 20

Most important - Carbon dioxide
Other - Ozone

Question 21

When should ozone NOT be used to help preserve food

Answer 21

Should not be used on high-lipid-content foods since it would cause an increase in rancidity.

Question 22

Why is relative humidity important for storing food

Answer 22

Foods that undergo surface spoilage from moulds, yeasts, and certain bacteria should be stored under conditions of low Relative Humidity

Question 23

Name the 8 reasons food can be rejected as spoiled

Answer 23

1. Organoleptic changes.
2. Chemical changes.
3. Physical damage.
4. Freezer burn.
5. Staling.
6. Ripening.
7. Presence of foreign bodies.
8. Contamination with chemical agents

Question 24

How are organoleptic changes caused and what 4 changes occur

Answer 24

Brought about by the growth of microorganisms
Changes in taste, odour, appearance and texture

Question 25

Give 2 examples of chemical changes that can spoil foods

Answer 25

Chemical oxidation of fats produces rancidity Browning of fruit and veg in contact with air

Question 26

Name the 2 processes by which meat changes colour (spoiled)

Answer 26

1. Oxygenation of myoglobin (Mb) and formation of oxymyoglobin (MbO2) 2. Oxidation of myoglobin and formation of MetMb (metmyoglobin)

Question 27

Give 2 examples of physical damage that can spoil food

Answer 27

Improper handling Biological risks - insects entering the food

Question 28

What causes freezer burn of food

Answer 28

Frozen food loses moisture which migrates to the coldest place => side of the freezer The loss of the water molecules causes food the become dehydrated = freezer burn

Question 29

Name the cause of food becoming stale

Answer 29

Loss of water

Question 30

Why is food rejected as spoiled due to foreign bodies (x2)

Answer 30

Hard or sharp foreign bodies can cause the consumer injury Foreign bodies can introduce harmful bacteria

Question 31

Name the 4 main categories or animal origin products

Answer 31

Meat and meat products. Milk and Dairy products. Fish and fish products. Poultry and poultry products

Question 32

Name a method of meat preservation

Answer 32

Meat fermentation

Question 33

Why is nitrite essential in a. starter culture for fermentation

Answer 33

To prevent decolourization of the meat. To prevent oxidative rancidity.

Question 34

Describe the process of ripening of fermented meats

Answer 34

Protein is hydrolysed by microbial proteinases to give amino acids and other breakdown products

Question 35

Why does fermentation give stability and safety

Answer 35

Combination of - Low pH - due to presence of lactic acid - Reduced water activity - bay addition of salt and drying

Question 36

Name the 5 common defects of fermented meats

Answer 36

1. Growth of green or black moulds on the surface. 2. Surface bacterial slime. 3. Souring due to excess lactic acid production. 4. Gassiness due to heterofermentative lactic acid bacteria. 5. Greening of the meat pigment caused by the production of hydrogen peroxide by Lactobacillus viridans.

Question 37

Name 4 reasons canned food can spoil

Answer 37

Underfilling. Quality of the can seam. Improper handling. Hygiene of the can transport system

Question 38

Apart from fermentation, name 2 other methods of food preservation

Answer 38

Canning Smoking

Question 39

Name 2 causes of yogurt not setting

Answer 39

Antibiotic residues present The culture is destroyed by bacteriophages

Question 40

Name the 3 types of yogurt

Answer 40

Set Stirred Yogurt drinks

Question 41

Name 3 microbial problems in cheese

Answer 41

Blowing effect - bacterial gas formation producing cracks Mould growth Bacteriophages attacking the started

Question 42

Name 7 reasons why microbiology can be applied in the food industry

Answer 42

1. HACCP-based systems. 2. Risk assessment. 3. Raw materials/ingredients. 4. Hygiene monitoring. 5. Process monitoring. 6. Finished products. 7. Crisis management.

Question 43

Name 4 routes of hygiene monitoring in the food industry

Answer 43

Swabs - surfaces Solid or liquid samples Personnel - hand swabbing Air - air sampling

Question 44

What does microbial criteria set limits for in food (x4)

Answer 44

Pathogen Microbial toxins Indicator microorganisms Spoilage microorganisms

Question 45

What is a two-class sampling plan

Answer 45

Consists of n, c and m n = the number of sample units from a lot that must be examined to satisfy a sampling plan c = the maximum acceptable number of sample units that can exceed the microbiological criterion m m = the maximum number or level of relevant bacteria per gram, values above this level are either marginally acceptable or unacceptable

Question 46

What is a three-class sampling plan

Answer 46

Consists of n, c, m and M n = the number of sample units from a lot that must be examined to satisfy a sampling plan c = the maximum acceptable number of sample units that can exceed the microbiological criterion m m = the maximum number or level of relevant bacteria per gram, values above this level are either marginally acceptable or unacceptable M = the quantity which is used to separate marginally acceptable from unacceptable quality foods

Question 47

When would you use a two-class vs a three-class sampling plan

Answer 47

Two-class = used for presence or absence tests Three-class = used for count or concentration tests

Question 48

What parameters are used to evaluate shelf life of a product

Answer 48

Deterioration in specific organoleptic qualities Microbial growth

Question 49

What is challenge testing used to determine

Answer 49

Growth, death or survival of an organism under controlled temperatures and conditions