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

Define health

Answer 2

Our optimum physical an mental function

Question 3

Give 5 criteria that food must fulfill

Answer 3

Safe to eat
Good taste
Easy to use
well packed
Good price

Question 4

Describe Food Chain Management

Answer 4

Involves the management of all activities involved in the production, transformation, storage, distribution and the holistic farm to table approach.

Question 5

What is the main purpose of food preservation?

Answer 5

The main aim of food preservation is to minimize the growth of microorganisms during the storage period, thus promoting longer shelf life and reduced hazard from eating the food.

Question 6

Describe food processing

Answer 6

Food processing is the set of methods or techniques used to transform raw materials into food.

Question 7

Give four intrinsic factors that control in microbial action on food

Answer 7

The nutrient content of food
The pH change and its ability to resist pH change (buffering capacity)
The oxidation reduction potential (Eh) of the food and its ability to resist redox change (poising capacity)
The water activity of the food (αw)

Question 8

What 5 factors do microorganisms require to grow and function normally in food?

Answer 8

Water (higher requirement for moulds)
Source of energy (sugars, alcohols and amino acids)
Source of nitrogen (e.g. amino acids)
Vitamins
Minerals

Question 9

Describe three natural antimicrobials

Answer 9

Essential oils in some plant species e.g. eugenol in cloves and allicin in garlic
Cows milk (lactoferrin etc)
Lysozyme in eggs and also milk

Question 10

Describe the buffering of food

Answer 10

Meat buffered better than vegetables due to high protein content

Question 11

Describe Eh in relation to food

Answer 11

The O/R potential of a substrate may be defined generally as the ease with which the substrate loses or gains electrons:
Looses electrons – Oxidised.
Gains electrons – Reduced.
Aerobic microorganisms require positive Eh values (oxidized) for growth, whereas anaerobes require negative Eh values (reduced).

Question 12

What determines O/R

Answer 12

The characteristic O/R potential of the original food.
The poising capacity; that is, the resistance to change in potential of the food.
The oxygen tension of the atmosphere around the food.
The access that the atmosphere has to the food.
Microorganisms affect the Eh of their environments during growth just as they do pH.

Question 13

Define water activity

Answer 13

Water activity is a measure of how efficiently the water present can take part in a chemical (physical) reaction.

Question 14

How is water activity involved in microbial growth?

Answer 14

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

Question 15

Give four extrinsic factors involved in microbial growth

Answer 15

Temperature.
Gaseous atmosphere surrounding the food.
Relative humidity of the atmosphere surrounding the food.
Time.

Question 16

Describe D value

Answer 16

D value (decimal reduction time) is the time taken for the population to pass through a log cycle (90% of the population is killed) at a certain temperature.

D121 – the time requires to kill 90% of a population of microorganisms at 121ºC.

Question 17

Describe the scale of thermal processing with D Values

Answer 17

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

Question 18

How do you work out a the number of spores left after heat treatment using D values?

Answer 18

Treatment Time/D value = x log cycles

10(pow of)original colony -x = no. of spores remaining

Question 19

Define Z value

Answer 19

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

Question 20

What is MAP in relation to food preservation?

Answer 20

Modified Atmosphere Packaging - uses CO2 to control microorganism growth

Question 21

Define spoiled food

Answer 21

A spoiled food is simply a food that is unacceptable to a consumer for reasons of smell, taste, appearance, texture or the presence of foreign bodies.

Question 22

What is an organoleptic change

Answer 22

Organoleptic changes brought about by the growth of microorganisms is by far the most important and common source of food spoilage.
(include yeast in yogurt - safe to eat)

Question 23

Describe a chemical change in food spoilage

Answer 23

Chemical oxidation of fats producing rancidity (oxidative rancidity).

Browning of fruits and vegetables in contact with air.

Question 24

Describe why meat is rejected as spoiled due to colour change

Answer 24

Meat is rejected as spoiled due to colour change:
Oxygenation of myoglobin (Mb) and formation of oxymyoglobin (MbO2) - dark red
Oxidation of myoglobin and formation of MetMb (metmyoglobin) - brown

Question 25

Describe freezer burn

Answer 25

A frozen food is loosing moisture due to poor packaging/wrapping:
The molecules migrate from the steak to the coldest place they can find, which is often the side of the freezer. The loss of these water molecules causes the food (i.e. steak) to become dehydrated.

Question 26

Describe staling and how it could be avoided/made to take longer

Answer 26

A chemical and physical process in bread and other foods that reduces their palatability:
Loss of water. 
- Reduced By - 
Check recipe. 
Increase water level. 
Reduce resting time. 
Increase baking temperature. 
Reduce baking time.

Question 27

What is added to fermented sausages and why?

Answer 27

• Nitrite and/or nitrate
  (Suppresses natural Gram- flora
  Promotes the growth of streptococci, micrococci)
  Sugar content
  Only 0.1% glucose as fermentable carbohydrate in raw meat
  -Lactic acid also decreases the water binding capacity of the meat protein. (Assists the drying process)

Question 28

What controls the rate of fermentation in fermented sausages?

Answer 28

The speed of the fermentation depends on the level of carbohydrate used.
Low level of carbohydrates give slow rate of fermentation.

Question 29

Name three commonly used organisms as starter cultures for fermented sausages

Answer 29

Lactobacillus plantarum.
Pediococcus acidilacti.
Yeasts can also be used
(micrococcus - if nitrate and not nitrite)

Question 30

Why is nitrite essential in fermented sausages?

Answer 30

To prevent decolourization of the meat.

To prevent oxidative rancidity

Question 31

Describe ripening of fermented sausages

Answer 31

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

Question 32

What creates the stability and safety of fermented sausages

Answer 32

Low pH - Lactic acid

Reduced water activity - addition of salt and drying

Question 33

What is the minimum heat process required for canning meat?

Answer 33

The minimum heat process applied to low acid canned foods is a process that gives a 12 decimal reductions of C. botulinium.
At 121 oC D value is 0.21 minutes (12 x 0.21 = 2.52 minutes).

Question 34

Give four reasons for spoilage of canned foods

Answer 34

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

Question 35

Describe how smoking can be used to reduce

microorganism growth in food

Answer 35

Wood smoke contains a number of substances that have antimicrobial activity.
Formaldehyde and higher aldehydes, phenols and methanol.
Highly inhibitory to miroorganisms.

Question 36

Describe the biochemical process that produces yoghurt

Answer 36

Yoghurt is a product of bacterial fermentation of milk

Lactose is converted by the bacteria into lactic acid.

Question 37

Name two factors that will affect yoghurt production

Answer 37

Milk for yogurt production needs to be free from antibiotic residues
The culture will not multiply in the presence of antibiotics, the pH will not drop and the yoghurt will not set

Yogurt will also not set if the culture is destroyed by bacteriophages

Question 38

Describe three microbial problems with cheese

Answer 38

Blowing (Early due to coliforms. Late due to gas producing Clostridia) - production of gas producing cracks and holes
Mould growth.
Bacteriophages attacking starter.

Question 39

Describe the four stages of risk assessment

Answer 39

Hazard identification
Hazard characterization
Exposure assessment
Risk characterization

Question 40

Describe the microbial criteria (important in purchase agreements)

Answer 40

A statement of the microorganisms and/or their toxins of concern to the food.
The methods to be used for their detection and/or enumeration.
A sampling plan.
The microbiological limits to be used in assessing the results
Guidance for interpreting the results.
Number of sample units that should conform to the limits.

Question 41

Describe a sampling plan

Answer 41

A sampling plan is a statement of the criteria of acceptance applied to a lot based on appropriate examinations of a required number of sample units by specified methods

Question 42

Describe a two class sampling plan

Answer 42

For presence/absence tests
n = number of sample units that must be tested per lot
c = maximum acceptable number hat can exceed the microbiological critrion
m= maximum number of relevant bacteria per gram

Question 43

Describe a three class sampling plan

Answer 43

For count and concentration plan
n = number of sample units that must be tested per lot
c = maximum acceptable number hat can exceed the microbiological critrion
m= maximum number of relevant bacteria per gram
M = quantity used to separate marginally acceptable quality from unacceptable quality

Question 44

Which regulation covers the microbiological criteria for foods

Answer 44

EC 2073/2005

Question 45

Describe a shelf life evaluation

Answer 45

A variety of parameters are used to determine the shelf life of a product:
Deterioration in specific organoleptic qualities (flavour, aroma, appearance, texture).
Microbial growth (bacterial pathogens, bacterial indicator organisms and spoilage organisms.
Shelf life evaluation of perishable chilled products usually involves storage of finished products at ‘specified’ and at abuse temperatures.

Question 46

Describe challenge testing

Answer 46

During challenge testing varying levels of the organism in concern e.g. Listeria monocytogenes, are inoculated into pack of the food under consideration.

Food is then stored together with un-inoculated control pack, under controlled temperature and conditions.

Examination at various intervals to determine:
Growth
Death or
Survival