Food Technology Flashcards
Define food technology
Food technology is the study of how different foods can be used and made into food products from production to consumption
What is the main aims of food preservation
Minimising microbial growth therefore promoting longer shelf life and reduced hazards from eating food
Name the 6 intrinsic factors which affect microbial behaviours in food
- Nutrient content of food
- Natural antimicrobial substances in food
- pH change and the food’s ability to resist pH change
- The oxidation-reduction potential, and its ability to resist redox change
- The water activity of the food
- Mechanical barriers to microbial invasion
What are the nutritional requirements of microorganisms to grow in food (x4)
Water
Energy source e.g. sugars, amino acids, alcohols
Source of nitrogen - primary source is amino acids
Vitamins and minerals
Name some antimicrobial substances which naturally reside in food
Essential oils in some plants e.g. garlic and cloves
Milk - lactoferrin, rotavirus inhibitor, conglutinin, lactoperoxidase system
Lysozyme in eggs and milk
Discuss how pH affects microbial growth in food
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
Discuss how the oxidation-reduction potential of food relates to microbial growth
Aerobic microorganisms require an oxidised environment to grow
Anaerobes require a reduced environment t grow
What determines the oxidation-reduction potential of food
- The resistance to change in potential of the food (poising capacity)
- The oxygen tension of the atmosphere around the food.
- The access that the atmosphere has to the food.
How does water activity relate to microbial growth
Reducing the amount of water available for microbial growth is an extremely important and very ancient way of preserving foods:
Give an example of a mechanical barrier agains micro-organisms
Skin - meat or veg
Fermented meat products
Name the 4 extrinsic factors that affect microbial growth in food
- Temperature
- Gaseous atmosphere surrounding food
- Relative humidity surrounding the food
- Time
What is the optimum temperature of growth for psychrotrophs
Optimum = 20-30 degrees
Will grow at 7 degrees
What is the optimum temperature of growth for psychrophiles
Optimum = 15 degrees or lower
What is the optimum temperature of growth for mesophiles
Optimum = 30-40 degrees
What is the optimum temperature of growth for thermophiles
Optimum = 55-65 degrees
What is the D value when referring to the thermal destruction of bacteria
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
What does the thermal processing of 1D, 2D, 3D and 4D mean
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
Why are some bacteria so much more heat resistant
They are spore forming
What is the Z value when referring to the thermal destruction of bacteria
The Z value is the temperature change that is required to change the D value by a factor of 10.
Which atmospheric gas is the most important in controlling microorganisms in food, and wha other gas can be used
Most important - Carbon dioxide
Other - Ozone
When should ozone NOT be used to help preserve food
Should not be used on high-lipid-content foods since it would cause an increase in rancidity.
Why is relative humidity important for storing food
Foods that undergo surface spoilage from moulds, yeasts, and certain bacteria should be stored under conditions of low Relative Humidity
Name the 8 reasons food can be rejected as spoiled
- Organoleptic changes.
- Chemical changes.
- Physical damage.
- Freezer burn.
- Staling.
- Ripening.
- Presence of foreign bodies.
- Contamination with chemical agents
How are organoleptic changes caused and what 4 changes occur
Brought about by the growth of microorganisms
Changes in taste, odour, appearance and texture
Give 2 examples of chemical changes that can spoil foods
Chemical oxidation of fats produces rancidity
Browning of fruit and veg in contact with air
Name the 2 processes by which meat changes colour (spoiled)
- Oxygenation of myoglobin (Mb) and formation of oxymyoglobin (MbO2)
- Oxidation of myoglobin and formation of MetMb (metmyoglobin)
Give 2 examples of physical damage that can spoil food
Improper handling
Biological risks - insects entering the food
What causes freezer burn of food
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
Name the cause of food becoming stale
Loss of water
Why is food rejected as spoiled due to foreign bodies (x2)
Hard or sharp foreign bodies can cause the consumer injury
Foreign bodies can introduce harmful bacteria
Name the 4 main categories or animal origin products
Meat and meat products.
Milk and Dairy products.
Fish and fish products.
Poultry and poultry products
Name a method of meat preservation
Meat fermentation
Why is nitrite essential in a. starter culture for fermentation
To prevent decolourization of the meat.
To prevent oxidative rancidity.
Describe the process of ripening of fermented meats
Protein is hydrolysed by microbial proteinases to give amino acids and other breakdown products
Why does fermentation give stability and safety
Combination of
- Low pH - due to presence of lactic acid
- Reduced water activity - bay addition of salt and drying
Name the 5 common defects of fermented meats
- Growth of green or black moulds on the surface.
- Surface bacterial slime.
- Souring due to excess lactic acid production.
- Gassiness due to heterofermentative lactic acid bacteria.
- Greening of the meat pigment caused by the production of hydrogen peroxide by Lactobacillus viridans.
Name 4 reasons canned food can spoil
Underfilling.
Quality of the can seam.
Improper handling.
Hygiene of the can transport system
Apart from fermentation, name 2 other methods of food preservation
Canning
Smoking
Name 2 causes of yogurt not setting
Antibiotic residues present
The culture is destroyed by bacteriophages
Name the 3 types of yogurt
Set
Stirred
Yogurt drinks
Name 3 microbial problems in cheese
Blowing effect - bacterial gas formation producing cracks
Mould growth
Bacteriophages attacking the started
Name 7 reasons why microbiology can be applied in the food industry
- HACCP-based systems.
- Risk assessment.
- Raw materials/ingredients.
- Hygiene monitoring.
- Process monitoring.
- Finished products.
- Crisis management.
Name 4 routes of hygiene monitoring in the food industry
Swabs - surfaces
Solid or liquid samples
Personnel - hand swabbing
Air - air sampling
What does microbial criteria set limits for in food (x4)
Pathogen
Microbial toxins
Indicator microorganisms
Spoilage microorganisms
What is a two-class sampling plan
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
What is a three-class sampling plan
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
When would you use a two-class vs a three-class sampling plan
Two-class = used for presence or absence tests
Three-class = used for count or concentration tests
What parameters are used to evaluate shelf life of a product
Deterioration in specific organoleptic qualities
Microbial growth
What is challenge testing used to determine
Growth, death or survival of an organism under controlled temperatures and conditions
