Food hygiene and safety Flashcards
Conditions needed for bacterial growth are?
- Warmth
- Moisture
- Food
- Time
- Suitable pH (less acidic foods)
How does warmth help bacterial growth?
The temperature a food is stored, prepared and cooked at is crucial. If this is not followed correctly then the food will not be safe to eat. The optimum temperature range for bacterial growth is between 5-63℃. This is known as the danger zone as it is dangerous for some foods to be in this temperature range for long periods of time.
How does moisture help bacterial growth?
Bacteria need moisture in order to grow. This is why they grow on foods with high moisture content such as chicken. Foods that are dehydrated or freeze-dried can be stored for much longer as the moisture has been removed.
How does food help bacterial growth?
Food provides energy and nutrients for bacteria to grow. High risk foods particularly protein foods such as chicken and dairy products are rich in nutrients and moisture and so promote bacterial growth.
How does time help bacterial growth?
If provided with the optimum conditions for growth, bacteria can multiply to millions over a small period of time via binary fission. This is when a bacterium divides in two every 20 minutes.
How does the pH help bacterial growth?
Most bacteria reproduce best at a neutral pH level of 7. Acidic foods with a pH below 7, or alkaline foods with a pH above 7, may stop or slow down the rate of bacterial growth.
What 3 ways can food be contaminated?
- Physical
- Chemical
- Biological
Physical Contamination means?
Anything physical entering the food Eg. Pieces of glass, plastic or metal getting into the food.
Chemical Contamination means?
Chemicals entering the food Eg. toxins, cleaning chemicals, pesticides.
Biological Contamination means?
Micro-organisms entering the food, Eg. poor personal hygiene, pests, (cross contamination)
What are micro-organisms that cause food poisoning called?
Pathogenic/ pathogens
High risk foods mean?
Foods that favour the growth and multiplication e.g. meat, seafood, eggs dairy.
Low risk foods mean?
Foods that are less favourable to bacteria, usually low in moisture.
What are the 3 groups of micro-organisms?
1) Bacteria
2) Moulds
3) Yeast
Where are micro-organisms found?
Many different places – soil, water, sewage, dust, dirt, on surfaces & equipment, in the air, on people, animals, insects, & in food.
Why are bacteria spores dangerous?
A spore is a protective outer coating to the cell. The bacteria will remain inactive until the right conditions return & the bacteria become active again, producing deadly toxins. Spores can be resistant to heat & acid so are very difficult to destroy
What is mould?
Mould belongs to the fungi group, which includes mushrooms. They are small plants and when they grow on the surface of food they are visible without a microscope. Moulds on food make it unfit to eat, except for edible moulds that are used in the production of food. You cannot just cut it off as the ‘hyphae’ remain inside
What is yeast?
Yeasts are also fungi, but are single celled, so tend to be treated separately from mould. Wild yeast spores are found in the air & settle on foods, especially those with sugar e.g. fruit, & started to ferment them. It appears as pale brown colonies on the skin of the decomposing fruit
What is enzymic browning?
Enzymes can spoil food by causing enzymic browning – e.g. when you cut open an apple or potato, and its surface becomes brown or black. When cells are broken open, the enzymes inside cells cause the oxygen from the air to react with the substances. This is a form of oxidation.
How can you prevent enzymic browning?
- Adding an acid (e.g. lemon juice in a fruit salad)
- By cooking the food
- By blanching vegetables
- By putting in the cold water - this blocks the oxygen
What are the 4 C’s to prevent food poisoning?
- Cleaning
- Cooling/chilling
- Cooking
- Cross contamination (avoiding it)
What temp. can bacteria be killed on?
75 degrees C or higher
What is the fridge and freezer temperature?
Fridge- 0 degrees C to 5 degrees C
Freezer- -18 degrees C
What is the danger zone?
5-63°C is the danger zone: Binary fission occurs here – rapid multiplication. Only ambient food should be kept within the danger zone. High risk food should be here for a minimum & only be taken out when required.
What is ambient food?
Food that can be stored at room temp, eg. pasta, tinned and canned foods, dried fruits.
What temp. can meat and poultry be fully cooked on?
75 degrees C or higher.
What are the sources of bacteria?
Bacteria lives in the intestines of the animal. This can get onto the meat/juices & multiply. Plant foods can be contaminated with bacteria from the soil.
Where can contamination happen?
- Surfaces
- Equipment
- Cloths
- Food handler (via dirty hands, tasting foods and ‘double dipping’)
- Pests
- Waste/bins
How to reduce contamination?
Better personal and kitchen hygiene.
How do you use a food probe?
-Clean with an antibacterial wipe before AND after use
-Check the largest piece of meat
-Measure the core temperature of the food (not the edge of the food, or the baking tray)
-Calibrate by placing in ice water – it should read 0°C
What is the different between the best before date and expiry/use by date?
Best before: The sensory quality (colour, flavour, texture) is reduced after this date, BUT it is still safe to eat. Usually found on non-perishable or low risk foods
Use by: Unsafe to eat after this date, it’s usually found on perishable or high risk food .
Types of food poisoning:
- Salmonella
- E coli
- Bacillus cereus
- Campylobacter
- Staphylococcus aureus
- Listeria
Salmonella-
Source: Uncooked meat, raw egg, dairy
Incubation: 3 days
Illness: 1 week
Symptoms: Fever
E coli-
Source: Faecal contamination, Undercooked meat products (e.g. burgers) & raw milk
Incubation: 1 week
Illness: 2 weeks
Symptoms: Bloody diarrhea, Can lead to organ failure, Can be fatal
Bacillus cereus-
Source: Cooked rice, leftovers
Incubation: 5 hours
Illness: Varies
Campylobacter-
Source: Uncooked poultry, raw egg, dairy
Incubation: 10 days
Illness: 1 week (can reappear)
Symptoms: Bloody diarrhea, headaches
Staphylococcus aureus-
Source: On human skin and throats
Deli & meat produce, egg, salad, dairy.
Incubation: 7 hours
Illness: 1 day
Listeria-
Source: Dirt Soil, decaying vegetation, water, pate, unpasteurized milk (plus cheese made from this)
Incubation: 3 months
Illness: Varies
Symptoms: Similar to flu – fever, aches, chills, septicemia, miscarriage sometimes carriers can show no symptoms.
Microorganisms in food production:
- Bacteria – cheese, yoghurt, beer, butter milk, soured cream
- Mould – cheese, miso, chocolate, soy sauce, salami and wine
- Yeast – bread, cider, beer, wine, yeast extract (Marmite)
How do you make cheese?
- Warm the milk
- Add the starter culture (bacteria)
- Add the rennet (enzyme)
How do you make yoghurt?
- Different bacteria are added to warmed milk and allowed to multiply.
- It becomes slightly tangy due of lactose converting into lactic acid.
- Lactic acid coagulates the milk proteins to thicken it.
