Food Safety Flashcards
What are microorganisms?
A tiny living thing that includes bacteria, moulds and yeasts.
What are the five conditions for bacterial growth?
- Warm temperature
- Plenty of moisture
- Plenty of nutrients (food)
- The right pH (not too acidic or alkaline)
- Enough time (bacteria split every 10-20 minutes)
Why are pathogenic microorganisms dangerous?
They can spoil food and cause food poisoning.
What can you do to change the conditions?
- Use a fridge to change the temperature
- Pickle the food in vinegar to change the pH
- Add salt, which removes moisture (absorbs water), drying it out.
What are high-risk foods?
- Ready-to-eat foods that, if not stored correctly, could grow harmful bacteria.
- They’re moist and high in protein (protein = food for bacteria).
- They have a short shelf life - they can’t be kept for too long or bacteria might multiply to dangerous levels.
What are examples of high-risk foods?
- Cooked meat, fish and poultry
- Dairy products (eggs, cheese, etc)
- Gravies, stocks and sauces
- Shellfish
- Cooked rice
Can you identify if a high risk food is spoiling?
Sometimes you can identify if a high-risk is spoilt, e.g. meat going slimy, milk smelling sour, or cheese going mouldy.
But pathogenic bacteria leave no signs - taste, colour, odour and texture aren’t affected.
How can you check there are no visible signs of spoilage on high risk foods?
- Fresh meat should be brightly coloured, firm and have a fresh smell.
- Fresh fish should have shiny skin, red gills, clear eyes and a smell clean or slightly salty.
What are enzymes?
Special proteins that act as biological catalysts - they speed up chemical reactions.
Their actions on food is a type of natural decay that causes food poisoning.
How do enzymes cause ripening?
- Enzymes in fruit cause them to ripen, which affects the sweetness, colour and texture of the fruit.
- E.g. Unripe bananas are green and firm - enzymes break down starch inside them which makes the banana softer and sweeter.
What is enzymic browning?
- When you slice fruit (pears, apples, etc), the oxygen in the air will turn the fruit brown (oxidation).
- Enzymes in the fruit speed up this process.
- Leaving some fruit (bananas, avocados, etc) to overripen will give them a brown colour too.
How can you slow down or prevent the effects of enzymes?
- Adding an acid - enzymes work best at a certain pH. If you dip fruit slices into lemon juice, the acidic conditions will stop enzymic browning.
- Blanching (plunging into boiling water for a short time period) - it is used to prepare food for freezing. Freezing slows enzymes down, and blanching destroys the ripening enzymes, so vegetables retain their colour, nutrients, etc.
What is mould?
A microorganism (fungi) that spoil bread, cheese and fruit - they can change the look, smell and taste of the food. It can easily be spotted due to its ‘fuzzy’ appearance.
- Waste products from moulds can cause food poisoning; toxins will still remain even if scraped off.
What are yeasts?
- Microorganisms (fungi) commonly found on the surfaces of fruit (e.g. grapes, blackberries and tomatoes)
- They spoil fruit by fermenting the sugars into alcohol and carbon dioxide.
How can yeast and mould growth be prevented?
By correctly storing food, e.g. storing bread in dry, cool conditions and most fruits in the fridhe.
What happens to bacterial growth at 75°C and above?
(Cooking/reheating)
- Cooking food above 75°C kills bacteria.
- It’s important to reheat food to above 75°C for at least 3 minutes (and only once).
- Check food is at least 75°C with a temperature probe.
What happens to bacterial growth between 5°C and 63°C?
- Bacteria grow and multiply quickly between 5-63°C.
- This is called the danger zone.
- Hot food should be held above 63°C.
- The optimum temperature for bacterial growth is 37°C.
What happens to bacterial growth between 0°C and 5°C?
(Chilling)
- Keeping food between 0 - 5°C slows down the growth of bacteria.
- This extends the shelf life of the food.
- Chilling food doesn’t change its properties much - chilled food looks and tastes the same - but it may have a harder texture.
What happens to bacterial growth at -18°C?
( Freezing )
- Freezing food below -18°C stops bacteria growing - they become dormant.
- Freezing greatly extends the shelf life of the food and the nutrients aren’t lost.
- It doesn’t kill the bacteria though. They become active again when the food defrosts.
How do you use a fridge correctly?
- Fridges should be 0 - 5°C, ideal for chilling foods (especially high-risk foods).
- Keep food covered or stored in containers to prevent contaminating other foods.
- Don’t let the blood and juices of raw meat drip onto other food - always store raw meat, poultry, and fish on the bottom shelf in the fridge.
- Don’t overstock otherwise air can’t circulate so heat can’t be removed efficiently.
How do you use a freezer correctly?
- Freezers are set around -18°C.
- Food should have clear labels with the date they were frozen.
- Defrost meat and poultry thoroughly in a fridge - if food is partially frozen the recommended cooking time may not be sufficient to kill bacteria
- … Or if cooking from frozen, follow the ‘cook from frozen’ time.
- Don’t overstock otherwise air can’t circulate so heat can’t be removed efficiently.
What are ambient foods?
Foods that can be stored at room temperature.
Where can ambient food be stored?
In a cool fry place in their original packaging or an airtight container.
Why can some food be stored in a cool dry place?
They contain little moisture or have been processed and preserved to make conditions difficult for microorganisms to grow.
What does the method of drying include?
Food is dehydrated to reduce the amount of moisture. Popular methods of drying include smoking and freeze-drying.
What is the method of canning/bottling?
Food is sealed in a can or jar and heated to kill off organisms.
What is the method of pickling?
Food (e.g. gherkins, onions) are plunged in brine or vinegar, making it too acidic for microorganisms to grow.
What is the method of jam-making?
Fruit is boiled with sugar and pectin, and sealed in a glass jar. The high sugar content prevents microorganism growth.
What is the method of vacuum-packing?
Food is put into plastic packaging, and the air is sucked out.
Some microorganisms can’t survive without enough oxygen.
What is the method of modified atmospheric packaging (MAP)?
Food (e.g. seafood, meat) is packaged with a specific mixture of gases (nitrogen, carbon dioxide and oxygen) depending on the food.
What is the use-by date?
A date mark on the packaging on food that is a safety warning about when the food is likely going to be unsafe to eat (e.g. high risk foods).
What is the Best Before date?
A date mark on the packaging of lower-risk food that tells you when the food is expected to deteriorate in quality.
What is cross-contamination?
Transferring potential harmful bacteria from one thing to another.
Where can cross-contamination happen?
- Raw meat juices drip onto cooked food
- Using unclean equipment, dirty work surfaces
- Mixing food types on the same chopping board
- Poor personal hygiene
- Pests (walk over/eating food/laying eggs)
What should you do to reduce the risks when preparing food?
- Follow personal hygiene procedures.
- Separate raw and cooked foods.
- Use coloured chopping boards
- Wash raw vegetables
- Use clean equipment and antibacterial spray
- Defrost frozen food fully
What should you do to reduce the risks when cooking food?
- Cook food at the right temperatures and correct times.
- Make sure food is cooked all the way through.
- Test temperature inside using a food probe (sterilise before and after use)
What should you do to reduce the risks when serving food?
- Serve hot food straight away
- If serving cold or storing it, let it cool for at least 90 minutes.
- Keep food covered (and put in the fridge)
- Avoid wasting food
- Check waste bins are not overfilled
What are the general symptoms of food poisoning?
- Sickness
- Diarrhoea
- Stomach cramps
- Fever
- Death in extreme cases
What can cause food poisoning?
Eating contaminated food containing pathogenic bacteria.
What are the five main types of bacteria?
- Salmonella
- E. coli 0157
- Staphylococcus aureus
- Listeria
- Campylobacter
Where is campylobacter found?
- Found mainly in raw/undercooked poultry
- Raw meat
- Untreated milk/water.
Where is staphylococcus aureus found?
- Skin, hair, noses of people and animals.
- Poor personal hygiene can contaminate food.
Where can listeria be found?
Soft cheese, pate and shellfish
Where can salmonella be found?
Raw poultry, untreated milk and eggs
Where can E. coli 0157 be found?
- In the intestines of animals
- Can contaminate raw beef, untreated milk/water, unwashed vegetables and salad leaves.
What is done to treat milk from harmful bacteria?
Pasteurisation - milk is heated at around 72°C for 15 seconds before being chilled.
What is done to treat eggs from harmful bacteria?
Vaccinations - hens are vaccinated against salmonella.
What is the symbol to show eggs have been treated?
The British Lion Quality mark
What happens in the fermentation process?
Yeast converts sugars into carbon dioxide and ethanol (also known as alcohol).
How is yeast used as a raising agent?
Yeast is added to flour and water to form a dough. Salt is added to strengthen gluten in the dough.
- yeast quickly starts to grow in ideal conditions.
- Yeast ferments the sugar to produce carbon dioxide, which causes the bread to rise.
Why is mould added to cheese?
It can give the cheese a creamy texture and a distinctive sharp, tangy flavour.
How is bacteria added to pasteurised milk to make yoghurt?
- Bacteria ferments lactose (milk sugar) and produce lactic acid.
- The lactic acid acts on the protein in the milk to thicken it and gives it a sour or tangy taste.
What are probiotics?
Live bacteria that is said to give health benefits.
What are prebiotics?
Non digestible fibre compounds which help the growth of probiotics.
How do bacteria make fermented meats (salami and chorizo)?
- Raw meat is mixed with a combination of ingredients, including salt, sugar, flavourings and a ‘starter culture’ of bacteria.
- The bacteria ferment the sugar and produce lactic acid - lowering the meat’s pH causing the proteins to denature and coagulate and force the water out of the meat.
- Lack of moisture and low pH makes the meat safer for longer.
