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.
