Food spoilage Flashcards
What do microorganisms include
Bacteria
moulds
yeasts
What five conditions do microorganisms need to grow and multiply?
1)A warm temperature
2)Plenty of moisture(water)
3)Plenty of food
4)The right pH(not too acidic or alkaline)
5)Enough time
What could you to to maintain microorganism growth?
Use a fridge
Pickle the food to change pH(add vinegar)
Add salt which absorbs water
High risks food definition and examples
High risk foods include:
cooked meat
dairy products
shellfish
gravies, stocks etc
cooked rice
High risk foods are ready to eat foods that if not stored correctly could grow harmful bacteria.
How do you know if a food is high risk?
They have a short shelf life
Meat goes slimy, milk smelling sour or cheese going mouldy
What are enzymes?
Enzymes are special proteins that act as biological catalysts-they speed up chemical reactions.
How does enzymes affect fruit and vegetables?
Enzymes in fruit causes them to ripen, which affects the sweetness, colour and texture of the fruit.
How can you slow or stop an enzyme from working?
1)Adding an acid-enzymes work best at a certain pH If you dip slices of fruit into lemon juice the acidic conditions will stop enzymic browning
2)Blanching(plunging into boiling water for a short period)is used to prepare vegetables for freezing. Blanching destroys the ripening enzymes the vegetables retain their color,nutrients etc.
How does mould and yeast spoil food ?
Moulds can spoil bread cheese and fruit they can change the look smell taste of the food.
Waste products cause food poisoning-even if you scrape it off,toxins may remain
Yeasts can spoil fruit by fermenting the sugars turning them into alcohol and carbon dioxide
What is the right temperature to cook and reheat food?
75°C
Cooking food above this kills bacteria
Its only important to reheat food once.
Reheat for at least 3 minutes
Check with thermometer
What is the danger zone?
5°C to 63°C
Bacteria grow and multiply quickly in temperatures from this.
This is called the danger zone
Hot food should be held above 63°C
The optimum temperature for bacterial growth is 37°C
What is the chilling temperature?
0°C to 5°C
Keeping food between this slows down the growth of bacteria
This extends the shelf life
Makes the food have a harder texture
What is the freezing temperature
below -18°C
stops bacteria growing and allows to become dormant
nutrients aren’t lost it doesn’t kill bacteria(they become active once defrosted)
How to use a fridge correctly?
Fridges should be 0°C to 5°C ideal for chilling foods
Keep food covered or stored in containers to prevent contaminating food.
Don’t let blood and juices from raw meat drip down onto other foods
always store raw meat, poultry and fish on the bottom shelf in the fridge
How to use a freezer correctly?
Freezers are set at around -18°C
Food should have clear labels with the date they were frozen
Defrost meat and poultry thoroughly in a fridge
Explain how brushing bananas slices with lemon juice affects enzymic activity?
Banana slices are exposed to the air so enzymes will react with oxygen to cause browning
Lime juice is highly acidic
Change in pH will stop the activity of the enzymes and banana slices wont brown
Ahmed cooks the beef and places the leftovers back in the fridge. Explain the benefit of refrigerating the cooked beef
The cooked beef is a high risk food.Refridgerating will slow down the growth of bacteria and increase the shelf life
Ambient foods?
Foods that can be stored safely at room temperature
Example of ambient foods
Cereal
Pasta
Pickled otter
etc
Use by date
The use by date is shown on products with a short shelf life
They are used so that if something is after the use by date it is no longer safe to eat and could cause food poisoning
Best before date
Best before date is for food with a long shelf life
They are used so that if something is after the best before date it is safe to eat but it wont taste the same as it was at its best
Cross contamination?
Passing bacteria from things like raw meat to work surfaces equipment and your hands which is easily transferred to food.
How can it happen?
Other contaminated food
Utensils equipment and work surfaces
People
Pests
How to avoid it?
Follow personal hygiene procedures-wash hands,use apron, clean desktop,wear a hat or hairnet
Separate raw and cooked foods with chopping boards
Wash raw vegetables
Use clean quipment
Defrost frozen food fully in the bottom of the fridge
