food spoilage and preservation Flashcards

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1
Q

what cause food spoilage on a product?

A

microorganisms

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2
Q

how do microorganisms cause food poisoning?

A

by producing toxins, waste products or poisons that contaminate the foods

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3
Q

what are the typical microorganisms?

A

bacteria, yeast, moulds

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4
Q

what the signs of food spoilage?

A

-a sour smell or taste
-areas of mould on food
-slimy feel to the surface of the food
-a loss of moisture leading to wrinkled food that can be discoloured

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5
Q

what are bacteria most likely to cause?

A

food poisoning

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6
Q

what are the conditions needed for bacteria growth?

A

-time (every 20 minutes- called binary fission)
-temperature- (24C=optimum temp + 5C->63C is the danger zone)
-Food- (hbv protein and moisture= ‘high risk food’)
-moisture
-pH(bacteria needs neutral conditions to grow)
-oxygen

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7
Q

what is binary fission?

A

where the bacteria multiplies every 20 minutes

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8
Q

what is the danger zone?

A

between 5->63C

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9
Q

what is the optimum temp for growth of bacteria?

A

24C

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10
Q

what is a ‘high risk food’?

A

a food that promotes the growth of bacteria and eventually causes food poisoning. a hbv protein with moisture

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11
Q

what does acid do to bacteria?

A

slows down growth

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12
Q

what are some high risk foods?

A

meat, eggs, fish, cheese, milk

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13
Q

how does food poisoning happen?

A

if harmful bacteria contaminate food and then have the correct conditions to grow

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14
Q

what are some causes of food spoilage?

A

insects, pets, cleaning products (bleach), dust

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15
Q

why may pathogenic bacteria cause death in young children, pregnant women and elderly?

A

as they have lowered immune systems and their stomach acid can’t fight all the bacteria

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16
Q

what are some examples of pathogenic bacteria?

A

salmonella and stapphylococcus aureus

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17
Q

what are the sources of salmonella?

A

raw poultry, eggs, raw meat, milk

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18
Q

what are some symptoms of salmonella?

A

onset diarrhoea, vomiting, fever

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19
Q

how should you prevent cross contamination?

A

-wash hands before and after handling food
-never wash raw chicken
-store all foods in the correct position in fridge
-cook meat, eggs and fish thoroughly
-wash fruit and veg
-keep animals away from food
- cover cuts, tie back hair
-use correct chopping boards

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20
Q

how stop/prevent bacterial growth?

A

chill (fridge)
freeze
cook-chill
cook-freeze
canning
bottling/UHT/pasteurisation + sterilisation

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21
Q

what temperature should a fridge be kept at?

A

between 1-4C

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22
Q

what should be kept on the top shelf of the fridge? and why?

A

dairy products, deli items
as the fridge temp cools as rises and they are ‘high risk foods’ so should be kept at the coldest part to prevent food spoilage

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23
Q

what should be kept on the middle shelf of the fridge?

A

cooked foods, leftovers- must be cooled, cakes, jams, pickles
these should all be kept in leak proof container and they need to be kept away from raw foods to prevent cross contamination

24
Q

what should happen to leftovers before getting put in a fridge and why?

A

they should be cooled first as if not steam rises and causes moisture to build up and the liquid can drop and cross contaminate other foods

25
Q

how long do leftovers have to cool before being placed in a fridge?

A

90 minutes

26
Q

what should be kept on the bottom shelf of the fridge?

A

raw meats and fish
these should be kept in leak proof containers and kept at the bottom as they could leak and cause cross contamination

27
Q

what should be kept in the crisp drawers of the fridge?

A

fruit and vegetables to prevent oxygen entering and causing spoilage

28
Q

what can be kept on the door of the fridge? and why?

A

drinks, butter etc…
as they only need light refrigeration

29
Q

what should happen to old and new foods in a fridge?

A

they should be rotated, so newest at the back and oldest at the front to prevent food waste

30
Q

what does storing food in a fridge do to the bacteria?

A

it reduces the growth/ slows it down and extends the shelf life by 5 days

31
Q

what temperature should a freezer be kept at?

A

-18C

32
Q

what is the shelf life of food in a freezer?

A

3 months

33
Q

what does freezing do the bacteria?

A

it makes the bacteria dormant

34
Q

what temp should a commercial freezer be kept at and what is the shelf life of foods when stored in it?

A

-29C and extends shelf life of up to 1 year

35
Q

what are some rules when storing foods in a freezer?

A
  • don’t leave the door open
  • temp should be -18C
  • label all foods
  • don’t re-freeze defrosted foods
  • all foods should be kept in air tight containers to prevent cross contamination
36
Q

why should defrosted foods never be refrozen?

A

as people can lose track of use-by date, during this time of defrosting bacteria has had time to multiply, increased chance of food poisoning and will decrease the sensory qualities

37
Q

why do freezer’s have star ratings?

A

is to let the user know how long the food can safely be stored
e.g. **= 1 month at -12C
***= 3 months at -18C

38
Q

what temperature should food be cooked to before chilling and storing in a fridge? and what does this do?

A

63C
kills all bacteria

39
Q

how long can already cooked be stored in a fridge?

A

3 days

40
Q

what happens to foods that are canned?

A

food is sterilised in airtight containers

41
Q

if food is stored at room temp, how should it be stored?

A

in an airtight containers, in neutral conditions, use an acids to slow down bacteria growth as it’s at its optimum temp (24C) at room temp

42
Q

what is a use-by date?

A

is the date which after there is no guarantee that the food is safe to eat (about safety). food usually shouldn’t be consumed after this date.

43
Q

what is the best before date?

A

encouraged date that the food will be at its best quality and won’t have changed (nothing to do with safety)

44
Q

what is temperature probe?

A

a sensor that is used to measure the internal temperature of food.

45
Q

why is a temperature prope placed in the centre of food?

A

as the core cooks last

46
Q

what temperature should the core of the food be to prevent food poisoning?

A

73C and usually used in high risk foods

47
Q

how should a temperature probe be used?

A

-turn on and reset
-sterilise probe
-insert into centre
-don’t let probe touch metal tray (as may affect the final temperature)

48
Q

what are each coloured chopping used for?

A

red=raw meat
blue=raw fish
green= fruit and veg
white= hot food

49
Q

what is food preservation?

A

helps keep food fresh and edible for longer to prevent it from spoilage

50
Q

what are some alternative methods to food preservation then chilling (fridge) and freezing?

A

drying, vacuum packing, sugaring, pickling, canning, MAP, chemical preservation, salting, smoking

51
Q

when drying food, what does it do?

A

it slows down the actions of enzymes and it removes the moisture in foods so that bacteria can’t grow. this happens with fruit, e.g apricots
also happens at room temp

52
Q

when freezing, what do it do?

A

freezing turns the liquid into ice. bacteria cannot grow live liquid. once defrosted the food should be consumed quickly
happens at -18C

53
Q

when vacuum packing food, what does it?

A

it removes all the air. e.g. cheese , bacon

54
Q

when chilling food, what does it do?

A

slows down the growth of bacteria and extends shelf life by 5 days
happens between 1-4C

55
Q

when pickling food, what does it?

A

it uses vinegar, which acidic that micro-organisms cannot grow in it

56
Q

when canning food, what does it?

A

this is when food is cooked and then sealed in cans or jars. the heat kills micro-organisms and then sealed so that it will keep the food fresh for a very long.

57
Q

when MAP food, what does it do?

A

its a mixture of gases that surrounds food and extends the product e.g crisps or bags of salad.